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<front> <front>
<title abbrev="Path Properties">A Vocabulary of Path Properties</title> <title abbrev="Path Properties">A Vocabulary of Path Properties</title>
<seriesInfo name="Internet-Draft" value="draft-irtf-panrg-path-properties-08 "/> <seriesInfo name="RFC" value="9473"/>
<author initials="R." surname="Enghardt" fullname="Reese Enghardt"> <author initials="R." surname="Enghardt" fullname="Reese Enghardt">
<organization>Netflix</organization> <organization>Netflix</organization>
<address> <address>
<email>ietf@tenghardt.net</email> <email>ietf@tenghardt.net</email>
</address> </address>
</author> </author>
<author initials="C." surname="Krähenbühl" fullname="Cyrill Krähenbühl"> <author initials="C." surname="Krähenbühl" fullname="Cyrill Krähenbühl">
<organization>ETH Zürich</organization> <organization>ETH Zürich</organization>
<address> <address>
<email>cyrill.kraehenbuehl@inf.ethz.ch</email> <email>cyrill.kraehenbuehl@inf.ethz.ch</email>
</address> </address>
</author> </author>
<date year="2023" month="March" day="06"/> <date year="2023" month="September"/>
<area>IRTF</area> <workgroup>Path Aware Networking</workgroup>
<workgroup>PANRG</workgroup>
<keyword>Internet-Draft</keyword> <keyword>PAN</keyword>
<keyword>path-aware network</keyword>
<keyword>path property</keyword>
<keyword>path selection</keyword>
<abstract> <abstract>
<t>This document is a product of the Path Aware Networking Research Group <t>Path properties express information about paths across a
(PANRG). network and the services provided via such paths. In a path-aware
Path properties express information about paths across a network and the service network, path properties may be fully or partially available to entities
s provided via such paths. such as endpoints. This document defines and categorizes path
In a path-aware network, path properties may be fully or partially available to properties. Furthermore, the document identifies several path
entities such as endpoints. properties that might be useful to endpoints or other entities, e.g.,
This document defines and categorizes path properties. for selecting between paths or for invoking some of the provided
Furthermore, the document identifies several path properties which might be usef services. This document is a product of the Path Aware Networking
ul to endpoints or other entities, Research Group (PANRG).</t>
e.g., for selecting between paths or for invoking some of the provided services.
</t>
</abstract> </abstract>
<note removeInRFC="true">
<name>Discussion Venues</name>
<t>Discussion of this document takes place on the
"Path-Aware Networking Research Group" mailing list (PANRG),
which is archived at <eref target="https://mailarchive.ietf.org/arch/browse/
panrg/"/>.
Subscription information is at <eref target="https://www.ietf.org/mailman/li
stinfo/panrg/"/>.</t>
<t>Source for this draft and an issue tracker can be found at
<eref target="https://github.com/panrg/path-properties/"/>.</t>
</note>
</front> </front>
<middle> <middle>
<section anchor="introduction" numbered="true" toc="default"> <section anchor="introduction" numbered="true" toc="default">
<name>Introduction</name> <name>Introduction</name>
<t>The current Internet architecture does not explicitly support endpoint <t>The current Internet architecture does not explicitly support
discovery of forwarding paths through the network nor the discovery of propertie endpoint discovery of forwarding paths through the network nor the
s and services associated with these paths. discovery of properties and services associated with these paths.
Path-aware networking, as defined in Section 1.1 of <xref target="RFC9217" forma Path-aware networking, as defined in <xref target="RFC9217"
t="default"/>, describes sectionFormat="of" section="1.1"/>, describes "endpoint discovery of the
"endpoint discovery of the properties of paths they use for communication across properties of paths they use for communication across an internetwork,
an internetwork, and endpoint reaction to these properties that affects routing and endpoint reaction to these properties that affects routing and/or
and/or data transfer". data transfer". This document provides a generic definition of path
This document provides a generic definition of path properties, addressing the f properties, addressing the first of the questions in path-aware
irst of the questions in path-aware networking <xref target="RFC9217" format="de networking <xref target="RFC9217" format="default"/>.</t>
fault"/>.</t> <t>As terms related to paths have been used with different meanings in
<t>As terms related to paths have been used with different meanings in dif different areas of networking, first, this document provides a common
ferent areas of networking, first, this document provides a common terminology t terminology to define paths, path elements, and flows. Based on these
o define paths, path elements, and flows. Based on these terms, the document def terms, the document defines path properties. Then, this document
ines path properties. provides some examples of use cases for path properties. Finally, the
Then, this document provides some examples of use cases for path properties. document lists several path properties that may be useful for the
Finally, the document lists several path properties that may be useful for the m mentioned use cases. This list is intended to be neither exhaustive nor
entioned use cases. This list is intended to be neither exhaustive nor definitiv definitive.</t>
e.</t> <t>Note that this document does not assume that any of the listed path
<t>Note that this document does not assume that any of the listed path pro properties are actually available to any entity. The question of how
perties are actually available to any entity. The question of how entities can d entities can discover and distribute path properties in a trustworthy
iscover and distribute path properties in a trustworthy way is out of scope for way is out of scope for this document.</t>
this document.</t>
<t>This document represents the consensus of the Path Aware Networking Res earch Group (PANRG).</t> <t>This document represents the consensus of the Path Aware Networking Res earch Group (PANRG).</t>
</section> </section>
<section anchor="terminology" numbered="true" toc="default"> <section anchor="terminology" numbered="true" toc="default">
<name>Terminology</name> <name>Terminology</name>
<dl> <dl spacing="normal" newline="false">
<dt> <dt>Entity:</dt>
Entity: </dt>
<dd> <dd>
<t>A physical or virtual device or function, or a collection of device <t>A physical or virtual device or function, or a collection of
s or functions, which plays a role related to path-aware networking for particul devices or functions, that plays a role related to path-aware
ar paths and flows. networking for particular paths and flows. An entity can be on-path
An entity can be on-path or off-path: On the path, an entity may participate in or off-path. On the path, an entity may participate in forwarding
forwarding the flow, i.e., what may be called data plane functionality. the flow, i.e., what may be called "data plane functionality". On or
On or off the path, an entity may influence aspects of how the flow is forwarded off the path, an entity may influence aspects of how the flow is
, i.e., what may be called control plane functionality, such as Path Selection o forwarded, i.e., what may be called "control plane functionality",
r Service Invocation. such as path selection or service invocation. An entity influencing
An entity influencing forwarding aspects is usually aware of path properties, e. forwarding aspects is usually aware of path properties, e.g., by
g., by observing or measuring them or by learning them from another entity.</t> observing or measuring them or by learning them from another
entity.</t>
</dd> </dd>
<dt> <dt>Node:</dt>
Node: </dt>
<dd> <dd>
<t>An on-path entity which processes packets, e.g., sends, receives, f <t>An on-path entity that processes packets, e.g., sends, receives,
orwards, or modifies them. A node may be physical or virtual, e.g., a physical d forwards, or modifies them. A node may be physical or virtual, e.g.,
evice, a service function provided as a virtual element, or even a single queue a physical device, a service function provided as a virtual element,
within a switch. A node may also be an entity which consists of a collection of or even a single queue within a switch. A node may also be an entity
devices or functions, e.g., an entire Autonomous System (AS).</t> that consists of a collection of devices or functions, e.g., an
entire Autonomous System (AS).</t>
</dd> </dd>
<dt> <dt>Link:</dt>
Link: </dt>
<dd> <dd>
<t>A medium or communication facility that connects two or more nodes <t>A medium or communication facility that connects two or more
with each other. A link enables a node to send packets to other nodes. nodes with each other. A link enables a node to send packets to
Links can be physical, e.g., a Wi-Fi network which connects an Access Point to s other nodes. Links can be physical, e.g., a Wi-Fi network that
tations, or virtual, e.g., a virtual switch which connects two virtual machines connects an Access Point to stations, or virtual, e.g., a virtual
hosted on the same physical machine. A link is unidirectional. As such, bidirect switch that connects two virtual machines hosted on the same
ional communication can be modeled as two links between the same nodes in opposi physical machine. A link is unidirectional. As such, bidirectional
te directions.</t> communication can be modeled as two links between the same nodes in
opposite directions.</t>
</dd> </dd>
<dt> <dt>Path element:</dt>
Path element: </dt>
<dd> <dd>
<t>Either a node or a link. For example, a path element can be an Abst <t>Either a node or a link. For example, a path element can be an
ract Network Element (ANE) as defined in <xref target="I-D.ietf-alto-path-vector Abstract Network Element (ANE) as defined in <xref target="RFC9275"
" format="default"/>.</t> format="default"/>.</t>
</dd> </dd>
<dt> <dt>Path:</dt>
Path: </dt>
<dd> <dd>
<t>A sequence of adjacent path elements over which a packet can be tra <t>A sequence of adjacent path elements over which a packet can be
nsmitted, starting and ending with a node. transmitted, starting and ending with a node.</t>
</t> <t>Paths are unidirectional and time dependent, i.e., there can be a
<t>Paths are unidirectional and time-dependent, i.e., there can be a v variety of paths from one node to another, and the path over which
ariety of paths from one node to another, and the path over which packets are tr packets are transmitted may change. A path definition can be strict
ansmitted may change. (i.e., the exact sequence of path elements remains the same) or
A path definition can be strict (i.e., the exact sequence of path elements remai loose (i.e., the start and end node remain the same, but the path
ns the same) or loose (i.e., the start and end node remain the same, but the pat elements between them may vary over time).</t>
h elements between them may vary over time).</t> <t>The representation of a path and its properties may depend on the
<t>The representation of a path and its properties may depend on the e entity considering the path. On the one hand, the representation
ntity considering the path. may differ due to entities having partial visibility of path
On the one hand, the representation may differ due to entities having partial vi elements comprising a path or their visibility changing over time.
sibility of path elements comprising a path or their visibility changing over ti On the other hand, the representation may differ due to treating
me. path elements at different levels of abstraction. For example, a
On the other hand, the representation may differ due to treating path elements a path may be given as a sequence of physical nodes and the links
t different levels of abstraction. connecting these nodes, be given as a sequence of logical nodes such
For example, a path may be given as a sequence of physical nodes and the links c as a sequence of ASes or an Explicit Route Object (ERO), or only
onnecting these nodes, a sequence of logical nodes such as a sequence of ASes or consist of a specific source and destination that is known to be
an Explicit Route Object (ERO), or only consist of a specific source and destin reachable from that source.</t>
ation which is known to be reachable from that source.</t> <t>A multicast or broadcast setting where a packet is sent by one
<t>A multicast or broadcast setting, where a packet is sent by one nod node and received by multiple nodes is described by multiple paths
e and received by multiple nodes, is described by multiple paths over which the over which the packet is sent, one path for each combination of
packet is sent, one path for each combination of sending and receiving node; the sending and receiving node; these paths do not have to be disjoint
se paths do not have to be disjoint as defined by the Disjointness path property as defined by the disjointness path property, see <xref
, see <xref target="examples" format="default"/>.</t> target="examples" format="default"/>.</t>
</dd> </dd>
<dt> <dt>Endpoint:</dt>
Endpoint: </dt>
<dd> <dd>
<t>The endpoints of a path are the start and end node of the path. For <t>The endpoints of a path are the start and end node of the
example, an endpoint can be a host as defined in <xref target="RFC1122" format= path. For example, an endpoint can be a host as defined in <xref
"default"/>, which can be a client (e.g., a node running a web browser) or a ser target="RFC1122" format="default"/>, which can be a client (e.g., a
ver (e.g., a node running a web server).</t> node running a web browser) or a server (e.g., a node running a web
server).</t>
</dd> </dd>
<dt> <dt>Reverse Path:</dt>
Reverse Path: </dt>
<dd> <dd>
<t>The path that is used by a remote node in the context of bidirectio <t>The path that is used by a remote node in the context of
nal communication.</t> bidirectional communication.</t>
</dd> </dd>
<dt> <dt>Subpath:</dt>
Subpath: </dt>
<dd> <dd>
<t>Given a path, a subpath is a sequence of adjacent path elements of <t>Given a path, a subpath is a sequence of adjacent path elements
this path.</t> of this path.</t>
</dd> </dd>
<dt> <dt>Flow:</dt>
Flow: </dt>
<dd> <dd>
<t>One or multiple packets to which the traits of a path or set of sub <t>One or multiple packets to which the traits of a path or set of
paths may be applied in a functional sense. For example, a flow can consist of a subpaths may be applied in a functional sense. For example, a flow
ll packets sent within a TCP session with the same five-tuple between two hosts, can consist of all packets sent within a TCP session with the same
or it can consist of all packets sent on the same physical link.</t> five-tuple between two hosts, or it can consist of all packets sent
on the same physical link.</t>
</dd> </dd>
<dt> <dt>Property:</dt>
Property: </dt>
<dd> <dd>
<t>A trait of one or a sequence of path elements, or a trait of a flow <t>A trait of one or a sequence of path elements, or a trait of a
with respect to one or a sequence of path elements. An example of a link proper flow with respect to one or a sequence of path elements. An example
ty is the maximum data rate that can be sent over the link. An example of a node of a link property is the maximum data rate that can be sent over
property is the administrative domain that the node belongs to. An example of a the link. An example of a node property is the administrative domain
property of a flow with respect to a subpath is the aggregated one-way delay of that the node belongs to. An example of a property of a flow with
the flow being sent from one node to another node over this subpath. respect to a subpath is the aggregated one-way delay of the flow
A property is thus described by a tuple containing the path element(s), the flow being sent from one node to another node over this subpath. A
or an empty set if no packets are relevant for the property, the name of the pr property is thus described by a tuple containing the path
operty (e.g., maximum data rate), and the value of the property (e.g., 1Gbps).</ element(s), the flow or an empty set if no packets are relevant for
t> the property, the name of the property (e.g., maximum data rate),
and the value of the property (e.g., 1 Gbps).</t>
</dd> </dd>
<dt> <dt>Aggregated property:</dt>
Aggregated property: </dt>
<dd> <dd>
<t>A collection of multiple values of a property into a single value, <t>A collection of multiple values of a property into a single
according to a function. A property can be aggregated over multiple path element value, according to a function. A property can be aggregated
s (i.e., a subpath), e.g., the MTU of a path as the minimum MTU of all links on over:</t>
the path, over multiple packets (i.e., a flow), e.g., the median one-way latency <ul spacing="normal">
of all packets between two nodes, or over both, e.g., the mean of the queueing <li>multiple path elements (i.e., a subpath), for example, the MTU
delays of a flow on all nodes along a path. of a path as the minimum MTU of all links on the path,</li>
The aggregation function can be numerical, e.g., median, sum, minimum, it can be <li>multiple packets (i.e., a flow), for example, the median
logical, e.g., "true if all are true", "true if at least 50% of values are true one-way latency of all packets between two nodes,</li>
", or an arbitrary function which maps multiple input values to an output value. <li>or both path elements and packets, for example, the mean of
</t> the queueing delays of a flow on all nodes along a path.</li>
</ul>
<t>The aggregation function can be numerical (e.g., median, sum,
minimum) or logical (e.g., "true if all are true", "true if at
least 50% of values are true"), or it can be an arbitrary function
that maps multiple input values to an output value.</t>
</dd> </dd>
<dt> <dt>Observed property:</dt>
Observed property: </dt>
<dd> <dd>
<t>A property that is observed for a specific path element, subpath, o <t>A property that is observed for a specific path element, subpath,
r path, e.g., using measurements. For example, the one-way delay of a specific p or path. A property may be observed using measurements, for example,
acket transmitted from one node to another node can be measured.</t> the one-way delay of a specific packet transmitted from node to
node.</t>
</dd> </dd>
<dt> <dt>Assessed property:</dt>
Assessed property: </dt>
<dd> <dd>
<t>An approximate calculation or assessment of the value of a property <t>An approximate calculation or assessment of the value of a
. An assessed property includes the reliability of the calculation or assessment property. An assessed property includes the reliability of the
. The notion of reliability depends on the property. calculation or assessment. The notion of reliability depends on the
For example, a path property based on an approximate calculation may describe th property. For example, a path property based on an approximate
e expected median one-way latency of packets sent on a path within the next seco calculation may describe the expected median one-way latency of
nd, including the confidence level and interval. A non-numerical assessment may packets sent on a path within the next second, including the
instead include the likelihood that the property holds.</t> confidence level and interval. A non-numerical assessment may
instead include the likelihood that the property holds.</t>
</dd> </dd>
<dt> <dt>Target property:</dt>
Target property: </dt>
<dd> <dd>
<t>An objective that is set for a property over a path element, subpat <t>An objective that is set for a property over a path element,
h, or path. subpath, or path. Note that a target property can be set for
Note that a target property can be set for observed properties, such as one-way observed properties, such as one-way delay, and also for properties
delay, but also for properties that cannot be observed by the entity setting the that cannot be observed by the entity setting the target, such as
target, such as inclusion of certain nodes on a path.</t> inclusion of certain nodes on a path.</t>
</dd> </dd>
</dl> </dl>
<section anchor="terminology-usage-for-specific-technologies" numbered="tr ue" toc="default"> <section anchor="terminology-usage-for-specific-technologies" numbered="tr ue" toc="default">
<name>Terminology usage for specific technologies</name> <name>Terminology Usage for Specific Technologies</name>
<t>The terminology defined in this document is intended to be general an <t>The terminology defined in this document is intended to be general
d applicable to existing and future path-aware technologies. and applicable to existing and future path-aware technologies. Using
Using this terminology, a path-aware technology can define and consider specific this terminology, a path-aware technology can define and consider
path elements and path properties on a specific level of abstraction. specific path elements and path properties on a specific level of
For instance, a technology may define path elements as IP routers, e.g., in sour abstraction. For instance, a technology may define path elements as
ce routing (<xref target="RFC1940" format="default"/>). Alternatively, it may co IP routers, e.g., in source routing <xref target="RFC1940"
nsider path elements on a different layer of the Internet Architecture (<xref ta format="default"/>. Alternatively, it may consider path elements on a
rget="RFC1122" format="default"/>) or as a collection of entities not tied to a different layer of the Internet architecture <xref target="RFC1122"
specific layer, such as an AS or an ERO. format="default"/> or as a collection of entities not tied to a
Even within a single path-aware technology, specific definitions might differ de specific layer, such as an AS or ERO. Even within a single path-aware
pending on the context in which they are used. technology, specific definitions might differ depending on the context
For example, the endpoints might be the communicating hosts in the context of th in which they are used. For example, the endpoints might be the
e transport layer, ASes that contain the hosts in the context of routing, or spe communicating hosts in the context of the transport layer, ASes that
cific applications in the context of the application layer.</t> contain the hosts in the context of routing, or specific applications
in the context of the application layer.</t>
</section> </section>
</section> </section>
<section anchor="use-cases" numbered="true" toc="default"> <section anchor="use-cases" numbered="true" toc="default">
<name>Use Cases for Path Properties</name> <name>Use Cases for Path Properties</name>
<t>When a path-aware network exposes path properties to endpoints or other <t>When a path-aware network exposes path properties to endpoints or
entities, other entities, these entities may use this information to achieve
these entities may use this information to achieve different goals. different goals. This section lists several use cases for path
This section lists several use cases for path properties.</t> properties.</t>
<t>Note that this is not an exhaustive list, as with every new technology <t>Note that this is not an exhaustive list; as with every new
and protocol, novel use cases may emerge, and new path properties may become rel technology and protocol, novel use cases may emerge, and new path
evant. properties may become relevant. Moreover, for any particular
Moreover, for any particular technology, entities may have visibility of and con technology, entities may have visibility of and control over different
trol over different path elements and path properties, and consider them on diff path elements and path properties and consider them on different levels
erent levels of abstraction. of abstraction. Therefore, a new technology may implement an existing
Therefore, a new technology may implement an existing use case related to differ use case related to different path elements or on a different level of
ent path elements or on a different level of abstraction.</t> abstraction.</t>
<section anchor="path-selection" numbered="true" toc="default"> <section anchor="path-selection" numbered="true" toc="default">
<name>Path Selection</name> <name>Path Selection</name>
<t>Nodes may be able to send flows via one (or a subset) out of multiple <t>Nodes may be able to send flows via one (or a subset) out of
possible paths, and an entity may be able to influence the decision which path( multiple possible paths, and an entity may be able to influence the
s) to use. decision about which path(s) to use. Path selection may be feasible
Path Selection may be feasible if there are several paths to the same destinatio if there are several paths to the same destination (e.g., in case of a
n (e.g., in case of a mobile device with two wireless interfaces, both providing mobile device with two wireless interfaces, both providing a path) or
a path), or if there are several destinations, and thus several paths, providin if there are several destinations, and thus several paths, providing
g the same service (e.g., Application-Layer Traffic Optimization (ALTO) <xref ta the same service (e.g., Application-Layer Traffic Optimization (ALTO)
rget="RFC5693" format="default"/>, an application layer peer-to-peer protocol al <xref target="RFC5693" format="default"/>, an application layer
lowing endpoints a better-than-random peer selection). peer-to-peer protocol allowing endpoints a better-than-random peer
Entities can express their intent to achieve a specific goal by specifying targe selection). Entities can express their intent to achieve a specific
t properties for their paths, e.g., related to performance or security. goal by specifying target properties for their paths, e.g., related to
Then, paths can be selected which best meet the target properties, e.g., the ent performance or security. Then, paths can be selected that best meet
ity can select these paths from all available paths or express the target proper the target properties, e.g., the entity can select these paths from
ties to the network and rely on the network to select appropriate paths.</t> all available paths or express the target properties to the network
<t>Target properties relating to network performance typically refer to and rely on the network to select appropriate paths.</t>
observed properties, such as One-Way Delay, One-Way Packet Loss, and Link Capaci <t>Target properties relating to network performance typically refer
ty. to observed properties, such as one-way delay, one-way packet loss,
Entities then select paths based on their target property and the assessed prope and link capacity. Entities then select paths based on their target
rty of the available paths that best match the application requirements. property and the assessed property of the available paths that best
For such performance-related target properties, the observed property is similar match the application requirements. For such performance-related
to a service level indicator (SLI) and the assessed property is similar to a se target properties, the observed property is similar to a Service Level
rvice level objective (SLO) for IETF network slices <xref target="I-D.ietf-teas- Indicator (SLI), and the assessed property is similar to a Service
ietf-network-slices" format="default"/>. Level Objective (SLO) for IETF Network Slices <xref
As an example path selection strategy, for sending a small delay-sensitive query target="I-D.ietf-teas-ietf-network-slices" format="default"/>. As an
, an entity may select a path with a short One-Way Delay, while for retrieving a example path-selection strategy, an entity may select a path with a
large file, it may select a path with high Link Capacities on all links.</t> short one-way delay for sending a small delay-sensitive query, while
<t>It is also possible for an entity to set target properties which it c it may select a path with high link capacities on all links for
annot (directly) observe, similar to service level expectations (SLEs) for IETF retrieving a large file.</t>
network slices <xref target="I-D.ietf-teas-ietf-network-slices" format="default" <t>It is also possible for an entity to set target properties that it
/>. cannot (directly) observe, similar to Service Level Expectations
For example, this can apply to security-related target properties and path selec (SLEs) for IETF Network Slices <xref
tion, such as allowing or disallowing sending flows over paths that involve spec target="I-D.ietf-teas-ietf-network-slices" format="default"/>. This
ific networks or nodes to enforce traffic policies or mandating that all enterpr may apply to security-related target properties (e.g., to mandate that
ise traffic goes through a specific firewall.</t> all enterprise traffic goes through a specific firewall) and path
<t>Care needs to be taken when selecting paths based on observed path pr selection (e.g., to enforce traffic policies by allowing or disallowing
operties, as path properties that were previously measured may not be helpful in sending flows over paths that involve specific networks or nodes).</t>
predicting current or future path properties and such path selection may lead t <t>Care needs to be taken when selecting paths based on observed path
o unintended feedback loops. Also, there may be trade-offs between path properti properties, as path properties that were previously measured may not
es (e.g., One-Way Delay and Link Capacity), and entities may influence these tra be helpful in predicting current or future path properties, and such
de-offs with their choices. path selection may lead to unintended feedback loops. Also, there may
Finally, path selection may impact fairness. be trade-offs between path properties (e.g., one-way delay and link
For example, if multiple entities concurrently attempt to meet their target prop capacity), and entities may influence these trade-offs with their
erties using the same network resources, one entity's choices may influence the choices. Finally, path selection may impact fairness. For example,
conditions on the path as experienced by flows of another entity.</t> if multiple entities concurrently attempt to meet their target
<t>As a baseline, a path selection algorithm should aim to do a better j properties using the same network resources, one entity's choices may
ob at meeting the target properties, and consequently accommodating the user's r influence the conditions on the path as experienced by flows of
equirements, than the default case of not selecting a path most of the time.</t> another entity.</t>
<t>Path selection can be done either by the communicating node(s) or by
other entities within the network: <t>As a baseline, a path-selection algorithm should aim to do a better
A network (e.g., an AS) can adjust its path selection for internal or external r job of meeting the target properties, and consequently accommodating
outing based on path properties. the user's requirements, than the default case of not selecting a path
In BGP, the Multi Exit Discriminator (MED) attribute is used in the decision-mak most of the time.</t>
ing process to select which path to choose among those having the same AS PATH l <t>Path selection can be done either by the communicating node(s) or
ength and origin <xref target="RFC4271" format="default"/>; in a path-aware netw by other entities within the network. A network (e.g., an AS) can
ork, instead of using this single MED value, other properties such as Link Capac adjust its path selection for internal or external routing based on
ity or Link Usage could additionally be used to improve load balancing or perfor path properties. In BGP, the Multi-Exit Discriminator (MED) attribute
mance <xref target="I-D.ietf-idr-performance-routing" format="default"/>.</t> is used in the decision-making process to select which path to choose
among those having the same AS path length and origin <xref
target="RFC4271" format="default"/>; in a path-aware network, instead
of using this single MED value, other properties such as link capacity
or link usage could additionally be used to improve load balancing or
performance <xref target="I-D.ietf-idr-performance-routing"
format="default"/>.</t>
</section> </section>
<section anchor="protocol-selection" numbered="true" toc="default"> <section anchor="protocol-selection" numbered="true" toc="default">
<name>Protocol Selection</name> <name>Protocol Selection</name>
<t>Before sending data over a specific path, an entity may select an app <t>Before sending data over a specific path, an entity may select an
ropriate protocol or configure protocol parameters depending on path properties. appropriate protocol or configure protocol parameters depending on
For example, an endpoint may cache state on whether a path allows the use of QUI path properties. For example, an endpoint may cache state if
C <xref target="RFC9000" format="default"/> and if so, first attempt to connect a path allows the use of QUIC <xref target="RFC9000"
using QUIC before falling back to another protocol when connecting over this pat format="default"/>; if so, it may first attempt to connect using QUIC
h again. before falling back to another protocol when connecting over this path
A video streaming application may choose an (initial) video quality based on the again. A video-streaming application may choose an (initial) video
achievable data rate or the monetary cost of sending data (e.g., volume-base or quality based on the achievable data rate or the monetary cost of
flat-rate cost model).</t> sending data (e.g., volume-based or flat-rate cost model).</t>
</section> </section>
<section anchor="service-invocation" numbered="true" toc="default"> <section anchor="service-invocation" numbered="true" toc="default">
<name>Service Invocation</name> <name>Service Invocation</name>
<t>In addition to path or protocol selection, an entity may choose to in <t>In addition to path or protocol selection, an entity may choose to
voke additional functions in the context of Service Function Chaining <xref targ invoke additional functions in the context of Service Function
et="RFC7665" format="default"/>, which may influence what nodes are on the path. Chaining <xref target="RFC7665" format="default"/>, which may
For example, a 0-RTT Transport Converter <xref target="RFC8803" format="default" influence which nodes are on the path. For example, a 0-RTT Transport
/> will be involved in a path only when invoked by an endpoint; such invocation Converter <xref target="RFC8803" format="default"/> will be involved
will lead to the use of MPTCP <xref target="RFC8684" format="default"/> or TCPin in a path only when invoked by an endpoint; such invocation will lead
c <xref target="RFC8547" format="default"/> <xref target="RFC8548" format="defau to the use of Multipath TCP (MPTCP) <xref target="RFC8684"
lt"/> capabilities while such use is not supported via the default forwarding pa format="default"/> or tcpcrypt <xref target="RFC8548"
th. format="default"/> capabilities, while such use is not supported via
Another example is a connection which is composed of multiple streams where each the default forwarding path. Another example is a connection that is
stream has specific service requirements. An endpoint may decide to invoke a gi composed of multiple streams where each stream has specific service
ven service function (e.g., transcoding) only for some streams while others are requirements. An endpoint may decide to invoke a given service
not processed by that service function.</t> function (e.g., transcoding) only for some streams while others are
not processed by that service function.</t>
</section> </section>
</section> </section>
<section anchor="examples" numbered="true" toc="default"> <section anchor="examples" numbered="true" toc="default">
<name>Examples of Path Properties</name> <name>Examples of Path Properties</name>
<t>This Section gives some examples of path properties which may be useful <t>This section gives some examples of path properties that may be
, e.g., for the use cases described in <xref target="use-cases" format="default" useful, e.g., for the use cases described in <xref target="use-cases"
/>.</t> format="default"/>.</t>
<t>Within the context of any particular technology, available path propert <t>Within the context of any particular technology, available path
ies may differ properties may differ as entities have insight into and are able to
as entities have insight into and are able to influence different path elements influence different path elements and path properties. For example, an
and path properties. endpoint may have some visibility into path elements that are close and on
For example, an endpoint may have some visibility into path elements that are on a low
a low level of abstraction and close, e.g., individual nodes within the first f level of abstraction (e.g., individual nodes within the first
ew hops, or it may have visibility into path elements that are far away and/or o few hops), or it may have visibility into path elements that are far away
n a higher level of abstraction, e.g., the list of ASes traversed. and/or on a higher level of abstraction (e.g., the list of ASes
This visibility may depend on factors such as the physical or network distance o traversed). This visibility may depend on factors such as the physical
r the existence of trust or contractual relationships between the endpoint and t or network distance or the existence of trust or contractual
he path element(s). relationships between the endpoint and the path element(s). A path
A path property can be defined relative to individual path elements, a sequence property can be defined relative to individual path elements, a sequence
of path elements, or "end-to-end", i.e., relative to a path that comprises of tw of path elements, or "end-to-end", i.e., relative to a path that
o endpoints and a single virtual link connecting them.</t> comprises of two endpoints and a single virtual link connecting
<t>Path properties may be relatively dynamic, e.g., the one-way delay of a them.</t>
packet sent over a specific path, or non-dynamic, e.g., the MTU of an Ethernet <t>Path properties may be relatively dynamic, e.g., the one-way delay of
link which only changes infrequently. a packet sent over a specific path, or non-dynamic, e.g., the MTU of an
Usefulness over time differs depending on how dynamic a property is: Ethernet link that only changes infrequently. Usefulness over time
The merit of a momentarily observed dynamic path propety may diminish greatly as differs depending on how dynamic a property is: the merit of a
time goes on, e.g., momentarily observed dynamic path property may diminish greatly as time
it is possible for the observed values of One-Way Delay to change on timescales goes on, e.g., it is possible for the observed values of one-way delay
which are shorter than the One-Way Delay between the measurement point and an en to change on timescales that are shorter than the one-way delay between
tity making a decision such as Path Selection, which may cause the measurement t the measurement point and an entity making a decision such as path
o be outdated when it reaches the decision-making entity. Therefore, consumers o selection, which may cause the measurement to be outdated when it
f dynamic path properties need to apply caution when using them, e.g., by aggreg reaches the decision-making entity. Therefore, consumers of dynamic path
ating them appropriately or applying a dampening function to their changes to av properties need to apply caution when using them, e.g., by aggregating
oiding oscillation. them appropriately or applying a dampening function to their changes to
In contrast, the observed value of a less dynamic path property might stay relev avoid oscillation. In contrast, the observed value of a less dynamic
ant for a longer period of time, e.g. a NAT typically stays on a particular path path property might stay relevant for a longer period of time, e.g., a
during the lifetime of a connection involving packets sent over this path.</t> NAT typically stays on a particular path during the lifetime of a
<dl> connection involving packets sent over this path.</t>
<dt> <dl spacing="normal" newline="false">
Access Technology: </dt> <dt>Access Technology:</dt>
<dd> <dd>
<t>The physical or link layer technology used for transmitting or rece <t>The physical- or link-layer technology used for transmitting or
iving a flow on one or multiple path elements. If known, the Access Technology m receiving a flow on one or multiple path elements. If known, the
ay be given as an abstract link type, e.g., as Wi-Fi, Wired Ethernet, or Cellula access technology may be given as an abstract link type, e.g., as
r. It may also be given as a specific technology used on a link, e.g., 3GPP cell Wi-Fi, wired Ethernet, or cellular. It may also be given as a
ular, or 802.11 WiFi. Other path elements relevant to the access technology may specific technology used on a link, e.g., 3GPP cellular or 802.11
include nodes related to processing packets on the physical or link layer, such Wireless Local Area Network (WLAN). Other path elements relevant to
as elements of a cellular core network. Note that there is no common registry of the access technology may include nodes related to processing
possible values for this property.</t> packets on the physical or link layer, such as elements of a
cellular core network. Note that there is no common registry of
possible values for this property.</t>
</dd> </dd>
<dt> <dt>Monetary Cost:</dt>
Monetary Cost: </dt>
<dd> <dd>
<t>The price to be paid to transmit or receive a specific flow across <t>The price to be paid to transmit or receive a specific flow
a network to which one or multiple path elements belong.</t> across a network to which one or multiple path elements belong.</t>
</dd> </dd>
<dt> <dt>Service Function:</dt>
Service function: </dt>
<dd> <dd>
<t>A service function that a path element applies to a flow, see <xref <t>A service function that a path element applies to a flow, see
target="RFC7665" format="default"/>. Examples of abstract service functions inc <xref target="RFC7665" format="default"/>. Examples of abstract
lude firewalls, Network Address Translation (NAT), and TCP Performance Enhancing service functions include firewalls, Network Address Translation
Proxies. Some stateful service functions, such as NAT, need to observe the same (NAT), and TCP Performance Enhancing Proxies. Some stateful service
flow in both directions, e.g., by being an element of both the path and the rev functions, such as NAT, need to observe the same flow in both
erse path.</t> directions, e.g., by being an element of both the path and the
reverse path.</t>
</dd> </dd>
<dt> <dt>Transparency:</dt>
Transparency: </dt>
<dd> <dd>
<t>When a node performs an action A on a flow F, the node is transpare
nt to F with respect to some (meta-)information M if the node performs A indepen <t>When a node performs an action A on a flow F, the node is
dently of M. transparent to F with respect to some (meta-)information M if the
M can for example be the existence of a protocol (header) in a packet or the con node performs A independently of M. M can, for example, be the
tent of a protocol header, payload, or both. existence of a protocol (header) in a packet or the content of a
For example, A can be blocking packets or reading and modifying (other protocol) protocol header, payload, or both. For example, A can be blocking
headers or payloads. packets or reading and modifying (other protocol) headers or
Transparency can be modeled using a function f, which takes as input F and M and payloads. Transparency can be modeled using a function f, which
outputs the action taken by the node. takes as input F and M and outputs the action taken by the node. If
If a taint analysis shows that the output of f is not tainted (impacted) by M or a taint analysis shows that the output of f is not tainted
if the output of f is constant for arbitrary values of M, then the node is cons (impacted) by M, or if the output of f is constant for arbitrary
idered to be transparent. values of M, then the node is considered to be transparent. An IP
An IP router could be transparent to transport protocol headers such as TCP/UDP router could be transparent to transport protocol headers such as
but not transparent to IP headers since its forwarding behavior depends on the I TCP/UDP but not transparent to IP headers since its forwarding
P headers. behavior depends on the IP headers. A firewall that only allows
A firewall that only allows outgoing TCP connections by blocking all incoming TC outgoing TCP connections by blocking all incoming TCP SYN packets
P SYN packets regardless of their IP address is transparent to IP but not to TCP regardless of their IP address is transparent to IP but not to TCP
headers. headers. Finally, a NAT that actively modifies IP and TCP/UDP
Finally, a NAT that actively modifies IP and TCP/UDP headers based on their cont headers based on their content is not transparent to either IP or
ent is not transparent to either IP or TCP/UDP headers. TCP/UDP headers. Note that according to this definition, a node that
Note that according to this definition, a node that modifies packets in accordan modifies packets in accordance with the endpoints, such as a
ce with the endpoints, such as a transparent HTTP proxy, as defined in <xref tar transparent HTTP proxy, as defined in <xref target="RFC9110"
get="RFC2616" format="default"/>, and a node listening and reacting to implicit format="default"/>, and a node listening and reacting to implicit or
or explicit signals, see <xref target="RFC8558" format="default"/>, are not cons explicit signals, see <xref target="RFC8558" format="default"/>, are
idered transparent. not considered transparent.</t>
</t> <t>Transparency only applies to nodes and not to links, as a link
<t>Transparency only applies to nodes and not to links, as a link cann cannot modify or perform any other actions on the packets by
ot modify or perform any other actions on the packets by itself. For example, if itself. For example, if the content of a packet is altered when
the content of a packet is altered when forwarded over a Generic Routing Encaps forwarded over a Generic Routing Encapsulation (GRE) tunnel <xref
ulation (GRE) tunnel <xref target="RFC2784" format="default"/><xref target="RFC7 target="RFC2784" format="default"/> <xref target="RFC7676"
676" format="default"/>, this document considers as nodes the software instances format="default"/>, per this document the software instances that
that terminate the tunnel over which the actions are performed; thus, the trans terminate the tunnel are considered nodes over which the actions are
parency definition applies to these nodes.</t> performed; thus, the transparency definition applies to these
nodes.</t>
</dd> </dd>
<dt> <dt>Administrative Domain:</dt>
Administrative Domain: </dt>
<dd> <dd>
<t>The identity of an individual or an organization that controls acce <t>The identity of an individual or an organization that controls
ss to a path element (or several path elements). access to a path element (or several path elements). Examples of
Examples of administrative domains are an IGP area, an AS, or a service provider administrative domains are an IGP area, an AS, or a service provider
network.</t> network.</t>
</dd> </dd>
<dt> <dt>Routing Domain Identifier:</dt>
Routing Domain Identifier: </dt>
<dd> <dd>
<t>An identifier indicating the routing domain of a path element. <t>An identifier indicating the routing domain of a path element.
Path elements in the same routing domain are in the same administrative domain a Path elements in the same routing domain are in the same
nd use a common routing protocol to communicate with each other. administrative domain and use a common routing protocol to
An example of a routing domain identifier is the globally unique autonomous syst communicate with each other. An example of a routing domain
em number (ASN) as defined in <xref target="RFC1930" format="default"/>.</t> identifier is the globally unique Autonomous System Number (ASN) as
defined in <xref target="RFC1930" format="default"/>.</t>
</dd> </dd>
<dt> <dt>Disjointness:</dt>
Disjointness: </dt>
<dd> <dd>
<t>For a set of two paths or subpaths, the number of shared path eleme <t>For a set of two paths or subpaths, the number of shared path
nts can be a measure of intersection (e.g., Jaccard coefficient, which is the nu elements can be a measure of intersection (e.g., Jaccard
mber of shared elements divided by the total number of elements). Conversely, th coefficient, which is the number of shared elements divided by the
e number of non-shared path elements can be a measure of disjointness (e.g., 1 - total number of elements). Conversely, the number of non-shared path
Jaccard coefficient). A multipath protocol might use disjointness as a metric t elements can be a measure of disjointness (e.g., 1 - Jaccard
o reduce the number of single points of failure. As paths can be defined at diff coefficient). A multipath protocol might use disjointness as a
erent levels of abstraction, two paths may be disjoint at one level of abstracti metric to reduce the number of single points of failure. As paths
on, but not on another.</t> can be defined at different levels of abstraction, two paths may be
disjoint at one level of abstraction but not on another.</t>
</dd> </dd>
<dt> <dt>Symmetric Path:</dt>
Symmetric Path: </dt>
<dd> <dd>
<t>Two paths are symmetric if the path and its reverse path consist of <t>Two paths are symmetric if the path and its reverse path consist
the same path elements on the same level of abstraction, but in reverse order. of the same path elements on the same level of abstraction, but in
For example, a path which consists of layer 3 switches and links between them an reverse order. For example, a path that consists of layer 3
d a reverse path with the same path elements but in reverse order are considered switches and links between them and a reverse path with the same
"routing" symmetric, as the same path elements on the same level of abstraction path elements but in reverse order are considered "routing"
(IP forwarding) are traversed in the opposite direction. symmetric, as the same path elements on the same level of
Symmetry can depend on the level of abstraction on which the path is defined or abstraction (IP forwarding) are traversed in the opposite direction.
modeled: If there are two parallel physical links between two nodes, modeling th Symmetry can depend on the level of abstraction on which the path is
em as separate links may result in a flow using asymmetric paths, and modeling t defined or modeled. If there are two parallel physical links between
hem as a single virtual link may result in symmetric paths, e.g., if the differe two nodes, modeling them as separate links may result in a flow
nce between the two physical links is irrelevant in a particular context.</t> using asymmetric paths, and modeling them as a single virtual link
may result in symmetric paths, e.g., if the difference between the
two physical links is irrelevant in a particular context.</t>
</dd> </dd>
<dt> <dt>Path MTU:</dt>
Path MTU: </dt>
<dd> <dd>
<t>The maximum size, in octets, of a packet or frame that can be trans <t>The maximum size, in octets, of a packet or frame that can be
mitted without fragmentation.</t> transmitted without fragmentation.</t>
</dd> </dd>
<dt> <dt>Transport Protocols available:</dt>
Transport Protocols available: </dt>
<dd> <dd>
<t>Whether a specific transport protocol can be used to establish a co <t>Whether a specific transport protocol can be used to establish a
nnection over a path or subpath, e.g., whether the path is QUIC-capable or MPTCP connection over a path or subpath, e.g., whether the path is
-capable, based on input such as policy, cached knowledge, or probing results.</ QUIC-capable or MPTCP-capable, based on input such as policy, cached
t> knowledge, or probing results.</t>
</dd> </dd>
<dt> <dt>Protocol Features available:</dt>
Protocol Features available: </dt>
<dd> <dd>
<t>Whether a specific protocol feature is available over a path or sub <t>Whether a specific protocol feature is available over a path or
path, e.g., Explicit Congestion Notification (ECN), or TCP Fast Open.</t> subpath, e.g., Explicit Congestion Notification (ECN) or TCP Fast
Open.</t>
</dd> </dd>
</dl> </dl>
<t>Some path properties express the performance of the transmission of a p
acket or flow over a link or subpath. <t>Some path properties express the performance of the transmission of a
Such transmission performance properties can be observed or assessed, e.g., by e packet or flow over a link or subpath. Such transmission performance
ndpoints or by path elements on the path, or they may be available as cost metri properties can be observed or assessed, e.g., by endpoints or by path
cs, see <xref target="I-D.ietf-alto-performance-metrics" format="default"/>. elements on the path, or they may be available as cost metrics, see
Transmission performance properties may be made available in an aggregated form, <xref target="RFC9439" format="default"/>. Transmission performance
such as averages or minimums. properties may be made available in an aggregated form, such as averages
Properties related to a path element which constitutes a single layer 2 domain a or minimums. Properties related to a path element that constitutes a
re abstracted from the used physical and link layer technology, similar to <xref single layer 2 domain are abstracted from the used physical- and link-laye
target="RFC8175" format="default"/>.</t> r technology, similar to <xref target="RFC8175"
<dl> format="default"/>.</t>
<dt>
Link Capacity: </dt> <dl spacing="normal" newline="false">
<dt>Link Capacity:</dt>
<dd> <dd>
<t>The link capacity is the maximum data rate at which data that was s <t>The link capacity is the maximum data rate at which data that was
ent over a link can correctly be received at the node adjacent to the link. sent over a link can correctly be received at the node adjacent to
This property is analogous to the link capacity defined in <xref target="RFC5136 the link. This property is analogous to the link capacity defined
" format="default"/> and <xref target="RFC9097" format="default"/> but not restr in <xref target="RFC5136" format="default"/> and <xref
icted to IP-layer traffic.</t> target="RFC9097" format="default"/> but is not restricted to IP-layer
traffic.</t>
</dd> </dd>
<dt> <dt>Link Usage:</dt>
Link Usage: </dt>
<dd> <dd>
<t>The link usage is the actual data rate at which data that was sent
over a link is correctly received at the node adjacent to the link. <t>The link usage is the actual data rate at which data that was
This property is analogous to the link usage defined in <xref target="RFC5136" f sent over a link is correctly received at the node adjacent to the
ormat="default"/> and <xref target="RFC9097" format="default"/> but not restrict link. This property is analogous to the link usage defined in <xref
ed to IP-layer traffic.</t> target="RFC5136" format="default"/> and <xref target="RFC9097"
format="default"/> but is not restricted to IP-layer traffic.</t>
</dd> </dd>
<dt> <dt>One-Way Delay:</dt>
One-Way Delay: </dt>
<dd> <dd>
<t>The one-way delay is the delay between a node sending a packet and <t>The one-way delay is the delay between a node sending a packet
another node on the same path receiving the packet. and another node on the same path receiving the packet. This
This property is analogous to the one-way delay defined in <xref target="RFC7679 property is analogous to the one-way delay defined in <xref
" format="default"/> but not restricted to IP-layer traffic.</t> target="RFC7679" format="default"/> but is not restricted to IP-layer
traffic.</t>
</dd> </dd>
<dt> <dt>One-Way Delay Variation:</dt>
One-Way Delay Variation: </dt>
<dd> <dd>
<t>The variation of the one-way delays within a flow. <t>The variation of the one-way delays within a flow. This property
This property is similar to the one-way delay variation defined in <xref target= is similar to the one-way delay variation defined in <xref
"RFC3393" format="default"/> but not restricted to IP-layer traffic and defined target="RFC3393" format="default"/>, but it is not restricted to IP-la
for packets on the same flow instead of packets sent between a source and destin yer
ation IP address.</t> traffic and it is defined for packets on the same flow instead of pack
ets
sent between a source and destination IP address.</t>
</dd> </dd>
<dt> <dt>One-Way Packet Loss:</dt>
One-Way Packet Loss: </dt>
<dd> <dd>
<t>Packets sent by a node but not received by another node on the same <t>Packets sent by a node but not received by another node on the
path after a certain time interval are considered lost. same path after a certain time interval are considered lost. This
This property is analogous to the one-way loss defined in <xref target="RFC7680" property is analogous to the one-way loss defined in <xref
format="default"/> but not restricted to IP-layer traffic. target="RFC7680" format="default"/> but is not restricted to IP-layer
Metrics such as loss patterns <xref target="RFC3357" format="default"/> and loss traffic. Metrics such as loss patterns <xref target="RFC3357"
episodes <xref target="RFC6534" format="default"/> can be expressed as aggregat format="default"/> and loss episodes <xref target="RFC6534"
ed properties.</t> format="default"/> can be expressed as aggregated properties.</t>
</dd> </dd>
</dl> </dl>
</section> </section>
<section anchor="security-considerations" numbered="true" toc="default"> <section anchor="security-considerations" numbered="true" toc="default">
<name>Security Considerations</name> <name>Security Considerations</name>
<t>If entities are basing policy or path selection decisions on path prope <t>If entities are basing policy or path-selection decisions on path
rties, they need to rely on the accuracy of path properties that other devices c properties, they need to rely on the accuracy of path properties that
ommunicate to them. other devices communicate to them. In order to be able to trust such
In order to be able to trust such path properties, entities may need to establis path properties, entities may need to establish a trust relationship or
h a trust relationship or be able to independently verify the authenticity, inte be able to independently verify the authenticity, integrity, and
grity, and correctness of path properties received from another entity.</t> correctness of path properties received from another entity.</t>
<t>Entities that reveal their target path properties to the network can ne <t>Entities that reveal their target path properties to the network can
gatively impact their own privacy, e.g., if the target property leaks personal i negatively impact their own privacy, e.g., if the target property leaks
nformation about a user, such as their identity or which (type of) application i personal information about a user, such as their identity or which (type
s used. of) application is used. Such information could then allow network
Such information could then allow network operators to block or re-prioritize tr operators to block or reprioritize traffic for certain users and/or
affic for certain users and/or application. applications. Conversely, if privacy-enhancing technologies, e.g.,
Conversely, if privacy enhancing technologies, e.g., MASQUE proxies <xref target MASQUE proxies <xref target="RFC9298" format="default"/>, are used on a
="RFC9298" format="default"/>, are used on a path, the path may only be partiall path, the path may only be partially visible to any single entity. This
y visible to any single entity. may diminish the usefulness of path-aware technologies over this
This may diminish the usefulness of path-aware technologies over this path.</t> path.</t>
<t>The need for, and potential definition of, security and privacy related <t>The need for, and potential definition of, security- and privacy-relate
path properties, such as confidentiality and integrity protection of payloads, d path properties, such as confidentiality and integrity
are the subject of ongoing discussion and research, e.g., see <xref target="RFC9 protection of payloads, are the subject of ongoing discussion and
049" format="default"/> and <xref target="RFC9217" format="default"/>. As the di research, for example, see <xref target="RFC9049" format="default"/> and <
scussion of such properties is not mature enough, they are out of scope for this xref
document. target="RFC9217" format="default"/>. As the discussion of such
One aspect discussed in this context is that security related properties are dif properties is not mature enough, they are out of scope for this
ficult to characterize since they are only meaningful with respect to a threat m document. One aspect discussed in this context is that security-related
odel which depends on the use case, application, environment, and other factors. properties are difficult to characterize since they are only meaningful
Likewise, properties for trust relations between entities cannot be meaningfully with respect to a threat model that depends on the use case,
defined without a concrete threat model, and defining a threat model is out of application, environment, and other factors. Likewise, properties for
scope for this document. trust relations between entities cannot be meaningfully defined without
Properties related to confidentiality, integrity, and trust seem to be orthogona a concrete threat model, and defining a threat model is out of scope for
l to the path terminology and path properties defined in this document, since th this document. Properties related to confidentiality, integrity, and
ey are tied to the communicating nodes and the protocols they use (e.g., client trust seem to be orthogonal to the path terminology and path properties
and server using HTTPS, or client and remote network node using a VPN service) a defined in this document, since they are tied to the communicating nodes
s well as additional context, such as keying material and who has access to such and the protocols they use (e.g., client and server using HTTPS, or
a context. In contrast, the path as defined in this document is typically obliv client and remote network node using a VPN service) as well as
ious to these aspects. additional context, such as keying material and who has access to such a
Intuitively, the path describes what function the network applies to packets, wh context. In contrast, the path as defined in this document is typically
ile confidentiality, integrity, and trust describe what function the communicati oblivious to these aspects. Intuitively, the path describes what
ng parties apply to packets.</t> function the network applies to packets, while confidentiality,
integrity, and trust describe what function the communicating parties
apply to packets.</t>
</section> </section>
<section anchor="iana-considerations" numbered="true" toc="default"> <section anchor="iana-considerations" numbered="true" toc="default">
<name>IANA Considerations</name> <name>IANA Considerations</name>
<t>This document has no IANA actions.</t> <t>This document has no IANA actions.</t>
</section> </section>
</middle> </middle>
<back> <back>
<references>
<name>Informative References</name>
<reference anchor="I-D.ietf-idr-performance-routing">
<front>
<title>Performance-based BGP Routing Mechanism</title>
<author fullname="Xiaohu Xu" initials="X." surname="Xu">
<organization>Alibaba, Inc</organization>
</author>
<author fullname="Shraddha Hegde" initials="S." surname="Hegde">
<organization>Juniper</organization>
</author>
<author fullname="Ketan Talaulikar" initials="K." surname="Talaulikar"
>
<organization>Cisco</organization>
</author>
<author fullname="Mohamed Boucadair" initials="M." surname="Boucadair"
>
<organization>France Telecom</organization>
</author>
<author fullname="Christian Jacquenet" initials="C." surname="Jacquene
t">
<organization>France Telecom</organization>
</author>
<date day="22" month="December" year="2020"/>
<abstract>
<t> The current BGP specification doesn't use network performance
metrics
(e.g., network latency) in the route selection decision process.
This document describes a performance-based BGP routing mechanism in
which network latency metric is taken as one of the route selection
criteria. This routing mechanism is useful for those server
providers with global reach to deliver low-latency network
connectivity services to their customers.
</t> <displayreference target="I-D.ietf-idr-performance-routing" to="PERFORMANCE-ROUT
</abstract> ING"/>
</front> <displayreference target="I-D.ietf-teas-ietf-network-slices" to="NETWORK-SLICES"
<seriesInfo name="Internet-Draft" value="draft-ietf-idr-performance-rout />
ing-03"/>
</reference>
<reference anchor="I-D.ietf-alto-path-vector">
<front>
<title>An Extension for Application-Layer Traffic Optimization (ALTO):
Path Vector</title>
<author fullname="Kai Gao" initials="K." surname="Gao">
<organization>Sichuan University</organization>
</author>
<author fullname="Young Lee" initials="Y." surname="Lee">
<organization>Samsung</organization>
</author>
<author fullname="Sabine Randriamasy" initials="S." surname="Randriama
sy">
<organization>Nokia Bell Labs</organization>
</author>
<author fullname="Y. Richard Yang" initials="Y. R." surname="Yang">
<organization>Yale University</organization>
</author>
<author fullname="Jingxuan Zhang" initials="J." surname="Zhang">
<organization>Tongji University</organization>
</author>
<date day="20" month="March" year="2022"/>
<abstract>
<t>This document is an extension to the base Application-Layer Traff
ic Optimization (ALTO) protocol. It extends the ALTO cost map and ALTO property
map services so that an application can decide to which endpoint(s) to connect
based not only on numerical/ordinal cost values but also on fine-grained abstrac
t information regarding the paths. This is useful for applications whose perfor
mance is impacted by specific components of a network on the end-to-end paths, e
.g., they may infer that several paths share common links and prevent traffic bo
ttlenecks by avoiding such paths. This extension introduces a new abstraction c
alled the "Abstract Network Element" (ANE) to represent these components and enc
odes a network path as a vector of ANEs. Thus, it provides a more complete but
still abstract graph representation of the underlying network(s) for informed tr
affic optimization among endpoints.
</t>
</abstract>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-alto-path-vector-25"
/>
</reference>
<reference anchor="I-D.ietf-alto-performance-metrics">
<front>
<title>ALTO Performance Cost Metrics</title>
<author fullname="Qin Wu" initials="Q." surname="Wu">
<organization>Huawei</organization>
</author>
<author fullname="Y. Richard Yang" initials="Y. R." surname="Yang">
<organization>Yale University</organization>
</author>
<author fullname="Young Lee" initials="Y." surname="Lee">
<organization>Samsung</organization>
</author>
<author fullname="Dhruv Dhody" initials="D." surname="Dhody">
<organization>Huawei</organization>
</author>
<author fullname="Sabine Randriamasy" initials="S." surname="Randriama
sy">
<organization>Nokia Bell Labs</organization>
</author>
<author fullname="Luis M. Contreras" initials="L. M." surname="Contrer
as">
<organization>Telefonica</organization>
</author>
<date day="21" month="March" year="2022"/>
<abstract>
<t> The cost metric is a basic concept in Application-Layer Traffi
c
Optimization (ALTO), and different applications may use different
types of cost metrics. Since the ALTO base protocol (RFC 7285)
defines only a single cost metric (namely, the generic "routingcost"
metric), if an application wants to issue a cost map or an endpoint
cost request in order to identify a resource provider that offers
better performance metrics (e.g., lower delay or loss rate), the base
protocol does not define the cost metric to be used.
This document addresses this issue by extending the specification to <references>
provide a variety of network performance metrics, including network <name>Informative References</name>
delay, delay variation (a.k.a, jitter), packet loss rate, hop count,
and bandwidth.
There are multiple sources (e.g., estimation based on measurements or <reference anchor="I-D.ietf-idr-performance-routing" target="https://datatracker
service-level agreement) to derive a performance metric. This .ietf.org/doc/html/draft-ietf-idr-performance-routing-03">
document introduces an additional "cost-context" field to the ALTO <front>
"cost-type" field to convey the source of a performance metric. <title>Performance-based BGP Routing Mechanism</title>
<author initials="X." surname="Xu" fullname="Xiaohu Xu">
<organization>Alibaba, Inc</organization>
</author>
<author initials="S." surname="Hegde" fullname="Shraddha Hegde">
<organization>Juniper</organization>
</author>
<author initials="K." surname="Talaulikar" fullname="Ketan Talaulikar">
<organization>Cisco</organization>
</author>
<author initials="M." surname="Boucadair" fullname="Mohamed Boucadair">
<organization>France Telecom</organization>
</author>
<author initials="C." surname="Jacquenet" fullname="Christian Jacquenet">
<organization>France Telecom</organization>
</author>
<date month="December" day="21" year="2020"/>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-idr-performance-routing-03"/
>
</reference>
</t> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9275.xml"
</abstract> />
</front> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9439.xml"
<seriesInfo name="Internet-Draft" value="draft-ietf-alto-performance-met />
rics-28"/>
</reference>
<reference anchor="I-D.ietf-teas-ietf-network-slices">
<front>
<title>A Framework for IETF Network Slices</title>
<author fullname="Adrian Farrel" initials="A." surname="Farrel">
<organization>Old Dog Consulting</organization>
</author>
<author fullname="John Drake" initials="J." surname="Drake">
<organization>Juniper Networks</organization>
</author>
<author fullname="Reza Rokui" initials="R." surname="Rokui">
<organization>Ciena</organization>
</author>
<author fullname="Shunsuke Homma" initials="S." surname="Homma">
<organization>NTT</organization>
</author>
<author fullname="Kiran Makhijani" initials="K." surname="Makhijani">
<organization>Futurewei</organization>
</author>
<author fullname="Luis M. Contreras" initials="L. M." surname="Contrer
as">
<organization>Telefonica</organization>
</author>
<author fullname="Jeff Tantsura" initials="J." surname="Tantsura">
<organization>Microsoft Inc.</organization>
</author>
<date day="21" month="January" year="2023"/>
<abstract>
<t> This document describes network slicing in the context of netw
orks
built from IETF technologies. It defines the term "IETF Network
Slice" and establishes the general principles of network slicing in
the IETF context.
The document discusses the general framework for requesting and <reference anchor="I-D.ietf-teas-ietf-network-slices"
operating IETF Network Slices, the characteristics of an IETF Network target="https://datatracker.ietf.org/doc/html/draft-ietf-teas-ietf-network-slice
Slice, the necessary system components and interfaces, and how s-22">
abstract requests can be mapped to more specific technologies. The <front>
document also discusses related considerations with monitoring and <title>A Framework for IETF Network Slices</title>
security. <author initials="A." surname="Farrel" fullname="Adrian Farrel" role="editor">
<organization>Old Dog Consulting</organization>
</author>
<author initials="J." surname="Drake" fullname="John Drake" role="editor">
<organization>Juniper Networks</organization>
</author>
<author initials="R." surname="Rokui" fullname="Reza Rokui">
<organization>Ciena</organization>
</author>
<author initials="S." surname="Homma" fullname="Shunsuke Homma">
<organization>NTT</organization>
</author>
<author initials="K." surname="Makhijani" fullname="Kiran Makhijani">
<organization>Futurewei</organization>
</author>
<author initials="L. M." surname="Contreras" fullname="Luis M. Contreras">
<organization>Telefonica</organization>
</author>
<author initials="J." surname="Tantsura" fullname="Jeff Tantsura">
<organization>Nvidia</organization>
</author>
<date month="August" year="2023"/>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-teas-ietf-network-slices-22"
/>
</reference>
This document also provides definitions of related terms to enable <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.1930.xml"
consistent usage in other IETF documents that describe or use aspects />
of IETF Network Slices. <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.3357.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.3393.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.4271.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.5136.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.5693.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6534.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7665.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7679.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7680.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8175.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8548.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8558.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8684.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8803.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9000.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9097.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9110.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9217.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9298.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.1122.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.1940.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.2784.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7676.xml"
/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9049.xml"
/>
</t>
</abstract>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-teas-ietf-network-sl
ices-19"/>
</reference>
<reference anchor="RFC1930">
<front>
<title>Guidelines for creation, selection, and registration of an Auto
nomous System (AS)</title>
<author fullname="J. Hawkinson" initials="J." surname="Hawkinson">
<organization/>
</author>
<author fullname="T. Bates" initials="T." surname="Bates">
<organization/>
</author>
<date month="March" year="1996"/>
<abstract>
<t>This memo discusses when it is appropriate to register and utiliz
e an Autonomous System (AS), and lists criteria for such. This document specifi
es an Internet Best Current Practices for the Internet Community, and requests d
iscussion and suggestions for improvements.</t>
</abstract>
</front>
<seriesInfo name="BCP" value="6"/>
<seriesInfo name="RFC" value="1930"/>
<seriesInfo name="DOI" value="10.17487/RFC1930"/>
</reference>
<reference anchor="RFC2616">
<front>
<title>Hypertext Transfer Protocol -- HTTP/1.1</title>
<author fullname="R. Fielding" initials="R." surname="Fielding">
<organization/>
</author>
<author fullname="J. Gettys" initials="J." surname="Gettys">
<organization/>
</author>
<author fullname="J. Mogul" initials="J." surname="Mogul">
<organization/>
</author>
<author fullname="H. Frystyk" initials="H." surname="Frystyk">
<organization/>
</author>
<author fullname="L. Masinter" initials="L." surname="Masinter">
<organization/>
</author>
<author fullname="P. Leach" initials="P." surname="Leach">
<organization/>
</author>
<author fullname="T. Berners-Lee" initials="T." surname="Berners-Lee">
<organization/>
</author>
<date month="June" year="1999"/>
<abstract>
<t>HTTP has been in use by the World-Wide Web global information ini
tiative since 1990. This specification defines the protocol referred to as "HTTP
/1.1", and is an update to RFC 2068. [STANDARDS-TRACK]</t>
</abstract>
</front>
<seriesInfo name="RFC" value="2616"/>
<seriesInfo name="DOI" value="10.17487/RFC2616"/>
</reference>
<reference anchor="RFC3357">
<front>
<title>One-way Loss Pattern Sample Metrics</title>
<author fullname="R. Koodli" initials="R." surname="Koodli">
<organization/>
</author>
<author fullname="R. Ravikanth" initials="R." surname="Ravikanth">
<organization/>
</author>
<date month="August" year="2002"/>
</front>
<seriesInfo name="RFC" value="3357"/>
<seriesInfo name="DOI" value="10.17487/RFC3357"/>
</reference>
<reference anchor="RFC3393">
<front>
<title>IP Packet Delay Variation Metric for IP Performance Metrics (IP
PM)</title>
<author fullname="C. Demichelis" initials="C." surname="Demichelis">
<organization/>
</author>
<author fullname="P. Chimento" initials="P." surname="Chimento">
<organization/>
</author>
<date month="November" year="2002"/>
</front>
<seriesInfo name="RFC" value="3393"/>
<seriesInfo name="DOI" value="10.17487/RFC3393"/>
</reference>
<reference anchor="RFC4271">
<front>
<title>A Border Gateway Protocol 4 (BGP-4)</title>
<author fullname="Y. Rekhter" initials="Y." role="editor" surname="Rek
hter">
<organization/>
</author>
<author fullname="T. Li" initials="T." role="editor" surname="Li">
<organization/>
</author>
<author fullname="S. Hares" initials="S." role="editor" surname="Hares
">
<organization/>
</author>
<date month="January" year="2006"/>
<abstract>
<t>This document discusses the Border Gateway Protocol (BGP), which
is an inter-Autonomous System routing protocol.</t>
<t>The primary function of a BGP speaking system is to exchange netw
ork reachability information with other BGP systems. This network reachability
information includes information on the list of Autonomous Systems (ASes) that r
eachability information traverses. This information is sufficient for constructi
ng a graph of AS connectivity for this reachability from which routing loops may
be pruned, and, at the AS level, some policy decisions may be enforced.</t>
<t>BGP-4 provides a set of mechanisms for supporting Classless Inter
-Domain Routing (CIDR). These mechanisms include support for advertising a set
of destinations as an IP prefix, and eliminating the concept of network "class"
within BGP. BGP-4 also introduces mechanisms that allow aggregation of routes,
including aggregation of AS paths.</t>
<t>This document obsoletes RFC 1771. [STANDARDS-TRACK]</t>
</abstract>
</front>
<seriesInfo name="RFC" value="4271"/>
<seriesInfo name="DOI" value="10.17487/RFC4271"/>
</reference>
<reference anchor="RFC5136">
<front>
<title>Defining Network Capacity</title>
<author fullname="P. Chimento" initials="P." surname="Chimento">
<organization/>
</author>
<author fullname="J. Ishac" initials="J." surname="Ishac">
<organization/>
</author>
<date month="February" year="2008"/>
<abstract>
<t>Measuring capacity is a task that sounds simple, but in reality c
an be quite complex. In addition, the lack of a unified nomenclature on this su
bject makes it increasingly difficult to properly build, test, and use technique
s and tools built around these constructs. This document provides definitions f
or the terms 'Capacity' and 'Available Capacity' related to IP traffic traveling
between a source and destination in an IP network. By doing so, we hope to pro
vide a common framework for the discussion and analysis of a diverse set of curr
ent and future estimation techniques. This memo provides information for the In
ternet community.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="5136"/>
<seriesInfo name="DOI" value="10.17487/RFC5136"/>
</reference>
<reference anchor="RFC5693">
<front>
<title>Application-Layer Traffic Optimization (ALTO) Problem Statement
</title>
<author fullname="J. Seedorf" initials="J." surname="Seedorf">
<organization/>
</author>
<author fullname="E. Burger" initials="E." surname="Burger">
<organization/>
</author>
<date month="October" year="2009"/>
<abstract>
<t>Distributed applications -- such as file sharing, real-time commu
nication, and live and on-demand media streaming -- prevalent on the Internet us
e a significant amount of network resources. Such applications often transfer l
arge amounts of data through connections established between nodes distributed a
cross the Internet with little knowledge of the underlying network topology. So
me applications are so designed that they choose a random subset of peers from a
larger set with which to exchange data. Absent any topology information guidin
g such choices, or acting on suboptimal or local information obtained from measu
rements and statistics, these applications often make less than desirable choice
s.</t>
<t>This document discusses issues related to an information-sharing
service that enables applications to perform better-than-random peer selection.
This memo provides information for the Internet community.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="5693"/>
<seriesInfo name="DOI" value="10.17487/RFC5693"/>
</reference>
<reference anchor="RFC6534">
<front>
<title>Loss Episode Metrics for IP Performance Metrics (IPPM)</title>
<author fullname="N. Duffield" initials="N." surname="Duffield">
<organization/>
</author>
<author fullname="A. Morton" initials="A." surname="Morton">
<organization/>
</author>
<author fullname="J. Sommers" initials="J." surname="Sommers">
<organization/>
</author>
<date month="May" year="2012"/>
<abstract>
<t>The IETF has developed a one-way packet loss metric that measures
the loss rate on a Poisson and Periodic probe streams between two hosts. Howeve
r, the impact of packet loss on applications is, in general, sensitive not just
to the average loss rate but also to the way in which packet losses are distribu
ted in loss episodes (i.e., maximal sets of consecutively lost probe packets).
This document defines one-way packet loss episode metrics, specifically, the fre
quency and average duration of loss episodes and a probing methodology under whi
ch the loss episode metrics are to be measured. [STANDARDS-TRACK]</t>
</abstract>
</front>
<seriesInfo name="RFC" value="6534"/>
<seriesInfo name="DOI" value="10.17487/RFC6534"/>
</reference>
<reference anchor="RFC7665">
<front>
<title>Service Function Chaining (SFC) Architecture</title>
<author fullname="J. Halpern" initials="J." role="editor" surname="Hal
pern">
<organization/>
</author>
<author fullname="C. Pignataro" initials="C." role="editor" surname="P
ignataro">
<organization/>
</author>
<date month="October" year="2015"/>
<abstract>
<t>This document describes an architecture for the specification, cr
eation, and ongoing maintenance of Service Function Chains (SFCs) in a network.
It includes architectural concepts, principles, and components used in the cons
truction of composite services through deployment of SFCs, with a focus on those
to be standardized in the IETF. This document does not propose solutions, prot
ocols, or extensions to existing protocols.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="7665"/>
<seriesInfo name="DOI" value="10.17487/RFC7665"/>
</reference>
<reference anchor="RFC7679">
<front>
<title>A One-Way Delay Metric for IP Performance Metrics (IPPM)</title
>
<author fullname="G. Almes" initials="G." surname="Almes">
<organization/>
</author>
<author fullname="S. Kalidindi" initials="S." surname="Kalidindi">
<organization/>
</author>
<author fullname="M. Zekauskas" initials="M." surname="Zekauskas">
<organization/>
</author>
<author fullname="A. Morton" initials="A." role="editor" surname="Mort
on">
<organization/>
</author>
<date month="January" year="2016"/>
<abstract>
<t>This memo defines a metric for one-way delay of packets across In
ternet paths. It builds on notions introduced and discussed in the IP Performan
ce Metrics (IPPM) Framework document, RFC 2330; the reader is assumed to be fami
liar with that document. This memo makes RFC 2679 obsolete.</t>
</abstract>
</front>
<seriesInfo name="STD" value="81"/>
<seriesInfo name="RFC" value="7679"/>
<seriesInfo name="DOI" value="10.17487/RFC7679"/>
</reference>
<reference anchor="RFC7680">
<front>
<title>A One-Way Loss Metric for IP Performance Metrics (IPPM)</title>
<author fullname="G. Almes" initials="G." surname="Almes">
<organization/>
</author>
<author fullname="S. Kalidindi" initials="S." surname="Kalidindi">
<organization/>
</author>
<author fullname="M. Zekauskas" initials="M." surname="Zekauskas">
<organization/>
</author>
<author fullname="A. Morton" initials="A." role="editor" surname="Mort
on">
<organization/>
</author>
<date month="January" year="2016"/>
<abstract>
<t>This memo defines a metric for one-way loss of packets across Int
ernet paths. It builds on notions introduced and discussed in the IP Performanc
e Metrics (IPPM) Framework document, RFC 2330; the reader is assumed to be famil
iar with that document. This memo makes RFC 2680 obsolete.</t>
</abstract>
</front>
<seriesInfo name="STD" value="82"/>
<seriesInfo name="RFC" value="7680"/>
<seriesInfo name="DOI" value="10.17487/RFC7680"/>
</reference>
<reference anchor="RFC8175">
<front>
<title>Dynamic Link Exchange Protocol (DLEP)</title>
<author fullname="S. Ratliff" initials="S." surname="Ratliff">
<organization/>
</author>
<author fullname="S. Jury" initials="S." surname="Jury">
<organization/>
</author>
<author fullname="D. Satterwhite" initials="D." surname="Satterwhite">
<organization/>
</author>
<author fullname="R. Taylor" initials="R." surname="Taylor">
<organization/>
</author>
<author fullname="B. Berry" initials="B." surname="Berry">
<organization/>
</author>
<date month="June" year="2017"/>
<abstract>
<t>When routing devices rely on modems to effect communications over
wireless links, they need timely and accurate knowledge of the characteristics
of the link (speed, state, etc.) in order to make routing decisions. In mobile
or other environments where these characteristics change frequently, manual conf
igurations or the inference of state through routing or transport protocols does
not allow the router to make the best decisions. This document introduces a ne
w protocol called the Dynamic Link Exchange Protocol (DLEP), which provides a bi
directional, event-driven communication channel between the router and the modem
to facilitate communication of changing link characteristics.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="8175"/>
<seriesInfo name="DOI" value="10.17487/RFC8175"/>
</reference>
<reference anchor="RFC8547">
<front>
<title>TCP-ENO: Encryption Negotiation Option</title>
<author fullname="A. Bittau" initials="A." surname="Bittau">
<organization/>
</author>
<author fullname="D. Giffin" initials="D." surname="Giffin">
<organization/>
</author>
<author fullname="M. Handley" initials="M." surname="Handley">
<organization/>
</author>
<author fullname="D. Mazieres" initials="D." surname="Mazieres">
<organization/>
</author>
<author fullname="E. Smith" initials="E." surname="Smith">
<organization/>
</author>
<date month="May" year="2019"/>
<abstract>
<t>Despite growing adoption of TLS, a significant fraction of TCP tr
affic on the Internet remains unencrypted. The persistence of unencrypted traff
ic can be attributed to at least two factors. First, some legacy protocols lack
a signaling mechanism (such as a STARTTLS command) by which to convey support fo
r encryption, thus making incremental deployment impossible. Second, legacy app
lications themselves cannot always be upgraded and therefore require a way to im
plement encryption transparently entirely within the transport layer. The TCP E
ncryption Negotiation Option (TCP-ENO) addresses both of these problems through
a new TCP option kind providing out-of-band, fully backward-compatible negotiati
on of encryption.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="8547"/>
<seriesInfo name="DOI" value="10.17487/RFC8547"/>
</reference>
<reference anchor="RFC8548">
<front>
<title>Cryptographic Protection of TCP Streams (tcpcrypt)</title>
<author fullname="A. Bittau" initials="A." surname="Bittau">
<organization/>
</author>
<author fullname="D. Giffin" initials="D." surname="Giffin">
<organization/>
</author>
<author fullname="M. Handley" initials="M." surname="Handley">
<organization/>
</author>
<author fullname="D. Mazieres" initials="D." surname="Mazieres">
<organization/>
</author>
<author fullname="Q. Slack" initials="Q." surname="Slack">
<organization/>
</author>
<author fullname="E. Smith" initials="E." surname="Smith">
<organization/>
</author>
<date month="May" year="2019"/>
<abstract>
<t>This document specifies "tcpcrypt", a TCP encryption protocol des
igned for use in conjunction with the TCP Encryption Negotiation Option (TCP-ENO
). Tcpcrypt coexists with middleboxes by tolerating resegmentation, NATs, and o
ther manipulations of the TCP header. The protocol is self-contained and specif
ically tailored to TCP implementations, which often reside in kernels or other e
nvironments in which large external software dependencies can be undesirable. Be
cause the size of TCP options is limited, the protocol requires one additional o
ne-way message latency to perform key exchange before application data can be tr
ansmitted. However, the extra latency can be avoided between two hosts that hav
e recently established a previous tcpcrypt connection.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="8548"/>
<seriesInfo name="DOI" value="10.17487/RFC8548"/>
</reference>
<reference anchor="RFC8558">
<front>
<title>Transport Protocol Path Signals</title>
<author fullname="T. Hardie" initials="T." role="editor" surname="Hard
ie">
<organization/>
</author>
<date month="April" year="2019"/>
<abstract>
<t>This document discusses the nature of signals seen by on-path ele
ments examining transport protocols, contrasting implicit and explicit signals.
For example, TCP's state machine uses a series of well-known messages that are
exchanged in the clear. Because these are visible to network elements on the pa
th between the two nodes setting up the transport connection, they are often use
d as signals by those network elements. In transports that do not exchange thes
e messages in the clear, on-path network elements lack those signals. Often, the
removal of those signals is intended by those moving the messages to confidenti
al channels. Where the endpoints desire that network elements along the path re
ceive these signals, this document recommends explicit signals be used.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="8558"/>
<seriesInfo name="DOI" value="10.17487/RFC8558"/>
</reference>
<reference anchor="RFC8684">
<front>
<title>TCP Extensions for Multipath Operation with Multiple Addresses<
/title>
<author fullname="A. Ford" initials="A." surname="Ford">
<organization/>
</author>
<author fullname="C. Raiciu" initials="C." surname="Raiciu">
<organization/>
</author>
<author fullname="M. Handley" initials="M." surname="Handley">
<organization/>
</author>
<author fullname="O. Bonaventure" initials="O." surname="Bonaventure">
<organization/>
</author>
<author fullname="C. Paasch" initials="C." surname="Paasch">
<organization/>
</author>
<date month="March" year="2020"/>
<abstract>
<t>TCP/IP communication is currently restricted to a single path per
connection, yet multiple paths often exist between peers. The simultaneous use
of these multiple paths for a TCP/IP session would improve resource usage within
the network and thus improve user experience through higher throughput and impr
oved resilience to network failure.</t>
<t>Multipath TCP provides the ability to simultaneously use multiple
paths between peers. This document presents a set of extensions to traditional
TCP to support multipath operation. The protocol offers the same type of service
to applications as TCP (i.e., a reliable bytestream), and it provides the compo
nents necessary to establish and use multiple TCP flows across potentially disjo
int paths.</t>
<t>This document specifies v1 of Multipath TCP, obsoleting v0 as spe
cified in RFC 6824, through clarifications and modifications primarily driven by
deployment experience.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="8684"/>
<seriesInfo name="DOI" value="10.17487/RFC8684"/>
</reference>
<reference anchor="RFC8803">
<front>
<title>0-RTT TCP Convert Protocol</title>
<author fullname="O. Bonaventure" initials="O." role="editor" surname=
"Bonaventure">
<organization/>
</author>
<author fullname="M. Boucadair" initials="M." role="editor" surname="B
oucadair">
<organization/>
</author>
<author fullname="S. Gundavelli" initials="S." surname="Gundavelli">
<organization/>
</author>
<author fullname="S. Seo" initials="S." surname="Seo">
<organization/>
</author>
<author fullname="B. Hesmans" initials="B." surname="Hesmans">
<organization/>
</author>
<date month="July" year="2020"/>
<abstract>
<t>This document specifies an application proxy, called Transport Co
nverter, to assist the deployment of TCP extensions such as Multipath TCP. A Tra
nsport Converter may provide conversion service for one or more TCP extensions.
The conversion service is provided by means of the 0-RTT TCP Convert Protocol (C
onvert).</t>
<t>This protocol provides 0-RTT (Zero Round-Trip Time) conversion se
rvice since no extra delay is induced by the protocol compared to connections th
at are not proxied. Also, the Convert Protocol does not require any encapsulatio
n (no tunnels whatsoever).</t>
<t>This specification assumes an explicit model, where the Transport
Converter is explicitly configured on hosts. As a sample applicability use case
, this document specifies how the Convert Protocol applies for Multipath TCP.</t
>
</abstract>
</front>
<seriesInfo name="RFC" value="8803"/>
<seriesInfo name="DOI" value="10.17487/RFC8803"/>
</reference>
<reference anchor="RFC9000">
<front>
<title>QUIC: A UDP-Based Multiplexed and Secure Transport</title>
<author fullname="J. Iyengar" initials="J." role="editor" surname="Iye
ngar">
<organization/>
</author>
<author fullname="M. Thomson" initials="M." role="editor" surname="Tho
mson">
<organization/>
</author>
<date month="May" year="2021"/>
<abstract>
<t>This document defines the core of the QUIC transport protocol. Q
UIC provides applications with flow-controlled streams for structured communicat
ion, low-latency connection establishment, and network path migration. QUIC incl
udes security measures that ensure confidentiality, integrity, and availability
in a range of deployment circumstances. Accompanying documents describe the int
egration of TLS for key negotiation, loss detection, and an exemplary congestion
control algorithm.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="9000"/>
<seriesInfo name="DOI" value="10.17487/RFC9000"/>
</reference>
<reference anchor="RFC9097">
<front>
<title>Metrics and Methods for One-Way IP Capacity</title>
<author fullname="A. Morton" initials="A." surname="Morton">
<organization/>
</author>
<author fullname="R. Geib" initials="R." surname="Geib">
<organization/>
</author>
<author fullname="L. Ciavattone" initials="L." surname="Ciavattone">
<organization/>
</author>
<date month="November" year="2021"/>
<abstract>
<t>This memo revisits the problem of Network Capacity Metrics first
examined in RFC 5136. This memo specifies a more practical Maximum IP-Layer Capa
city Metric definition catering to measurement and outlines the corresponding Me
thods of Measurement.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="9097"/>
<seriesInfo name="DOI" value="10.17487/RFC9097"/>
</reference>
<reference anchor="RFC9217">
<front>
<title>Current Open Questions in Path-Aware Networking</title>
<author fullname="B. Trammell" initials="B." surname="Trammell">
<organization/>
</author>
<date month="March" year="2022"/>
<abstract>
<t>In contrast to the present Internet architecture, a path-aware in
ternetworking architecture has two important properties: it exposes the properti
es of available Internet paths to endpoints, and it provides for endpoints and a
pplications to use these properties to select paths through the Internet for the
ir traffic. While this property of "path awareness" already exists in many Inter
net-connected networks within single domains and via administrative interfaces t
o the network layer, a fully path-aware internetwork expands these concepts acro
ss layers and across the Internet.</t>
<t>This document poses questions in path-aware networking, open as o
f 2021, that must be answered in the design, development, and deployment of path
-aware internetworks. It was originally written to frame discussions in the Path
Aware Networking Research Group (PANRG), and has been published to snapshot cur
rent thinking in this space.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="9217"/>
<seriesInfo name="DOI" value="10.17487/RFC9217"/>
</reference>
<reference anchor="RFC9298">
<front>
<title>Proxying UDP in HTTP</title>
<author fullname="D. Schinazi" initials="D." surname="Schinazi">
<organization/>
</author>
<date month="August" year="2022"/>
<abstract>
<t>This document describes how to proxy UDP in HTTP, similar to how
the HTTP CONNECT method allows proxying TCP in HTTP. More specifically, this doc
ument defines a protocol that allows an HTTP client to create a tunnel for UDP c
ommunications through an HTTP server that acts as a proxy.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="9298"/>
<seriesInfo name="DOI" value="10.17487/RFC9298"/>
</reference>
<reference anchor="RFC1122">
<front>
<title>Requirements for Internet Hosts - Communication Layers</title>
<author fullname="R. Braden" initials="R." role="editor" surname="Brad
en">
<organization/>
</author>
<date month="October" year="1989"/>
<abstract>
<t>This RFC is an official specification for the Internet community.
It incorporates by reference, amends, corrects, and supplements the primary pr
otocol standards documents relating to hosts. [STANDARDS-TRACK]</t>
</abstract>
</front>
<seriesInfo name="STD" value="3"/>
<seriesInfo name="RFC" value="1122"/>
<seriesInfo name="DOI" value="10.17487/RFC1122"/>
</reference>
<reference anchor="RFC1940">
<front>
<title>Source Demand Routing: Packet Format and Forwarding Specificati
on (Version 1)</title>
<author fullname="D. Estrin" initials="D." surname="Estrin">
<organization/>
</author>
<author fullname="T. Li" initials="T." surname="Li">
<organization/>
</author>
<author fullname="Y. Rekhter" initials="Y." surname="Rekhter">
<organization/>
</author>
<author fullname="K. Varadhan" initials="K." surname="Varadhan">
<organization/>
</author>
<author fullname="D. Zappala" initials="D." surname="Zappala">
<organization/>
</author>
<date month="May" year="1996"/>
<abstract>
<t>The purpose of SDRP is to support source-initiated selection of r
outes to complement the route selection provided by existing routing protocols f
or both inter-domain and intra-domain routes. This memo provides information fo
r the Internet community. This memo does not specify an Internet standard of an
y kind.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="1940"/>
<seriesInfo name="DOI" value="10.17487/RFC1940"/>
</reference>
<reference anchor="RFC2784">
<front>
<title>Generic Routing Encapsulation (GRE)</title>
<author fullname="D. Farinacci" initials="D." surname="Farinacci">
<organization/>
</author>
<author fullname="T. Li" initials="T." surname="Li">
<organization/>
</author>
<author fullname="S. Hanks" initials="S." surname="Hanks">
<organization/>
</author>
<author fullname="D. Meyer" initials="D." surname="Meyer">
<organization/>
</author>
<author fullname="P. Traina" initials="P." surname="Traina">
<organization/>
</author>
<date month="March" year="2000"/>
<abstract>
<t>This document specifies a protocol for encapsulation of an arbitr
ary network layer protocol over another arbitrary network layer protocol. [STAND
ARDS-TRACK]</t>
</abstract>
</front>
<seriesInfo name="RFC" value="2784"/>
<seriesInfo name="DOI" value="10.17487/RFC2784"/>
</reference>
<reference anchor="RFC7676">
<front>
<title>IPv6 Support for Generic Routing Encapsulation (GRE)</title>
<author fullname="C. Pignataro" initials="C." surname="Pignataro">
<organization/>
</author>
<author fullname="R. Bonica" initials="R." surname="Bonica">
<organization/>
</author>
<author fullname="S. Krishnan" initials="S." surname="Krishnan">
<organization/>
</author>
<date month="October" year="2015"/>
<abstract>
<t>Generic Routing Encapsulation (GRE) can be used to carry any netw
ork- layer payload protocol over any network-layer delivery protocol. Currently,
GRE procedures are specified for IPv4, used as either the payload or delivery p
rotocol. However, GRE procedures are not specified for IPv6.</t>
<t>This document specifies GRE procedures for IPv6, used as either t
he payload or delivery protocol.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="7676"/>
<seriesInfo name="DOI" value="10.17487/RFC7676"/>
</reference>
<reference anchor="RFC9049">
<front>
<title>Path Aware Networking: Obstacles to Deployment (A Bestiary of R
oads Not Taken)</title>
<author fullname="S. Dawkins" initials="S." role="editor" surname="Daw
kins">
<organization/>
</author>
<date month="June" year="2021"/>
<abstract>
<t>This document is a product of the Path Aware Networking Research
Group (PANRG). At the first meeting of the PANRG, the Research Group agreed to
catalog and analyze past efforts to develop and deploy Path Aware techniques, mo
st of which were unsuccessful or at most partially successful, in order to extra
ct insights and lessons for Path Aware networking researchers.</t>
<t>This document contains that catalog and analysis.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="9049"/>
<seriesInfo name="DOI" value="10.17487/RFC9049"/>
</reference>
</references> </references>
<section numbered="false" anchor="acknowledgments" toc="default"> <section numbered="false" anchor="acknowledgments" toc="default">
<name>Acknowledgments</name> <name>Acknowledgments</name>
<t>Thanks to the Path-Aware Networking Research Group for the discussion a <t>Thanks to the Path Aware Networking Research Group for the discussion
nd feedback. Specifically, thanks to Mohamed Boucadair for the detailed review, and feedback. Specifically, thanks to <contact fullname="Mohamed
various text suggestions, and shepherding, thanks to Brian Trammell for suggesti Boucadair"/> for the detailed review, various text suggestions, and
ng the flow definition, and thanks to Luis M. Contreras, Spencer Dawkins, Paul H shepherding; thanks to <contact fullname="Brian Trammell"/> for
offman, Jake Holland, Colin Perkins, Adrian Perrig, and Matthias Rost for the re suggesting the flow definition; and thanks to <contact fullname="Luis
views, comments, and suggestions. Many thanks to Dave Oran for his careful IRSG M. Contreras"/>, <contact fullname="Spencer Dawkins"/>, <contact
review.</t> fullname="Paul Hoffman"/>, <contact fullname="Jake Holland"/>, <contact
fullname="Colin Perkins"/>, <contact fullname="Adrian Perrig"/>, and
<contact fullname="Matthias Rost"/> for the reviews, comments, and
suggestions. Many thanks to <contact fullname="Dave Oran"/> for his
careful IRSG review.</t>
</section> </section>
</back> </back>
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