Path Monitoring System/Head-end based MPLS Ping and Traceroute in Inter-domain Segment Routing Networks
draft-ietf-mpls-spring-inter-domain-oam-20
| Document | Type | Active Internet-Draft (mpls WG) | |
|---|---|---|---|
| Authors | Shraddha Hegde , Kapil Arora , Mukul Srivastava , Samson Ninan , Nagendra Kumar Nainar | ||
| Last updated | 2024-08-16 (Latest revision 2024-06-26) | ||
| Replaces | draft-ninan-mpls-spring-inter-domain-oam | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | Proposed Standard | ||
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| 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 | ||
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draft-ietf-mpls-spring-inter-domain-oam-20
Routing area S. Hegde
Internet-Draft Juniper Networks Inc.
Intended status: Standards Track K. Arora
Expires: 28 December 2024 Individual Contributor
M. Srivastava
Juniper Networks Inc.
S. Ninan
Ciena
N. Kumar
Oracle
26 June 2024
Path Monitoring System/Head-end based MPLS Ping and Traceroute in Inter-
domain Segment Routing Networks
draft-ietf-mpls-spring-inter-domain-oam-20
Abstract
The Segment Routing (SR) architecture leverages source routing and
can be directly applied to the use of an MPLS data plane. An SR-MPLS
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 traverses multiple ASes or IGP
domains. This document outlines mechanisms to enable efficient LSP
ping and traceroute in inter-AS and inter-domain SR-MPLS networks
through a straightforward extension to the Operations,
Administration, and Maintenance (OAM) protocol, relying solely on
data plane forwarding for handling echo replies on transit nodes.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
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
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 28 December 2024.
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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 . . . . . . . . . . . . . . . . . . 5
2. Inter-domain Networks with Multiple IGPs . . . . . . . . . . 5
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 . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.3. Type D: IPv6 Node Address with Optional SID for SR
MPLS . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.4. Segment Flags . . . . . . . . . . . . . . . . . . . . . . 11
5. Detailed Procedures . . . . . . . . . . . . . . . . . . . . . 11
5.1. Sending an Echo Request . . . . . . . . . . . . . . . . . 11
5.2. Receiving an Echo Request . . . . . . . . . . . . . . . . 12
5.3. Sending an Echo Reply . . . . . . . . . . . . . . . . . . 12
5.4. Receiving an Echo Reply . . . . . . . . . . . . . . . . . 13
5.5. Building Reply Path TLV Dynamically . . . . . . . . . . . 13
5.5.1. The Procedures to Build the Return Path . . . . . . . 14
6. Security Considerations . . . . . . . . . . . . . . . . . . . 15
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
7.1. Segment Sub-TLV . . . . . . . . . . . . . . . . . . . . . 16
7.2. New Registry for Segment Sub-TLV Flags . . . . . . . . . 16
7.3. Reply Path Return Codes Registry . . . . . . . . . . . . 17
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 17
9. Implementation Status . . . . . . . . . . . . . . . . . . . . 17
9.1. Juniper Networks . . . . . . . . . . . . . . . . . . . . 18
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18
11. APPENDIX . . . . . . . . . . . . . . . . . . . . . . . . . . 18
11.1. Detailed Example . . . . . . . . . . . . . . . . . . . . 19
11.1.1. Procedures for Segment Routing LSP ping . . . . . . 19
11.1.2. Procedures for SR LSP traceroute . . . . . . . . . . 20
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11.1.3. Procedures for building Reply Path TLV
dynamically . . . . . . . . . . . . . . . . . . . . . 23
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
12.1. Normative References . . . . . . . . . . . . . . . . . . 24
12.2. 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. SR can be deployed in such
scenarios to provide end-to-end paths, traversing multiple Autonomous
systems (ASes).
[RFC8660] specifies SR with an MPLS data plane. [RFC8402] describes
BGP Peering Segments, and [RFC9087] describes Centralized BGP Egress
Peer Engineering, which will help in steering packets from one AS to
another. By utilizing these SR capabilities, it is possible to
create paths that span multiple ASes.
+----------------+
| 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 AS3 are SR
enabled and the egress links have PeerNode SID/PeerAdj SID/ PeerSet
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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, 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 always 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 mechanisms([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.
[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 SR 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 facilitate encoding
SR label stack. The return path can either be derived by a smart
application or a controller that has a full topology view or end-to-
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end view of a section of the topology. This document also proposes
mechanisms to derive the return path dynamically during traceroute
procedures.
This document focuses on the inter-domain use case. The protocol
extensions described may also indicate the return path for other use
cases, which are outside the scope of this document and are not
further detailed here. The SRv6 data plane is also not covered in
this document
1.1. Definition of Domain
In this document, the term "domain" refers to an IGP domain where
every node is visible to every other node for the purpose of shortest
path computation, implying an IGP area or level. An Autonomous
System (AS) comprises one or more IGP domains. The procedures
described herein are applicable to paths constructed across multiple
domains, including both inter-area and inter-AS paths. These
procedures and deployment scenarios are relevant for inter-AS paths
where the participating ASes are under closely coordinating
administrations or single ownership. This document pertains to SR-
MPLS networks where all nodes within each domain are SR-capable. It
also applies to SR-MPLS networks where SR functions as an overlay
with SR-incapable underlay nodes. In such networks, the 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 a large number of nodes, the nodes are
segregated 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].
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|-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 echo reply are equally applicable to
networks consisting of multiple IGP domains that use BGP-LU or label
stacking.
3. Reply Path TLV
Reply Path (RP) TLV is defined in [RFC7110]. SR networks statically
assign the labels to nodes and a PMS/head-end may know the entire
Link State Database (LSDB) along with assigned SIDs. 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. Reply mode 5, Reply via Specified Path is
defined in section 4.1 of [RFC7110]. 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 SR 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 LSDB of remote domains and compute the
return path based on the acquired LSDB. 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 head-end is to acquire the entire LSDB (of all
domains) and build a return path for every node along the SR-MPLS
path based on the knowledge of the LSDB. Another mechanism is to use
a dynamically computed return path as described in Section 5.5
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Some networks may consist of IPv4-only domains and IPv6-only domains.
Handling end-to-end MPLS OAM for such networks is out of the scope of
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
Section 4 of [RFC9256] defines various segment types. 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.
The below types of Segment sub-TLVs apply to the Reply Path TLV. The
code points for the sub-TLVs are taken from the IANA registry common
to TLVs 1, 16, and 21. This document defines the Type-A, Type-C, and
Type-D Segment sub-TLVs usage and processing when it appears in TLV
21(Reply Path TLV). If these sub-TLVs appear in TLVs 1 or 16,
appropriate error codes MUST be returned as defined in [RFC8029].
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:
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
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where:
Type: 2 octects. Carries value TBD1(to be assigned by IANA from the
registry "Sub-TLVs for TLV Types 1, 16, and 21").
Length: 2 octets. Carries value 8. The length value excludes the
length of the Type and Length Fields.
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. If the originator wants the receiver to
choose the TC value, it MUST set the Traffic Class (TC) field to
zero.
S: 1 bit Reserved.The S bit MUST be zero upon transmission, and MUST
be ignored upon reception.
TTL: 1 octet of TTL. If the originator wants the receiver to choose
the TTL value, it MUST set the TTL field to 255.
The label, TC, S, and TTL collectively referred to as SID.
The following applies to the Type-A Segment sub-TLV:
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:
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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 (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: 2 octets. Caries value 8 when no optional SID is included or
value 12 when optional SID is included.
Flags: 1 octet of flags as defined in Section 4.4.
RESERVED: 2 octets of reserved bits. MUST be set to zero when
sending; MUST be ignored on receipt.
SR Algorithm: 1 octet specifying SR Algorithm as described in section
3.1.1 in [RFC8402] or Flexible algorithm as defined in [RFC9350],
when A-Flag as defined in Section 4.4 is 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.
IPv4 Node Address: 4-octet IPv4 address representing a node. The
IPv4 Node Address MUST be present. It should be a stable address
belonging to the node (eg:loopback address).
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.
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:
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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(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: 2 Octets. Caries value 20 when no optional SID is included
or value 24 when optional SID is included.
Flags: 1 octet of flags as defined in Section 4.4.
RESERVED: 2-octets of reserved bits. MUST be set to zero when
sending; MUST be ignored on receipt.
SR Algorithm: 1 octet specifying SR-Algorithm as described in section
3.1.1 in [RFC8402] or Flexible algorithm as defined in [RFC9350],
when A-Flag as defined in Section 4.4 is 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 (MBZ) on
transmission and ignored on receipt.
IPv6 Node Address: 16-octet IPv6 address of one interface of a node.
The IPv6 Node Address MUST be present. It should be a stable address
belonging to the node (eg:loopback address).
SID: optional: 4-octet field containing label, TC, S and TTL as
defined in Section 4.1. 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.
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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.
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. Detailed Procedures
This section uses the term "initiator" for the node that initiates
the MPLS ping or MPLS traceroute procedure. The term "responder" is
used for the node that receives the echo request and sends the echo
reply. The term egress node is used to identify the last node where
the MPLS ping or traceroute is destined to. In an MPLS network any
node can be initiator or responder or egress.
5.1. Sending an Echo Request
In the inter-AS scenario, the procedures outlined in this document
are employed to specify the return path when IP connectivity to the
initiator is unavailable. These procedures may also be utilized
regardless of the availability of IP connectivity. The 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
SR Path in the reverse direction encoded as an ordered list of
segments. The first segment MUST correspond to the top segment in
the MPLS header that the responder MUST use while sending the echo
reply.
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5.2. 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 responder does not support
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 initiator according to the rules of
[RFC8029]. If the echo request message contains a malformed Segment
sub-TLV, such as incorrect length field, an echo reply with return
code set to "Malformed echo request received" and the Subcode set to
zero must be sent back to the initiator.
When a Reply Path TLV is received, the responder that supports
processing 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.
5.3. 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 of the Reply Path TLV. The remaining labels MUST be
constructed by following the order of the segments from the Reply
Path TLV. The MPLS header of the Echo Reply MUST be constructed from
the segments in Reply Path TLV and MUST NOT add any other label. The
S bit is set for the bottom label as per MPLS specifications
[RFC3032] The responder MAY check the reachability of the top label
in its own Label Forwarding Information Base (LFIB) before sending
the echo reply. If the top label is unreachable, the responder
SHOULD send the appropriate return code and follow procedures as per
section 5.2 of [RFC7110]. The exception case is when the responder
does not have IP reachability to the originator, in which case it may
not be possible to send an Echo Reply at all. Even if sent (for
example by following a default route present on the responder), the
Echo Reply might not reach the originator. The node MAY provide
necessary log information in case of unreachability. In certain
scenarios, the head-end MAY choose to send Type-C/Type-D segments
consisting of IPv4 addresses or IPv6 addresses, 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.
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In such cases, the node sending the echo reply MUST derive the MPLS
labels based on Node-SIDs associated with the IPv4/IPv6 addresses.
If optional MPLS SID is present in the Type-C/Type-D segments SID
MUST be used to encode the echo reply with MPLS labels. If the MPLS
SID does not match with the IPv4 or IPv6 address field in the Type-C
or Type-D SID, log information should be generated.
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 5.5 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.
5.4. Receiving an Echo Reply
The rules and processes 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" (defined in this document), the Reply Path TLV
from the echo Reply MUST be sent in the next echo request with TTL
incremented by 1. If the initiator node does not support the return
code "Use Reply Path TLV in the echo reply for building the next echo
request", log information should be generated indicating the return
code and the operator may choose to specify the return path
explicitly or use other mechanisms to verify the SR policy. If the
return code is TBA2, "Local policy does not allow dynamic Return Path
building", it indicates that the intermediate node does not support
building the dynamic return path. Log information should be
generated on the initiator receiving this return code and the
operator may choose to specify the return path explicitly or use
other mechanisms to verify the SR Policy. If the TTL is already 255,
the traceroute procedure MUST be ended with an appropriate log
message.
5.5. 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
routers in the path to build the reverse path for MPLS traceroute
procedures. For this purpose, the Reply Path TLV in the echo reply
corresponds to the return path to be used in building the next echo
request. A new return code "Use Reply Path TLV in the echo reply for
building the next echo request" is defined in this document.
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Value Meaning
------ ----------------------
TBA1 Use Reply Path TLV in the echo reply
for building the next echo request.
5.5.1. 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 head-end/PMS node may include its node label while initiating the
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
which can be inferred from the LSDB, 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 the ABR's own SRGB. This
is because downstream nodes in the path 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 the ASBR
is configured to build the return path dynamically, the ASBR should
build a Reply Path TLV and include it in the echo reply. The Reply
Path TLV should consist of its node label and an EPE-SID to the AS
from where the traceroute message was received. A Reply path return
code of TBA1 MUST be set in the echo reply to indicate that the next
echo request MUST use the return Path from the Reply Path TLV in 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. In case the ASBR identifies multiple paths to reach
the initiator, it MUST choose to send one such path in the Reply Path
TLV. 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
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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 to the echo requests MUST always translate the
Reply Path TLV to a label stack and build an MPLS header for 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 the 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 non-domain border nodes might 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 head-end node/PMS
that initiates the traceroute procedure MUST continue to send the
previously sent Reply Path TLV in the echo request message in every
subsequent 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, an 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.
6. 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 the same administration or closely cooperating
administrations. 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
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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
RECOMMENDED that an operator deploy security mechanisms such as
MACsec [IEEE-802.1AE] on inter-domain links or security-vulnerable
links to prevent spoofing attacks.
All the security considerations defined in [RFC8029] will be
applicable for this document. 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 Denial-of-service attacks as
described in [RFC8029].
7. IANA Considerations
7.1. Segment Sub-TLV
IANA should assign three new sub-TLVs from the "sub-TLVs for TLV
Types 1, 16, and 21" sub-registry of the "Multiprotocol 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)
7.2. 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 "Multiprotocol 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 7.
New entries are assigned by Standards Action. Initial entries in the
registry are as follows:
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Bit number | Name | Reference
------------+----------------------------+--------------
1 | A Flag | Section 4.4
| | of this document
7.3. Reply Path Return Codes Registry
IANA should assign new return codes in the "Reply path return codes"
registry under the "Multiprotocol 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).
8. Contributors
Carlos Pignataro
NC State University
cpignata@gmail.com
Zafar Ali
Cisco Systems, Inc.
zali@cisco.com
9. Implementation Status
This section is to be removed before publishing as an RFC.
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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.
9.1. 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
10. Acknowledgments
Thanks to Bruno Decraene 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 the use of Reply Path TLV. Thanks to Gregory Mirsky for
the detailed review which helped improve the readability of the
document to a great extent.
11. APPENDIX
This section elaborates examples of the inter-domain ping and
Traceroute procedures described in this document.
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11.1. Detailed Example
The example topology given in Figure 1 will be used in the below
sections to explain LSP ping and traceroute procedures. The PMS/
head-end has a complete view of the topology. PE1, P1, P2, ASBR1,
and ASBR2 are in AS1. Similarly, ASBR3, ASBR4, P3, P4, and PE4 are
in AS2.
AS1 and AS2 have SR 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 etc.
Adjacency-SIDs: Adj-PE1-P1, Adj-P1-P2 etc.
EPE-SIDs: EPE-ASBR2-ASBR3, EPE-ASBR1-ASBR4, EPE-ASBR3-ASBR2 etc.
11.1.1. 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 a controller-computed inter-domain
path, there may be no IP connectivity from PE4 to PE1 as they lie in
different ASes.
PE1 sends an echo request message to the endpoint 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, the 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.
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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 an 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 the Reply Path TLV. PE4
builds the echo reply packet with the MPLS label stack constructed
and imposes MPLS headers on top of the echo reply packet and sends
out the packet to PE1. This segment List stack can successfully
steer the reply back to the head-end node (PE1).
Let us consider a case when P3 node does not have a route to reach
N-PE4. On P3 ping packet would be dropped and the head-end node
(PE1) will not receive Echo Reply indicating failure.
11.1.2. Procedures for SR LSP traceroute
11.1.2.1. Procedures for SR LSP traceroute with the Same SRGB on All
Nodes
The traceroute procedure involves visiting every node on the path and
obtaining echo replies from every node. In this section, we describe
the traceroute mechanisms when the head-end/PMS has complete
visibility of the LSDB. The head-end/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
head-end/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 the border node's Node-SID, EPE-SID
in the reverse direction also needs to be added to the label stack.
The Inter-domain/inter-AS traceroute procedure uses the TTL expiry
mechanism as specified in [RFC8029] and [RFC8287]. Every echo
request packet head-end/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 5.1 and Section 5.2 to send
out an echo reply.
For Example:
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Let us consider a topology from Figure 1. Let us consider an 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 a Reply Path
TLV consisting of a Type-A segment containing a label derived from
its own SR Global Block (SRGB). Note that the type of segment used
in constructing the return Path is determined by 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 the traceroute reaches the first domain border
as the return IP path to PE1 is expected to be available inside the
first domain.
The 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 a single Label (PE1's node Label)
is used. When an 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 LSDB 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 LSDB
of all the domains to be available at the head-end/PMS.
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Let us consider a case when P3 node does not have a route to reach
N-PE4. When TTL of the packet is 5, the packet reaches P3 and the
packet TTL becomes zero and the packet is sent to the control plane.
The FEC validation Procedures are executed and the Echo Reply is sent
using the labels in Reply Path TLV which is [N-PE1, EPE-ASBR4-ASBR1,
N-ASBR4]. Head-end PE1 increases the TTL to 6 and sends next Echo
Request. The packet is dropped at P3 as there is no route on P3 to
forward to N-PE4. Traceroute identifies the path [N-P1, N-ASBR1,
EPE-ASBR1-ASBR4, N-PE4] is broken at P3.
11.1.2.2. Procedures for SR LSP Traceroute with the Different SRGBs
Section 11.1.2.1 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
SRGBs. In such scenarios, PE1 finds out the difference in SRGB by
looking into the LSDB and sends Type-C (or Type-D in the 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, head-end 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)].
If the packet needs to follow return path specific to an algorithm
(as defined in [RFC9350]), a Type-C Segment sub-TLV with
corresponding algorithm field set should be used. A-flag should be
set to indicate that the SID corresponding to the algorithm should be
used.
To extend the example to 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 head-end 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 ASBR8, the EPE-SID
from ASBR8 to ASBR6 is added to the Reply Path TLV. While visiting
nodes in AS3, the 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]
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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.
11.1.3. Procedures for building Reply Path TLV dynamically
Let us consider a topology from Figure 1. Let us consider an SR
policy path built from PE1 to PE4 with the label stack, N-P1,
N-ASBR1, EPE-ASBR1-ASBR4, N-PE4. PE1 begins traceroute with the 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 an echo
reply with the same Reply Path TLV with the 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 head-end continues to
use the same return path in the echo request that it used to send the
previous echo request.
When ASBR1 receives the echo request, in the case it receives the
Type-C/Type-D segment in the Reply Path TLV in the echo request, it
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 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 requests 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
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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]. The
next echo request with TTL 2 reaches the P node. It is an internal
node so it does not change the return Path. The echo request with
TTL 3 reaches ABR2 and it adds its node label so the Reply Path TLV
sent in the echo reply will be [N-ABR2, N-ABR1, N-PE1]. echo request
with 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 a 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
segment to the Reply Path TLV.
12. References
12.1. 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>.
12.2. Informative References
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[IEEE-802.1AE]
IEEE, "IEEE Standard for Local and metropolitan area
networks–Media Access Control (MAC) Security", August
2023.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
<https://www.rfc-editor.org/info/rfc3032>.
[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>.
[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>.
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[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>.
[RFC9350] Psenak, P., Ed., Hegde, S., Filsfils, C., Talaulikar, K.,
and A. Gulko, "IGP Flexible Algorithm", RFC 9350,
DOI 10.17487/RFC9350, February 2023,
<https://www.rfc-editor.org/info/rfc9350>.
[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
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Samson Ninan
Ciena
Email: samson.cse@gmail.com
Nagendra Kumar
Oracle
Email: nagendrakumar.nainar@gmail.com
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