rfc9655.original   rfc9655.txt 
Routing area D. Rathi, Ed. Internet Engineering Task Force (IETF) D. Rathi, Ed.
Internet-Draft Nokia Request for Comments: 9655 Nokia
Intended status: Standards Track S. Hegde, Ed. Category: Standards Track S. Hegde, Ed.
Expires: 14 December 2024 Juniper Networks Inc. ISSN: 2070-1721 Juniper Networks Inc.
K. Arora K. Arora
Individual Contributor Individual Contributor
Z. Ali Z. Ali
N. Nainar N. Nainar
Cisco Systems, Inc. Cisco Systems, Inc.
12 June 2024 November 2024
Egress Validation in Label Switched Path Ping and Traceroute Mechanisms Egress Validation in Label Switched Path Ping and Traceroute Mechanisms
draft-ietf-mpls-egress-tlv-for-nil-fec-15
Abstract Abstract
The MPLS ping and traceroute mechanisms, as described in [RFC8029] The MPLS ping and traceroute mechanisms described in RFC 8029 and the
and the related extensions for Segment Routing (SR) defined in related extensions for Segment Routing (SR) defined in RFC 8287 are
[RFC8287], is highly valuable for validating control plane and data highly valuable for validating control plane and data plane
plane synchronization. In certain environments, only some synchronization. In certain environments, only some intermediate or
intermediate or transit nodes may have been upgraded to support these transit nodes may have been upgraded to support these validation
validation procedures. A straightforward MPLS ping and traceroute procedures. A straightforward MPLS ping and traceroute mechanism
mechanism allows traversing any path without validating the control allows traversal of any path without validation of the control plane
plane state. [RFC8029] supports this mechanism with the Nil state. RFC 8029 supports this mechanism with the Nil Forwarding
Forwarding Equivalence Class (FEC). The procedures outlined in Equivalence Class (FEC). The procedures outlined in RFC 8029 are
[RFC8029] is primarily applicable when the Nil FEC is used as an primarily applicable when the Nil FEC is used as an intermediate FEC
intermediate FEC in the label stack. However, challenges arise when in the FEC stack. However, challenges arise when all labels in the
all labels in the label stack are represented using the Nil FEC. label stack are represented using the Nil FEC.
This document introduces a new Type-Length-Value (TLV) as an This document introduces a new Type-Length-Value (TLV) as an
extension to the existing Nil FEC. It describes MPLS ping and extension to the existing Nil FEC. It describes MPLS ping and
traceroute procedures using the Nil FEC with this extension to traceroute procedures using the Nil FEC with this extension to
address and overcome these challenges. address and overcome these challenges.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on 14 December 2024. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9655.
Copyright Notice Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/ Provisions Relating to IETF Documents
license-info) in effect on the date of publication of this document. (https://trustee.ietf.org/license-info) in effect on the date of
Please review these documents carefully, as they describe your rights publication of this document. Please review these documents
and restrictions with respect to this document. Code Components carefully, as they describe your rights and restrictions with respect
extracted from this document must include Revised BSD License text as to this document. Code Components extracted from this document must
described in Section 4.e of the Trust Legal Provisions and are include Revised BSD License text as described in Section 4.e of the
provided without warranty as described in the Revised BSD License. Trust Legal Provisions and are provided without warranty as described
in the Revised BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction
2. Problem with Nil FEC . . . . . . . . . . . . . . . . . . . . 4 1.1. Requirements Language
3. Egress TLV . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Problem with Nil FEC
4. Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Egress TLV
4.1. Sending Egress TLV in MPLS Echo Request . . . . . . . . . 6 4. Procedure
4.1.1. Ping Mode . . . . . . . . . . . . . . . . . . . . . . 6 4.1. Sending Egress TLV in MPLS Echo Request
4.1.2. Traceroute Mode . . . . . . . . . . . . . . . . . . . 7 4.1.1. Ping Mode
4.1.3. Detailed Example . . . . . . . . . . . . . . . . . . 7 4.1.2. Traceroute Mode
4.2. Receiving Egress TLV in MPLS Echo Request . . . . . . . . 8 4.1.3. Detailed Example
5. Backward Compatibility . . . . . . . . . . . . . . . . . . . 9 4.2. Receiving Egress TLV in MPLS Echo Request
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 5. Backward Compatibility
6.1. New TLV . . . . . . . . . . . . . . . . . . . . . . . . . 9 6. IANA Considerations
6.2. New Return code . . . . . . . . . . . . . . . . . . . . . 9 6.1. New TLV
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 6.2. New Return Code
8. Implementation Status . . . . . . . . . . . . . . . . . . . . 10 7. Security Considerations
8.1. Juniper Networks . . . . . . . . . . . . . . . . . . . . 10 8. References
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11 8.1. Normative References
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 8.2. Informative References
10.1. Normative References . . . . . . . . . . . . . . . . . . 11 Acknowledgements
10.2. Informative References . . . . . . . . . . . . . . . . . 12 Authors' Addresses
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction 1. Introduction
Segment routing supports the creation of explicit paths by using one Segment routing supports the creation of explicit paths by using one
or more Link State IGP Segments or BGP Segments defined in [RFC8402]. or more Link-State IGP Segments or BGP Segments defined in [RFC8402].
In certain use cases, the TE paths are built using mechanisms In certain use cases, the TE paths are built using mechanisms
described in [RFC9256] by stacking the labels that represent the described in [RFC9256] by stacking the labels that represent the
nodes and links in the explicit path. Controllers are often deployed nodes and links in the explicit path. Controllers are often deployed
to construct paths across multi-domain networks. In such to construct paths across multi-domain networks. In such
deployments, the head-end routers may have the link state database of deployments, the headend routers may have the link-state database of
its domain and may not be aware of the FEC associated with labels their domain and may not be aware of the FEC associated with labels
that are used by the controller to build paths across multiple that are used by the controller to build paths across multiple
domains. A very useful Operations, Administration, and Maintenance domains. A very useful Operations, Administration, and Maintenance
(OAM) requirement is to be able to ping and trace these paths. (OAM) requirement is to be able to ping and trace these paths.
[RFC8029] describes a simple and efficient mechanism to detect data- [RFC8029] describes a simple and efficient mechanism to detect data
plane failures in MPLS Label Switched Paths (LSPs). It defines a plane failures in MPLS Label Switched Paths (LSPs). It defines a
probe message called an "MPLS echo request" and a response message probe message called an "MPLS echo request" and a response message
called an "MPLS echo reply" for returning the result of the probe. called an "MPLS echo reply" for returning the result of the probe.
SR-related extensions to Echo Request/Echo Reply are specified in SR-related extensions for these are specified in [RFC8287].
[RFC8287]. [RFC8029] primarily provides mechanisms to validate the [RFC8029] provides mechanisms primarily to validate the data plane
data plane and, secondarily, to verify the consistency of the data and secondarily to verify the consistency of the data plane with the
plane with the control plane. It also provides the ability to control plane. It also provides the ability to traverse Equal-Cost
traverse Equal-cost Multiple Paths (ECMP) and validate each of the Multipaths (ECMPs) and validate each of the ECMP paths. The Target
ECMP paths. Target FEC Stack TLV [RFC8029] contains sub-TLVs that FEC Stack TLV [RFC8029] contains sub-TLVs that carry information
carry information about the label. This information gets validated about the label. This information gets validated on each node for
on each node for traceroute and on the egress for ping. The use of traceroute and on the egress for ping. The use of the Target FEC
Target FEC requires all nodes in the network to have implemented the Stack TLV requires all nodes in the network to have implemented the
validation procedures. All intermediate nodes may not have been validation procedures, but all intermediate nodes may not have been
upgraded to support validation procedures. In such cases, it is upgraded to support validation procedures. In such cases, it is
useful to have the ability to traverse the paths in ping/traceroute useful to have the ability to traverse the paths in ping/traceroute
mode without having to obtain the FEC for each label. mode without having to obtain the FEC for each label.
A simple MPLS Echo Request/Echo Reply mechanism allows for traversing A simple MPLS echo request/reply mechanism allows for traversing the
the SR Policy path without validating the control plane state. SR Policy path without validating the control plane state. [RFC8029]
[RFC8029] supports this mechanism with FECs like Nil FEC and Generic supports this mechanism with FECs like the Nil FEC and the Generic
FEC. However, there are challenges in reusing the Generic FEC and FECs (i.e., Generic IPv4 prefix and Generic IPv6 prefix). However,
Nil FEC for validation of SR policies [RFC9256]. Generic IPv4 prefix there are challenges in reusing the Nil FEC and Generic FECs for
and Generic IPv6 prefix FECs are used when the protocol that is validation of SR Policies [RFC9256]. The Generic IPv4 prefix and
Generic IPv6 prefix FECs are used when the protocol that is
advertising the label is unknown. The information that is carried in advertising the label is unknown. The information that is carried in
Generic FEC is the IPv4 or IPv6 prefix and prefix length. Thus the Generic FECs is the IPv4 or IPv6 prefix and prefix length. Thus,
Generic FEC types perform an additional control plane validation. the Generic FEC types perform an additional control plane validation.
However, the details of Generic FEC and validation procedures are not However, the Generic FECs and relevant validation procedures are not
very detailed in the [RFC8029]. The use-case mostly specifies inter- thoroughly detailed in [RFC8029]. The use case mostly specifies
AS VPNs as the motivation. Certain aspects of SR such as anycast inter-AS (Autonomous System) VPNs as the motivation. Certain aspects
SIDs require clear guidelines on how the validation procedure should of SR, such as anycast Segment Identifiers (SIDs), require clear
work. Also, Generic FEC may not be widely supported and if transit guidelines on how the validation procedure should work. Also, the
routers are not upgraded to support validation of Generic FEC, Generic FECs may not be widely supported, and if transit routers are
traceroute may fail. On the other hand, Nil FEC consists of the not upgraded to support validation of Generic FECs, traceroute may
label and there is no other associated FEC information. Nil FEC is fail. On the other hand, the Nil FEC consists of the label, and
used to traverse the path without validation for cases where the FEC there is no other associated FEC information. The Nil FEC is used to
is not defined or routers are not upgraded to support the FECs. traverse the path without validation for cases where the FEC is not
Thus, it can be used to check any combination of segments on any data defined or routers are not upgraded to support the FECs. Thus, it
path. The procedures described in [RFC8029] are mostly applicable can be used to check any combination of segments on any data path.
when the Nil FEC is used where the Nil FEC is intermediate in the The procedures described in [RFC8029] are mostly applicable when the
label stack. When all labels in the label-stack is represented using Nil FEC is used as an intermediate FEC in the FEC stack. Challenges
Nil FEC, it poses some challenges. arise when all labels in the label stack are represented using the
Nil FEC.
Section 2 discusses the problems associated with using Nil FEC in an Section 2 discusses the problems associated with using the Nil FEC in
MPLS ping/traceroute procedure and Section 3 and Section 4 discuss an MPLS ping/traceroute procedure, and Sections 3 and 4 discuss
simple extensions needed to solve the problem. simple extensions needed to solve the problem.
The problems and the solutions described in this document apply to The problems and the solutions described in this document apply to
MPLS data plane. SRv6 is out-of-scope for this document. the MPLS data plane. Segment Routing over IPv6 (SRv6) is out of
scope for this document.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Problem with Nil FEC 2. Problem with Nil FEC
The purpose of Nil FEC as described in [RFC8029] is to ensure hiding The purpose of the Nil FEC, as described in [RFC8029], is to ensure
of transit tunnel information and in some cases to avoid false that transit tunnel information is hidden and, in some cases, to
negatives when the FEC information is unknown. avoid false negatives when the FEC information is unknown.
This document uses a Nil FEC to represent the complete label stack in This document uses a Nil FEC to represent the complete label stack in
an MPLS Echo Request message in ping and traceroute mode. A single an MPLS echo request message in ping and traceroute mode. A single
Nil FEC is used in the MPLS Echo Request message irrespective of the Nil FEC is used in the MPLS echo request message irrespective of the
number of segments in the label stack. As described in sec 4.4.1 of number of segments in the label stack. Section 4.4.1 of [RFC8029]
[RFC8029], "If the outermost FEC of the Target FEC stack is the Nil notes:
FEC, then the node MUST skip the Target FEC validation completely."
When a router in the label-stack path receives an MPLS Echo Request | If the outermost FEC of the Target FEC stack is the Nil FEC, then
| the node MUST skip the Target FEC validation completely.
When a router in the label stack path receives an MPLS echo request
message, there is no definite way to decide whether it is the message, there is no definite way to decide whether it is the
intended egress router since Nil FEC does not carry any information intended egress router since the Nil FEC does not carry any
and no validation is performed by the router. So there is a high information and no validation is performed by the router. Thus,
possibility that the packet may be mis-forwarded to an incorrect there is a high possibility that the packet may be misforwarded to an
destination but the MPLS Echo Reply might still return success. incorrect destination but the MPLS echo reply might still return
success.
To mitigate this issue, it is necessary to include additional To mitigate this issue, it is necessary to include additional
information in the MPLS Echo Request message in both ping and information, along with the Nil FEC, in the MPLS echo request message
traceroute modes, along with the Nil FEC, to perform minimal in both ping and traceroute modes and to perform minimal validation
validation on the egress/destination router. This will enable the on the egress/destination router. This will enable the router to
router to send appropriate success and failure information to the send appropriate success and failure information to the headend
headend router of the SR Policy. This supplementary information router of the SR Policy. This supplementary information should
should assist in reporting transit router details to the headend assist in reporting transit router details to the headend router,
router, which can be utilized by an offline application to validate which can be utilized by an offline application to validate the
the traceroute path. traceroute path.
Consequently, the inclusion of egress information in the MPLS Echo Consequently, the inclusion of egress information in the MPLS echo
Request messages in ping and traceroute modes will facilitate the request messages in ping and traceroute modes will facilitate the
validation of Nil FEC on the egress router ensuring the correct validation of the Nil FEC on the egress router, ensuring the correct
destination. It can be employed to verify any combination of destination. Egress information can be employed to verify any
segments on any path without requiring upgrades to transit nodes. combination of segments on any path without requiring upgrades to
The code point used for Egress TLV is from the range 32768-65535 and transit nodes. The Egress TLV can be silently dropped if not
can be silently dropped if not recognized as per [RFC8029] and as per recognized; alternately, it may be stepped over, or an error message
clarifications from [RFC9041]. Alternately, the un-recognized TLV may be sent (per [RFC8029] and the clarifications in [RFC9041]
may be stepped over or an error message may be sent. regarding code points in the range 32768-65535).
If a transit node does not recognize the Egress TLV and chooses to If a transit node does not recognize the Egress TLV and chooses to
silently drop or step over the Egress TLV, headend will continue to silently drop or step over the Egress TLV, the headend will continue
send Egress TLV in the next echo request message and if egress to send the Egress TLV in the next echo request message, and if
recognizes the Egress TLV, egress validation will be executed at the egress recognizes the Egress TLV, egress validation will be executed
egress. If a transit node does not recognize the Egress TLV and at the egress. If a transit node does not recognize the Egress TLV
chooses to send an error message, the headend will log the message and chooses to send an error message, the headend will log the
for informational purposes and continue to send echo requests with message for informational purposes and continue to send echo requests
Egress TLV, with TTL incremented. If the egress node does not with the Egress TLV, with the TTL incremented. If the egress node
recognize the Egress TLV and chooses to silently drop or step over does not recognize the Egress TLV and chooses to silently drop or
the Egress TLV, egress validation will not be done and the ping/ step over the Egress TLV, egress validation will not be done, and the
traceroute procedure will proceed as if Egress TLV is not received. ping/traceroute procedure will proceed as if the Egress TLV were not
received.
3. Egress TLV 3. Egress TLV
The Egress TLV MAY be included in an MPLS Echo Request message. It The Egress TLV MAY be included in an MPLS echo request message. It
is an optional TLV and, if present, MUST appear before the FEC stack is an optional TLV and, if present, MUST appear before the Target FEC
TLV in the MPLS Echo Request packet. This TLV can only be used in Stack TLV in the MPLS echo request packet. This TLV can only be used
LSP ping/traceroute requests, generated by the head-end node of an in LSP ping/traceroute requests that are generated by the headend
LSP or SR policy for which verification is performed. In cases where node of an LSP or SR Policy for which verification is performed. In
multiple Nil FECs are present in the Target FEC Stack TLV, the Egress cases where multiple Nil FECs are present in the Target FEC Stack
TLV must be added corresponding to the ultimate egress of the label TLV, the Egress TLV must be added corresponding to the ultimate
stack. Explicit paths can be created using Node-SID, Adj-SID, egress of the label stack. Explicit paths can be created using Node-
Binding-SID, etc. The address field of the Egress TLV must be SID, Adj-SID, Binding SID, etc. The Address field of the Egress TLV
derived from the path egress/destination. The format is as specified must be derived from the path egress/destination. The format is as
below: specified in Figure 1.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 32771 (Egress TLV) | Length | | Type = 32771 (Egress TLV) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address (4 or 16 octets) | | Address (4 or 16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Egress TLV Figure 1: Egress TLV
Type : 32771 (Section 6.1) Type: 32771 (Section 6.1)
Length : variable based on IPV4/IPV6 address. Length excludes the
length of the Type and Length fields. Length will be 4 octets for
IPv4 and 16 octets for IPv6.
Address : This field carries a valid IPv4 address of length 4 octets Length: Variable (4 octets for IPv4 addresses and 16 octets for IPv6
or a valid IPv6 address of length 16 octets. It can be obtained from addresses). Length excludes the length of the Type and Length
the egress of the path. It corresponds to the last label in the fields.
label stack or the SR policy endpoint field
[I.D-ietf-idr-sr-policy-safi]. Address: This field carries a valid 4-octet IPv4 address or a valid
16-octet IPv6 address. The address can be obtained from the
egress of the path and corresponds to the last label in the label
stack or the SR Policy Endpoint field [SR-POLICY-BGP].
4. Procedure 4. Procedure
This section describes aspects of LSP ping and traceroute operations This section describes aspects of LSP ping and traceroute operations
that require further considerations beyond [RFC8029]. that require further considerations beyond those detailed in
[RFC8029].
4.1. Sending Egress TLV in MPLS Echo Request 4.1. Sending Egress TLV in MPLS Echo Request
As previously mentioned, when the sender node constructs an Echo As previously mentioned, when the sender node constructs an echo
Request with a Target FEC Stack TLV, the Egress TLV, if present, MUST request with a Target FEC Stack TLV, the Egress TLV, if present, MUST
appear before the Target FEC Stack TLV in the MPLS Echo Request appear before the Target FEC Stack TLV in the MPLS echo request
packet. packet.
4.1.1. Ping Mode 4.1.1. Ping Mode
When the sender node constructs an Echo Request with target FEC Stack When the sender node constructs an echo request with a Target FEC
TLV that contains a single Nil FEC corresponding to the last segment Stack TLV that contains a single Nil FEC corresponding to the last
of the SR Policy path, the sender node MUST add an Egress TLV with segment of the SR Policy path, the sender node MUST add an Egress TLV
the address obtained from the SR policy endpoint field with the address obtained from the SR Policy Endpoint field
[I.D-ietf-idr-sr-policy-safi]. The Label value in the Nil FEC MAY be [SR-POLICY-BGP]. The Label value in the Nil FEC MAY be set to zero
set to zero when a single Nil FEC is added for multiple labels in the when a single Nil FEC is added for multiple labels in the label
label stack. In case the endpoint is not specified or is equal to stack. In case the endpoint is not specified or is equal to zero
zero (Sec 8.8.1 [RFC9256]), the sender MUST use the address (Section 8.8.1 of [RFC9256]), the sender MUST use the address
corresponding to the last segment of the SR Policy in the address corresponding to the last segment of the SR Policy in the Address
field for Egress TLV. Some specific cases on how to derive the field of the Egress TLV. Some specific cases on how to derive the
address field in the Egress TLV are listed below: Address field in the Egress TLV are listed below:
a. If the last SID in the SR policy is an Adj-SID, the address * If the last SID in the SR Policy is an Adj-SID, the Address field
field in the Egress TLV is derived from the node at the remote end in the Egress TLV is derived from the node at the remote end of
of the corresponding adjacency. the corresponding adjacency.
b. If the last SID in the SR policy is a Binding SID, the address * If the last SID in the SR Policy is a Binding SID, the Address
field in the Egress TLV is derived from the last node of the path field in the Egress TLV is derived from the last node of the path
represented by the Binding SID. represented by the Binding SID.
4.1.2. Traceroute Mode 4.1.2. Traceroute Mode
When the sender node builds an Echo Request with target FEC Stack TLV When the sender node builds an echo request with a Target FEC Stack
that contains Nil FEC corresponding to the last segment of the TLV that contains a Nil FEC corresponding to the last segment of the
segment-list of the SR Policy, the sender node MUST add an Egress TLV segment list of the SR Policy, the sender node MUST add an Egress TLV
with the address obtained from the SR policy endpoint field with the address obtained from the SR Policy Endpoint field
[I.D-ietf-idr-sr-policy-safi]. [SR-POLICY-BGP].
Although there is no requirement to do so, an implementation MAY send Although there is no requirement to do so, an implementation MAY send
multiple Nil FECs if that makes it easier for the implementation. In multiple Nil FECs if that makes it easier for the implementation. If
case the SR Policy headend sends multiple Nil FECs the last one MUST the SR Policy headend sends multiple Nil FECs, the last one MUST
correspond to the Egress TLV. The Label value in the Nil FEC MAY be correspond to the Egress TLV. The Label value in the Nil FEC MAY be
set to zero for the last Nil FEC. In case the endpoint is not set to zero for the last Nil FEC. If the endpoint is not specified
specified or is equal to zero (Sec 8.8.1 [RFC9256]), the sender MUST or is equal to zero (Section 8.8.1 of [RFC9256]), the sender MUST use
use the address corresponding to the last segment endpoint of the SR the address corresponding to the last segment endpoint of the SR
Policy path i.e. ultimate egress as the address for the Egress TLV. Policy path (i.e., the ultimate egress is used as the address in the
Egress TLV).
4.1.3. Detailed Example 4.1.3. Detailed Example
----R3---- ----R3----
/ (1003) \ / (1003) \
(1001) / \(1005) (1007) (1001) / \(1005) (1007)
R1----R2(1002) R5----R6----R7(address X) R1----R2(1002) R5----R6----R7(address X)
\ / (1006) \ / (1006)
\ (1004) / \ (1004) /
----R4---- ----R4----
Figure 2: Egress TLV processing on sample topology Figure 2: Egress TLV Processing in Sample Topology
Consider the SR Policy configured on router R1, to destination X, Consider the SR Policy configured on router R1 to destination X,
configured with label-stack as 1002, 1004, 1007. Segment 1007 configured with label stack as 1002, 1004, 1007. Segment 1007
belongs to R7, which has the address X locally configured on it. belongs to R7, which has the address X locally configured on it.
Let us look at an example of a ping Echo Request message. The Echo Let us look at an example of a ping echo request message. The echo
Request message contains a Target FEC stack TLV with the Nil FEC sub- request message contains a Target FEC Stack TLV with the Nil FEC sub-
TLV. An Egress TLV is added before the Target FEC Stack TLV. The TLV. An Egress TLV is added before the Target FEC Stack TLV. The
address field contains X (corresponding to a locally configured Address field contains X (corresponding to a locally configured
address on R7). X could be an IPv4 or IPv6 address and the Length address on R7). X could be an IPv4 or IPv6 address, and the Length
field in the Egress TLV will be 4 or 16 based on the address X's field in the Egress TLV will be either 4 or 16 octets, based on the
address type. address type of address X.
Let us look at an example of an Echo Request message in a traceroute Let us look at an example of an echo request message in a traceroute
packet. The Echo Request message contains a Target FEC stack TLV packet. The echo request message contains a Target FEC Stack TLV
with the Nil FEC sub-TLV corresponding to the complete label-stack with the Nil FEC sub-TLV corresponding to the complete label stack
(1002, 1004, 1007). An Egress TLV is added before the Target FEC (1002, 1004, 1007). An Egress TLV is added before the Target FEC
Stack TLV. The address field contains X (corresponding to a locally Stack TLV. The Address field contains X (corresponding to a locally
configured address on destination R7). X could be an IPv4 or IPv6 configured address on destination R7). X could be an IPv4 or IPv6
address and the Length field in the Egress TLV will be 4 or 16 based address, and the Length field in the Egress TLV will be either 4 or
on the address X's address type. If the destination/endpoint is set 16 octets, based on the address type of address X. If the
to zero (as in the case of the color-only SR Policy) sender should destination/endpoint is set to zero (as in the case of the color-only
use the endpoint of segment 1007 (the last segment in the segment SR Policy), the sender should use the endpoint of segment 1007 (the
list) as an address for the Egress TLV. last segment in the segment list) as the address for the Egress TLV.
4.2. Receiving Egress TLV in MPLS Echo Request 4.2. Receiving Egress TLV in MPLS Echo Request
Any node that receives the MPLS Echo Request message and processes Any node that receives an MPLS echo request message and processes it
it, is referred to as the "receiver". In case of the ping procedure, is referred to as the "receiver". In the case of the ping procedure,
the actual destination/egress is the receiver. In the case of the actual destination/egress is the receiver. In the case of
traceroute, every node is a receiver. This document does not propose traceroute, every node is a receiver. This document does not propose
any change in the processing for Nil FEC as defined in [RFC8029] in any change in the processing of the Nil FEC (as defined in [RFC8029])
the Target FEC stack TLV Node that receives an MPLS echo request. in the node that receives an MPLS echo request with a Target FEC
The presence of Egress TLV does not affect the validation of Target Stack TLV. The presence of the Egress TLV does not affect the
FEC Stack sub-TLV at FEC-stack-depth if it is different than Nil FEC. validation of the Target FEC Stack sub-TLV at FEC-stack-depth if it
is different than Nil FEC.
Additional processing MUST be done for the Egress TLV on the receiver Additional processing MUST be done for the Egress TLV on the receiver
node as follows: node as follows. Note that <RSC> refers to the Return Subcode.
1. If the Label-stack-depth is greater than 0 and the Target FEC 1. If the Label-stack-depth is greater than 0 and the Target FEC
Stack sub-TLV at FEC-stack-depth is Nil FEC, set Best-return-code to Stack sub-TLV at FEC-stack-depth is Nil FEC, set Best-return-code
8 ("Label switched at stack-depth") and Best-return-subcode to Label- to 8 ("Label switched at stack-depth <RSC>") and Best-rtn-subcode
stack-depth to report transit switching in MPLS Echo Reply message. to Label-stack-depth to report transit switching in the MPLS echo
reply message.
2. If the Label-stack-depth is 0 and the Target FEC Stack sub-TLV at 2. If the Label-stack-depth is 0 and the Target FEC Stack sub-TLV at
FEC-stack-depth is Nil FEC then do the lookup for an exact match of FEC-stack-depth is Nil FEC, then do a lookup for an exact match
the Egress TLV address field to any of the locally configured of the Address field of the Egress TLV to any of the locally
interfaces or loopback addresses. configured interfaces or loopback addresses.
2a. If the Egress TLV address lookup succeeds, set Best-return-code a. If the Egress TLV address lookup succeeds, set Best-return-
to 36 ("Replying router is an egress for the address in Egress TLV code to 36 ("Replying router is an egress for the address in
for the FEC at stack depth RSC") (Section 6.2) in MPLS Echo Reply the Egress TLV for the FEC at stack depth <RSC>")
message. (Section 6.2) in the MPLS echo reply message.
2b. If the Egress TLV address lookup fails, set the Best-return-code b. If the Egress TLV address lookup fails, set the Best-return-
to 10, "Mapping for this FEC is not the given label at stack-depth code to 10 ("Mapping for this FEC is not the given label at
RSC" stack-depth <RSC>").
3. In cases where multiple Nil FECs are sent from the SR Policy 3. In cases where multiple Nil FECs are sent from the SR Policy
headend, one each corresponding to the labels in the label stack headend, one each corresponding to the labels in the label stack
along with Egress TLV, when the packet reaches the egress, the number along with the Egress TLV, when the packet reaches the egress,
of labels in the received packet (Size of stack-R) becomes zero or a the number of labels in the received packet (Size of stack-R)
label with Bottom-of-Stack bit set to 1 is processed, all Nil FEC becomes zero or a label with the Bottom-of-Stack bit set to 1 is
sub-TLVs MUST be removed and the Egress TLV MUST be validated. processed, all Nil FEC sub-TLVs MUST be removed and the Egress
TLV MUST be validated.
5. Backward Compatibility 5. Backward Compatibility
The extensions defined in this document is backward compatible with The extensions defined in this document are backward compatible with
procedures described in [RFC8029]. A Router that does not support the procedures described in [RFC8029]. A router that does not
Egress TLV, will ignore it and use current the Nil-FEC procedures support the Egress TLV will ignore it and use the Nil FEC procedures
described in [RFC8029]. described in [RFC8029].
When the egress node in the path does not support the extensions When the egress node in the path does not support the extensions
defined in this document egress validation will not be done and Best- defined in this document, egress validation will not be done, and
return-code as 3 ("Replying router is an egress for the FEC at stack- Best-return-code will be set to 3 ("Replying router is an egress for
depth") and Best-return- subcode set to stack-depth to will be set in the FEC at stack-depth <RSC>") and Best-rtn-subcode to stack-depth in
the MPLS Echo Reply message. the MPLS echo reply message.
When the transit node in the path does not support the extensions When the transit node in the path does not support the extensions
defined in this document Best-return-code as 8 ("Label switched at defined in this document, Best-return-code will be set to 8 ("Label
stack-depth") and Best-return-subcode as Label-stack-depth to report switched at stack-depth <RSC>") and Best-rtn-subcode to Label-stack-
transit switching will be set in the MPLS Echo Reply message. depth to report transit switching in the MPLS echo reply message.
6. IANA Considerations 6. IANA Considerations
The code points in section Section 6.1 and Section 6.2 have been
assigned by [IANA] by early allocation on 2023-10-05 and 2021-11-08
respectively.
6.1. New TLV 6.1. New TLV
[IANA] is requested to update the early allocation for Egress TLV in IANA has added the following entry to the "TLVs" registry within the
the "Multi-Protocol Label Switching (MPLS) Label Switched Paths "Multiprotocol Label Switching (MPLS) Label Switched Paths (LSPs)
(LSPs) Ping Parameters" in the "TLVs" sub-registry to reference this Ping Parameters" registry group [IANA-MPLS-LSP]:
document when published as an RFC.
+=======+=============+============================+ +=======+============+===========+
| Value | Description | Reference | | Type | TLV Name | Reference |
+=======+=============+============================+ +=======+============+===========+
| 32771 | Egress TLV | Section 3 of this document | | 32771 | Egress TLV | RFC 9655 |
+-------+-------------+----------------------------+ +-------+------------+-----------+
Table 1: TLVs Sub-Registry Table 1: TLVs Registry
6.2. New Return code 6.2. New Return Code
[IANA] is requested to update the early allocation of the Return Code IANA has added the following entry to the "Return Codes" registry
for "Replying router is an egress for the address in Egress TLV" in within the "Multiprotocol Label Switching (MPLS) Label Switched Paths
the "Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters" registry group [IANA-MPLS-LSP]:
(LSPs) Ping Parameters" in the "Return Codes" sub-registry to
reference this document when published as an RFC.
+=======+================================+=============+ +=======+==================================+===========+
| Value | Description | Reference | | Value | Meaning | Reference |
+=======+================================+=============+ +=======+==================================+===========+
| 36 | Replying router is an egress | Section 4.2 | | 36 | Replying router is an egress for | RFC 9655 |
| | for the address in Egress TLV | of this | | | the address in the Egress TLV | |
| | for the FEC at stack depth RSC | document | | | for the FEC at stack depth <RSC> | |
+-------+--------------------------------+-------------+ +-------+----------------------------------+-----------+
Table 2: Return code Sub-Registry Table 2: Return Codes Registry
7. Security Considerations 7. Security Considerations
This document defines additional MPLS LSP ping TLVs and follows the This document defines an additional TLV for MPLS LSP ping and
mechanisms defined in [RFC8029]. All the security considerations conforms to the mechanisms defined in [RFC8029]. All the security
defined in [RFC8287] will be applicable for this document and, in considerations defined in [RFC8287] apply to this document. This
addition, they do not impose any additional security challenges to be document does not introduce any additional security challenges to be
considered. considered.
8. Implementation Status 8. References
This section is to be removed before publishing as an RFC.
RFC-Editor: Please clean up the references cited by this section
before publication.
This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in [RFC7942].
The description of implementations in this section is intended to
assist the IETF in its decision processes in progressing drafts to
RFCs. Please note that the listing of any individual implementation
here does not imply endorsement by the IETF. Furthermore, no effort
has been spent to verify the information presented here that was
supplied by IETF contributors. This is not intended as, and must not
be construed to be, a catalog of available implementations or their
features. Readers are advised to note that other implementations may
exist.
8.1. Juniper Networks
Organization: Juniper Networks
Implementation: JUNOS
Description: Implementation for sending and validating Egress TLV
Maturity Level: Released
Coverage: Full
Contact: shraddha@juniper.net
9. Acknowledgements
The authors would like to thank Stewart Bryant, Greg Mirsky,
Alexander Vainshtein, Sanga Mitra Rajgopal, and Adrian Farrel for
their careful review and comments.
10. References
10.1. Normative References 8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N., [RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
Aldrin, S., and M. Chen, "Detecting Multiprotocol Label Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
Switched (MPLS) Data-Plane Failures", RFC 8029, Switched (MPLS) Data-Plane Failures", RFC 8029,
DOI 10.17487/RFC8029, March 2017, DOI 10.17487/RFC8029, March 2017,
skipping to change at page 12, line 5 skipping to change at line 479
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>. July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC9041] Andersson, L., Chen, M., Pignataro, C., and T. Saad, [RFC9041] Andersson, L., Chen, M., Pignataro, C., and T. Saad,
"Updating the MPLS Label Switched Paths (LSPs) Ping "Updating the MPLS Label Switched Paths (LSPs) Ping
Parameters IANA Registry", RFC 9041, DOI 10.17487/RFC9041, Parameters IANA Registry", RFC 9041, DOI 10.17487/RFC9041,
July 2021, <https://www.rfc-editor.org/info/rfc9041>. July 2021, <https://www.rfc-editor.org/info/rfc9041>.
[RFC9256] Filsfils, C., Talaulikar, K., Ed., Bogdanov, A., Mattes, [RFC9256] Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov,
P., and D. Voyer, "Segment Routing Policy Architecture", A., and P. Mattes, "Segment Routing Policy Architecture",
RFC 9256, DOI 10.17487/RFC9256, July 2020, RFC 9256, DOI 10.17487/RFC9256, July 2022,
<https://www.rfc-editor.org/info/rfc9256>. <https://www.rfc-editor.org/info/rfc9256>.
10.2. Informative References 8.2. Informative References
[I.D-ietf-idr-sr-policy-safi]
Filsfils, C., Ed., Previdi, S., Ed., Talaulikar, K.,
Mattes, P., Rosen, E., Jain, D., and S. Lin, "Advertising
Segment Routing Policies in BGP", draft-ietf-idr-sr-
policy-safi-04, work in progress, April 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-sr-
policy-safi-04>.
[IANA] IANA, "Multiprotocol Label Switching (MPLS) Label Switched [IANA-MPLS-LSP]
IANA, "Multiprotocol Label Switching (MPLS) Label Switched
Paths (LSPs) Ping Parameters", Paths (LSPs) Ping Parameters",
<http://www.iana.org/assignments/mpls-lsp-ping- <http://www.iana.org/assignments/mpls-lsp-ping-
parameters>. parameters>.
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running [SR-POLICY-BGP]
Code: The Implementation Status Section", BCP 205, Previdi, S., Filsfils, C., Talaulikar, K., Ed., Mattes,
RFC 7942, DOI 10.17487/RFC7942, July 2016, P., and D. Jain, "Advertising Segment Routing Policies in
<https://www.rfc-editor.org/info/rfc7942>. BGP", Work in Progress, Internet-Draft, draft-ietf-idr-sr-
policy-safi-10, 7 November 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-sr-
policy-safi-10>.
Acknowledgements
The authors would like to thank Stewart Bryant, Greg Mirsky,
Alexander Vainshtein, Sanga Mitra Rajgopal, and Adrian Farrel for
their careful review and comments.
Authors' Addresses Authors' Addresses
Deepti N. Rathi (editor) Deepti N. Rathi (editor)
Nokia Nokia
Manyata Embassy Business Park Manyata Embassy Business Park
Bangalore 560045 Bangalore 560045
Karnataka Karnataka
India India
Email: deepti.nirmalkumarji_rathi@nokia.com Email: deepti.nirmalkumarji_rathi@nokia.com
Shraddha Hegde (editor) Shraddha Hegde (editor)
Juniper Networks Inc. Juniper Networks Inc.
Exora Business Park Exora Business Park
Bangalore 560103 Bangalore 560103
KA Karnataka
India India
Email: shraddha@juniper.net Email: shraddha@juniper.net
Kapil Arora Kapil Arora
Individual Contributor Individual Contributor
Email: kapil.it@gmail.com Email: kapil.it@gmail.com
Zafar Ali Zafar Ali
Cisco Systems, Inc. Cisco Systems, Inc.
Email: zali@cisco.com Email: zali@cisco.com
Nagendra Kumar Nainar Nagendra Kumar Nainar
Cisco Systems, Inc. Cisco Systems, Inc.
Email: naikumar@cisco.com Email: naikumar@cisco.com
 End of changes. 70 change blocks. 
341 lines changed or deleted 306 lines changed or added

This html diff was produced by rfcdiff 1.48.