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<front> <front>
<title abbrev="SRv6 Mobile User-Plane">
Segment Routing IPv6 for Mobile User Plane</title> <title abbrev="SRv6 Mobile User Plane">Segment Routing over IPv6 for the Mob
<seriesInfo name="Internet-Draft" value="draft-ietf-dmm-srv6-mobile-uplane-2 ile
4"/> User Plane</title>
<seriesInfo name="RFC" value="9433"/>
<author fullname="Satoru Matsushima" initials="S." surname="Matsushima" role ="editor"> <author fullname="Satoru Matsushima" initials="S." surname="Matsushima" role ="editor">
<organization abbrev="SoftBank">SoftBank</organization> <organization abbrev="SoftBank">SoftBank</organization>
<address> <address>
<postal> <postal>
<street/> <street/>
<city/> <city/>
<region/> <region/>
<code/> <code/>
<country>Japan</country> <country>Japan</country>
</postal> </postal>
skipping to change at line 84 skipping to change at line 85
<postal> <postal>
<street/> <street/>
<city/> <city/>
<region/> <region/>
<code/> <code/>
<country>Canada</country> <country>Canada</country>
</postal> </postal>
<email>daniel.voyer@bell.ca</email> <email>daniel.voyer@bell.ca</email>
</address> </address>
</author> </author>
<date year="2023"/> <date year="2023" month="July" />
<workgroup>DMM Working Group</workgroup> <area>int</area>
<workgroup>dmm</workgroup>
<abstract> <abstract>
<t> <t>
This document discusses the applicability of SRv6 (Segment Routing IPv6) This document discusses the applicability of Segment Routing over IPv6
to the user-plane of mobile networks. The network programming nature (SRv6) to the user plane of mobile networks. The network programming
of SRv6 accomplishes mobile user-plane functions in a simple manner. nature of SRv6 accomplishes mobile user-plane functions in a simple
The statelessness of SRv6 and its ability to control both service manner. The statelessness of SRv6 and its ability to control both
layer path and underlying transport can be beneficial to the mobile service layer path and underlying transport can be beneficial to the
user-plane, providing flexibility, end-to-end network slicing, and mobile user plane, providing flexibility, end-to-end network slicing,
SLA control for various applications. </t> and Service Level Agreement (SLA) control for various
applications. </t>
<t> <t>
This document discusses how SRv6 (Segment Routing over IPv6) could be us This document discusses how SRv6 could be used as the user plane of
ed as user-plane of mobile networks. This document also specifies the SRv6 Segme mobile networks. This document also specifies the SRv6
nt Endpoint behaviors required for mobility use-cases. Endpoint Behaviors required for mobility use cases.
</t> </t>
</abstract> </abstract>
</front> </front>
<middle> <middle>
<section numbered="true" toc="default"> <section numbered="true" toc="default">
<name>Introduction</name> <name>Introduction</name>
<t> In mobile networks, mobility systems provide <t>In mobile networks, mobility systems provide connectivity over a
connectivity over a wireless link to stationary and non-stationary nodes wireless link to stationary and non-stationary nodes. The user plane
. establishes a tunnel between the mobile node and its anchor node over
The user-plane establishes a tunnel between the mobile node and its anch IP-based backhaul and core networks. </t>
or <t>This document specifies the applicability of SRv6 <xref
node over IP-based backhaul and core networks. </t> target="RFC8754" format="default"/> <xref target="RFC8986"
<t> This document specifies the applicability of SRv6 (Segment format="default"/> to mobile networks. </t>
Routing IPv6) <xref target="RFC8754" format="default"/><xref target="RFC
8986" format="default"/> to mobile networks. </t> <t>Segment Routing (SR) <xref target="RFC8402" format="default"/> is a
<t>Segment Routing <xref target="RFC8402" format="default"/> is a source r source-routing architecture: a node steers a packet through an ordered
outing architecture: a node steers a packet through an ordered list of instructi list of instructions called "segments". A segment can represent any
ons called "segments". A segment can represent any instruction, topological or s instruction, topological or service based.</t>
ervice based.</t> <t>SRv6 applied to mobile networks enables a mobile architecture based
<t>SRv6 applied to mobile networks enables a source-routing based on source routing, where operators can explicitly indicate a route for
mobile architecture, where operators can explicitly indicate a route the packets to and from the mobile node. The SRv6 Endpoint nodes serve
for the packets to and from the mobile node. The SRv6 Endpoint nodes as mobile user-plane anchors.</t>
serve as mobile user-plane anchors.</t>
</section> </section>
<!-- End section "Introduction" -->
<section numbered="true" toc="default"> <section numbered="true" toc="default">
<name>Conventions and Terminology</name> <name>Conventions and Terminology</name>
<t> <t>
The key words "MUST", "MUST NOT", The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>",
"REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL
"RECOMMENDED", "NOT RECOMMENDED", NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>",
"MAY", and "OPTIONAL" in this document are "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
to be interpreted as described in BCP 14 <xref target="RFC2119" format=" "<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are
default"/> to be interpreted as described in BCP&nbsp;14 <xref target="RFC2119"/>
<xref target="RFC8174" format="default"/> when, and only when, they ap <xref target="RFC8174"/> when, and only when, they appear in all capitals,
pear in all capitals, as shown here. as shown here.
</t> </t>
<section anchor="terms" numbered="true" toc="default"> <section anchor="terms" numbered="true" toc="default">
<name>Terminology</name> <name>Terminology</name>
<ul spacing="compact"> <dl spacing="normal" newline="false">
<li>CNF: Cloud-native Network Function</li> <dt>CNF:</dt> <dd>Cloud-native Network Function</dd>
<li>NFV: Network Function Virtualization </li> <dt>NFV:</dt> <dd>Network Function Virtualization </dd>
<li>PDU: Packet Data Unit</li> <dt>PDU:</dt> <dd>Packet Data Unit</dd>
<li>PDU Session: Context of a UE connected to a mobile network.</li> <dt>PDU Session:</dt> <dd>Context of a UE connected to a mobile
<li>UE: User Equipment</li> network</dd>
<li>gNB: gNodeB <xref target="TS.23501" format="default"/></li> <dt>UE:</dt> <dd>User Equipment</dd>
<li>UPF: User Plane Function </li> <dt>gNB:</dt> <dd>gNodeB <xref target="TS.23501"
<li>VNF: Virtual Network Function</li> format="default"/></dd>
<li>DN: Data Network</li> <dt>UPF:</dt> <dd>User Plane Function </dd>
<li>Uplink: from the UE towards the DN</li> <dt>VNF:</dt> <dd>Virtual Network Function</dd>
<li>Downlink: from the DN towards the UE</li> <dt>DN:</dt> <dd>Data Network</dd>
</ul> <dt>Uplink:</dt> <dd>from the UE towards the DN</dd>
<t>The following terms used within this document are defined in <dt>Downlink:</dt> <dd>from the DN towards the UE</dd>
<xref target="RFC8402" format="default"/>: Segment Routing, SR Domai </dl>
n, Segment ID (SID), SRv6, SRv6 <t>The following terms used within this document are defined in <xref
SID, Active Segment, SR Policy, Prefix SID, Adjacency SID and Bindin target="RFC8402" format="default"/>: Segment Routing, SR domain,
g SID.</t> Segment ID (SID), SRv6, SRv6 SID, Active Segment, SR Policy, and Binding
<t> The following terms used within this document are defined in SID (BSID).</t>
<xref target="RFC8754" format="default"/>: SRH, SR Source Node, Tran <t>The following terms used within this document are defined in <xref
sit Node, SR Segment Endpoint target="RFC8754" format="default"/>: Segment Routing Header (SRH) and Re
Node and Reduced SRH.</t> duced
<t>The following terms used within this document are defined in <xref ta SRH.</t>
rget="RFC8986" format="default"/>: NH, SL, FIB, SA, DA, SRv6 SID behavior, SRv6
Segment Endpoint Behavior.</t> <t>The following terms used within this document are defined in <xref
target="RFC8986" format="default"/>: NH (next header), SL (the Segments
Left field of the SRH), FIB (Forwarding Information Base), SA (Source
Address), DA (Destination Address), and SRv6
Endpoint Behavior.</t>
</section> </section>
<!-- End subsection "Terminology" -->
<section anchor="conventions" numbered="true" toc="default"> <section anchor="conventions" numbered="true" toc="default">
<name>Conventions</name> <name>Conventions</name>
<t>An SR Policy is resolved to a SID list. A SID list is represented as &lt;S1, S2, S3&gt; where S1 is the first SID to visit, S2 is the second SID to v isit, and S3 is the last SID to visit along the SR path.</t> <t>An SR Policy is resolved to a SID list. A SID list is represented as &lt;S1, S2, S3&gt; where S1 is the first SID to visit, S2 is the second SID to v isit, and S3 is the last SID to visit along the SR path.</t>
<t>(SA,DA) (S3, S2, S1; SL) represents an IPv6 packet with:</t>
<ul spacing="compact">
<li>Source Address is SA, Destination Address is DA, and next-header i
s SRH</li>
<li>SRH with SID list &lt;S1, S2, S3&gt; with Segments Left = SL</li>
<li>Note the difference between the &lt;&gt; and () symbols: &lt;S1, S
2, S3&gt; represents a SID list where S1 is the first SID and S3 is the last SID
to traverse. (S3, S2, S1; SL) represents the same SID list but encoded in the S
RH format where the rightmost SID in the SRH is the first SID and the leftmost S
ID in the SRH is the last SID. When referring to an SR policy in a high-level us
e-case, it is simpler to use the &lt;S1, S2, S3&gt; notation. When referring to
an illustration of the detailed packet behavior, the (S3, S2, S1; SL) notation i
s more convenient.</li>
<li>The payload of the packet is omitted.</li>
</ul>
<t>(SA1,DA1) (SA2, DA2) represents an IPv6 packet with:</t>
<ul spacing="compact">
<li>Source Address is SA1, Destination Address is DA1, and next-header
is IP</li>
<li>Source Address is SA2, Destination Address is DA2.</li>
</ul>
<t>Throughout the document the representation SRH[n] is used as shorter
representation of Segment List[n], as defined in <xref target="RFC8754" format="
default"/>.</t>
<t>This document uses the following conventions throughout the different <t>(SA,DA) (S3, S2, S1; SL) represents an IPv6 packet where:</t>
examples:</t> <ul spacing="normal">
<ul spacing="compact"> <li>Source Address is SA, Destination Address is DA, and
<li> gNB::1 is an IPv6 address (SID) assigned to the gNB.</li> next header is SRH</li>
<li> U1::1 is an IPv6 address (SID) assigned to UPF1.</li> <li><t>SRH with SID list &lt;S1, S2, S3&gt; with Segments Left =
<li> U2::1 is an IPv6 address (SID) assigned to UPF2.</li> SL</t>
<li> U2:: is the Locator of UPF2.</li>
<t>Note the difference between the &lt;&gt; and ()
symbols. &lt;S1, S2, S3&gt; represents a SID list where S1 is the
first SID and S3 is the last SID to traverse. (S3, S2, S1; SL)
represents the same SID list but encoded in the SRH format where
the rightmost SID in the SRH is the first SID and the leftmost
SID in the SRH is the last SID. When referring to an SR Policy
in a high-level use case, it is simpler to use the &lt;S1, S2,
S3&gt; notation. When referring to an illustration of the
detailed packet behavior, the (S3, S2, S1; SL) notation is more
convenient.</t>
</li>
<li>The payload of the packet is omitted.</li>
</ul>
<t>(SA1,DA1) (SA2, DA2) represents an IPv6 packet where:</t>
<ul spacing="normal">
<li>Source Address is SA1, Destination Address is DA1, and
next header is IP.</li>
<li>Source Address is SA2, and Destination Address is DA2.</li>
</ul>
<t>Throughout the document, the representation SRH[n] is used as a
shorter representation of Segment List[n], as defined in <xref
target="RFC8754" format="default"/>.</t>
<t>This document uses the following conventions throughout the
different examples:</t>
<ul spacing="normal">
<li>gNB::1 is an IPv6 address (SID) assigned to the gNB.</li>
<li>U1::1 is an IPv6 address (SID) assigned to UPF1.</li>
<li>U2::1 is an IPv6 address (SID) assigned to UPF2.</li>
<li>U2:: is the Locator of UPF2.</li>
</ul> </ul>
</section> </section>
<!-- End subsection "Conventions" -->
<section anchor="srv6-funcs" numbered="true" toc="default"> <section anchor="srv6-funcs" numbered="true" toc="default">
<name>Predefined SRv6 Endpoint Behaviors</name> <name>Predefined SRv6 Endpoint Behaviors</name>
<t>
The following SRv6 Endpoint Behaviors are defined in <t>
The following SRv6 Endpoint Behaviors are used throughout this docume
nt. They are defined in
<xref target="RFC8986" format="default"/>. <xref target="RFC8986" format="default"/>.
</t> </t>
<ul spacing="compact"> <ul spacing="normal">
<li> End.DT4: Decapsulation and Specific IPv4 Table Lookup</li> <li>End.DT4: Decapsulation and Specific IPv4 Table Lookup</li>
<li> End.DT6: Decapsulation and Specific IPv6 Table Lookup</li> <li>End.DT6: Decapsulation and Specific IPv6 Table Lookup</li>
<li> End.DT46: Decapsulation and Specific IP Table Lookup</li> <li>End.DT46: Decapsulation and Specific IP Table Lookup</li>
<li> End.DX4: Decapsulation and IPv4 Cross-Connect</li> <li>End.DX4: Decapsulation and IPv4 Cross-Connect</li>
<li> End.DX6: Decapsulation and IPv6 Cross-Connect</li> <li>End.DX6: Decapsulation and IPv6 Cross-Connect</li>
<li> End.DX2: Decapsulation and L2 Cross-Connect</li> <li>End.DX2: Decapsulation and L2 Cross-Connect</li>
<li> End.T: Endpoint with specific IPv6 Table Lookup</li> <li>End.T: Endpoint with specific IPv6 Table Lookup</li>
</ul> </ul>
<t> <t>
This document defines new SRv6 Segment Endpoint Behaviors in <xref ta rget="srv6_functions" format="default"/>.</t> This document defines new SRv6 Endpoint Behaviors in <xref target="sr v6_functions" format="default"/>.</t>
</section> </section>
<!-- End section "Predefined SRv6 Functions" -->
</section> </section>
<!-- End section "Conventions and Terminology" -->
<section anchor="motivations" numbered="true" toc="default"> <section anchor="motivations" numbered="true" toc="default">
<name>Motivation</name> <name>Motivation</name>
<t> Mobile networks are becoming more challenging to operate. <t> Mobile networks are becoming more challenging to operate. On one
On one hand, traffic is constantly growing, and latency requirements hand, traffic is constantly growing, and latency requirements are
are tighter; on the other-hand, there are new use-cases like tighter; on the other hand, there are new use cases like distributed NFV
distributed NFV Infrastructure that are also challenging network operatio Infrastructure that are also challenging network operations. On top of
ns. On top of this, the number of devices connected is steadily growing, causing this, the number of devices connected is steadily growing, causing
scalability problems in mobile entities as the state to maintain keeps increasi scalability problems in mobile entities as the state to maintain keeps
ng.</t> increasing.</t>
<t> The current architecture of mobile networks does not take into account
the underlying transport. The user-plane is rigidly fragmented into <t> The current architecture of mobile networks does not take into
radio access, core and service networks, connected by tunneling account the underlying transport. The user plane is rigidly fragmented
according to user-plane roles such as access and anchor nodes. These into radio access, core, and service networks that connected by tunneling
factors have made it difficult for the operator according to user-plane roles such as access and anchor nodes. These
to optimize and operate the data-path. factors have made it difficult for the operator to optimize and operate
the data path.
</t> </t>
<t> In the meantime, <t> In the meantime,
applications have shifted to use IPv6, and network operators applications have shifted to use IPv6, and network operators
have started adopting IPv6 as their IP transport. have started adopting IPv6 as their IP transport.
SRv6, the IPv6 dataplane instantiation of Segment Routing SRv6, the IPv6 data plane instantiation of Segment Routing
<xref target="RFC8402" format="default"/>, integrates both <xref target="RFC8402" format="default"/>, integrates both
the application data-path and the underlying transport layer into the application data path and the underlying transport layer into
a single protocol, allowing operators to optimize the network in a a single protocol, allowing operators to optimize the network in a
simplified manner and removing forwarding state from the network. It is a lso simplified manner and removing forwarding state from the network. It is a lso
suitable for virtualized environments, like VNF/CNF to VNF/CNF networking. SRv suitable for virtualized environments, like VNF/CNF-to-VNF/CNF networking. SRv
6 has been deployed in dozens of networks <xref target="I-D.matsushima-spring-sr 6 has been deployed in dozens of networks <xref target="I-D.matsushima-spring-sr
v6-deployment-status" format="default"/>.</t> v6-deployment-status" format="default"/>.</t>
<t> SRv6 defines the network-programming concept <xref target="RFC8986" fo <t> SRv6 defines the network programming concept <xref target="RFC8986" fo
rmat="default"/>. rmat="default"/>.
Applied to mobility, SRv6 can provide the user-plane behaviors needed Applied to mobility, SRv6 can provide the user-plane behaviors needed
for mobility management. SRv6 takes advantage of the underlying transport for mobility management. SRv6 takes advantage of the underlying transport
awareness and flexibility together with the ability to also include services t awareness and flexibility together with the ability to also include services t
o optimize the end-to-end mobile dataplane.</t> o optimize the end-to-end mobile data plane.</t>
<t>The use-cases for SRv6 mobility are discussed in <xref target="I-D.cama <t>The use cases for SRv6 mobility are discussed in <xref target="I-D.cama
rilloelmalky-springdmm-srv6-mob-usecases" format="default"/>, and the architectu rilloelmalky-springdmm-srv6-mob-usecases" format="default"/>, and the architectu
ral benefits are discussed in <xref target="I-D.kohno-dmm-srv6mob-arch" />. </t> ral benefits are discussed in <xref target="I-D.kohno-dmm-srv6mob-arch" />. </t>
</section> </section>
<!-- End section "Motivation" -->
<section anchor="scenarios" numbered="true" toc="default"> <section anchor="scenarios" numbered="true" toc="default">
<name>3GPP Reference Architecture</name> <name>3GPP Reference Architecture</name>
<t> This section presents the 3GPP Reference Architecture and possible dep loyment <t> This section presents the 3GPP reference architecture and possible dep loyment
scenarios.</t> scenarios.</t>
<t> <xref target="fig_5g-ref-arch" format="default"/> shows a reference di agram from <t> <xref target="fig_5g-ref-arch" format="default"/> shows a reference di agram from
the 5G packet core architecture <xref target="TS.23501" format="default" />.</t> the 5G packet core architecture <xref target="TS.23501" format="default" />.</t>
<t> The user plane described in this document does not depend on any <t> The user plane described in this document does not depend on any
specific architecture. The 5G packet core architecture as shown is specific architecture. The 5G packet core architecture as shown is
based on the 3GPP standards.</t> based on the 3GPP standards.</t>
<figure anchor="fig_5g-ref-arch">
<name>3GPP 5G Reference Architecture</name> <figure anchor="fig_5g-ref-arch">
<artwork align="center" name="" type="" alt=""><![CDATA[ <name>3GPP 5G Reference Architecture</name>
<artwork align="center" name="" type="" alt=""><![CDATA[
+-----+ +-----+
| AMF | | AMF |
/+-----+ /+-----+
/ | [N11] / | [N11]
[N2] / +-----+ [N2] / +-----+
+------/ | SMF | +------/ | SMF |
/ +-----+ / +-----+
/ / \ / / \
/ / \ [N4] / / \ [N4]
/ / \ ________ / / \ ________
/ / \ / \ / / \ / \
+--+ +-----+ [N3] +------+ [N9] +------+ [N6] / \ +--+ +-----+ [N3] +------+ [N9] +------+ [N6] / \
|UE|------| gNB |------| UPF1 |--------| UPF2 |--------- \ DN / |UE|------| gNB |------| UPF1 |--------| UPF2 |--------- \ DN /
+--+ +-----+ +------+ +------+ \________/ +--+ +-----+ +------+ +------+ \________/
]]></artwork> ]]></artwork>
</figure> </figure>
<ul spacing="compact">
<li>UE: User Equipment</li> <dl spacing="normal" newline="false">
<li>gNB: gNodeB with N3 interface towards packet core (and N2 for contro <dt>UE:</dt>
l plane)</li> <dd>User Equipment</dd>
<li>UPF1: UPF with Interfaces N3 and N9 (and N4 for control plane)</li> <dt>gNB:</dt>
<li>UPF2: UPF with Interfaces N9 and N6 (and N4 for control plane)</li> <dd>gNodeB with N3 interface towards packet core (and N2 for control
<li>SMF: Session Management Function </li> plane)</dd>
<li>AMF: Access and Mobility Management Function </li> <dt>UPF1:</dt>
<li>DN: Data Network e.g., operator services, Internet access </li> <dd>UPF with Interfaces N3 and N9 (and N4 for control plane)</dd>
</ul> <dt>UPF2:</dt>
<dd>UPF with Interfaces N9 and N6 (and N4 for control plane)</dd>
<dt>SMF:</dt>
<dd>Session Management Function</dd>
<dt>AMF:</dt>
<dd>Access and Mobility Management Function</dd>
<dt>DN:</dt>
<dd>Data Network, e.g., operator services and Internet access </dd>
</dl>
<t> This reference diagram does not depict a UPF that is only connected <t> This reference diagram does not depict a UPF that is only connected
to N9 interfaces, although the mechanisms defined in this document to N9 interfaces, although the mechanisms defined in this document
also work in such a case.</t> also work in such a case.</t>
<t> Each session from a UE gets assigned to a UPF. Sometimes multiple <t> Each session from a UE gets assigned to a UPF. Sometimes multiple
UPFs may be used, providing richer service functions. A UE gets its UPFs may be used, providing richer service functions. A UE gets its
IPv4 address, or IPv6 prefix, from the DHCP block of its UPF. IPv4 address, or IPv6 prefix, from the DHCP block of its UPF. The UPF
The UPF advertises that IP address block toward the Internet, advertises that IP address block toward the Internet, ensuring that
ensuring that return traffic is routed to the right UPF. </t> return traffic is routed to the right UPF. </t>
</section> </section>
<!-- End section "A 3GPP Reference Architecture" -->
<section anchor="uplane-functions" numbered="true" toc="default"> <section anchor="uplane-functions" numbered="true" toc="default">
<name>User-plane modes</name> <name>User-Plane Modes</name>
<t>This section introduces an SRv6 based mobile user-plane.It presents two <t>This section introduces an SRv6-based mobile user plane. It presents
different two different "modes" that vary with respect to the use of SRv6.</t>
"modes" that vary with respect to the use of SRv6. <t>The first mode is the "Traditional mode", which inherits the current
The first one is the "Traditional mode", which inherits the 3GPP mobile architecture. In this mode, the <xref target="TS.29281"
current 3GPP mobile architecture. In this mode format="default">GTP-U protocol</xref> is replaced by SRv6. However, the
<xref target="TS.29281" format="default">GTP-U protocol</xref> is replace N3, N9, and N6 interfaces are still point-to-point interfaces with no
d by SRv6, however the N3, N9 and N6 interfaces are still point-to-point interfa intermediate waypoints as in the current mobile network
ces with no intermediate waypoints as in the current mobile network architecture architecture.</t>
.</t> <t> The second mode is the "Enhanced mode". This is an evolution from
<t> The second mode is the "Enhanced mode". the "Traditional mode". In this mode, the N3, N9, or N6 interfaces have
This is an evolution from the "Traditional mode". In this mode the N3, N9 intermediate waypoints (SIDs) that are used for traffic engineering or
or N6 interfaces have intermediate waypoints -SIDs- that are used for Traffic En VNF purposes transparent to 3GPP functionalities. This results in
gineering or VNF purposes transparent to 3GPP functionalities. This results in o optimal end-to-end policies across the mobile network with transport and
ptimal end-to-end policies across the mobile network with transport and services services awareness.</t>
awareness.</t> <t>In both the Traditional and the Enhanced modes, this document assumes
<t>In both, the Traditional and the Enhanced modes, this document assumes that the gNB as well as the UPFs are SR-aware (N3, N9, and potentially
that the N6 interfaces are SRv6).</t>
gNB as well as the UPFs are SR-aware (N3, N9 and -potentially- N6 <t>In addition to those two modes, this document introduces three
interfaces are SRv6).</t> mechanisms for interworking with legacy access networks (those where the
<t>In addition to those two modes, this document introduces three mechanis N3 interface is unmodified). In this document, they are introduced as a
ms for interworking with legacy variant to the Enhanced mode, but they are equally applicable to the
access networks (those where the N3 interface is unmodified). In this docume Traditional mode.</t>
nt they are introduced as a variant to the Enhanced mode, however they are equal
ly applicable to the Traditional mode.</t>
<t>One of these mechanisms is designed to interwork with legacy gNBs <t>One of these mechanisms is designed to interwork with legacy gNBs
using GTP-U/IPv4. The second mechanism is designed to interwork with using GTP-U/IPv4. The second mechanism is designed to interwork with
legacy gNBs using GTP-U/IPv6. The third of those mechanisms is another mo legacy gNBs using GTP-U/IPv6. The third mechanism is another mode that
de that allows deploying SRv6 when legacy gNBs and UPFs that still run GTP-U.</t allows deploying SRv6 when legacy gNBs and UPFs still run GTP-U.</t>
> <t> This document uses the SRv6 Endpoint Behaviors defined in
<t> This document uses SRv6 Segment Endpoint Behaviors defined in <xref target="RFC8986" format="default"/> as well as the new SRv6
<xref target="RFC8986" format="default"/> as well Endpoint Behaviors designed for the mobile user plane that are
as new SRv6 Segment Endpoint Behaviors designed for the mobile user plane defined in <xref target="srv6_functions" format="default"/> of this
that are defined in this document in <xref target="srv6_functions" format="defa document.
ult"/>.
</t> </t>
<section anchor="traditional_mode" numbered="true" toc="default"> <section anchor="traditional_mode" numbered="true" toc="default">
<name>Traditional mode</name> <name>Traditional Mode</name>
<t> In the traditional mode, the existing mobile UPFs remain unchanged <t> In the Traditional mode, the existing mobile UPFs remain unchanged
with the sole exception of the use of SRv6 as the data with the sole exception of the use of SRv6 as the data plane instead
plane instead of GTP-U. There is no impact to the rest of the of GTP-U. There is no impact to the rest of the mobile system.</t>
mobile system.</t>
<t> In existing 3GPP mobile networks, a PDU Session is mapped 1-for-1 <t> In existing 3GPP mobile networks, a PDU Session is mapped 1-for-1
with a specific GTP-U tunnel (Tunnel Endpoint Identifier - TEID). Thi with a specific GTP-U tunnel (Tunnel Endpoint Identifier (TEID)). This
s 1-for-1 mapping is 1-for-1 mapping is mirrored here to replace GTP-U encapsulation with
mirrored here to replace GTP-U encapsulation with the SRv6 the SRv6 encapsulation, while not changing anything else. There will
encapsulation, while not changing anything else. There will be a uniq be a unique SRv6 SID associated with each PDU Session, and the SID
ue SRv6 SID list only contains a single SID.</t>
associated with each PDU Session, and the SID list only contains a si <t> The Traditional mode minimizes the required changes to the mobile
ngle SID.</t> system; hence, it is a good starting point for forming common
<t> The traditional mode minimizes the changes required to the mobile ground.</t>
system; hence it is a good starting point for forming a common ground <t> The gNB/UPF control plane (N2/N4 interface) is unchanged;
.</t> specifically, a single IPv6 address is provided to the gNB. The same
<t> The gNB/UPF control-plane (N2/N4 interface) is unchanged, specifical control plane signaling is used, and the gNB/UPF decides to use SRv6
ly based on signaled GTP-U parameters per local policy. The only
a single IPv6 address is provided to the gNB. The same control plane signa information from the GTP-U parameters used for the SRv6 policy is the
lling TEID, QFI (QoS Flow Identifier), and the IPv6 Destination Address.</t>
is used, and the gNB/UPF decides to use SRv6 based on signaled GTP-U param <t> Our example topology is shown in <xref target="fig_traditional"
eters per local policy. The only information from the GTP-U parameters used for format="default"/>. The gNB and the UPFs are SR-aware. In the
the SRv6 policy is the TEID, QFI -QoS Flow Identifier-, and the IPv6 Destination descriptions of the uplink and downlink packet flow, A is an IPv6
Address.</t> address of the UE, and Z is an IPv6 address reachable within the DN.
<t> Our example topology is shown in <xref target="fig_traditional" form End.MAP, a new SRv6 Endpoint Behavior defined in <xref
at="default"/>. target="end-map-function" format="default"/>, is used.</t>
The gNB and the UPFs are SR-aware.
In the descriptions of the uplink and downlink packet flow, <figure anchor="fig_traditional">
A is an IPv6 address of the UE, and Z is an IPv6 address reachable <name>Traditional Mode - Example Topology</name>
within the Data Network DN. A new SRv6 Endpoint Behavior, End.MAP, d <artwork align="center" name="" type="" alt=""><![CDATA[
efined
in <xref target="end-map-function" format="default"/>, is used.</t>
<figure anchor="fig_traditional">
<name>Traditional mode - example topology</name>
<artwork align="center" name="" type="" alt=""><![CDATA[
________ ________
SRv6 SRv6 / \ SRv6 SRv6 / \
+--+ +-----+ [N3] +------+ [N9] +------+ [N6] / \ +--+ +-----+ [N3] +------+ [N9] +------+ [N6] / \
|UE|------| gNB |------| UPF1 |--------| UPF2 |--------- \ DN / |UE|------| gNB |------| UPF1 |--------| UPF2 |--------- \ DN /
+--+ +-----+ +------+ +------+ \________/ +--+ +-----+ +------+ +------+ \________/
SRv6 node SRv6 node SRv6 node SRv6 node SRv6 node SRv6 node
]]></artwork> ]]></artwork>
</figure> </figure>
<section anchor="traditional_up" numbered="true" toc="default"> <section anchor="traditional_up" numbered="true" toc="default">
<name>Packet flow - Uplink</name> <name>Packet Flow - Uplink</name>
<t> The uplink packet flow is as follows:</t> <t> The uplink packet flow is as follows:</t>
<artwork align="center" name="" type="" alt=""><![CDATA[
<artwork align="center" name="" type="" alt=""><![CDATA[
UE_out : (A,Z) UE_out : (A,Z)
gNB_out : (gNB, U1::1) (A,Z) -> H.Encaps.Red <U1::1> gNB_out : (gNB, U1::1) (A,Z) -> H.Encaps.Red <U1::1>
UPF1_out: (gNB, U2::1) (A,Z) -> End.MAP UPF1_out: (gNB, U2::1) (A,Z) -> End.MAP
UPF2_out: (A,Z) -> End.DT4 or End.DT6]]></artwork> UPF2_out: (A,Z) -> End.DT4 or End.DT6
<t> When the UE packet arrives at the gNB, the gNB performs a ]]></artwork>
H.Encaps.Red operation. Since there is only one SID,
there is no need to push an SRH (reduced SRH). gNB only adds an out <t> When the UE packet arrives at the gNB, the gNB performs an
er IPv6 H.Encaps.Red operation. Since there is only one SID, there is no
header with IPv6 DA U1::1. gNB obtains the SID need to push an SRH (reduced SRH). gNB only adds an outer IPv6
U1::1 from the existing control plane (N2 interface). U1::1 represe header with IPv6 DA U1::1. gNB obtains the SID U1::1 from the
nts an anchoring existing control plane (N2 interface). U1::1 represents an anchoring
SID specific for that session at UPF1.</t> SID specific for that session at UPF1.</t>
<t> When the packet arrives at UPF1, the SID U1::1 is associated with <t> When the packet arrives at UPF1, the SID U1::1 is associated
the End.MAP SRv6 Endpoint Behavior. End.MAP replaces U1::1 by U2::1, that with the End.MAP SRv6 Endpoint Behavior. End.MAP replaces U1::1 with
belongs to the next UPF (U2).</t> U2::1, which belongs to the next UPF (U2).</t>
<t> When the packet arrives at UPF2, the SID U2::1 corresponds to <t> When the packet arrives at UPF2, the SID U2::1 corresponds to an
an End.DT4/End.DT6/End.DT46 SRv6 Endpoint Behavior. UPF2 decapsulat End.DT4/End.DT6/End.DT46 SRv6 Endpoint Behavior. UPF2 decapsulates
es the packet, performs a the packet, performs a lookup in a specific table associated with
lookup in a specific table associated with that mobile network and that mobile network, and forwards the packet toward the DN.</t>
forwards the packet toward the data network (DN).</t>
</section> </section>
<!-- End section "Packet flow - Uplink" -->
<section anchor="traditional_dn" numbered="true" toc="default"> <section anchor="traditional_dn" numbered="true" toc="default">
<name>Packet flow - Downlink</name> <name>Packet Flow - Downlink</name>
<t>The downlink packet flow is as follows:</t> <t>The downlink packet flow is as follows:</t>
<artwork align="center" name="" type="" alt=""><![CDATA[
<artwork align="center" name="" type="" alt=""><![CDATA[
UPF2_in : (Z,A) UPF2_in : (Z,A)
UPF2_out: (U2::, U1::2) (Z,A) -> H.Encaps.Red <U1::2> UPF2_out: (U2::, U1::2) (Z,A) -> H.Encaps.Red <U1::2>
UPF1_out: (U2::, gNB::1) (Z,A) -> End.MAP UPF1_out: (U2::, gNB::1) (Z,A) -> End.MAP
gNB_out : (Z,A) -> End.DX4, End.DX6, End.DX2 gNB_out : (Z,A) -> End.DX4, End.DX6, End.DX2
]]></artwork> ]]></artwork>
<t> When the packet arrives at the UPF2, the UPF2 maps that flow into
a PDU Session. This PDU Session is associated with the segment <t> When the packet arrives at the UPF2, the UPF2 maps that flow
endpoint &lt;U1::2&gt;. UPF2 performs into a PDU Session. This PDU Session is associated with the segment
a H.Encaps.Red operation, encapsulating the packet into endpoint &lt;U1::2&gt;. UPF2 performs an H.Encaps.Red operation,
a new IPv6 header with no SRH since there is only one SID.</t> encapsulating the packet into a new IPv6 header with no SRH since
<t> Upon packet arrival on UPF1, the SID U1::2 is a local SID associat there is only one SID.</t>
ed with the End.MAP <t> Upon packet arrival on UPF1, the SID U1::2 is a local SID
SRv6 Endpoint Behavior. It maps the SID to the next anchoring associated with the End.MAP SRv6 Endpoint Behavior. It maps the SID
point and replaces U1::2 by gNB::1, that belongs to the next to the next anchoring point and replaces U1::2 with gNB::1, which
hop.</t> belongs to the next hop.</t>
<t> Upon packet arrival on gNB, the SID gNB::1 corresponds to an <t> Upon packet arrival on gNB, the SID gNB::1 corresponds to an
End.DX4, End.DX6 or End.DX2 behavior (depending on the PDU Session End.DX4, End.DX6, or End.DX2 behavior (depending on the PDU Session
Type). The gNB decapsulates the packet, Type). The gNB decapsulates the packet, removing the IPv6 header and
removing the IPv6 header and all its extensions headers, and all its extensions headers, and forwards the traffic toward the
forwards the traffic toward the UE.</t> UE.</t>
</section> </section>
<!-- End section "Packet flow - Downlink" -->
</section> </section>
<!-- End section "Traditional mode" -->
<section anchor="enhanced_mode" numbered="true" toc="default"> <section anchor="enhanced_mode" numbered="true" toc="default">
<name>Enhanced mode</name> <name>Enhanced Mode</name>
<t> Enhanced mode improves scalability, provides traffic engineering cap <t> Enhanced mode improves scalability, provides traffic engineering
abilities, and allows service capabilities, and allows service programming <xref
programming <xref target="I-D.ietf-spring-sr-service-programming" for target="I-D.ietf-spring-sr-service-programming" format="default"/>,
mat="default"/>, thanks to the use of multiple SIDs in the SID list (instead of a
thanks to the use of multiple SIDs in the SID list (instead of a dire direct connectivity in between UPFs with no intermediate waypoints as
ct connectivity in between UPFs with no intermediate waypoints as in Traditional in Traditional mode).</t>
Mode).</t> <t>Thus, the main difference is that the SR Policy <bcp14>MAY</bcp14>
<t>Thus, the main difference is that the SR policy MAY include SIDs for traffic engineering and service programming in
include SIDs for traffic engineering and service programming addition to the anchoring SIDs at UPFs.</t>
in addition to the anchoring SIDs at UPFs.</t> <t>Additionally, in this mode, the operator may choose to aggregate
<t>Additionally in this mode the operator may choose to aggregate severa several devices under the same SID list (e.g., stationary residential
l devices under the same SID list (e.g., stationary residential meters [water/en meters (water and energy) connected to the same cell) to improve
ergy] connected to the same cell) to improve scalability.</t> scalability.</t>
<t>The gNB/UPF control-plane (N2/N4 interface) is unchanged, specificall <t>The gNB/UPF control plane (N2/N4 interface) is unchanged;
y specifically, a single IPv6 address is provided to the gNB. A local
a single IPv6 address is provided to the gNB. A local policy instruct policy instructs the gNB to use SRv6.</t>
s the gNB to use SRv6.</t> <t> The gNB resolves the IP address received via the control plane
<t> The gNB resolves the IP address received via the control plane into into a SID list. The resolution mechanism is out of the scope of this
a SID list. The resolution mechanism is out of the scope of this document.</t> document.</t>
<t> Note that the SIDs MAY use the arguments <xref target="arguments-for <t> Note that the SIDs <bcp14>MAY</bcp14> use the argument <xref
-mobility" format="default">Args.Mob.Session </xref> if target="arguments-for-mobility" format="default">Args.Mob.Session
required by the UPFs.</t> </xref> if required by the UPFs.</t>
<t> <xref target="fig_enhanced" format="default"/> shows an Enhanced mod <t> <xref target="fig_enhanced" format="default"/> shows an Enhanced
e topology. mode topology. The gNB and the UPF are SR-aware. The figure
The gNB and the UPF are SR-aware. shows two service segments,
The Figure shows two service segments, S1 and C1. S1 and C1. S1 represents a VNF in the network, and C1
S1 represents a VNF in the network, and C1 represents an intermediate represents an intermediate router used for traffic engineering
router used for Traffic Engineering purposes to enforce a low-latency path in t purposes to enforce a low-latency path in the network. Note that
he network. neither S1 nor C1 are required to have an N4 interface.</t>
Note that neither S1 nor C1 are required to have an N4 interface.</t>
<figure anchor="fig_enhanced"> <figure anchor="fig_enhanced">
<name>Enhanced mode - Example topology</name> <name>Enhanced Mode - Example Topology</name>
<artwork align="center" name="" type="" alt=""><![CDATA[ <artwork align="center" name="" type="" alt=""><![CDATA[
+----+ SRv6 _______ +----+ SRv6 _______
SRv6 --| C1 |--[N3] / \ SRv6 --| C1 |--[N3] / \
+--+ +-----+ [N3] / +----+ \ +------+ [N6] / \ +--+ +-----+ [N3] / +----+ \ +------+ [N6] / \
|UE|----| gNB |-- SRv6 / SRv6 --| UPF1 |------\ DN / |UE|----| gNB |-- SRv6 / SRv6 --| UPF1 |------\ DN /
+--+ +-----+ \ [N3]/ TE +------+ \_______/ +--+ +-----+ \ [N3]/ TE +------+ \_______/
SRv6 node \ +----+ / SRv6 node SRv6 node \ +----+ / SRv6 node
-| S1 |- -| S1 |-
+----+ +----+
SRv6 node SRv6 node
VNF VNF
]]></artwork> ]]></artwork>
</figure> </figure>
<section anchor="enhanced_uplink" numbered="true" toc="default"> <section anchor="enhanced_uplink" numbered="true" toc="default">
<name>Packet flow - Uplink</name> <name>Packet Flow - Uplink</name>
<t>The uplink packet flow is as follows:</t> <t>The uplink packet flow is as follows:</t>
<artwork align="center" name="" type="" alt=""><![CDATA[
<artwork align="center" name="" type="" alt=""><![CDATA[
UE_out : (A,Z) UE_out : (A,Z)
gNB_out : (gNB, S1)(U1::1, C1; SL=2)(A,Z)->H.Encaps.Red<S1,C1,U1::1> gNB_out : (gNB, S1)(U1::1, C1; SL=2)(A,Z)->H.Encaps.Red<S1,C1,U1::1>
S1_out : (gNB, C1)(U1::1, C1; SL=1)(A,Z) S1_out : (gNB, C1)(U1::1, C1; SL=1)(A,Z)
C1_out : (gNB, U1::1)(A,Z) ->End with PSP C1_out : (gNB, U1::1)(A,Z) ->End with PSP
UPF1_out: (A,Z) ->End.DT4,End.DT6,End.DT2U UPF1_out: (A,Z) ->End.DT4,End.DT6,End.DT2U
]]></artwork> ]]></artwork>
<t> UE sends its packet (A,Z) on a specific bearer to its gNB.
gNB's control plane associates that session from the UE(A) with <t> UE sends its packet (A,Z) on a specific bearer to its
the IPv6 address B. gNB resolves B into a SID list. gNB. gNB's control plane associates that session from the UE(A)
&lt;S1, C1, U1::1&gt;. </t> with the IPv6 address B. gNB resolves B into a SID list &lt;S1,
C1, U1::1&gt;. </t>
<t> When gNB transmits the packet, it contains all the segments of <t> When gNB transmits the packet, it contains all the segments of
the SR policy. The SR policy includes segments for the SR Policy. The SR Policy includes segments for traffic
traffic engineering (C1) and for service programming (S1). </t> engineering (C1) and for service programming (S1). </t>
<t> Nodes S1 and C1 perform their related Endpoint functionality <t> Nodes S1 and C1 perform their related Endpoint functionality and
and forward the packet. The End with PSP functionality referes to t forward the packet. The "End with PSP" functionality refers to the
he Endpoint behavior with Penultimate Segment Popping as defined in RFC8986.</t> Endpoint Behavior with Penultimate Segment Popping as defined in
<t> When the packet arrives at UPF1, the active segment (U1::1) is <xref target="RFC8986" format="default"/>.</t>
an End.DT4/End.DT6/End.DT2U which performs the decapsulation (remov <t> When the packet arrives at UPF1, the active segment (U1::1) is an
ing the End.DT4/End.DT6/End.DT2U, which performs the
IPv6 header with all its extension headers) and forwards toward decapsulation (removing the IPv6 header with all its extension
the data network.</t> headers) and forwards toward the DN.</t>
</section> </section>
<!-- End section "Packet flow - Uplink" -->
<section numbered="true" toc="default"> <section numbered="true" toc="default">
<name>Packet flow - Downlink</name> <name>Packet Flow - Downlink</name>
<t>The downlink packet flow is as follows:</t> <t>The downlink packet flow is as follows:</t>
<artwork align="center" name="" type="" alt=""><![CDATA[
<artwork align="center" name="" type="" alt=""><![CDATA[
UPF1_in : (Z,A) ->UPF1 maps the flow w/ UPF1_in : (Z,A) ->UPF1 maps the flow w/
SID list <C1,S1, gNB> SID list <C1,S1, gNB>
UPF1_out: (U1::1, C1)(gNB::1, S1; SL=2)(Z,A)->H.Encaps.Red UPF1_out: (U1::1, C1)(gNB::1, S1; SL=2)(Z,A)->H.Encaps.Red
C1_out : (U1::1, S1)(gNB::1, S1; SL=1)(Z,A) C1_out : (U1::1, S1)(gNB::1, S1; SL=1)(Z,A)
S1_out : (U1::1, gNB::1)(Z,A) ->End with PSP S1_out : (U1::1, gNB::1)(Z,A) ->End with PSP
gNB_out : (Z,A) ->End.DX4/End.DX6/End.DX2 gNB_out : (Z,A) ->End.DX4/End.DX6/End.DX2
]]></artwork> ]]></artwork>
<t>When the packet arrives at the UPF1, the UPF1 maps that <t>When the packet arrives at the UPF1, the UPF1 maps that
particular flow into a UE PDU Session. This UE PDU Session is assoc particular flow into a UE PDU Session. This UE PDU Session is
iated associated with the policy &lt;C1, S1, gNB&gt;. The UPF1 performs a
with the policy &lt;C1, S1, gNB&gt;. The UPF1 performs a H.Encaps.Red operation, encapsulating the packet into a new IPv6
H.Encaps.Red operation, encapsulating the packet into a header with its corresponding SRH.</t>
new IPv6 header with its corresponding SRH.</t>
<t>The nodes C1 and S1 perform their related Endpoint processing.</t> <t>The nodes C1 and S1 perform their related Endpoint processing.</t>
<t>Once the packet arrives at the gNB, the IPv6 DA corresponds to <t>Once the packet arrives at the gNB, the IPv6 DA corresponds to an
an End.DX4, End.DX6 or End.DX2 behavior at the gNB (depending on th End.DX4, End.DX6, or End.DX2 behavior at the gNB (depending on the
e underlying traffic). underlying traffic). The gNB decapsulates the packet, removing the
The gNB decapsulates the packet, removing the IPv6 header, IPv6 header, and forwards the traffic towards the UE. The SID gNB::1
and forwards the traffic is one example of a SID associated to this service.</t>
towards the UE. The SID gNB::1 is one example of a SID associated t <t>Note that there are several means to provide the UE session
o this service.</t> aggregation. The decision about which one to use is a local decision
<t>Note that there are several means to provide the UE session aggrega made by the operator. One option is to use <xref
tion. The decision on which one to use is a local decision made by the operator. target="arguments-for-mobility" format="default">Args.Mob.Session
One option is to use the <xref target="arguments-for-mobility" format="default" </xref>. Another option comprises the gNB performing an IP lookup on
>Args.Mob.Session </xref>. Another option comprises the gNB performing an IP loo the inner packet by using the End.DT4, End.DT6, and End.DT2U
kup on the inner packet by using the End.DT4, End.DT6, and End.DT2U behaviors.</ behaviors.</t>
t>
</section> </section>
<!-- End section "Packet flow - Downlink" -->
<section numbered="true" toc="default"> <section numbered="true" toc="default">
<name>Scalability</name> <name>Scalability</name>
<t>The Enhanced Mode improves scalability since it allows the aggregat <t>The Enhanced mode improves scalability since it allows the
ion aggregation of several UEs under the same SID list. For example, in
of several UEs under the same SID list. For example, in t the case of stationary residential meters that are connected to the
he same cell, all such devices can share the same SID list. This
case of stationary residential meters that are connected improves scalability compared to Traditional mode (unique SID per
to the same cell, all such devices can share the same SID UE) and compared to GTP-U (TEID per UE).</t>
list.
This improves scalability compared to Traditional Mode
(unique SID per UE) and compared to GTP-U (TEID per UE).<
/t>
</section> </section>
</section> </section>
<!-- End section "Enhanced Mode" -->
<section anchor="enhanced_gtp" numbered="true" toc="default"> <section anchor="enhanced_gtp" numbered="true" toc="default">
<name>Enhanced mode with unchanged gNB GTP-U behavior</name> <name>Enhanced Mode with Unchanged gNB GTP-U Behavior</name>
<t> This section describes two mechanisms for interworking with legacy <t> This section describes two mechanisms for interworking with legacy
gNBs that still use GTP-U: one for IPv4, and another for IPv6.</t> gNBs that still use GTP-U: one for IPv4 and another for IPv6.</t>
<t> In the interworking scenarios as illustrated in <t> In the interworking scenarios illustrated in <xref
<xref target="fig_interworking" format="default"/>, the gNB does not target="fig_interworking" format="default"/>, the gNB does not support
support SRv6. SRv6. The gNB supports GTP-U encapsulation over IPv4 or IPv6. To
The gNB supports GTP-U encapsulation over IPv4 or IPv6. To achieve achieve interworking, an SR Gateway (SRGW) entity is added. The SRGW
interworking, an SR Gateway (SRGW) entity is added. The SRGW is a new is a new entity that maps the GTP-U traffic into SRv6. It is deployed
entity that maps the GTP-U traffic into SRv6. It is deployed at the boundary of at the boundary of the SR domain and performs the mapping
the SR Domain and performs the mapping functionality for inbound/outbound traff functionality for inbound and outbound traffic.</t>
ic.</t>
<t> The SRGW is not an anchor point and maintains very little state. <t> The SRGW is not an anchor point and maintains very little state.
For this reason, For this reason,
both IPv4 and IPv6 methods scale to millions of UEs.</t> both IPv4 and IPv6 methods scale to millions of UEs.</t>
<figure anchor="fig_interworking">
<name>Example topology for interworking</name> <figure anchor="fig_interworking">
<artwork align="center" name="" type="" alt=""><![CDATA[ <name>Example Topology for Interworking</name>
<artwork align="center" name="" type="" alt=""><![CDATA[
_______ _______
IP GTP-U SRv6 / \ IP GTP-U SRv6 / \
+--+ +-----+ [N3] +------+ [N9] +------+ [N6] / \ +--+ +-----+ [N3] +------+ [N9] +------+ [N6] / \
|UE|------| gNB |------| SRGW |--------| UPF |---------\ DN / |UE|------| gNB |------| SRGW |--------| UPF |---------\ DN /
+--+ +-----+ +------+ +------+ \_______/ +--+ +-----+ +------+ +------+ \_______/
SR Gateway SRv6 node SR Gateway SRv6 node
]]></artwork> ]]></artwork>
</figure> </figure>
<t>Both of the mechanisms described in this section are applicable to ei
ther the Traditional Mode or the Enhanced Mode.</t> <t>Both of the mechanisms described in this section are applicable to th
e Traditional mode and the Enhanced mode.</t>
<section numbered="true" toc="default"> <section numbered="true" toc="default">
<name>Interworking with IPv6 GTP-U</name> <name>Interworking with IPv6 GTP-U</name>
<t>In this interworking mode the gNB at the N3 interface uses GTP-U <t>In this interworking mode, the gNB at the N3 interface uses GTP-U
over IPv6.</t> over IPv6.</t>
<t>Key points: <t>Key points:
</t> </t>
<ul spacing="compact"> <ul spacing="normal">
<li> The gNB is unchanged (control-plane or user-plane) and <li> The gNB is unchanged (control plane or user plane) and
encapsulates into GTP-U (N3 interface is not modified).</li> encapsulates into GTP-U (N3 interface is not modified).</li> <li>
<li> The 5G Control-Plane towards the gNB (N2 interface) is unmodifi The 5G control plane towards the gNB (N2 interface) is unmodified,
ed, though multiple UPF addresses need to be used - one IPv6 address (i.e. a BSI though multiple UPF addresses need to be used. One IPv6 address
D at the SRGW) is needed per &lt;SLA, PDU session type&gt;. The SRv6 SID is diff (i.e., a BSID at the SRGW) is needed per &lt;SLA, PDU Session
erent depending on the required &lt;SLA, PDU session type&gt; combination.</li> Type&gt;. The SRv6 SID is different depending on the required
<li> In the uplink, the SRGW removes GTP-U header, finds the SID lis &lt;SLA, PDU Session Type&gt; combination.</li>
t related to the IPv6 DA, <li> In the uplink, the SRGW removes the GTP-U header, finds the
and adds SRH with the SID list.</li> SID list related to the IPv6 DA, and adds SRH with the SID
list.</li>
<li> There is no state for the downlink at the SRGW.</li> <li> There is no state for the downlink at the SRGW.</li>
<li> There is simple state in the uplink at the SRGW; using <li> There is simple state in the uplink at the SRGW; using
Enhanced mode results in fewer SR policies on this node. Enhanced mode results in fewer SR Policies on this node. An SR
An SR policy is shared across UEs as long as they belong to the s Policy is shared across UEs as long as they belong to the same
ame context (i.e., tenant). A set of many different policies (i.e., different SL context (i.e., tenant). A set of many different policies (i.e.,
As) increases the amount of state required.</li> different SLAs) increases the amount of state required.</li>
<li> When a packet from the UE leaves the gNB, it is SR-routed. <li> When a packet from the UE leaves the gNB, it is SR-routed.
This simplifies network slicing This simplifies network slicing
<xref target="I-D.ietf-lsr-flex-algo" format="default"/>.</li> <xref target="RFC9350" format="default"/>.</li>
<li> In the uplink, the SRv6 BSID steers traffic <li> In the uplink, the SRv6 BSID steers traffic
into an SR policy when it arrives at the SRGW.</li> into an SR Policy when it arrives at the SRGW.</li>
</ul> </ul>
<t> An example topology is shown in <t> An example topology is shown in
<xref target="fig_interworking_ipv6" format="default"/>.</t> <xref target="fig_interworking_ipv6" format="default"/>.</t>
<t> S1 and C1 are two service segments. <t> S1 and C1 are two service segments.
S1 represents a VNF in the network, and C1 represents a router S1 represents a VNF in the network, and C1 represents a router
configured for Traffic Engineering.</t> configured for traffic engineering.</t>
<figure anchor="fig_interworking_ipv6">
<name>Enhanced mode with unchanged gNB IPv6/GTP-U behavior</name> <figure anchor="fig_interworking_ipv6">
<artwork align="center" name="" type="" alt=""><![CDATA[ <name>Enhanced Mode with Unchanged gNB IPv6/GTP-U Behavior</name>
<artwork align="center" name="" type="" alt=""><![CDATA[
+----+ +----+
IPv6/GTP-U -| S1 |- ___ IPv6/GTP-U -| S1 |- ___
+--+ +-----+ [N3] / +----+ \ / +--+ +-----+ [N3] / +----+ \ /
|UE|--| gNB |- SRv6 / SRv6 \ +----+ +------+ [N6] / |UE|--| gNB |- SRv6 / SRv6 \ +----+ +------+ [N6] /
+--+ +-----+ \ [N9]/ VNF -| C1 |---| UPF2 |------\ DN +--+ +-----+ \ [N9]/ VNF -| C1 |---| UPF2 |------\ DN
GTP-U \ +------+ / +----+ +------+ \___ GTP-U \ +------+ / +----+ +------+ \___
-| SRGW |- SRv6 SRv6 -| SRGW |- SRv6 SRv6
+------+ TE +------+ TE
SR Gateway SR Gateway
]]></artwork> ]]></artwork>
</figure> </figure>
<section numbered="true" toc="default"> <section numbered="true" toc="default">
<name>Packet flow - Uplink</name> <name>Packet Flow - Uplink</name>
<t>The uplink packet flow is as follows:</t> <t>The uplink packet flow is as follows:</t>
<artwork align="center" name="" type="" alt=""><![CDATA[
<artwork align="center" name="" type="" alt=""><![CDATA[
UE_out : (A,Z) UE_out : (A,Z)
gNB_out : (gNB, B)(GTP: TEID T)(A,Z) -> Interface N3 unmodified gNB_out : (gNB, B)(GTP: TEID T)(A,Z) -> Interface N3 unmodified
(IPv6/GTP) (IPv6/GTP)
SRGW_out: (SRGW, S1)(U2::T, C1; SL=2)(A,Z) -> B is an End.M.GTP6.D SRGW_out: (SRGW, S1)(U2::T, C1; SL=2)(A,Z) -> B is an End.M.GTP6.D
SID at the SRGW SID at the SRGW
S1_out : (SRGW, C1)(U2::T, C1; SL=1)(A,Z) S1_out : (SRGW, C1)(U2::T, C1; SL=1)(A,Z)
C1_out : (SRGW, U2::T)(A,Z) -> End with PSP C1_out : (SRGW, U2::T)(A,Z) -> End with PSP
UPF2_out: (A,Z) -> End.DT4 or End.DT6 UPF2_out: (A,Z) -> End.DT4 or End.DT6
]]></artwork> ]]></artwork>
<t> The UE sends a packet destined to Z toward the gNB on a <t> The UE sends a packet destined to Z toward the gNB on a
specific bearer for that session. The gNB, which is unmodified, specific bearer for that session. The gNB, which is unmodified,
encapsulates the packet into IPv6, UDP, and GTP-U headers. encapsulates the packet into IPv6, UDP, and GTP-U headers. The
The IPv6 DA B, and the GTP-U TEID T are the ones received in the IPv6 DA B and the GTP-U TEID T are the ones received in the N2
N2 interface.</t> interface.</t>
<t> The IPv6 address that was signaled over the N2 interface for <t> The IPv6 address that was signaled over the N2 interface for
that UE PDU Session, B, is now the IPv6 DA. B is an SRv6 Binding that UE PDU Session, B, is now the IPv6 DA. B is an SRv6
SID at the SRGW. Hence the packet is routed to the SRGW.</t> Binding SID at the SRGW. Hence, the packet is routed to the
<t> When the packet arrives at the SRGW, the SRGW identifies SRGW.</t>
B as an End.M.GTP6.D Binding SID <t> When the packet arrives at the SRGW, the SRGW identifies B as
(see <xref target="End-M-GTP6-D" format="default"/>). Hence, the an End.M.GTP6.D Binding SID (see <xref target="End-M-GTP6-D"
SRGW removes format="default"/>). Hence, the SRGW removes the IPv6, UDP, and
the IPv6, UDP, and GTP-U headers, and pushes an IPv6 GTP-U headers and pushes an IPv6 header with its own SRH
header with its own SRH containing the SIDs bound to the containing the SIDs bound to the SR Policy associated with this
SR policy associated with this BindingSID. There Binding SID. There is at least one instance of the End.M.GTP6.D SID
at least one instance of the End.M.GTP6.D SID per PDU type.</t> per PDU type.</t>
<t> S1 and C1 perform their related Endpoint functionality <t> S1 and C1 perform their related Endpoint functionality and
and forward the packet.</t> forward the packet.</t>
<t> When the packet arrives at UPF2, the active segment is (U2::T) <t> When the packet arrives at UPF2, the active segment is (U2::T),
which is bound to End.DT4/6. UPF2 then decapsulates which is bound to End.DT4/6. UPF2 then decapsulates (removing the
(removing the outer IPv6 header with all its extension headers) outer IPv6 header with all its extension headers) and forwards the
and forwards the packet toward the data network.</t> packet toward the DN.</t>
</section> </section>
<!-- End section "Packet flow - Uplink" -->
<section numbered="true" toc="default"> <section numbered="true" toc="default">
<name>Packet flow - Downlink</name> <name>Packet Flow - Downlink</name>
<t>The downlink packet flow is as follows:</t> <t>The downlink packet flow is as follows:</t>
<artwork align="center" name="" type="" alt=""><![CDATA[
<artwork align="center" name="" type="" alt=""><![CDATA[
UPF2_in : (Z,A) -> UPF2 maps the flow with UPF2_in : (Z,A) -> UPF2 maps the flow with
<C1, S1, SRGW::TEID,gNB> <C1, S1, SRGW::TEID,gNB>
UPF2_out: (U2::1, C1)(gNB, SRGW::TEID, S1; SL=3)(Z,A) -> H.Encaps.Red UPF2_out: (U2::1, C1)(gNB, SRGW::TEID, S1; SL=3)(Z,A) -> H.Encaps.Red
C1_out : (U2::1, S1)(gNB, SRGW::TEID, S1; SL=2)(Z,A) C1_out : (U2::1, S1)(gNB, SRGW::TEID, S1; SL=2)(Z,A)
S1_out : (U2::1, SRGW::TEID)(gNB, SRGW::TEID, S1, SL=1)(Z,A) S1_out : (U2::1, SRGW::TEID)(gNB, SRGW::TEID, S1, SL=1)(Z,A)
SRGW_out: (SRGW, gNB)(GTP: TEID=T)(Z,A) -> SRGW/96 is End.M.GTP6.E SRGW_out: (SRGW, gNB)(GTP: TEID=T)(Z,A) -> SRGW/96 is End.M.GTP6.E
gNB_out : (Z,A) gNB_out : (Z,A)
]]></artwork> ]]></artwork>
<t> When a packet destined to A arrives at the UPF2, the UPF2 <t> When a packet destined to A arrives at the UPF2, the UPF2
performs a lookup in the table associated to A and finds the performs a lookup in the table associated to A and finds the
SID list &lt;C1, S1, SRGW::TEID, gNB&gt;. The UPF2 performs SID list &lt;C1, S1, SRGW::TEID, gNB&gt;. The UPF2 performs
an H.Encaps.Red operation, encapsulating the packet into an H.Encaps.Red operation, encapsulating the packet into
a new IPv6 header with its corresponding SRH.</t> a new IPv6 header with its corresponding SRH.</t>
<t> C1 and S1 perform their related Endpoint processing.</t> <t> C1 and S1 perform their related Endpoint processing.</t>
<t> Once the packet arrives at the SRGW, the SRGW identifies the <t> Once the packet arrives at the SRGW, the SRGW identifies the
active SID as an End.M.GTP6.E function. The SRGW removes active SID as an End.M.GTP6.E function. The SRGW removes
the IPv6 header and all its extensions headers. The SRGW the IPv6 header and all its extensions headers. The SRGW
generates new IPv6, UDP, and GTP-U headers. The new IPv6 DA generates new IPv6, UDP, and GTP-U headers. The new IPv6 DA
is the gNB which is the last SID in the received SRH. is the gNB, which is the last SID in the received SRH.
The TEID in the generated GTP-U header is an argument of the The TEID in the generated GTP-U header is also an argument of the
received End.M.GTP6.E SID. The SRGW pushes the headers to received End.M.GTP6.E SID. The SRGW pushes the headers to
the packet and forwards the packet toward the gNB. There the packet and forwards the packet toward the gNB. There
is one instance of the End.M.GTP6.E SID per PDU type.</t> is one instance of the End.M.GTP6.E SID per PDU type.</t>
<t> Once the packet arrives at the gNB, the packet is a regular <t> Once the packet arrives at the gNB, the packet is a regular
IPv6/GTP-U packet. The gNB looks for the specific radio bearer IPv6/GTP-U packet. The gNB looks for the specific radio bearer
for that TEID and forwards it on the bearer. This gNB behavior for that TEID and forwards it on the bearer. This gNB behavior
is not modified from current and previous generations.</t> is not modified from current and previous generations.</t>
</section> </section>
<!-- End section "Packet flow - Downlink" -->
<section numbered="true" toc="default"> <section numbered="true" toc="default">
<name>Scalability</name> <name>Scalability</name>
<t> For the downlink traffic, the SRGW is stateless. All the state
is in the SRH pushed by the UPF2. The UPF2 must have the UE <t> For downlink traffic, the SRGW is stateless. All the state
states since it is the UE's session anchor point.</t> is in the SRH pushed by the UPF2. The UPF2 must have the UE
<t> For the uplink traffic, the state at the SRGW does not state since it is the UE's session anchor point.</t>
necessarily need to be unique per PDU Session; the SR policy <t> For uplink traffic, the state at the SRGW does not
can be shared among UEs. This enables more necessarily need to be unique per PDU Session; the SR Policy can
scalable SRGW deployments compared to a be shared among UEs. This enables more scalable SRGW deployments
solution holding millions of states, one or more per UE.</t> compared to a solution holding millions of states, one or more per
UE.</t>
</section> </section>
<!-- End section "Scalability" -->
</section> </section>
<!-- End section "Interworking with IPv6 GTP" -->
<section numbered="true" toc="default"> <section numbered="true" toc="default">
<name>Interworking with IPv4 GTP-U</name> <name>Interworking with IPv4 GTP-U</name>
<t> In this interworking mode the gNB uses GTP <t> In this interworking mode, the gNB uses GTP over IPv4 in the N3
over IPv4 in the N3 interface</t> interface.</t>
<t> Key points: <t> Key points:
</t> </t>
<ul spacing="compact"> <ul spacing="normal">
<li> The gNB is unchanged and encapsulates packets into GTP-U <li> The gNB is unchanged and encapsulates packets into GTP-U (the
(the N3 interface is not modified).</li> N3 interface is not modified).</li>
<li>N2 signaling is not changed, though multiple UPF addresses need <li>N2 signaling is not changed, though multiple UPF addresses
to be provided - one for each PDU Session Type.</li> need to be provided -- one for each PDU Session Type.</li>
<li> In the uplink, traffic is classified by SRGW's <li> In the uplink, traffic is classified by SRGW's classification
classification engine and steered into an SR policy. engine and steered into an SR Policy. The SRGW may be implemented
The SRGW may be implemented in a UPF or as a separate entity. How in a UPF or as a separate entity. How the classification engine
the classification engine rules are set up is outside the scope of this documen rules are set up is outside the scope of this document, though one
t, though one example is using BGP signaling from a Mobile User Plane Controller example is using BGP signaling from a Mobile User Plane (MUP) Contro
<xref target="I-D.mhkk-dmm-srv6mup-architecture" format="default"/>.</li> ller
<li> SRGW removes GTP-U header, finds the SID list related to DA, an <xref target="I-D.mhkk-dmm-srv6mup-architecture"
d adds format="default"/>.</li>
an SRH with the SID list.</li> <li> SRGW removes the GTP-U header, finds the SID list related to DA
,
and adds an SRH with the SID list.</li>
</ul> </ul>
<t> An example topology is shown in <t> An example topology is shown in <xref
<xref target="fig_interworking_ipv4" format="default"/>. In this target="fig_interworking_ipv4" format="default"/>. In this mode, the
mode gNB is an unmodified gNB using IPv4/GTP. The UPFs are SR-aware. As
the gNB is an unmodified gNB using IPv4/GTP. before, the SRGW maps the IPv4/GTP-U traffic to SRv6.</t>
The UPFs are SR-aware. As before, the SRGW maps the <t> S1 and C1 are two service segment endpoints. S1 represents a
IPv4/GTP-U traffic to SRv6.</t> VNF in the network, and C1 represents a router configured for
<t> S1 and C1 are two service segment endpoints. traffic engineering.</t>
S1 represents a VNF in the network, and C1 represents a router
configured for Traffic Engineering.</t> <figure anchor="fig_interworking_ipv4">
<figure anchor="fig_interworking_ipv4"> <name>Enhanced Mode with Unchanged gNB IPv4/GTP-U Behavior</name>
<name>Enhanced mode with unchanged gNB IPv4/GTP-U behavior</name> <artwork align="center" name="" type="" alt=""><![CDATA[
<artwork align="center" name="" type="" alt=""><![CDATA[
+----+ +----+
IPv4/GTP-U -| S1 |- ___ IPv4/GTP-U -| S1 |- ___
+--+ +-----+ [N3] / +----+ \ / +--+ +-----+ [N3] / +----+ \ /
|UE|--| gNB |- SRv6 / SRv6 \ +----+ +------+ [N6] / |UE|--| gNB |- SRv6 / SRv6 \ +----+ +------+ [N6] /
+--+ +-----+ \ [N9]/ VNF -| C1 |---| UPF2 |------\ DN +--+ +-----+ \ [N9]/ VNF -| C1 |---| UPF2 |------\ DN
GTP-U \ +------+ / +----+ +------+ \___ GTP-U \ +------+ / +----+ +------+ \___
-| UPF1 |- SRv6 SRv6 -| UPF1 |- SRv6 SRv6
+------+ TE +------+ TE
SR Gateway SR Gateway
]]></artwork> ]]></artwork>
</figure> </figure>
<section numbered="true" toc="default"> <section numbered="true" toc="default">
<name>Packet flow - Uplink</name> <name>Packet Flow - Uplink</name>
<t>The uplink packet flow is as follows:</t> <t>The uplink packet flow is as follows:</t>
<artwork align="center" name="" type="" alt=""><![CDATA[
<artwork align="center" name="" type="" alt=""><![CDATA[
gNB_out : (gNB, B)(GTP: TEID T)(A,Z) -> Interface N3 gNB_out : (gNB, B)(GTP: TEID T)(A,Z) -> Interface N3
unchanged IPv4/GTP unchanged IPv4/GTP
SRGW_out: (SRGW, S1)(U2::1, C1; SL=2)(A,Z) -> H.M.GTP4.D function SRGW_out: (SRGW, S1)(U2::1, C1; SL=2)(A,Z) -> H.M.GTP4.D function
S1_out : (SRGW, C1)(U2::1, C1; SL=1)(A,Z) S1_out : (SRGW, C1)(U2::1, C1; SL=1)(A,Z)
C1_out : (SRGW, U2::1) (A,Z) -> PSP C1_out : (SRGW, U2::1) (A,Z) -> PSP
UPF2_out: (A,Z) -> End.DT4 or End.DT6 UPF2_out: (A,Z) -> End.DT4 or End.DT6
]]></artwork> ]]></artwork>
<t> The UE sends a packet destined to Z toward the gNB on a <t> The UE sends a packet destined to Z toward the gNB on a
specific bearer for that session. The gNB, which is unmodified, specific bearer for that session. The gNB, which is unmodified,
encapsulates the packet into a new IPv4, UDP, and GTP-Uheaders. encapsulates the packet into a new IPv4, UDP, and GTP-U headers.
The IPv4 DA, B, and the GTP-UTEID are the ones received at the The IPv4 DA, B, and the GTP-UTEID are the ones received at the N2
N2 interface.</t> interface.</t>
<t> When the packet arrives at the SRGW for UPF1, the SRGW has an <t> When the packet arrives at the SRGW for UPF1, the SRGW has a
classification engine rule for incoming traffic from the classification engine rule for incoming traffic from the gNB that
gNB, that steers the traffic into an SR policy by using the steers the traffic into an SR Policy by using the function
function H.M.GTP4.D. The SRGW removes the IPv4, UDP, and GTP H.M.GTP4.D. The SRGW removes the IPv4, UDP, and GTP headers and
headers and pushes an IPv6 header with its own SRH containing pushes an IPv6 header with its own SRH containing the SIDs related
the SIDs related to the SR policy associated with this traffic. to the SR Policy associated with this traffic. The SRGW forwards
The SRGW forwards according to the new IPv6 DA.</t> according to the new IPv6 DA.</t>
<t> S1 and C1 perform their related Endpoint <t> S1 and C1 perform their related Endpoint functionality and
functionality and forward the packet.</t> forward the packet.</t>
<t> When the packet arrives at UPF2, the active segment is (U2::1) <t> When the packet arrives at UPF2, the active segment is (U2::1),
which is bound to End.DT4/6 which performs the decapsulation which is bound to End.DT4/6, which performs the decapsulation
(removing the outer IPv6 header with all its extension headers) (removing the outer IPv6 header with all its extension headers)
and forwards toward the data network.</t> and forwards toward the DN.</t>
<t>Note that the interworking mechanisms for IPv4/GTP-U and IPv6/GTP-U diffe <t>Note that the interworking mechanisms for IPv4/GTP-U and IPv6/GTP-U
rs. This is due to the fact that IPv6/GTP-U can leverage the remote steering cap differ. This is due to the fact that IPv6/GTP-U can leverage the remote
abilities provided by the Segment Routing BSID. In IPv4 this construct is not av steering capabilities provided by the Segment Routing BSID. In IPv4, this
ailable, and building a similar mechanism would require a significant address co construct is not available, and building a similar mechanism would require
nsumption.</t> a significant address consumption.</t>
</section> </section>
<!-- End section "Packet flow - Uplink" -->
<section numbered="true" toc="default"> <section numbered="true" toc="default">
<name>Packet flow - Downlink</name> <name>Packet Flow - Downlink</name>
<t>The downlink packet flow is as follows:</t> <t>The downlink packet flow is as follows:</t>
<artwork align="center" name="" type="" alt=""><![CDATA[
<artwork align="center" name="" type="" alt=""><![CDATA[
UPF2_in : (Z,A) -> UPF2 maps flow with SID UPF2_in : (Z,A) -> UPF2 maps flow with SID
<C1, S1,GW::SA:DA:TEID> <C1, S1,GW::SA:DA:TEID>
UPF2_out: (U2::1, C1)(GW::SA:DA:TEID, S1; SL=2)(Z,A) ->H.Encaps.Red UPF2_out: (U2::1, C1)(GW::SA:DA:TEID, S1; SL=2)(Z,A) ->H.Encaps.Red
C1_out : (U2::1, S1)(GW::SA:DA:TEID, S1; SL=1)(Z,A) C1_out : (U2::1, S1)(GW::SA:DA:TEID, S1; SL=1)(Z,A)
S1_out : (U2::1, GW::SA:DA:TEID)(Z,A) S1_out : (U2::1, GW::SA:DA:TEID)(Z,A)
SRGW_out: (GW, gNB)(GTP: TEID=T)(Z,A) -> End.M.GTP4.E SRGW_out: (GW, gNB)(GTP: TEID=T)(Z,A) -> End.M.GTP4.E
gNB_out : (Z,A) gNB_out : (Z,A)
]]></artwork> ]]></artwork>
<t>When a packet destined to A arrives at the UPF2, the UPF2 <t>When a packet destined to A arrives at the UPF2, the UPF2
performs a lookup in the table associated to A and finds the performs a lookup in the table associated to A and finds the SID
SID list &lt;C1, S1, SRGW::SA:DA:TEID&gt;. The UPF2 performs list &lt;C1, S1, SRGW::SA:DA:TEID&gt;. The UPF2 performs an
a H.Encaps.Red operation, encapsulating the packet into H.Encaps.Red operation, encapsulating the packet into a new IPv6
a new IPv6 header with its corresponding SRH.</t> header with its corresponding SRH.</t>
<t>The nodes C1 and S1 perform their related Endpoint <t>The nodes C1 and S1 perform their related Endpoint
processing.</t> processing.</t>
<t>Once the packet arrives at the SRGW, the SRGW identifies the <t>Once the packet arrives at the SRGW, the SRGW identifies the
active SID as an End.M.GTP4.E function. The SRGW removes active SID as an End.M.GTP4.E function. The SRGW removes the IPv6
the IPv6 header and all its extensions headers. The SRGW header and all its extensions headers. The SRGW generates IPv4,
generates an IPv4, UDP, and GTP-U headers. The IPv4 SA and UDP, and GTP-U headers. The IPv4 SA and DA are received as SID
DA are received as SID arguments. arguments. The TEID in the generated GTP-U header is the
The TEID in the generated GTP-U header is also the arguments argument of the received End.M.GTP4.E SID. The SRGW pushes the
of the received End.M.GTP4.E SID. The SRGW pushes the headers headers to the packet and forwards the packet toward the gNB.</t>
to the packet and forwards the packet toward the gNB.</t>
<t> When the packet arrives at the gNB, the packet is a regular <t> When the packet arrives at the gNB, the packet is a regular
IPv4/GTP-U packet. The gNB looks for the specific radio bearer IPv4/GTP-U packet. The gNB looks for the specific radio bearer for
for that TEID and forwards it on the bearer. This gNB behavior that TEID and forwards it on the bearer. This gNB behavior is not
is not modified from current and previous generations.</t> modified from current and previous generations.</t>
</section> </section>
<!-- End section "Packet flow - Downlink" -->
<section numbered="true" toc="default"> <section numbered="true" toc="default">
<name>Scalability</name> <name>Scalability</name>
<t>For the downlink traffic, the SRGW is stateless. All the <t>For downlink traffic, the SRGW is stateless. All the state
state is in the SRH pushed by the UPF2. The UPF must have is in the SRH pushed by the UPF2. The UPF must have this UE-base
this UE-base state anyway (since it is its anchor point).</t> state anyway (since it is its anchor point).</t>
<t>For the uplink traffic, the state at the SRGW is dedicated on a <t>For uplink traffic, the state at the SRGW is dedicated on a
per UE/session basis according to a classification engine. per-UE/session basis according to a classification engine. There
There is state for steering the different sessions in the form of is state for steering the different sessions in the form of an SR
an SR Policy. However, SR policies are shared Policy. However, SR Policies are shared among several
among several UE/sessions.</t> UE/sessions.</t>
</section> </section>
<!-- End section "Scalability" -->
</section> </section>
<!-- End section "Interworking with IPv4 GTP" -->
<section numbered="true" toc="default"> <section numbered="true" toc="default">
<name>Extensions to the interworking mechanisms</name> <name>Extensions to the Interworking Mechanisms</name>
<t>This section presents two mechanisms for interworking <t>This section presents two mechanisms for interworking with gNBs
with gNBs and UPFs that do not support SRv6. These mechanisms are u and UPFs that do not support SRv6. These mechanisms are used to
sed support GTP-U over IPv4 and IPv6.</t>
to support GTP-U over IPv4 and IPv6.</t>
<t>Even though these methods are presented as an extension to <t> Even though these methods are presented as an extension to the
the "Enhanced mode", it is straightforward in its Enhanced mode, they are also applicable to the Traditional mode.
applicability to the "Traditional mode".</t> </t>
</section> </section>
<!-- End section "Extensions .. interworking mechanisms" -->
</section> </section>
<!-- End "Enhanced mode with unchanged gNB GTP-U ..." -->
<section anchor="drop_in" numbered="true" toc="default"> <section anchor="drop_in" numbered="true" toc="default">
<name>SRv6 Drop-in Interworking</name> <name>SRv6 Drop-In Interworking</name>
<t>This section introduces another mode useful for legacy gNB and UPFs t <t>This section introduces another mode useful for legacy gNB and UPFs
hat still operate with GTP-U. that still operate with GTP-U. This mode provides an SRv6-enabled
This mode provides an SRv6-enabled user plane in between user plane in between two GTP-U tunnel endpoints.</t>
two GTP-U tunnel endpoints.</t> <t>This mode employs two SRGWs that map GTP-U traffic to SRv6 and
<t>This mode employs two SRGWs that map GTP-U traffic to SRv6 and vice-v vice versa.</t>
ersa.</t> <t>Unlike other interworking modes, in this mode, both of the mobility
<t>Unlike other interworking modes, in this mode both of the mobility ov overlay endpoints use GTP-U. Two SRGWs are deployed in either an N3 or
erlay endpoints use GTP-U. N9 interface to realize an intermediate SR Policy.</t>
Two SRGWs are deployed in either N3 or N9 interface to realize an in
termediate SR policy.</t>
<figure anchor="fig_drop_in">
<name>Example topology for SRv6 Drop-in mode</name>
<artwork align="center" name="" type="" alt=""><![CDATA[
<figure anchor="fig_drop_in">
<name>Example Topology for SRv6 Drop-In Mode</name>
<artwork align="center" name="" type="" alt=""><![CDATA[
+----+ +----+
-| S1 |- -| S1 |-
+-----+ / +----+ \ +-----+ / +----+ \
| gNB |- SRv6 / SRv6 \ +----+ +--------+ +-----+ | gNB |- SRv6 / SRv6 \ +----+ +--------+ +-----+
+-----+ \ / VNF -| C1 |---| SRGW-B |----| UPF | +-----+ \ / VNF -| C1 |---| SRGW-B |----| UPF |
GTP[N3]\ +--------+ / +----+ +--------+ +-----+ GTP[N3]\ +--------+ / +----+ +--------+ +-----+
-| SRGW-A |- SRv6 SR Gateway-B GTP -| SRGW-A |- SRv6 SR Gateway-B GTP
+--------+ TE +--------+ TE
SR Gateway-A SR Gateway-A
]]></artwork>
</figure>
]]></artwork> <t>The packet flow of <xref target="fig_drop_in" format="default"/> is
</figure> as follows:</t>
<t>The packet flow of <xref target="fig_drop_in" format="default"/> is a
s <artwork align="center" name="" type="" alt=""><![CDATA[
follows:</t>
<artwork align="center" name="" type="" alt=""><![CDATA[
gNB_out : (gNB, U::1)(GTP: TEID T)(A,Z) gNB_out : (gNB, U::1)(GTP: TEID T)(A,Z)
GW-A_out: (GW-A, S1)(U::1, SGB::TEID, C1; SL=3)(A,Z)->U::1 is an GW-A_out: (GW-A, S1)(U::1, SGB::TEID, C1; SL=3)(A,Z)->U::1 is an
End.M.GTP6.D.Di End.M.GTP6.D.Di
SID at SRGW-A SID at SRGW-A
S1_out : (GW-A, C1)(U::1, SGB::TEID, C1; SL=2)(A,Z) S1_out : (GW-A, C1)(U::1, SGB::TEID, C1; SL=2)(A,Z)
C1_out : (GW-A, SGB::TEID)(U::1, SGB::TEID, C1; SL=1)(A,Z) C1_out : (GW-A, SGB::TEID)(U::1, SGB::TEID, C1; SL=1)(A,Z)
GW-B_out: (GW-B, U::1)(GTP: TEID T)(A,Z) ->SGB::TEID is an GW-B_out: (GW-B, U::1)(GTP: TEID T)(A,Z) ->SGB::TEID is an
End.M.GTP6.E End.M.GTP6.E
SID at SRGW-B SID at SRGW-B
UPF_out : (A,Z) UPF_out : (A,Z)
]]></artwork> ]]></artwork>
<t>When a packet destined to Z is sent to the gNB, which is
unmodified (control-plane and user-plane remain GTP-U), <t>When a packet destined to Z is sent to the gNB, which is unmodified
gNB performs encapsulation into a new IP, UDP, and (control plane and user plane remain GTP-U), gNB performs
GTP-U headers. The IPv6 DA, U::1, and the GTP-U TEID are the ones encapsulation into new IP, UDP, and GTP-U headers. The IPv6 DA, U::1,
received at the N2 interface.</t> and GTP-U TEID are the ones received at the N2 interface.</t>
<t>The IPv6 address that was signaled over the N2 interface for that <t>The IPv6 address that was signaled over the N2 interface for that
PDU Session, U::1, is now the IPv6 DA. U::1 is an SRv6 Binding PDU Session, U::1, is now the IPv6 DA. U::1 is an SRv6 Binding
SID at SRGW-A. Hence the packet is routed to the SRGW.</t> SID at SRGW-A. Hence, the packet is routed to the SRGW.</t>
<t>When the packet arrives at SRGW-A, the SRGW identifies U::1 as an <t>When the packet arrives at SRGW-A, the SRGW identifies U::1 as an
End.M.GTP6.D.Di Binding SID (see <xref target="End-M-GTP6-D-Di" format End.M.GTP6.D.Di Binding SID (see <xref target="End-M-GTP6-D-Di"
="default"/>). format="default"/>). Hence, the SRGW removes the IPv6, UDP, and GTP-U
Hence, the SRGW removes the IPv6, UDP, and GTP-U headers, and pushes a headers and pushes an IPv6 header with its own SRH containing the
n SIDs bound to the SR Policy associated with this Binding SID. There is
IPv6 header with its own SRH containing the SIDs bound to the SR one instance of the End.M.GTP6.D.Di SID per PDU type.</t>
policy associated with this Binding SID. There is one instance of the
End.M.GTP6.D.Di SID per PDU type.</t>
<t>S1 and C1 perform their related Endpoint functionality and forward <t>S1 and C1 perform their related Endpoint functionality and forward
the packet.</t> the packet.</t>
<t>Once the packet arrives at SRGW-B, the SRGW identifies the active <t>Once the packet arrives at SRGW-B, the SRGW identifies the active
SID as an End.M.GTP6.E function. The SRGW removes the IPv6 header and SID as an End.M.GTP6.E function. The SRGW removes the IPv6 header and
all its extensions headers. The SRGW generates new IPv6, UDP, and GTP all its extensions headers. The SRGW generates new IPv6, UDP, and GTP
headers. The new IPv6 DA is U::1 which is the last SID in the headers. The new IPv6 DA is U::1, which is the last SID in the
received SRH. The TEID in the generated GTP-U header is an argument of received SRH. The TEID in the generated GTP-U header is an argument of
the received End.M.GTP6.E SID. The SRGW pushes the headers to the the received End.M.GTP6.E SID. The SRGW pushes the headers to the
packet and forwards the packet toward UPF. There is one instance of packet and forwards the packet toward UPF. There is one instance of
the End.M.GTP6.E SID per PDU type.</t> the End.M.GTP6.E SID per PDU type.</t>
<t>Once the packet arrives at UPF, the packet is a regular IPv6/GTP <t>Once the packet arrives at UPF, the packet is a regular IPv6/GTP
packet. The UPF looks for the specific rule for that TEID to forward packet. The UPF looks for the specific rule for that TEID to forward
the packet. This UPF behavior is not modified from current and the packet. This UPF behavior is not modified from current and
previous generations.</t> previous generations.</t>
</section> </section>
<!-- End section "SRv6 Drop-in Interworking" -->
</section> </section>
<!-- End section "User-plane behaviors" -->
<section anchor="srv6_functions" numbered="true" toc="default"> <section anchor="srv6_functions" numbered="true" toc="default">
<name>SRv6 Segment Endpoint Mobility Behaviors</name> <name>SRv6 Segment Endpoint Mobility Behaviors</name>
<!-- Add text on functions used on UPF1, UPF2,... -->
<t>This section introduces new SRv6 Segment Endpoint Behaviors for the mob <t>This section introduces new SRv6 Endpoint Behaviors for the
ile user-plane. The behaviors described in this document are compatible with the mobile user plane. The behaviors described in this document are
NEXT and REPLACE flavors defined in <xref target="I-D.ietf-spring-srv6-srh-comp compatible with the NEXT and REPLACE flavors defined in <xref
ression" format="default" />.</t> target="I-D.ietf-spring-srv6-srh-compression" format="default" />.</t>
<section anchor="arguments-for-mobility" numbered="true" toc="default"> <section anchor="arguments-for-mobility" numbered="true" toc="default">
<name>Args.Mob.Session</name> <name>Args.Mob.Session</name>
<t>Args.Mob.Session provide per-session information for charging, buffer <t>Args.Mob.Session provides per-session information for charging,
ing or other purposes required by some mobile nodes. buffering, or other purposes required by some mobile nodes. The
The Args.Mob.Session argument format is used in combination with End.M Args.Mob.Session argument format is used in combination with the End.Map
ap, ,
End.DT4/End.DT6/End.DT46 and End.DX4/End.DX6/End.DX2 behaviors. Note t End.DT4/End.DT6/End.DT46, and End.DX4/End.DX6/End.DX2 behaviors. Note
hat proposed format is applicable for that proposed format is applicable for 5G networks, while similar
5G networks, while similar formats could be used for legacy networks. formats could be used for legacy networks.
</t> </t>
<figure>
<name>Args.Mob.Session format</name> <figure>
<artwork align="center" name="" type="" alt=""><![CDATA[ <name>Args.Mob.Session Format</name>
<artwork align="center" name="" type="" alt=""><![CDATA[
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| QFI |R|U| PDU Session ID | | QFI |R|U| PDU Session ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|PDU Sess(cont')| |PDU Sess(cont')|
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
]]></artwork> ]]></artwork>
</figure> </figure>
<ul spacing="compact">
<li> QFI: QoS Flow Identifier <xref target="TS.38415" format="default" <dl spacing="normal" newline="false">
/></li> <dt>QFI:</dt>
<li> R: Reflective QoS Indication <xref target="TS.23501" format="def <dd>QoS Flow Identifier <xref target="TS.38415"
ault"/>. format="default"/>.</dd>
This parameter indicates the activation of reflective QoS towards the <dt>R:</dt>
UE for the transferred packet. Reflective QoS enables the UE to map UL User Plan
e traffic to QoS Flows without SMF provided QoS rules.</li> <dd>Reflective QoS Indication <xref target="TS.23501"
<li>U: Unused and for future use. MUST be 0 on transmission and format="default"/>. This parameter indicates the activation of
ignored on receipt.</li> reflective QoS towards the UE for the transferred packet. Reflective
<li>PDU Session ID: Identifier of PDU Session. The GTP-U equivalent is QoS enables the UE to map uplink user-plane traffic to QoS flows withou
TEID.</li> t
</ul> SMF-provided QoS rules.</dd>
<t>Args.Mob.Session is required in case that one SID aggregates <dt>U:</dt>
multiple PDU Sessions. Since the SRv6 SID is likely NOT to be <dd>Unused and for future use. <bcp14>MUST</bcp14> be 0 on
instantiated per PDU session, Args.Mob.Session helps the UPF to transmission and ignored on receipt.</dd>
perform the behaviors which require per QFI and/or per PDU Session <dt>PDU Session ID:</dt>
granularity.</t> <dd>Identifier of PDU Session. The GTP-U equivalent is TEID.</dd>
<t>Note that the encoding of user-plane messages (e.g., Echo Request, Ec </dl>
ho Reply, Error Indication and End Marker) is out of the scope of this draft. <x <t>Args.Mob.Session is required in case one SID aggregates
ref target="I-D.murakami-dmm-user-plane-message-encoding" /> defines one possibl multiple PDU Sessions. Since the SRv6 SID is likely NOT to be
e encoding.</t> instantiated per PDU Session, Args.Mob.Session helps the UPF to
perform the behaviors that require granularity per QFI and/or per PDU Se
ssion.</t>
<t>Note that the encoding of user-plane messages (e.g., Echo Request,
Echo Reply, Error Indication, and End Marker) is out of the scope of
this document. <xref
target="I-D.murakami-dmm-user-plane-message-encoding" /> defines one
possible encoding method.</t>
</section> </section>
<section anchor="end-map-function" numbered="true" toc="default"> <section anchor="end-map-function" numbered="true" toc="default">
<name>End.MAP</name> <name>End.MAP</name>
<t>The "Endpoint behavior with SID mapping" behavior (End.MAP for <t>End.MAP (Endpoint Behavior with SID mapping)
short) is used in several scenarios. Particularly in mobility, is used in several scenarios. Particularly in mobility,
End.MAP is used by the intermediate UPFs.</t> End.MAP is used by the intermediate UPFs.</t>
<t>When node N receives a packet whose IPv6 DA is D and D is a local End <t>When node N receives a packet whose IPv6 DA is D and D is a local End
.MAP SID, N does:</t> .MAP SID, N does the following:</t>
<artwork name="" type="" align="left" alt=""><![CDATA[
<sourcecode type="pseudocode"><![CDATA[
S01. If (IPv6 Hop Limit <= 1) { S01. If (IPv6 Hop Limit <= 1) {
S02. Send an ICMP Time Exceeded message to the Source Address, S02. Send an ICMP Time Exceeded message to the Source Address with
Code 0 (Hop limit exceeded in transit), Code 0 (Hop limit exceeded in transit),
interrupt packet processing, and discard the packet. interrupt packet processing, and discard the packet.
S03. } S03. }
S04. Decrement IPv6 Hop Limit by 1 S04. Decrement IPv6 Hop Limit by 1
S05. Update the IPv6 DA with the new mapped SID S05. Update the IPv6 DA with the new mapped SID
S06. Submit the packet to the egress IPv6 FIB lookup for S06. Submit the packet to the egress IPv6 FIB lookup for
transmission to the new destination transmission to the new destination
]]></artwork> ]]></sourcecode>
<t>Notes:
The SRH is not modified (neither the SID, nor the SL value).</t> <t>Note: The SRH is not modified (neither the SID nor the SL
value).</t>
</section> </section>
<section anchor="End-M-GTP6-D" numbered="true" toc="default"> <section anchor="End-M-GTP6-D" numbered="true" toc="default">
<name>End.M.GTP6.D</name> <name>End.M.GTP6.D</name>
<t>The "Endpoint behavior with IPv6/GTP-U decapsulation into SR policy" <t>End.M.GTP6.D (Endpoint Behavior with IPv6/GTP-U decapsulation into SR
behavior (End.M.GTP6.D for short) is used in interworking scenario Policy) is used in the interworking
for the uplink towards SRGW from the legacy gNB using IPv6/GTP. scenario for the uplink towards SRGW from the legacy gNB using
Any SID instance of this behavior is associated with an SR Policy B IPv6/GTP. Any SID instance of this behavior is associated with an SR
and an IPv6 Source Address S. Policy B and an IPv6 Source Address S.
</t> </t>
<t>When the SR Gateway node N receives a packet destined to D and <t>When the SR Gateway node N receives a packet destined to D, and D
D is a local End.M.GTP6.D SID, N does:</t> is a local End.M.GTP6.D SID, N does the following:</t>
<artwork name="" type="" align="left" alt=""><![CDATA[
<sourcecode type="pseudocode"><![CDATA[
S01. When an SRH is processed { S01. When an SRH is processed {
S02. If (Segments Left != 0) { S02. If (Segments Left != 0) {
S03. Send an ICMP Parameter Problem to the Source Address, S03. Send an ICMP Parameter Problem to the Source Address with
Code 0 (Erroneous header field encountered), Code 0 (Erroneous header field encountered) and
Pointer set to the Segments Left field, Pointer set to the Segments Left field,
interrupt packet processing, and discard the packet. interrupt packet processing, and discard the packet.
S04. } S04. }
S05. Proceed to process the next header in the packet S05. Proceed to process the next header in the packet
S06. } S06. }
]]></artwork> ]]></sourcecode>
<t>When processing the Upper-layer header of a packet matching a FIB ent
ry locally instantiated as an End.M.GTP6.D SID, N does:</t> <t>When processing the Upper-Layer header of a packet matching a FIB ent
<artwork name="" type="" align="left" alt=""><![CDATA[ ry locally instantiated as an End.M.GTP6.D SID, N does the following:</t>
<sourcecode type="pseudocode"><![CDATA[
S01. If (Next Header (NH) == UDP & UDP_Dest_port == GTP) { S01. If (Next Header (NH) == UDP & UDP_Dest_port == GTP) {
S02. Copy the GTP-U TEID and QFI to buffer memory S02. Copy the GTP-U TEID and QFI to buffer memory
S03. Pop the IPv6, UDP, and GTP-U Headers S03. Pop the IPv6, UDP, and GTP-U headers
S04. Push a new IPv6 header with its own SRH containing B S04. Push a new IPv6 header with its own SRH containing B
S05. Set the outer IPv6 SA to S S05. Set the outer IPv6 SA to S
S06. Set the outer IPv6 DA to the first SID of B S06. Set the outer IPv6 DA to the first SID of B
S07. Set the outer Payload Length, Traffic Class, Flow Label, S07. Set the outer Payload Length, Traffic Class, Flow Label,
Hop Limit, and Next-Header (NH) fields Hop Limit, and Next Header (NH) fields
S08. Write in the SRH[0] the Args.Mob.Session based on S08. Write in the SRH[0] the Args.Mob.Session based on
the information of buffer memory the information in buffer memory
S09. Submit the packet to the egress IPv6 FIB lookup and S09. Submit the packet to the egress IPv6 FIB lookup for
transmission to the new destination transmission to the new destination
S10. } Else { S10. } Else {
S11. Process as per [RFC8986] Section 4.1.1 S11. Process as per [RFC8986], Section 4.1.1
S12. } S12. }
]]></artwork> ]]></sourcecode>
<t>Notes:
S07. The NH is set based on the SID parameter. There is one <t>Notes:</t>
instantiation of the End.M.GTP6.D SID per PDU Session Type, <ul spacing="normal">
hence the NH is already known in advance. For the IPv4v6 PDU <li>In line S07, the NH is set based on the SID parameter. There is one
Session Type, in addition the router inspects the first nibble of the instantiation of the End.M.GTP6.D SID per PDU Session Type;
PDU to know the NH value.</t> hence, the NH is already known in advance. In addition, for the IPv4v6
<t>The last segment SHOULD be PDU
followed by an Args.Mob.Session argument space which is used to Session Type, the router inspects the first nibble of the
provide the session identifiers, as shown in line S08.</t> PDU to know the NH value.</li>
<li>The last segment <bcp14>SHOULD</bcp14> be
followed by an Args.Mob.Session argument space, which is used to
provide the session identifiers, as shown in line S08.</li>
</ul>
</section> </section>
<!-- End section "End.M.GTP6.D" -->
<section anchor="End-M-GTP6-D-Di" numbered="true" toc="default"> <section anchor="End-M-GTP6-D-Di" numbered="true" toc="default">
<name>End.M.GTP6.D.Di</name> <name>End.M.GTP6.D.Di</name>
<t>The "Endpoint behavior with IPv6/GTP-U decapsulation into SR policy f <t>End.M.GTP6.D.Di (Endpoint Behavior with IPv6/GTP-U decapsulation into
or SR Policy
Drop-in Mode" behavior (End.M.GTP6.D.Di for short) is used in SRv6 for Drop-in Mode) is used in the SRv6
drop-in interworking scenario described in <xref target="drop_in" format drop-in interworking scenario described in <xref target="drop_in"
="default"/>. The format="default"/>. The difference between End.M.GTP6.D as another
difference between End.M.GTP6.D as another variant of IPv6/GTP variant of the IPv6/GTP decapsulation function is that the original IPv6
decapsulation function is that the original IPv6 DA of the GTP-U packet DA of the GTP-U packet is preserved as the last SID in SRH.</t>
is <t>Any SID instance of this behavior is associated with an SR Policy B
preserved as the last SID in SRH.</t> and an IPv6 Source Address S.</t>
<t>Any SID instance of this behavior is associated with an SR Policy B a <t>When the SR Gateway node N receives a packet destined to D, and
nd an IPv6 Source Address S.</t> D is a local End.M.GTP6.D.Di SID, N does the following:</t>
<t>When the SR Gateway node N receives a packet destined to D and
D is a local End.M.GTP6.D.Di SID, N does:</t> <sourcecode type="pseudocode"><![CDATA[
<artwork name="" type="" align="left" alt=""><![CDATA[
S01. When an SRH is processed { S01. When an SRH is processed {
S02. If (Segments Left != 0) { S02. If (Segments Left != 0) {
S03. Send an ICMP Parameter Problem to the Source Address, S03. Send an ICMP Parameter Problem to the Source Address with
Code 0 (Erroneous header field encountered), Code 0 (Erroneous header field encountered) and
Pointer set to the Segments Left field, Pointer set to the Segments Left field,
interrupt packet processing, and discard the packet. interrupt packet processing, and discard the packet.
S04. } S04. }
S05. Proceed to process the next header in the packet S05. Proceed to process the next header in the packet
S06. } S06. }
]]></artwork> ]]></sourcecode>
<t>When processing the Upper-layer header of a packet matching a FIB ent
ry locally instantiated as an End.M.GTP6.Di SID, N does:</t> <t>When processing the Upper-Layer header of a packet matching a FIB
<artwork name="" type="" align="left" alt=""><![CDATA[ entry locally instantiated as an End.M.GTP6.Di SID, N does the
following:</t>
<sourcecode type="pseudocode"><![CDATA[
S01. If (Next Header = UDP & UDP_Dest_port = GTP) { S01. If (Next Header = UDP & UDP_Dest_port = GTP) {
S02. Copy D to buffer memory S02. Copy D to buffer memory
S03. Pop the IPv6, UDP, and GTP-U Headers S03. Pop the IPv6, UDP, and GTP-U headers
S04. Push a new IPv6 header with its own SRH containing B S04. Push a new IPv6 header with its own SRH containing B
S05. Set the outer IPv6 SA to S S05. Set the outer IPv6 SA to S
S06. Set the outer IPv6 DA to the first SID of B S06. Set the outer IPv6 DA to the first SID of B
S07. Set the outer Payload Length, Traffic Class, Flow Label, S07. Set the outer Payload Length, Traffic Class, Flow Label,
Hop Limit, and Next-Header fields Hop Limit, and Next Header fields
S08. Prepend D to the SRH (as SRH[0]) and set SL accordingly S08. Prepend D to the SRH (as SRH[0]) and set SL accordingly
S09. Submit the packet to the egress IPv6 FIB lookup and S09. Submit the packet to the egress IPv6 FIB lookup for
transmission to the new destination transmission to the new destination
S10. } Else { S10. } Else {
S11. Process as per [RFC8986] Section 4.1.1 S11. Process as per [RFC8986], Section 4.1.1
S12. } S12. }
]]></artwork> ]]></sourcecode>
<t>Notes:
S07. The NH is set based on the SID parameter. There is one <t>Notes:</t>
instantiation of the End.M.GTP6.Di SID per PDU Session Type, <ul spacing="normal">
hence the NH is already known in advance. For the IPv4v6 PDU <li>In line S07, the NH is set based on the SID parameter. There is one
Session Type, in addition the router inspects the first nibble of the instantiation of the End.M.GTP6.Di SID per PDU Session Type; hence,
PDU to know the NH value.</t> the NH is already known in advance. In addition, for the IPv4v6 PDU Sess
<t>S SHOULD be an End.M.GTP6.E SID instantiated ion Type,
at the SR gateway.</t> the router inspects the first nibble of the PDU to know
the NH value.</li>
<li>S <bcp14>SHOULD</bcp14> be an End.M.GTP6.E SID instantiated
at the SR Gateway.</li>
</ul>
</section> </section>
<!-- End section "End.M.GTP6.D.Di" -->
<section numbered="true" toc="default"> <section numbered="true" toc="default">
<name>End.M.GTP6.E</name> <name>End.M.GTP6.E</name>
<t>The "Endpoint behavior with encapsulation for IPv6/GTP-U tunnel" <t>End.M.GTP6.E (Endpoint Behavior with encapsulation for IPv6/GTP-U tun
behavior (End.M.GTP6.E for short) is used among others in the interworki nel"
ng scenario behavior) is used among others in the
for the downlink toward the legacy gNB using IPv6/GTP.</t> interworking scenario for the downlink toward the legacy gNB using
<t>The prefix of End.M.GTP6.E SID MUST be followed by the IPv6/GTP.</t>
Args.Mob.Session argument space which is used to provide the session <t>The prefix of End.M.GTP6.E SID <bcp14>MUST</bcp14> be followed by
identifiers.</t> the Args.Mob.Session argument space, which is used to provide the
session identifiers.</t>
<t>When the SR Gateway node N receives a packet destined to D, and <t>When the SR Gateway node N receives a packet destined to D, and
D is a local End.M.GTP6.E SID, N does the following:</t> D is a local End.M.GTP6.E SID, N does the following:</t>
<artwork name="" type="" align="left" alt=""><![CDATA[
<sourcecode type="pseudocode"><![CDATA[
S01. When an SRH is processed { S01. When an SRH is processed {
S02. If (Segments Left != 1) { S02. If (Segments Left != 1) {
S03. Send an ICMP Parameter Problem to the Source Address, S03. Send an ICMP Parameter Problem to the Source Address with
Code 0 (Erroneous header field encountered), Code 0 (Erroneous header field encountered) and
Pointer set to the Segments Left field, Pointer set to the Segments Left field,
interrupt packet processing, and discard the packet. interrupt packet processing, and discard the packet.
S04. } S04. }
S05. Proceed to process the next header in the packet S05. Proceed to process the next header in the packet
S06. } S06. }
]]></artwork> ]]></sourcecode>
<t>When processing the Upper-layer header of a packet matching a FIB ent
ry locally instantiated as an End.M.GTP6.E SID, N does:</t> <t>When processing the Upper-Layer header of a packet matching a FIB ent
<artwork name="" type="" align="left" alt=""><![CDATA[ ry locally instantiated as an End.M.GTP6.E SID, N does the following:</t>
<sourcecode type="pseudocode"><![CDATA[
S01. Copy SRH[0] and D to buffer memory S01. Copy SRH[0] and D to buffer memory
S02. Pop the IPv6 header and all its extension headers S02. Pop the IPv6 header and all its extension headers
S03. Push a new IPv6 header with a UDP/GTP-U Header S03. Push a new IPv6 header with a UDP/GTP-U header
S04. Set the outer IPv6 SA to S S04. Set the outer IPv6 SA to S
S05. Set the outer IPv6 DA from buffer memory S05. Set the outer IPv6 DA from buffer memory
S06. Set the outer Payload Length, Traffic Class, Flow Label, S06. Set the outer Payload Length, Traffic Class, Flow Label,
Hop Limit, and Next-Header fields Hop Limit, and Next Header fields
S07. Set the GTP-U TEID (from buffer memory) S07. Set the GTP-U TEID (from buffer memory)
S08. Submit the packet to the egress IPv6 FIB lookup and S08. Submit the packet to the egress IPv6 FIB lookup for
transmission to the new destination transmission to the new destination
]]></artwork> ]]></sourcecode>
<t>Notes:
An End.M.GTP6.E SID MUST always be the penultimate SID. <t>Notes:</t>
<ul spacing="normal">
<li>An End.M.GTP6.E SID <bcp14>MUST</bcp14> always be the penultimate SI
D.
The TEID is extracted from the argument space of the current The TEID is extracted from the argument space of the current
SID.</t> SID.</li>
<t> The source address S SHOULD be an End.M.GTP6.D SID instantiated at t <li> The source address S <bcp14>SHOULD</bcp14> be an End.M.GTP6.D SID i
he egress SR gateway.</t> nstantiated at the egress SR Gateway.</li>
</ul>
</section> </section>
<!-- End section "End.M.GTP6.E" -->
<section numbered="true" toc="default"> <section numbered="true" toc="default">
<name>End.M.GTP4.E</name> <name>End.M.GTP4.E</name>
<t>The "Endpoint behavior with encapsulation for IPv4/GTP-U tunnel" <t>End.M.GTP4.E (Endpoint Behavior with encapsulation for IPv4/GTP-U
behavior (End.M.GTP4.E for short) is used in the downlink when tunnel) is used in the downlink when doing interworking with legacy
doing interworking with legacy gNB using IPv4/GTP.</t> gNB using IPv4/GTP.</t>
<t>When the SR Gateway node N receives a packet destined to S and S <t>When the SR Gateway node N receives a packet destined to S, and S
is a local End.M.GTP4.E SID, N does:</t> is a local End.M.GTP4.E SID, N does the following:</t>
<artwork name="" type="" align="left" alt=""><![CDATA[
<sourcecode type="pseudocode"><![CDATA[
S01. When an SRH is processed { S01. When an SRH is processed {
S02. If (Segments Left != 0) { S02. If (Segments Left != 0) {
S03. Send an ICMP Parameter Problem to the Source Address, S03. Send an ICMP Parameter Problem to the Source Address with
Code 0 (Erroneous header field encountered), Code 0 (Erroneous header field encountered) and
Pointer set to the Segments Left field, Pointer set to the Segments Left field,
interrupt packet processing, and discard the packet. interrupt packet processing, and discard the packet.
S04. } S04. }
S05. Proceed to process the next header in the packet S05. Proceed to process the next header in the packet
S06. } S06. }
]]></artwork> ]]></sourcecode>
<t>When processing the Upper-layer header of a packet matching a FIB ent
ry locally instantiated as an End.M.GTP4.E SID, N does:</t> <t>When processing the Upper-Layer header of a packet matching a FIB ent
<artwork name="" type="" align="left" alt=""><![CDATA[ ry locally instantiated as an End.M.GTP4.E SID, N does the following:</t>
<sourcecode type="pseudocode"><![CDATA[
S01. Store the IPv6 DA and SA in buffer memory S01. Store the IPv6 DA and SA in buffer memory
S02. Pop the IPv6 header and all its extension headers S02. Pop the IPv6 header and all its extension headers
S03. Push a new IPv4 header with a UDP/GTP-U Header S03. Push a new IPv4 header with a UDP/GTP-U header
S04. Set the outer IPv4 SA and DA (from buffer memory) S04. Set the outer IPv4 SA and DA (from buffer memory)
S05. Set the outer Total Length, DSCP, Time To Live, and S05. Set the outer Total Length, DSCP, Time To Live, and
Next-Header fields Next Header fields
S06. Set the GTP-U TEID (from buffer memory) S06. Set the GTP-U TEID (from buffer memory)
S07. Submit the packet to the egress IPv4 FIB lookup and S07. Submit the packet to the egress IPv4 FIB lookup for
transmission to the new destination transmission to the new destination
]]></artwork> ]]></sourcecode>
<t>Notes:
The End.M.GTP4.E SID in S has the following format:</t> <t>Notes:</t>
<figure> <ul spacing="normal">
<name>End.M.GTP4.E SID Encoding</name> <li><t>The End.M.GTP4.E SID in S has the following format:</t>
<artwork align="center" name="" type="" alt=""><![CDATA[
<figure>
<name>End.M.GTP4.E SID Encoding</name>
<artwork align="center" name="" type="" alt=""><![CDATA[
0 127 0 127
+-----------------------+-------+----------------+---------+ +-----------------------+-------+----------------+---------+
| SRGW-IPv6-LOC-FUNC |IPv4DA |Args.Mob.Session|0 Padded | | SRGW-IPv6-LOC-FUNC |IPv4DA |Args.Mob.Session|0 Padded |
+-----------------------+-------+----------------+---------+ +-----------------------+-------+----------------+---------+
128-a-b-c a b c 128-a-b-c a b c
]]></artwork>
</figure>
</li>
]]></artwork> <li><t>The IPv6 Source Address has the following format:</t>
</figure>
<t>The IPv6 Source Address has the following format:</t> <figure>
<figure> <name>IPv6 SA Encoding for End.M.GTP4.E</name>
<name>IPv6 SA Encoding for End.M.GTP4.E</name> <artwork align="center" name="" type="" alt=""><![CDATA[
<artwork align="center" name="" type="" alt=""><![CDATA[
0 127 0 127
+----------------------+--------+--------------------------+ +----------------------+--------+--------------------------+
| Source UPF Prefix |IPv4 SA | any bit pattern(ignored) | | Source UPF Prefix |IPv4 SA | any bit pattern(ignored) |
+----------------------+--------+--------------------------+ +----------------------+--------+--------------------------+
128-a-b a b 128-a-b a b
]]></artwork>
]]></artwork> </figure>
</figure> </li>
</ul>
</section> </section>
<!-- End section "End.M.GTP4.E" -->
<section numbered="true" toc="default"> <section numbered="true" toc="default">
<name>H.M.GTP4.D</name> <name>H.M.GTP4.D</name>
<t>The "SR Policy Headend with tunnel decapsulation and map to an SRv6 <t>H.M.GTP4.D (SR Policy Headend with tunnel decapsulation and map to an
policy" behavior (H.M.GTP4.D for short) is used in the direction SRv6
from legacy IPv4 user-plane to SRv6 user-plane network.</t> policy) is used in the direction
from the legacy IPv4 user plane to the SRv6 user-plane network.</t>
<t>When the SR Gateway node N receives a packet destined to a <t>When the SR Gateway node N receives a packet destined to a
SRGW-IPv4-Prefix, N does:</t> SRGW-IPv4-Prefix, N does the following:</t>
<artwork align="left" name="" type="" alt=""><![CDATA[
<artwork align="left" name="" type="" alt=""><![CDATA[
S01. IF Payload == UDP/GTP-U THEN S01. IF Payload == UDP/GTP-U THEN
S02. Pop the outer IPv4 header and UDP/GTP-U headers S02. Pop the outer IPv4 header and UDP/GTP-U headers
S03. Copy IPv4 DA, TEID to form SID B S03. Copy IPv4 DA and TEID to form SID B
S04. Copy IPv4 SA to form IPv6 SA B' S04. Copy IPv4 SA to form IPv6 SA B'
S05. Encapsulate the packet into a new IPv6 header S05. Encapsulate the packet into a new IPv6 header
S06. Set the IPv6 DA = B S06. Set the IPv6 DA = B
S07. Forward along the shortest path to B S07. Forward along the shortest path to B
S08. ELSE S08. ELSE
S09. Drop the packet S09. Drop the packet
]]></artwork> ]]></artwork>
<t>The SID B has the following format:</t> <t>The SID B has the following format:</t>
<figure>
<name>H.M.GTP4.D SID Encoding</name> <figure>
<artwork align="center" name="" type="" alt=""><![CDATA[ <name>H.M.GTP4.D SID Encoding</name>
<artwork align="center" name="" type="" alt=""><![CDATA[
0 127 0 127
+-----------------------+-------+----------------+---------+ +-----------------------+-------+----------------+---------+
|Destination UPF Prefix |IPv4DA |Args.Mob.Session|0 Padded | |Destination UPF Prefix |IPv4DA |Args.Mob.Session|0 Padded |
+-----------------------+-------+----------------+---------+ +-----------------------+-------+----------------+---------+
128-a-b-c a b c 128-a-b-c a b c
]]></artwork>
</figure>
]]></artwork> <t> The SID B <bcp14>MAY</bcp14> be an SRv6 Binding SID instantiated at
</figure> the first
<t> The SID B MAY be an SRv6 Binding SID instantiated at the first UPF (U1) to bind an SR Policy <xref target="RFC9256" format="default"/>.
UPF (U1) to bind an SR policy <xref target="RFC9256" format="default"/>. </t>
</t>
</section> </section>
<!-- End section "T.M.Tmap" -->
<section numbered="true" toc="default"> <section numbered="true" toc="default">
<name>End.Limit: Rate Limiting behavior</name> <name>End.Limit</name>
<t> The mobile user-plane requires a rate-limit feature. For this <t> The mobile user plane requires a rate-limit feature. For this
purpose, this document defines a new behavior "End.Limit". purpose, this document defines a new behavior, called "End.Limit".
The "End.Limit" behavior encodes in its arguments the The "End.Limit" behavior encodes in its arguments the rate-limiting
rate limiting parameter that should be applied to this packet. parameter that should be applied to this packet. Multiple flows of
Multiple flows of packets should have the same group identifier packets should have the same group identifier in the SID when those
in the SID when those flows are in the same AMBR (Aggregate Maximum B flows are in the same AMBR (Aggregate Maximum Bit Rate) group. The
it Rate) group. encoding format of the rate-limit segment SID is as follows:</t>
The encoding format of the rate limit
segment SID is as follows:</t> <figure>
<figure> <name>End.Limit: Rate-Limiting Behavior Argument Format</name>
<name>End.Limit: Rate limiting behavior argument format</name> <artwork align="center" name="" type="" alt=""><![CDATA[
<artwork align="center" name="" type="" alt=""><![CDATA[
+----------------------+----------+-----------+ +----------------------+----------+-----------+
| LOC+FUNC rate-limit | group-id | limit-rate| | LOC+FUNC rate-limit | group-id | limit-rate|
+----------------------+----------+-----------+ +----------------------+----------+-----------+
128-i-j i j 128-i-j i j
]]></artwork> ]]></artwork>
</figure> </figure>
<t> If the limit-rate bits are set to zero, the node should <t> If the limit-rate bits are set to zero, the node should
not do rate limiting unless static configuration or not do rate limiting unless static configuration or
control-plane sets the limit rate associated to the SID.</t> control plane sets the limit rate associated to the SID.</t>
</section> </section>
<!-- End section "End.Limit: Rate Limiting function" -->
</section> </section>
<!-- End section "" -->
<section anchor="pdu_sessions" numbered="true" toc="default"> <section anchor="pdu_sessions" numbered="true" toc="default">
<name>SRv6 supported 3GPP PDU session types</name> <name>SRv6-Supported 3GPP PDU Session Types</name>
<t>The 3GPP <xref target="TS.23501" format="default"/> defines the followi <t>The 3GPP <xref target="TS.23501" format="default"/> defines the
ng PDU session following PDU Session Types:
types:
</t> </t>
<ul spacing="compact"> <ul spacing="normal">
<li>IPv4</li> <li>IPv4</li>
<li>IPv6</li> <li>IPv6</li>
<li>IPv4v6</li> <li>IPv4v6</li>
<li>Ethernet</li> <li>Ethernet</li>
<li>Unstructured</li> <li>Unstructured</li>
</ul> </ul>
<t> SRv6 supports the 3GPP PDU session types without any protocol
overhead by using the corresponding SRv6 behaviors (End.DX4, <t> SRv6 supports the 3GPP PDU Session Types without any protocol
End.DT4 for IPv4 PDU sessions; End.DX6, End.DT6, End.T for IPv6 overhead by using the corresponding SRv6 behaviors:</t>
PDU sessions; End.DT46 for IPv4v6 PDU sessions; End.DX2 <ul spacing="normal">
for L2 and Unstructured PDU sessions).</t> <li>End.DX4 and End.DT4 for IPv4 PDU Sessions</li>
<li>End.DX6, End.DT6, and End.T for IPv6 PDU Sessions</li>
<li>End.DT46 for IPv4v6 PDU Sessions</li>
<li>End.DX2 for L2 and Unstructured PDU Sessions</li>
</ul>
</section> </section>
<!-- End section "SRv6 supported PDU session types" -->
<section anchor="netslice" numbered="true" toc="default"> <section anchor="netslice" numbered="true" toc="default">
<name>Network Slicing Considerations</name> <name>Network Slicing Considerations</name>
<t>A mobile network may be required to implement "network slices", <t>A mobile network may be required to implement "network slices",
which logically separate network resources within the same SR Domain. which logically separate network resources within the same SR domain.
</t> </t>
<t><xref target="RFC9256" format="default"/>
<t><xref target="RFC9256" format="default"/>
describes a solution to build basic network slices with SR. describes a solution to build basic network slices with SR.
Depending on the requirements, these slices can be further Depending on the requirements, these slices can be further
refined by adopting the mechanisms from: refined by adopting the mechanisms from:
</t> </t>
<ul spacing="compact"> <ul spacing="normal">
<li>IGP Flex-Algo <li>IGP Flex-Algo
<xref target="I-D.ietf-lsr-flex-algo" format="default"/></li> <xref target="RFC9350" format="default"/></li>
<li>Inter-Domain policies <li>Inter-Domain policies
<xref target="RFC9087" format="default"/></li> <xref target="RFC9087" format="default"/></li>
</ul> </ul>
<t>Furthermore, these can be combined with ODN/AS (On Demand Nexthop/Autom
ated Steering) <t>Furthermore, these can be combined with ODN/AS (On-Demand Next Hop / Au
tomated Steering)
<xref target="RFC9256" format="default"/> for <xref target="RFC9256" format="default"/> for
automated slice provisioning and traffic steering.</t> automated slice provisioning and traffic steering.</t>
<t>Further details on how these tools can be used to create <t>Further details on how these tools can be used to create
end to end network slices are documented in end-to-end network slices are documented in
<xref target="I-D.ali-spring-network-slicing-building-blocks" format=" <xref target="I-D.ali-teas-spring-ns-building-blocks" format="default"
default"/>.</t> />.</t>
</section> </section>
<!-- End section "Network Slicing Considerations" -->
<section anchor="c-plane" numbered="true" toc="default"> <section anchor="c-plane" numbered="true" toc="default">
<name>Control Plane Considerations</name> <name>Control Plane Considerations</name>
<t>This document focuses on user-plane behavior and its <t>This document focuses on user-plane behavior and its independence
independence from the control plane. While the SRv6 mobile user-plane from the control plane. While the SRv6 mobile user-plane behaviors may
behaviors may be utilized in emerging architectures, such as <xref target="I-D. be utilized in emerging architectures (for example, those described in
gundavelli-dmm-mfa" format="default"/>, <xref target="I-D.mhkk-dmm-srv6mup-archi <xref target="I-D.gundavelli-dmm-mfa" format="default"/> and <xref
tecture" format="default"/> for example, require control plane support for the u target="I-D.mhkk-dmm-srv6mup-architecture" format="default"/>), this
ser-plane, this document does not impose any change to the existent mobility con document does not impose any change to the existent mobility control
trol plane.</t> plane.
</t>
<t> <xref target="IANA" format="default"/> allocates SRv6 <t> <xref target="IANA" format="default"/> allocates SRv6
Segment Endpoint Behavior codepoints for the new behaviors defined in Endpoint Behavior codepoints for the new behaviors defined in this
this document.</t>
document.</t>
</section> </section>
<!-- End section "Control Plane Considerations" -->
<section numbered="true" toc="default"> <section numbered="true" toc="default">
<name>Security Considerations</name> <name>Security Considerations</name>
<t> The security considerations for Segment Routing are discussed in <t> The security considerations for Segment Routing are discussed in
<xref target="RFC8402" format="default"/>. More specifically for SRv <xref target="RFC8402" format="default"/>. More specifically, for SRv6,
6 the security considerations the security considerations and the mechanisms for securing an SR domain
and the mechanisms for securing an SR domain are discussed in are discussed in <xref target="RFC8754" format="default"/>. Together,
<xref target="RFC8754" format="default"/>. Together, they describe t they describe the required security mechanisms that allow establishment
he required security mechanisms of an SR domain of trust to operate SRv6-based services for internal
that allow establishment of an SR domain of trust to operate traffic while preventing any external traffic from accessing or
SRv6-based services for internal traffic while preventing any exploiting the SRv6-based services.</t>
external traffic from accessing or exploiting the SRv6-based <t>The technology described in this document is applied to a mobile
services.</t> network that is within the SR domain. It's important to note the
<t>The technology described in this document is applied to a mobile networ resemblance between the SR domain and the 3GPP Packet Core Domain.</t>
k that is within the SR Domain. It's important to note the ressemblance between <t>This document introduces new SRv6 Endpoint Behaviors. Those behaviors
the SR Domain and the 3GPP Packet Core Domain.</t> operate on control plane information, including information within the
<t>This document introduces new SRv6 Endpoint Behaviors. Those received SRH payload on which the behaviors operate. Altering the
behaviors operate on control plane information, including information behaviors requires that an attacker alter the SR domain as defined in
within the received SRH payload on which the behaviors operate. Altering <xref target="RFC8754" format="default"/>. Those behaviors do not need
the behaviors requires that an attacker alter the SR Domain as defined in <xre any special security consideration given that they are deployed within tha
f target="RFC8754" format="default"/>. t
Those behaviors do not need any special security consideration given that it is SR domain.</t>
deployed within that SR Domain.</t>
</section> </section>
<!-- End section "Security Considerations" -->
<section anchor="IANA" numbered="true" toc="default"> <section anchor="IANA" numbered="true" toc="default">
<name>IANA Considerations</name> <name>IANA Considerations</name>
<t> The following values have been allocated within the "SRv6 Endpoint Beh
aviors" <xref target="RFC8986" format="default"/> <t>The following values have been allocated in the "SRv6 Endpoint
sub-registry belonging to the top-level Behaviors" <xref target="RFC8986" format="default"/> subregistry
"Segment Routing Parameters" registry:</t> within the top-level "Segment Routing Parameters" registry:</t>
<table anchor="endpoint_opcodes" align="center"> <table anchor="endpoint_opcodes" align="center">
<name>SRv6 Mobile User-plane Endpoint Behavior Types</name> <name>SRv6 Mobile User-Plane Endpoint Behavior Types</name>
<thead> <thead>
<tr> <tr>
<th align="left">Value</th> <th align="left">Value</th>
<th align="center">Hex</th> <th align="center">Hex</th>
<th align="center">Endpoint behavior</th> <th align="center">Endpoint Behavior</th>
<th align="center">Reference</th> <th align="center">Reference</th>
<th align="center">Change Controller</th> <th align="center">Change Controller</th>
</tr> </tr>
</thead> </thead>
<tbody> <tbody>
<tr> <tr>
<td align="left">40</td> <td align="left">40</td>
<td align="center">0x0028</td> <td align="center">0x0028</td>
<td align="center">End.MAP</td> <td align="center">End.MAP</td>
<td align="center">[This.ID]</td> <td align="center">RFC 9433</td>
<td align="center">IETF</td> <td align="center">IETF</td>
</tr> </tr>
<tr> <tr>
<td align="left">41</td> <td align="left">41</td>
<td align="center">0x0029</td> <td align="center">0x0029</td>
<td align="center">End.Limit</td> <td align="center">End.Limit</td>
<td align="center">[This.ID]</td> <td align="center">RFC 9433</td>
<td align="center">IETF</td> <td align="center">IETF</td>
</tr> </tr>
<tr> <tr>
<td align="left">69</td> <td align="left">69</td>
<td align="center">0x0045</td> <td align="center">0x0045</td>
<td align="center">End.M.GTP6.D</td> <td align="center">End.M.GTP6.D</td>
<td align="center">[This.ID]</td> <td align="center">RFC 9433</td>
<td align="center">IETF</td> <td align="center">IETF</td>
</tr> </tr>
<tr> <tr>
<td align="left">70</td> <td align="left">70</td>
<td align="center">0x0046</td> <td align="center">0x0046</td>
<td align="center">End.M.GTP6.Di</td> <td align="center">End.M.GTP6.Di</td>
<td align="center">[This.ID]</td> <td align="center">RFC 9433</td>
<td align="center">IETF</td> <td align="center">IETF</td>
</tr> </tr>
<tr> <tr>
<td align="left">71</td> <td align="left">71</td>
<td align="center">0x0047</td> <td align="center">0x0047</td>
<td align="center">End.M.GTP6.E</td> <td align="center">End.M.GTP6.E</td>
<td align="center">[This.ID]</td> <td align="center">RFC 9433</td>
<td align="center">IETF</td> <td align="center">IETF</td>
</tr> </tr>
<tr> <tr>
<td align="left">72</td> <td align="left">72</td>
<td align="center">0x0048</td> <td align="center">0x0048</td>
<td align="center">End.M.GTP4.E</td> <td align="center">End.M.GTP4.E</td>
<td align="center">[This.ID]</td> <td align="center">RFC 9433</td>
<td align="center">IETF</td> <td align="center">IETF</td>
</tr> </tr>
</tbody> </tbody>
</table> </table>
</section> </section>
<!-- End section "IANA Considerations" -->
<section numbered="true" toc="default">
<name>Contributors</name>
<t>Kentaro Ebisawa
Toyota Motor Corporation
Japan</t>
<t>Email: ebisawa@toyota-tokyo.tech</t>
<t>Tetsuya Murakami
Arrcus, Inc.
United States of America</t>
<t>Email: tetsuya.ietf@gmail.com</t>
<t>Charles E. Perkins
Lupin Lodge
United States of America</t>
<t>Email: charliep@computer.org</t>
<t>Jakub Horn
Cisco Systems, Inc.
United States of America</t>
<t>Email: jakuhorn@cisco.com</t>
</section>
<!-- End section "Contributors" -->
<section anchor="acknowledge" numbered="true" toc="default">
<name>Acknowledgements</name>
<t>The authors would like to thank Daisuke Yokota, Bart Peirens,
Ryokichi Onishi, Kentaro Ebisawa, Peter Bosch, Darren Dukes,
Francois Clad, Sri Gundavelli, Sridhar Bhaskaran, Arashmid Akhavain,
Ravi Shekhar, Aeneas Dodd-Noble, Carlos Jesus Bernardos, Dirk v. Hugo
and Jeffrey Zhang for their useful comments of this work.</t>
</section>
<!-- End section "Acknowledgements" -->
</middle> </middle>
<back> <back>
<displayreference target="I-D.ietf-spring-sr-service-programming" to="SR-SERV-PR
OG"/>
<displayreference target="I-D.camarilloelmalky-springdmm-srv6-mob-usecases" to="
SRV6-MOB-USECASES"/>
<displayreference target="I-D.ali-teas-spring-ns-building-blocks" to="NETWORK-SL
ICE"/>
<displayreference target="I-D.mhkk-dmm-srv6mup-architecture" to="MUP-SR-ARCH"/>
<displayreference target="I-D.matsushima-spring-srv6-deployment-status" to="SRV6
-DEPLOY-STAT"/>
<displayreference target="I-D.kohno-dmm-srv6mob-arch" to="SRV6-MOB-ARCH-DISCUSS"
/>
<displayreference target="I-D.gundavelli-dmm-mfa" to="MFA"/>
<displayreference target="I-D.murakami-dmm-user-plane-message-encoding" to="SRV6
-UP-MSG-ENCODING"/>
<displayreference target="I-D.ietf-spring-srv6-srh-compression" to="SRV6-SRH-COM
PRESSION"/>
<references> <references>
<name>References</name> <name>References</name>
<references> <references>
<name>Normative References</name> <name>Normative References</name>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.2119.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.2119.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.8174.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.8174.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.8402.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.8402.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.8986.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.8986.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.8754.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.8754.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.9256.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.9256.xml"/>
skipping to change at line 1335 skipping to change at line 1499
<references> <references>
<name>References</name> <name>References</name>
<references> <references>
<name>Normative References</name> <name>Normative References</name>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.2119.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.2119.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.8174.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.8174.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.8402.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.8402.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.8986.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.8986.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.8754.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.8754.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.9256.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.9256.xml"/>
<reference anchor="TS.23501"> <reference anchor="TS.23501">
<front> <front>
<title>System Architecture for the 5G System</title> <title>System architecture for the 5G System (5GS)</title>
<author surname="3GPP" fullname="3GPP"> <author>
<organization>3GPP</organization>
</author> </author>
<date month="November" year="2017"/> <date month="June" year="2023"/>
</front> </front>
<seriesInfo name="3GPP TS 23.501" value="15.0.0"/> <seriesInfo name="3GPP TS" value="23.501"/>
<refcontent>Version 17.9.0</refcontent>
</reference> </reference>
</references> </references>
<references> <references>
<name>Informative References</name> <name>Informative References</name>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.9087.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R FC.9087.xml"/>
<xi:include href="https://datatracker.ietf.org/doc/bibxml3/draft-ietf-ls <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
r-flex-algo.xml"/> FC.9350.xml"/>
<xi:include href="https://datatracker.ietf.org/doc/bibxml3/draft-ietf-sp
ring-sr-service-programming.xml"/> <!-- [I-D.ietf-spring-sr-service-programming] IESG state I-D Exists. Updated to
<xi:include href="https://datatracker.ietf.org/doc/bibxml3/draft-camaril long version because missing editor role for Clad and Xu. -->
loelmalky-springdmm-srv6-mob-usecases.xml"/>
<xi:include href="https://datatracker.ietf.org/doc/bibxml3/draft-ali-spr <reference anchor="I-D.ietf-spring-sr-service-programming" target="https://datat
ing-network-slicing-building-blocks.xml"/> racker.ietf.org/doc/html/draft-ietf-spring-sr-service-programming-07">
<xi:include href="https://datatracker.ietf.org/doc/bibxml3/draft-mhkk-dm <front>
m-srv6mup-architecture.xml"/> <title>Service Programming with Segment Routing</title>
<xi:include href="https://datatracker.ietf.org/doc/bibxml3/draft-matsush <author initials="F." surname="Clad" fullname="Francois Clad" role="editor">
ima-spring-srv6-deployment-status.xml"/> <organization>Cisco Systems, Inc.</organization>
<xi:include href="https://datatracker.ietf.org/doc/bibxml3/draft-kohno-d </author>
mm-srv6mob-arch.xml"/> <author initials="X." surname="Xu" fullname="Xiaohu Xu" role="editor">
<xi:include href="https://datatracker.ietf.org/doc/bibxml3/draft-gundave <organization>China Mobile</organization>
lli-dmm-mfa.xml"/> </author>
<xi:include href="https://datatracker.ietf.org/doc/bibxml3/draft-murakam <author initials="C." surname="Filsfils" fullname="Clarence Filsfils">
i-dmm-user-plane-message-encoding.xml"/> <organization>Cisco Systems, Inc.</organization>
<xi:include href="https://datatracker.ietf.org/doc/bibxml3/draft-ietf-sp </author>
ring-srv6-srh-compression.xml"/> <author initials="D." surname="Bernier" fullname="Daniel Bernier">
<organization>Bell Canada</organization>
</author>
<author initials="C." surname="Li" fullname="Cheng Li">
<organization>Huawei</organization>
</author>
<author initials="B." surname="Decraene" fullname="Bruno Decraene">
<organization>Orange</organization>
</author>
<author initials="S." surname="Ma" fullname="Shaowen Ma">
<organization>Mellanox</organization>
</author>
<author initials="C." surname="Yadlapalli" fullname="Chaitanya Yadlapalli">
<organization>AT&amp;T</organization>
</author>
<author initials="W." surname="Henderickx" fullname="Wim Henderickx">
<organization>Nokia</organization>
</author>
<author initials="S." surname="Salsano" fullname="Stefano Salsano">
<organization>Universita di Roma "Tor Vergata"</organization>
</author>
<date month="February" day="15" year="2023"/>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-spring-sr-service-programmin
g-07"/>
</reference>
<!-- [I-D.camarilloelmalky-springdmm-srv6-mob-usecases] IESG state Expired. Upda
ted to long version because missing editor role for Camarillo and Elmalky. -->
<reference anchor="I-D.camarilloelmalky-springdmm-srv6-mob-usecases" target="htt
ps://datatracker.ietf.org/doc/html/draft-camarilloelmalky-springdmm-srv6-mob-use
cases-02">
<front>
<title>SRv6 Mobility Use-Cases</title>
<author initials="P." surname="Camarillo" fullname="Pablo Camarillo" role="edito
r">
<organization>Cisco Systems, Inc.</organization>
</author>
<author initials="C." surname="Filsfils" fullname="Clarence Filsfils">
<organization>Cisco Systems, Inc.</organization>
</author>
<author initials="H." surname="Elmalky" fullname="Hani Elmalky" role="editor">
<organization>Individual</organization>
</author>
<author initials="S." surname="Matsushima" fullname="Satoru Matsushima">
<organization>SoftBank</organization>
</author>
<author initials="D." surname="Voyer" fullname="Daniel Voyer">
<organization>Bell Canada</organization>
</author>
<author initials="A." surname="Cui" fullname="Anna Cui">
<organization>AT&amp;T</organization>
</author>
<author initials="B." surname="Peirens" fullname="Bart Peirens">
<organization>Proximus</organization>
</author>
<date month="August" day="15" year="2019"/>
</front>
<seriesInfo name="Internet-Draft" value="draft-camarilloelmalky-springdmm-srv6-m
ob-usecases-02"/>
</reference>
<!-- [I-D.ali-teas-spring-ns-building-blocks] IESG state Expired -->
<xi:include href="https://bib.ietf.org/public/rfc/bibxml3/reference.I-D.
ali-teas-spring-ns-building-blocks.xml"/>
<!-- [I-D.mhkk-dmm-srv6mup-architecture] IESG state I-D Exists -->
<xi:include href="https://bib.ietf.org/public/rfc/bibxml3/reference.I-D.
mhkk-dmm-srv6mup-architecture.xml"/>
<!-- [I-D.matsushima-spring-srv6-deployment-status] IESG state Expired -->
<xi:include href="https://bib.ietf.org/public/rfc/bibxml3/reference.I-D.
matsushima-spring-srv6-deployment-status.xml"/>
<!-- [I-D.kohno-dmm-srv6mob-arch] IESG state Exists. Updated to long version bec
ause xi:include shows March 12, 2023, as the date when it's axtually march 9, 20
23 -->
<reference anchor="I-D.kohno-dmm-srv6mob-arch" target="https://datatracker.ietf.
org/doc/html/draft-kohno-dmm-srv6mob-arch-06">
<front>
<title>Architecture Discussion on SRv6 Mobile User plane</title>
<author initials="M." surname="Kohno" fullname="Miya Kohno">
<organization>Cisco Systems, Inc.</organization>
</author>
<author initials="F." surname="Clad" fullname="Francois Clad">
<organization>Cisco Systems, Inc.</organization>
</author>
<author initials="P." surname="Camarillo" fullname="Pablo Camarillo">
<organization>Cisco Systems, Inc.</organization>
</author>
<author initials="Z." surname="Ali" fullname="Zafar Ali">
<organization>Cisco Systems, Inc.</organization>
</author>
<date month="March" day="9" year="2023"/>
</front>
<seriesInfo name="Internet-Draft" value="draft-kohno-dmm-srv6mob-arch-06"/>
</reference>
<!-- [I-D.gundavelli-dmm-mfa] IESG state Expired -->
<xi:include href="https://bib.ietf.org/public/rfc/bibxml3/reference.I-D.
gundavelli-dmm-mfa.xml"/>
<!-- [I-D.murakami-dmm-user-plane-message-encoding] IESG state Expired -->
<xi:include href="https://bib.ietf.org/public/rfc/bibxml3/reference.I-D.
murakami-dmm-user-plane-message-encoding.xml"/>
<!-- [I-D.ietf-spring-srv6-srh-compression] IESG state I-D Exists. Updated to lo
ng version because missing editor role for Cheng and Clad-->
<reference anchor="I-D.ietf-spring-srv6-srh-compression" target="https://datatra
cker.ietf.org/doc/html/draft-ietf-spring-srv6-srh-compression-05">
<front>
<title>Compressed SRv6 Segment List Encoding in SRH</title>
<author initials="W." surname="Cheng" fullname="Weiqiang Cheng" role="editor">
<organization>China Mobile</organization>
</author>
<author initials="C." surname="Filsfils" fullname="Clarence Filsfils">
<organization>Cisco Systems</organization>
</author>
<author initials="Z." surname="Li" fullname="Zhenbin Li">
<organization>Huawei Technologies</organization>
</author>
<author initials="B." surname="Decraene" fullname="Bruno Decraene">
<organization>Orange</organization>
</author>
<author initials="F." surname="Clad" fullname="Francois Clad" role="editor">
<organization>Cisco Systems</organization>
</author>
<date month="June" day="20" year="2023"/>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-spring-srv6-srh-compression-
05"/>
</reference>
<reference anchor="TS.29281"> <reference anchor="TS.29281">
<front> <front>
<title>General Packet Radio System (GPRS) Tunnelling Protocol User P lane (GTPv1-U)</title> <title>General Packet Radio System (GPRS) Tunnelling Protocol User P lane (GTPv1-U)</title>
<author surname="3GPP" fullname="3GPP"> <author>
<organization>3GPP</organization>
</author> </author>
<date month="December" year="2017"/> <date month="September" year="2022"/>
</front> </front>
<seriesInfo name="3GPP TS 29.281" value="15.1.0"/> <seriesInfo name="3GPP TS" value="29.281"/>
<refcontent>Version 17.4.0</refcontent>
</reference> </reference>
<reference anchor="TS.38415"> <reference anchor="TS.38415">
<front> <front>
<title>Draft Specification for 5GS container (TS 38.415)</title> <title>PDU session user plane protocol</title>
<author surname="3GPP" fullname="3GPP"> <author>
<organization>3GPP</organization>
</author> </author>
<date month="August" year="2017"/> <date month="April" year="2022"/>
</front> </front>
<seriesInfo name="3GPP R3-174510" value="0.0.0"/> <seriesInfo name="3GPP TS" value="38.415"/>
<refcontent>Version 17.0.0</refcontent>
</reference> </reference>
</references> </references>
</references> </references>
<section anchor="Implementations" numbered="true" toc="default">
<name>Implementations</name> <section anchor="acknowledge" numbered="false" toc="default">
<t>RFC Editor: Please remove this section prior to publication.</t> <name>Acknowledgements</name>
<t>This document introduces new SRv6 Endpoint Behaviors. These behaviors h <t>The authors would like to thank <contact fullname="Daisuke Yokota"/>,
ave an <contact fullname="Bart Peirens"/>, <contact fullname="Ryokichi
open-source P4 implementation available in Onishi"/>, <contact fullname="Kentaro Ebisawa"/>, <contact
<eref target="https://github.com/ebiken/p4srv6"/>.</t> fullname="Peter Bosch"/>, <contact fullname="Darren Dukes"/>, <contact
<t>Additionally, a full open-source implementation of this document is ava fullname="Francois Clad"/>, <contact fullname="Sri Gundavelli"/>,
ilable in Linux Foundation FD.io VPP project since release 20.05. More informati <contact fullname="Sridhar Bhaskaran"/>, <contact fullname="Arashmid
on available here: Akhavain"/>, <contact fullname="Ravi Shekhar"/>, <contact
<eref target="https://docs.fd.io/vpp/20.05/d7/d3c/srv6_mobile_plugin_doc.htm fullname="Aeneas Dodd-Noble"/>, <contact fullname="Carlos Jesus
l"/>.</t> Bernardos"/>, <contact fullname="Dirk von Hugo"/>, and <contact
<t>There are also experimental implementations in M-CORD NGIC and Open Air fullname="Jeffrey Zhang"/> for their useful comments of this work.</t>
Interface (OAI).</t>
</section> </section>
<!-- End section "Implementations" -->
</back> <section numbered="false" toc="default">
</rfc> <name>Contributors</name>
<contact fullname="Kentaro Ebisawa">
<organization>Toyota Motor Corporation</organization>
<address>
<postal>
<country>Japan</country>
</postal>
<email>ebisawa@toyota-tokyo.tech</email>
</address>
</contact>
<contact fullname="Tetsuya Murakami" >
<organization>Arrcus, Inc.</organization>
<address>
<postal>
<street></street>
<city></city>
<country>United States of America</country>
</postal>
<email>tetsuya.ietf@gmail.com</email>
</address>
</contact>
<contact fullname="Charles E. Perkins" >
<organization>Lupin Lodge</organization>
<address>
<postal>
<street></street>
<city></city>
<country>United States of America</country>
</postal>
<email>charliep@computer.org</email>
</address>
</contact>
<contact fullname="Jakub Horn" >
<organization>Cisco Systems, Inc.</organization>
<address>
<postal>
<street></street>
<city></city>
<country>United States of America</country>
</postal>
<email>jakuhorn@cisco.com</email>
</address>
</contact>
</section>
</back> </rfc>
 End of changes. 227 change blocks. 
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