Path Monitoring System/Head-end based MPLS Ping and Traceroute in Inter-domain Segment Routing Networks
draft-ietf-mpls-spring-inter-domain-oam-12
| Document | Type | Active Internet-Draft (mpls WG) | |
|---|---|---|---|
| Authors | Shraddha Hegde , Kapil Arora , Mukul Srivastava , Samson Ninan , Nagendra Kumar Nainar | ||
| Last updated | 2024-03-20 (Latest revision 2024-02-19) | ||
| Replaces | draft-ninan-mpls-spring-inter-domain-oam | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | Proposed Standard | ||
| Formats | |||
| Reviews | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Adrian Farrel | ||
| Shepherd write-up | Show Last changed 2024-02-20 | ||
| IESG | IESG state | Publication Requested | |
| Action Holder | |||
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | Jim Guichard | ||
| Send notices to | adrian@olddog.co.uk |
draft-ietf-mpls-spring-inter-domain-oam-12
Routing area S. Hegde
Internet-Draft Juniper Networks Inc.
Intended status: Standards Track K. Arora
Expires: 22 August 2024 Individual Contributor
M. Srivastava
Juniper Networks Inc.
S. Ninan
Ciena
N. Kumar
Cisco Systems, Inc.
19 February 2024
Path Monitoring System/Head-end based MPLS Ping and Traceroute in Inter-
domain Segment Routing Networks
draft-ietf-mpls-spring-inter-domain-oam-12
Abstract
The Routing (SR) architecture leverages source routing and tunneling
paradigms and can be directly applied to the use of a Multiprotocol
Label Switching (MPLS) data plane. A network may consist of multiple
IGP domains or multiple Autonomous Systems(ASes) under the control of
the same organization. It is useful to have the Label Switched Path
(LSP) ping and traceroute procedures when an SR end-to-end path spans
across multiple ASes or domains. This document describes mechanisms
to facilitate LSP ping and traceroute in inter-AS/inter-domain SR-
MPLS networks in an efficient manner with a simple Operations,
Administration and Maintenance (OAM) protocol extension which uses
data plane forwarding alone for forwarding echo replies on transit
nodes.
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
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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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
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 22 August 2024.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Definition of Domain . . . . . . . . . . . . . . . . . . 5
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 6
2. Inter-domain Networks with Multiple IGPs . . . . . . . . . . 6
3. Reply Path TLV . . . . . . . . . . . . . . . . . . . . . . . 6
4. Segment Sub-TLV . . . . . . . . . . . . . . . . . . . . . . . 7
4.1. Type-A: SID only, in the form of MPLS Label . . . . . . . 7
4.2. Type-C: IPv4 Node Address with Optional SID for
SR-MPLS . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.3. Type D: IPv6 Node Address with Optional SID for SR
MPLS . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.4. Segment Flags . . . . . . . . . . . . . . . . . . . . . . 11
5. SRv6 Dataplane . . . . . . . . . . . . . . . . . . . . . . . 12
6. Detailed Procedures . . . . . . . . . . . . . . . . . . . . . 12
6.1. Sending an Echo Request . . . . . . . . . . . . . . . . . 12
6.2. Receiving an Echo Request . . . . . . . . . . . . . . . . 12
6.3. Sending an Echo Reply . . . . . . . . . . . . . . . . . . 13
6.4. Receiving an Echo Reply . . . . . . . . . . . . . . . . . 13
7. Detailed Example . . . . . . . . . . . . . . . . . . . . . . 14
7.1. Procedures for Segment Routing LSP ping . . . . . . . . . 14
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7.2. Procedures for Segment Routing LSP traceroute . . . . . . 15
7.2.1. Procedures for Segment Routing LSP traceroute with the
Same SRGB on All Nodes . . . . . . . . . . . . . . . 15
7.2.2. Procedures for Segment Routing LSP Traceroute with the
Different SRGBs . . . . . . . . . . . . . . . . . . . 17
8. Building Reply Path TLV Dynamically . . . . . . . . . . . . . 18
8.1. The procedures to Build the Return Path . . . . . . . . . 18
8.2. Details with Example . . . . . . . . . . . . . . . . . . 20
9. Security Considerations . . . . . . . . . . . . . . . . . . . 21
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
10.1. Segment Sub-TLV . . . . . . . . . . . . . . . . . . . . 21
10.2. New Registry for Segment Sub-TLV Flags . . . . . . . . . 22
10.3. Reply Path Return Codes Registry . . . . . . . . . . . . 22
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 22
12. Implementation Status . . . . . . . . . . . . . . . . . . . . 23
12.1. Juniper Networks . . . . . . . . . . . . . . . . . . . . 23
13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 24
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
14.1. Normative References . . . . . . . . . . . . . . . . . . 24
14.2. Informative References . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26
1. Introduction
Many network deployments have built their networks consisting of
multiple ASes either for the ease of operations or as a result of
network mergers and acquisitions. Segment Routing can be deployed in
such scenarios to provide end-to-end paths, traversing multiple
Autonomous systems(ASes). These paths consist of Segment Identifiers
(SIDs) of different types as per [RFC8402].
[RFC8660] specifies Segment Routing with an MPLS data plane.
[RFC9087] describes BGP peering SIDs, which will help in steering
packet from one AS to another. Using the above SR capabilities,
paths that span across multiple ASes can be created.
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+----------------+
| Controller/PMS |
+----------------+
|---AS1-----| |------AS2------| |----AS3---|
ASBR2----ASBR3 ASBR5------ASBR7
/ \ / \
/ \ / \
PE1----P1---P2 P3---P4---PE4 P5---P6--PE5
\ / \ /
\ / \ /
ASBR1----ASBR4 ASBR6------ASBR8
Autonomous System: AS1, AS2, AS3
Provider Edge: PE1, PE4, PE5
Provider: P1, P2, P3, P4, P5, P6
AS Boundary Router:ASBR1, ASBR2, ASBR3, ASBR4,
ASBR5, ASBR6, ASBR7, ASBR8
Figure 1: Inter-AS Segment Routing Topology
For example, Figure 1 describes an inter-AS network scenario
consisting of ASes AS1, AS2 and AS3. AS1, AS2 and AS2 are Segment
Routing enabled and the egress links have PeerNode SID/PeerAdj SID/
PeerSet SID configured and advertised via [RFC9086]. PeerNode SID/
PeerAdj SID/PeerSet SID are referred to as Egress Peer Engineering
SIDs (EPE-SIDs) in this document. The controller or the head-end can
build an end-to-end Traffic-Engineered path consisting of Node-SIDs,
Adjacency-SIDs and EPE-SIDs. It is useful for operators to be able
to perform LSP ping and traceroute procedures on these inter-AS SR-
MPLS paths, in order to detect and diagnose failed deliveries and to
determine the actual path that traffic takes through the network.
LSP ping/traceroute procedures use IP connectivity for echo reply to
reach the head-end. In inter-AS networks, IP connectivity may not be
there from each router in the path. For example, in Figure 1, P3 and
P4 may not have IP connectivity for PE1.
It is not possible to carry out LSP ping and traceroute functionality
on these paths to verify basic connectivity and fault isolation using
existing LSP ping and traceroute mechanism([RFC8287] and [RFC8029]).
That is because there might not always be IP connectivity from a
responding node back to the source address of the ping packet when
the responding node is in a different AS from the source of the ping.
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[RFC8403] describes mechanisms to carry out MPLS ping/traceroute from
a Path Monitoring System (PMS). It is possible to build GRE tunnels
or static routes to each router in the network to get IP connectivity
for the reverse path. This mechanism is operationally very heavy and
requires the PMS to be capable of building a huge number of GRE
tunnels or installing the necessary static routes, which may not be
feasible.
[RFC7743] describes an Echo-relay based solution based on advertising
a new Relay Node Address Stack TLV containing a stack of Echo-relay
IP addresses. These mechanisms can be applied to SR networks as
well. The [RFC7743] mechanism requires the return ping packet to be
processed on the slow path or as a bump-in-the-wire on every relay
node. The motivation of the current document is to provide an
alternate mechanism for ping/traceroute in inter-domain segment-
routing networks. The definition of the term "domain" as applicable
to this document is defined in Section 1.1.
This document describes a new mechanism that is efficient and simple
and can be easily deployed in SR-MPLS networks. This mechanism uses
MPLS paths and no changes are required in the forwarding path. Any
MPLS-capable node will be able to forward the echo-reply packet in
the fast path. The current document describes a mechanism that uses
the Reply Path TLV [RFC7110] to convey the reverse path. Three new
sub-TLVs are defined for the Reply path TLV that faciliate encoding
SR label stack. The return path can either be derived by a smart
application or controller which has a full topology view. This
document also proposes mechanisms to derive the return path
dynamically during traceroute procedures.
The current document is focused on the inter-domain use case.
However, the protocol extensions described in this document may be
applied to indicate the return path for other use cases as well.
1.1. Definition of Domain
The term domain used in this document implies an IGP domain where
every node is visible to every other node for shortest path
computation. The domain implies an IGP area or level. An AS
consists of one or more IGP domains. The procedures described in
this document apply to paths built across multiple domains which
include inter-area as well as inter-AS paths. The procedures and
deployment scenarios described in this document apply to inter-AS
paths where the participating ASes belong to closely coordinating
administrations or to a single ownership. This document applies to
SR-MPLS networks where all nodes in each of the domains are SR
capable. It is also applies to SR-MPLS networks where SR acts an an
overlay having SR incapable underlay nodes. In such networks, the
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traceroute procedure is executed only on the overlay SR nodes.
1.2. 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. Inter-domain Networks with Multiple IGPs
When the network consists of large number of nodes, the nodes are
seggregated into multiple IGP domains as shown in Figure 2. The
connectivity to the remote PEs can be achieved using BGP-Labeled
Unicast (BGP-LU) [RFC8277] or by stacking the labels for each domain
as described in [RFC8604].
|-Domain 1|-------Domain 2-----|--Domain 3-|
PE1------ABR1--------P--------ABR2------PE4
\ / \ /\ /
-------- ----------------- -------
BGP-LU BGP-LU BGP-LU
Figure 2: Inter-domain Networks with Multiple IGPs
It is useful to support MPLS ping and traceroute mechanisms for these
networks. The procedures described in this document for constructing
Reply Path TLV and its use in an echo reply is equally applicable to
networks consisting of multiple IGP domains that use BGP-LU or label
stacking.
3. Reply Path TLV
Segment Routing networks statically assign the labels to nodes and a
PMS/Head-end may know the entire database. The reverse path can be
built from the PMS/Head-end by stacking segments for the reverse
path. Reply Path TLV as defined in [RFC7110] is used to carry the
return path. While using the procedures described in this document,
the reply mode is set to 5 (Reply via Specified Path), and Reply Path
TLV is included in the echo request message as described in
[RFC7110]. The Reply Path TLV is constructed as per Section 4.2 of
[RFC7110]. This document defines three new sub-TLVs to encode the
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Segment Routing path.
The type of segment that the head-end chooses to send in the Reply
Path TLV is governed by local policy. Implementations MAY provide
Command Line Interface (CLI) input parameters in the form of Labels/
IPv4 addresses/IPv6 addresses or a combination of these which get
encoded in the Reply Path TLV. Implementations MAY also provide
mechanisms to acquire the database of remote domains and compute the
return path based on the acquired database. For traceroute purposes,
the return path will have to consider the reply being sent from every
node along the path. The return path changes when the traceroute
progresses and crosses each domain. One of the ways this can be
implemented on the headend is to acquire the entire database (of all
domains) and build a return path for every node along the SR-MPLS
path based on the knowledge of the database. Another mechanism is to
use a dynamically computed return path as described in Section 8
Some networks may consist of pure IPv4 domains and pure IPv6 domains.
Handling end-to-end MPLS OAM for such networks is out of the scope
for this document. It is recommended to use dual-stack in such cases
and use end-to-end IPv6 addresses for MPLS ping and traceroute
procedures.
4. Segment Sub-TLV
[RFC9256] defines various types of segments. The types of segments
applicable to this document have been defined in this section for the
use of MPLS OAM. The intention was to keep the definitions as close
to those in [RFC9256] as possible with modifications only when
needed. One or more Segment Sub-TLVs can be included in the Reply
Path TLV. The Segment Sub-TLVs included in a Reply Path TLV MAY be
of different types.
Below types of Segment Sub-TLVs are applicable to the Reply Path TLV.
Type-A: SID only, in the form of MPLS Label
Type-C: IPv4 Node Address with optional SID
Type-D: IPv6 Node Address with optional SID for SR MPLS
4.1. Type-A: SID only, in the form of MPLS Label
The Type A Segment Sub-TLV encodes a single SID in the form of an
MPLS label. The format is as follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Type-A Segment Sub-TLV
where:
Type: TBD1(to be assigned by IANA from the registry "Sub-TLVs for TLV
Types 1, 16, and 21").
Length is 8.
Flags: 1 octet of flags as defined in Section 4.4.
RESERVED: 3 octets of reserved bits. MUST be set to zero when
sending; MUST be ignored on receipt..
Label: 20 bits of label value.
TC: 3 bits of traffic class
S: 1 bit Reserved
TTL: 1 octet of TTL.
The following applies to the Type-A Segment Sub-TLV:
The S bit SHOULD be zero upon transmission, and MUST be ignored upon
reception.
If the originator wants the receiver to choose the TC value, it sets
the Traffic Class(TC) field to zero.
If the originator wants the receiver to choose the TTL value, it sets
the TTL field to 255.
If the originator wants to recommend a value for these fields, it
puts those values in the TC and/or TTL fields.
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The receiver MAY override the originator's values for these fields.
This would be determined by local policy at the receiver. One
possible policy would be to override the fields only if the fields
have the default values specified above.
4.2. Type-C: IPv4 Node Address with Optional SID for SR-MPLS
The Type-C Segment Sub-TLV encodes an IPv4 node address, SR Algorithm
and an optional SID in the form of an MPLS label. The format is as
follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | RESERVED (MBZ) | SR Algorithm |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Node Address (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (optional, 4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Type-C Segment Sub-TLV
where:
Type: TBD2 (to be assigned by IANA from the registry "Sub-TLVs for
TLV Types 1, 16, and 21").
Length is 8 or 12.
Flags: 1 octet of flags as defined in Section 4.4.
SR Algorithm: 1 octet specifying SR Algorithm as described in section
3.1.1 in [RFC8402], when A-Flag as defined in Section 4.4is present.
SR Algorithm is used by the receiver to derive the Label. When
A-flag is unset, this field has no meaning and thus MUST be set to
zero on transmission and ignored on receipt.
RESERVED: 2 octets of reserved bits. MUST be set to zero when
sending; MUST be ignored on receipt.
IPv4 Node Address: 4-octet IPv4 address representing a node.
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SID: optional: 4-octet field containing label, TC, S and TTL as
defined in Section 4.1. When the SID field is present, it MUST be
used for constructing the Reply Path.
The following applies to the Type-C Segment Sub-TLV:
The IPv4 Node Address MUST be present.
The SID is optional and specifies a 4-octet MPLS SID containing
label, TC, S and TTL as defined in Section 4.1.
If the length is 8, then only the IPv4 Node Address is present.
If the length is 12, then the IPv4 Node Address and the MPLS SID are
present.
4.3. Type D: IPv6 Node Address with Optional SID for SR MPLS
The Type-D Segment Sub-TLV encodes an IPv6 node address, SR Algorithm
and an optional SID in the form of an MPLS label. The format is as
follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | RESERVED(MBZ) | SR Algorithm |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// IPv6 Node Address (16 octets) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (optional, 4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Type-D Segment Sub-TLV
where:
Type: TBD3 (to be assigned by IANA from the registry "Sub-TLVs for
TLV Types 1, 16, and 21").
Length is 20 or 24.
Flags: 1 octet of flags as defined in Section 4.4.
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SR Algorithm: 1 octet specifying SR Algorithm as described in section
3.1.1 in [RFC8402], when A-Flag as defined in Section 4.4 is present.
SR Algorithm is used by the receiver to derive the label.W hen A-flag
is unset, this field has no meaning and thus MUST be set to zero
(MBZ) on transmission and ignored on receipt.
RESERVED: 2-octet of reserved bits. MUST be set to zero when
sending; MUST be ignored on receipt.
IPv6 Node Address: 16-octet IPv6 address representing a node.
SID: optional: 4-octet field containing label, TC, S and TTL as
defined in Section 4.1
The following applies to the Type-D Segment Sub-TLV:
The IPv6 Node Address MUST be present.
The SID is optional and specifies a 4-octet MPLS SID containing
label, TC, S and TTL as defined in Section 4.1.When the SID field is
present, it MUST be used for constructing the Reply Path.
If the length is 20, then only the IPv6 Node Address is present.
If the length is 24, then the IPv6 Node Address and the MPLS SID are
present.
4.4. Segment Flags
The Segment Types described above contain the following flags in the
"Flags" field (codes to be assigned by IANA from the new registry
"Segment Sub-TLV Flags" )
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| |A| |
+-+-+-+-+-+-+-+-+
Figure 6: Flags
where:
A-Flag: This flag indicates the presence of SR Algorithm ID in the
"SR-Algorithm" field applicable to various Segment Types.
Unused bits in the Flag octet MUST be set to zero upon transmission
and MUST be ignored upon receipt.
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The following applies to the Segment Flags:
A-Flag applies to Segment Type-C and Type-D. If A-Flag appears with
Type-A Segment Type, it MUST be ignored.
5. SRv6 Dataplane
SRv6 dataplane is not in the scope of this document.
6. Detailed Procedures
6.1. Sending an Echo Request
In the inter-AS scenario, the procedures described in this document
are used to specify the return path, if IP connectivity to the
initiator is not available, and may be used in any case. LSP ping
initiator MUST set the Reply Mode of the echo request to 5 "Reply via
Specified Path", and a Reply Path TLV MUST be carried in the echo
request message correspondingly. The Reply Path TLV MUST contain the
Segment Routing Path in the reverse direction encoded as an ordered
list of segments. The first Segment MUST correspond to the top
Segment in MPLS header that the responder MUST use while sending the
echo reply.
6.2. Receiving an Echo Request
As described in [RFC7110], when Reply mode is set to 5 (Reply via
Specified Path), the echo request must contain the Reply path TLV.
Absence of Reply Path TLV is treated as a malformed echo request.
When an echo request is received, if the egress LSR does not know the
Reply Mode 5 defined in [RFC7110], an echo reply with the return code
set to "Malformed echo request received" and the Subcode set to zero
must be sent back to the ingress LSR according to the rules of
[RFC8029]. When a Reply Path TLV is received, and the responder that
supports processing it, it MUST use the segments in Reply Path TLV to
build the echo reply. The responder MUST follow the normal FEC
validation procedures as described in [RFC8029] and [RFC8287] and
this document does not suggest any change to those procedures. When
the echo reply has to be sent out the Reply Path TLV MUST be used to
construct the MPLS packet to send out.
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6.3. Sending an Echo Reply
The echo reply message is sent as an MPLS packet with an MPLS label
stack. The echo reply message MUST be constructed as described in
the [RFC8029]. An MPLS packet is constructed with an echo reply in
the payload. The top label MUST be constructed from the first
Segment from the Reply Path TLV. The remaining labels MUST follow
the order from the Reply Path TLV. The responder MAY check the
reachability of the top label in its own Label Forwarding Information
Base (LFIB) before sending the echo reply and provide necessary log
information in case of unreachabilty. In certain scenarios, the
head-end MAY choose to send Type-C/Type-D segments consisting of IPV4
address or IPv6 address, when it is unable to derive the SID from
available topology information. Optionally SID may also be
associated with the Type-C/Type-D segment, if such information is
available from the controller or via operator input. In such cases,
the node sending the echo reply MUST derive the MPLS labels based on
Node-SIDs associated with the IPv4 /IPv6 addresses or from the
optional MPLS SIDs in the Type-C/Type-D segments and encode the echo
reply with MPLS labels.
The reply path return code is set as described in section 7.4 of
[RFC7110].According to section 5.3 of [RFC7110] The Reply Path TLV is
included in an echo reply indicating the specified return path that
the echo reply message is required to follow.
When the node is configured to dynamically create a return path for
the next echo request, the procedures described in Section 8 MUST be
used. The reply path return code MUST be set to TBA1 and the same
Reply Path TLV or a new Reply Path TLV MUST be included in the echo
reply.
6.4. Receiving an Echo Reply
The rules and process defined in Section 4.6 of [RFC8029] and section
5.4 of [RFC7110] apply here. In addition, if the Reply path return
code is "Use Reply Path TLV in the echo reply for building the next
echo request", the Reply Path TLV from the echo Reply MUST be sent in
the next echo request with TTL incremented by 1. If the TTL is
already 255, the traceroute procedure MUST be ended with an
appropriate log message.
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7. Detailed Example
The example topology given in Figure 1 will be used will be used in
the below sections to explain LSP ping and traceroute procedures.
The PMS/Head-end has a complete view of topology. PE1, P1, P2, ASBR1
and ASBR2 are in AS1. Similarly ASBR3, ASBR4, P3, P4 and PE4 are in
AS2.
AS1 and AS2 have Segment Routing enabled. IGPs like OSPF/ISIS are
used to flood SIDs in each AS. The ASBR1, ASBR2, ASBR3 and ASBR4
advertise BGP EPE-SIDs for the inter-AS links. Topology of AS1 and
AS2 are advertised via BGP-Link State (BGP-LS) to the controller/PMS
or Head-end node. The EPE-SIDs are also advertised via BGP-LS as
described in [RFC9086]. The example uses EPE-SIDs for the inter-AS
links but the same could be achieved using adjacency-SIDs advertised
for a passive IGP link.
The description in the document uses below notations for Segment
Identifiers(SIDs).
Node SIDs: N-PE1, N-P1, N-ASBR1 N-ABR1, N-ABR2etc.
Adjacency SIDs: Adj-PE1-P1, Adj-P1-P2 etc.
EPE-SIDs: EPE-ASBR2-ASBR3, EPE-ASBR1-ASBR4, EPE-ASBR3-ASBR2 etc.
Let us consider a traffic-engineered path built from PE1 to PE4 with
Segment List stack as below. N-P1, N-ASBR1, EPE-ASBR1-ASBR4, N-PE4
for following procedures. This stack may be programmed by
controller/PMS or Head-end router PE1 may have imported the whole
topology information from BGP-LS and computed the inter-AS path.
7.1. Procedures for Segment Routing LSP ping
Consider an SR-MPLS path from PE1 to PE4 consisting of a label stack
[N-P1, N-ASBR1, EPE-ASBR1-ASBR4, N-PE4] from Figure 1. In order to
perform MPLS ping procedures on this path, the remote end (PE4) needs
IP connectivity to head end PE1, for the echo reply to travel back to
PE1. In a deployment that uses controller-computed inter-domain
path, there may be no IP connectivity from PE4 to PE1 as they lie in
different ASes.
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PE1 sends an echo request message to the end-point PE4 along the path
that consists of label stacks [N-P1, N-ASBR1, EPE-ASBR1-ASBR4,
N-PE4]. PE1 adds the return path from PE4 to PE1 in the echo request
message in the Reply Path TLV. As an example, Reply Path TLV for PE1
to PE4 for LSP ping is [N-ASBR4, EPE-ASBR4-ASBR1, N-PE1]. This
example path provides the entire return path up to the head-end node
PE1. The mechanism used to construct the return path is
implementation dependent.
An implementation may also build a return Path consisting of labels
to reach its own AS. Once the label stack is popped off the echo
reply message will be exposed. The further packet forwarding will be
based on IP lookup. An example return Path for this case could be
[N-ASBR4, EPE-ASBR4-ASBR1].
On receiving MPLS echo request PE4 first validates FEC in the echo
request. PE4 then builds a label stack to send the response from PE4
to PE1 by copying the labels from Reply Path TLV. PE4 builds the
echo reply packet with the MPLS label stack constructed and imposes
MPLS headers on top of echo reply packet and sends out the packet
towards PE1. This Segment List stack can successfully steer reply
back to the Head-end node (PE1).
7.2. Procedures for Segment Routing LSP traceroute
7.2.1. Procedures for Segment Routing LSP traceroute with the Same SRGB
on All Nodes
The traceroute procedure involves visiting every node on the path and
echo replies sent from every node. In this section, we describe the
traceroute mechanims when the headend/PMS has complete visibility of
the database. Headend/PMS computes the return path from each node in
the entire SR-MPLS path that is being tracerouted. The return path
computation is implementation dependent. As the headend/PMS
completely controls the return path, it can use proprietary
computations to build the return path.
One of the ways the return path can be built, is to use the principle
of building label stacks by adding each domain border node's Node SID
on the return path label stack as the traceroute progresses. For
inter-AS networks, in addition to border node's Node-SID, EPE-SID in
the reverse direction also needs to be added to the label stack.
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The Inter-domain/inter-as traceroute procedure uses the TTL expiry
mechanism as specified in [RFC8029] and [RFC8287]. Every echo
request packet Headend/PMS will include the appropriate return path
in the Reply Path TLV. The node that receives the echo request will
follow procedures described in section Section 6.1 and section
Section 6.2 to send out an echo reply.
For Example:
Let us consider a topology from Figure 1. Let us consider a SR-MPLS
path [N-P1, N-ASBR1, EPE-ASBR1-ASBR4, N-PE4]. The traceroute is
being executed for this inter-AS path for destination PE4. PE1 sends
the first echo request with TTL set to 1 and includes Reply Path TLV
consisting of Type-A Segment containing label derived from its own SR
Global Block (SRGB). Note that the type of segment used in
constructing the return Path is local policy. If the entire network
has the same SRGB configured, Type-A segments can be used. The TTL
expires on P1 and P1 sends an echo reply using the return path. Note
that implementations may choose to exclude the Reply Path TLV until
traceroute reaches the first domain border as the return IP path to
PE1 is expected to be available inside the first domain.
TTL is set to 2 and the next the echo request is sent out. Until the
traceroute procedure reaches the domain border node ASBR1, the same
return path TLV consisting of single Label (PE1's node Label) is
used. When echo request reaches the border node ASBR1, and an echo
reply is received from ASBR1, the next echo request needs to include
an additional label as ASBR1 is a border node. The head-end node has
complete visibility of the network database learned via BGP-LS
[RFC9552] and [RFC9086] and can derive the details of Autonomous
System Boundary Router (ASBR) nodes. The Reply Path TLV is built
based on the forward path. As the forward path consists of EPE-
ASBR1-ASBR4, an EPE-SID in the reverse direction is included in the
Reply Path TLV. The return path now consists of two labels [EPE-
ASBR4-ASBR1, N-PE1]. The echo reply from ASBR4 will use this return
path to send the reply.
The next echo request after visiting the border node ASBR4 will
update the return path with the Node-SID label of ASBR4. The return
path beyond ASBR4 will be [N-ASBR4, EPE-ASBR4-ASBR1, N-PE1]. This
same return path is used until the traceroute procedure reaches the
next set of border nodes. When there are multiple ASes the
traceroute procedure will continue by adding a set of Node-SIDs and
EPE-SIDs as the border nodes are visited.
Note that the above return path-building procedure requires the
database of all the domains to be available at the headend/PMS.
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7.2.2. Procedures for Segment Routing LSP Traceroute with the Different
SRGBs
The Section 7.2.1 assumes the same SRGB is configured on all nodes
along the path. The SRGB may differ from one node to another node
and the SR architecture [RFC8402] allows the nodes to use different
SRGB. In such scenarios, PE1 sends Type-C (or Type-D in case of IPv6
networks) segment with the Node address of PE1 and with optional MPLS
SID associated with the Node address. The receiving node derives the
label for the return path based on its own SRGB. When the traceroute
procedure crosses the border ASBR1, headend PE1 should send a Type-A
segment for N-PE1 based on the label derived from ASBR1's SRGB. This
is required because, ASBR4, P3, P4 etc may not have the topology
information to derive SRGB for PE1. After the traceroute procedure
reaches ASBR4 the return path will be [N-PE1 (Type-A with label based
on ASBR1's SRGB), EPE-ASBR4-ASBR1, N-ASBR4 (Type-C)].
To extend the example to multiple ASes consisting of 3 or more ASes,
let us consider a traceroute from PE1 to PE5 in Figure 1. In this
example, the PE1 to PE5 path has to cross 3 domains AS1, AS2 and AS3.
Let us consider a path from PE1 to PE5 that goes through [PE1, ASBR1,
ASBR4, ASBR6, ASBR8,PE5]. When the traceroute procedure is visiting
the nodes in AS1, the Reply Path TLV sent from the headend consists
of [N-PE1]. When the traceroute procedure reaches the ASBR4, the
return Path consists of [N-PE1, EPE-ASBR4-ASBR1]. While visiting
nodes in AS2, the traceroute procedure consists of Reply Path TLV
[N-PE1, EPE-ASBR4-ASBR1, N-ASBR4]. similarly, while visiting the
ASBR8 Reply Path TLV adds the EPE-SID from ASBR8 to ASBR6. While
visiting nodes in AS3 Node-SId of ASBR8 would also be added which
makes the return Path [N-PE1, EPE-ASBR4-ASBR1, N-ASBR4, EPE-
ASBR8-ASBR6, N-ASBR8]
Let us consider another example from topology Figure 2. This
topology consists of multi-domain IGP with a common border node
between the domains. This could be achieved with multi-area or
multi-level IGP or multiple instances of IGP deployed on the same
node. The return path computation for this topology is similar to
the multi-AS computation except that the return path consists of a
single border node label. When the traceroute procedure visits node
P, the return path consists of [N-PE1, N-ABR1].
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8. Building Reply Path TLV Dynamically
In some cases, the head-end may not have complete visibility of
Inter-AS/Inter-domain topology. In such cases, it can rely on
downstream routers to build the reverse path for MPLS traceroute
procedures. For this purpose, Reply Path TLV in the echo reply
corresponds to the return path to be used in building the next echo
request.
Value Meaning
------ ----------------------
TBA1 Use Reply Path TLV in the echo reply
for building the next echo request.
8.1. The procedures to Build the Return Path
To dynamically build the return Path for the traceroute procedures,
the domain border nodes along the path being traced should support
the procedures described in this section. Local policy on the domain
border nodes should determine whether the domain border node
participates in building the return path dynamically during
traceroute.
The headend/PMS node may include its node label while initiating
traceroute procedure. When an Area Border Router (ABR) receives the
echo request, if the local policy implies building a dynamic return
path, ABR should include its Node label in the reply path TLV and
send it in the echo reply. If there is a Reply Path TLV included in
the received echo request message, the ABR's node label is added
before the existing segments. The type of segment added is based on
local policy. In cases when SRGB is not uniform across the network,
it is RECOMMENDED to add a Type-C or a Type-D segment, but
implementations MAY safely use other approaches if they see benefits
in doing so. If the existing segment in the Reply Path TLV is a
Type-C/Type-D segment, that segment should be converted to a Type-A
segment based on ABR's own SRGB.This is because downstream nodes will
not know what SRGB to use to translate the IP address to a label. As
the ABR added its own Node label, it is guaranteed that this ABR will
be in the return path and will be forwarding the traffic based on the
next label after its label.
When an ASBR receives an echo request from another AS, and ASBR is
configured to build the return path dynamically, ASBR should build a
Reply Path TLV and include it in the echo reply. The Reply Path TLV
should consist of its own node label and an EPE-SID to the AS from
where the traceroute message was received. A Reply path return code
of TBA1 should be set in the echo reply to indicate that the next
echo request should use the return Path from the Reply Path TLV in
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the echo reply. ASBR should locally decide the outgoing interface
for the echo reply packet. Generally, remote ASBR will choose the
interface on which the incoming OAM packet was received to send the
echo reply out. Reply Path TLV is built by adding two segment sub
TLVs. The top segment sub TLV consists of the ASBR's Node SID and
the second segment consists of the EPE-SID in the reverse direction
to reach the AS from which the OAM packet was received. The type of
segment chosen to build Reply Path TLV is a local policy. It is
recommended to use the Type-C/Type-D segment for the top segment when
the SRGB is not guaranteed to be uniform in the domain.
Irrespective of which type of segment is included in the Reply Path
TLV, the responder of echo requests should always translate the Reply
Path TLV to a label stack and build an MPLS header for the the echo
reply packet. This procedure can be applied to an end-to-end path
consisting of multiple ASes. Each ASBR that receives an echo request
from another AS adds its Node-SID and EPE-SID on top of existing
segments in the Reply Path TLV.
An ASBR that receives the echo request from a neighbor belonging to
the same AS, MUST look at the Reply Path TLV received in the echo
request. If the Reply Path TLV consists of a Type-C/Type-D segment,
it MUST convert the Type-C/Type-D segment to a Type-A segment by
deriving a label from its own SRGB. The ASBR MUST set the reply path
return code to TBA1 and send the newly constructed Reply Path TLV in
the echo reply.
Internal nodes or nondomain border nodes MAY not set the Reply Path
TLV return code to TBA1 in the echo reply message as there is no
change in the return Path. In these cases, the headend node/PMS that
initiates the traceroute procedure MUST continue to send previously
sent Reply Path TLV in the echo request message in every next echo
request.
Note that an ASBR's local policy may prohibit it from participating
in the dynamic traceroute procedures. If such an ASBR is encountered
in the forward path, dynamic return path-building procedures will
fail. In such cases, ASBR that supports this document MUST set the
return code TBA2 to indicate local policies do not allow the dynamic
return path building.
Value Meaning
------ ---------------------------------------------------
TBA2 Local policy does not allow dynamic return Path
building.
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8.2. Details with Example
Let us consider a topology from Figure 1. Let us consider an SR
policy path built from PE1 to PE4 with a label stack as below. N-P1,
N-ASBR1, EPE-ASBR1-ASBR4, N-PE4. PE1 begins traceroute with TTL set
to 1 and includes [N-PE1] in the Reply Path TLV. The traceroute
packet TTL expires on P1 and P1 processes the traceroute as per the
procedures described in [RFC8029] and [RFC8287]. P1 sends echo reply
with the same Reply Path TLV with reply path return code set to 6.
The return code of the echo reply itself is set to the return code as
per [RFC8029] and [RFC8287]. This traceroute doesn't need any
changes to the Reply Path TLV till it leaves AS1. The same Reply
Path TLV that is received may be included in the echo reply by P1 and
P2 or no Reply Path TLV included so that headend continues to use the
same return path in echo request that it used to send previous echo
request.
When ASBR1 receives the echo request, in case it received Type-C/
Type-D segment in the Reply Path TLV in the echo request, converts
that Type-C/Type-D segment to Type-A based on its own SRGB. When
ASBR4 receives the echo request, it should form this Reply Path TLV
using its own Node SID (N-ASBR4) and EPE-SID (EPE-ASRB4-ASBR1) labels
and set the reply path return code to TBA1. Then PE1 should use this
Reply Path TLV in subsequent echo requests. In this example, when
the subsequent echo request reaches P3, it should use this Reply Path
TLV for sending the echo reply. The same Reply Path TLV is
sufficient for any router in AS2 to send the reply. Because the
first label(N-ASBR4) can direct echo reply to ASBR4 and the second
one (EPE-ASBR4-ASBR1) to direct echo reply to AS1. Once the echo
reply reaches AS1, normal IP forwarding or the N-PE1 helps it to
reach PE1.
The example described in the above paragraphs can be extended to
multiple ASes by following the same procedure of each ASBR adding
Node-SID and EPE-SID on receiving echo request from neighboring AS.
Let us consider a topology from Figure 2. It consists of multiple
IGP domains with multiple areas/levels or separate IGP instances.
There is a single border node that separates the two domains. In
this case, PE1 sends a traceroute packet with TTL set to 1 and
includes N-PE1 in the Reply Path TLV. ABR1 receives the echo request
and while sending the echo reply adds its node Label to the Reply
Path TLV and sets the Reply path return code to TBA1. The Reply Path
TLV in the echo reply from ABR1 consists of [N-ABR1, N-PE1]. Next
echo request with TTL 2 reaches the P node. It is an internal node
so it does not change the return Path. Echo request with TTL 3
reaches ABR2 and it adds its own Node label so the Reply Path TLV
sent in echo reply will be [N-ABR2, N-ABR1, N-PE1]. echo request with
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TTL 4 reaches PE4 and it sends an echo reply return code as Egress.
PE4 does not include any Reply Path TLV in the echo reply. The above
example assumes uniform SRGB throughout the domain. In the case of
different SRGBs, the top segment will be a Type-C/Type-D segment and
all other segments will be Type-A. Each border node converts the
Type-C/Type-D segment to Type-A before adding its own segment to the
Reply Path TLV.
9. Security Considerations
The procedures described in this document enable LSP ping and
traceroute to be executed across multiple IGP domains or multiple
ASes that belong to same administration or closely co-operating
administration. It is assumed that sharing domain internal
information across such domains does not pose a security risk.
However, procedures described in this document may be used by an
attacker to extract the domain's internal information. An operator
MUST deploy appropriate filter policies as described in [RFC8029] to
restrict the LSP ping/traceroute packets based on origin. It is also
suggested that an operator SHOULD deploy security mechanisms such as
MACsec on inter-domain links or security-vulnerable links to prevent
spoofing attacks.
Appropriate filter policies SHOULD be applied at the edges to prevent
attackers from getting into the network. In the event of such a
security breach, the network devices MUST have mechanisms to prevent
of Denial-of-service attacks as described in [RFC8029].
10. IANA Considerations
10.1. Segment Sub-TLV
IANA should assign three new sub-TLVs from the "sub-TLVs for TLV
Types 1, 16, and 21" subregistry of the "Multi-Protocol Label
Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters"
registry.
Sub-Type Sub-TLV Name Reference
-------- ----------------- ------------
TBD1 SID only in the form of MPLS Section 4.1
label of this document
TBD2 IPv4 Node Address with Section 4.2
optional SID for SR-MPLS of this document
TBD3 IPv6 Node Address with Section 4.3
optional SID for SR-MPLS of this document
The allocation of code points for the Segment Sub-TLVs should be done
from the Standards Action range (0-16383)
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10.2. New Registry for Segment Sub-TLV Flags
IANA should create a new "Segment ID sub-TLV flags" (see
Section Section 4.4) registry under the "Multi-Protocol Label
Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters"
registry.
This registry tracks the assignment of 8 flags in the Segment ID sub-
TLV flags field. The flags are numbered from 0 (most significant
bit, transmitted first) to 8.
New entries are assigned by Standards Action. Initial entries in the
registry are as follows:
Bit number | Name | Reference
------------+----------------------------+--------------
1 | A Flag | Section 4.4
| | of this document
10.3. Reply Path Return Codes Registry
IANA should assign new return codes in the "Reply path return code"
registry under the "Multi-Protocol Label Switching (MPLS) Label
Switched Paths (LSPs) Ping Parameters" registry.
Value Meaning Reference
-------- ----------------- ------------
TBA1 Use Reply Path TLV This document
from this echo reply
for building next
echo request.
TBA2 Local policy does This document
not allow dynamic
return Path building.
The return codes should be assigned from the Standards Action range
(0x0000-0xFFFB).
11. Contributors
1.Carlos Pignataro
NC State University
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cpignata@gmail.com
2. Zafar Ali
Cisco Systems, Inc.
zali@cisco.com
12. Implementation Status
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.
12.1. Juniper Networks
Organization: Juniper Networks
Implementation: JUNOS.
Description: Implementation for sending Return path TLV with Type-A
segment subTLV
Maturity Level: Prototype
Coverage: Partial. Type-A SIDs in Return Path TLV
Contact: shraddha@juniper.net
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13. Acknowledgments
Thanks to Bruno Decreane for suggesting the use of generic Segment
Sub-TLV. Thanks to Adrian Farrel, Huub van Helvoort, Dhruv Dhody,
Dongjie, for careful review and comments. Thanks to Mach Chen for
suggesting to use Reply Path TLV. Thanks to Gregory Mirsky for the
detailed review which helped improve the readability of the document
to a great extent.
14. References
14.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC7110] Chen, M., Cao, W., Ning, S., Jounay, F., and S. Delord,
"Return Path Specified Label Switched Path (LSP) Ping",
RFC 7110, DOI 10.17487/RFC7110, January 2014,
<https://www.rfc-editor.org/info/rfc7110>.
[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
Switched (MPLS) Data-Plane Failures", RFC 8029,
DOI 10.17487/RFC8029, March 2017,
<https://www.rfc-editor.org/info/rfc8029>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8287] Kumar, N., Ed., Pignataro, C., Ed., Swallow, G., Akiya,
N., Kini, S., and M. Chen, "Label Switched Path (LSP)
Ping/Traceroute for Segment Routing (SR) IGP-Prefix and
IGP-Adjacency Segment Identifiers (SIDs) with MPLS Data
Planes", RFC 8287, DOI 10.17487/RFC8287, December 2017,
<https://www.rfc-editor.org/info/rfc8287>.
14.2. Informative References
[RFC7743] Luo, J., Ed., Jin, L., Ed., Nadeau, T., Ed., and G.
Swallow, Ed., "Relayed Echo Reply Mechanism for Label
Switched Path (LSP) Ping", RFC 7743, DOI 10.17487/RFC7743,
January 2016, <https://www.rfc-editor.org/info/rfc7743>.
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[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>.
[RFC8277] Rosen, E., "Using BGP to Bind MPLS Labels to Address
Prefixes", RFC 8277, DOI 10.17487/RFC8277, October 2017,
<https://www.rfc-editor.org/info/rfc8277>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8403] Geib, R., Ed., Filsfils, C., Pignataro, C., Ed., and N.
Kumar, "A Scalable and Topology-Aware MPLS Data-Plane
Monitoring System", RFC 8403, DOI 10.17487/RFC8403, July
2018, <https://www.rfc-editor.org/info/rfc8403>.
[RFC8604] Filsfils, C., Ed., Previdi, S., Dawra, G., Ed.,
Henderickx, W., and D. Cooper, "Interconnecting Millions
of Endpoints with Segment Routing", RFC 8604,
DOI 10.17487/RFC8604, June 2019,
<https://www.rfc-editor.org/info/rfc8604>.
[RFC8660] Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing with the MPLS Data Plane", RFC 8660,
DOI 10.17487/RFC8660, December 2019,
<https://www.rfc-editor.org/info/rfc8660>.
[RFC9086] Previdi, S., Talaulikar, K., Ed., Filsfils, C., Patel, K.,
Ray, S., and J. Dong, "Border Gateway Protocol - Link
State (BGP-LS) Extensions for Segment Routing BGP Egress
Peer Engineering", RFC 9086, DOI 10.17487/RFC9086, August
2021, <https://www.rfc-editor.org/info/rfc9086>.
[RFC9087] Filsfils, C., Ed., Previdi, S., Dawra, G., Ed., Aries, E.,
and D. Afanasiev, "Segment Routing Centralized BGP Egress
Peer Engineering", RFC 9087, DOI 10.17487/RFC9087, August
2021, <https://www.rfc-editor.org/info/rfc9087>.
[RFC9256] Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov,
A., and P. Mattes, "Segment Routing Policy Architecture",
RFC 9256, DOI 10.17487/RFC9256, July 2022,
<https://www.rfc-editor.org/info/rfc9256>.
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Internet-Draft Inter-as-OAM February 2024
[RFC9552] Talaulikar, K., Ed., "Distribution of Link-State and
Traffic Engineering Information Using BGP", RFC 9552,
DOI 10.17487/RFC9552, December 2023,
<https://www.rfc-editor.org/info/rfc9552>.
Authors' Addresses
Shraddha Hegde
Juniper Networks Inc.
Exora Business Park
Bangalore 560103
KA
India
Email: shraddha@juniper.net
Kapil Arora
Individual Contributor
Email: kapil.it@gmail.com
Mukul Srivastava
Juniper Networks Inc.
Email: msri@juniper.net
Samson Ninan
Ciena
Email: samson.cse@gmail.com
Nagendra Kumar
Cisco Systems, Inc.
Email: naikumar@cisco.com
Hegde, et al. Expires 22 August 2024 [Page 26]