Networking Working Group P. Psenak, Ed.
Internet-Draft C. Filsfils
Updates: 7370 (if approved) Cisco Systems
Intended status: Standards Track A. Bashandy
Expires: April 23, 2022 Individual
B. Decraene
Orange
Z. Hu
Huawei Technologies
October 20, 2021
IS-IS Extensions to Support Segment Routing over IPv6 Dataplane
draft-ietf-lsr-isis-srv6-extensions-18
Abstract
The Segment Routing (SR) architecture allows flexible definition of
the end-to-end path by encoding it as a sequence of topological
elements called "segments". It can be implemented over the MPLS or
the IPv6 data plane. This document describes the IS-IS extensions
required to support Segment Routing over the IPv6 data plane.
This document updates RFC 7370 by modifying an existing registry.
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.
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."
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This Internet-Draft will expire on April 23, 2022.
Copyright Notice
Copyright (c) 2021 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 Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. SRv6 Capabilities sub-TLV . . . . . . . . . . . . . . . . . . 4
3. Advertising Supported Algorithms . . . . . . . . . . . . . . 5
4. Advertising Maximum SRv6 SID Depths . . . . . . . . . . . . . 5
4.1. Maximum Segments Left MSD Type . . . . . . . . . . . . . 5
4.2. Maximum End Pop MSD Type . . . . . . . . . . . . . . . . 5
4.3. Maximum H.Encaps MSD Type . . . . . . . . . . . . . . . . 5
4.4. Maximum End D MSD Type . . . . . . . . . . . . . . . . . 6
5. SRv6 SIDs and Reachability . . . . . . . . . . . . . . . . . 6
6. Advertising Anycast Property . . . . . . . . . . . . . . . . 8
7. Advertising Locators and End SIDs . . . . . . . . . . . . . . 9
7.1. SRv6 Locator TLV Format . . . . . . . . . . . . . . . . . 9
7.2. SRv6 End SID sub-TLV . . . . . . . . . . . . . . . . . . 11
8. Advertising SRv6 Adjacency SIDs . . . . . . . . . . . . . . . 12
8.1. SRv6 End.X SID sub-TLV . . . . . . . . . . . . . . . . . 13
8.2. SRv6 LAN End.X SID sub-TLV . . . . . . . . . . . . . . . 14
9. SRv6 SID Structure Sub-Sub-TLV . . . . . . . . . . . . . . . 16
10. Advertising Endpoint Behaviors . . . . . . . . . . . . . . . 17
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
11.1. SRv6 Locator TLV . . . . . . . . . . . . . . . . . . . . 18
11.1.1. SRv6 End SID sub-TLV . . . . . . . . . . . . . . . . 18
11.1.2. Revised sub-TLV table . . . . . . . . . . . . . . . 19
11.2. SRv6 Capabilities sub-TLV . . . . . . . . . . . . . . . 19
11.3. Sub-Sub-TLVs of the SRv6 Capability sub-TLV . . . . . . 20
11.4. SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs . . . . . 20
11.5. MSD Types . . . . . . . . . . . . . . . . . . . . . . . 20
11.6. Sub-Sub-TLVs for SID Sub-TLVs . . . . . . . . . . . . . 21
11.7. Prefix Attribute Flags Sub-TLV . . . . . . . . . . . . . 21
11.8. ISIS SRv6 Capabilities sub-TLV Flags Registry . . . . . 21
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11.9. ISIS SRv6 Locator TLV Flags Registry . . . . . . . . . . 22
11.10. ISIS SRv6 End SID sub-TLV Flags Registry . . . . . . . . 22
11.11. ISIS SRv6 End.X SID and LAN End.X SID sub-TLVs Flags
Registry . . . . . . . . . . . . . . . . . . . . . . . . 23
12. Security Considerations . . . . . . . . . . . . . . . . . . . 23
13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 24
14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 25
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 26
15.1. Normative References . . . . . . . . . . . . . . . . . . 26
15.2. Informative References . . . . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
1. Introduction
With Segment Routing (SR) [RFC8402], a node steers a packet through
an ordered list of instructions, called segments.
Segments are identified through Segment Identifiers (SIDs).
Segment Routing can be directly instantiated on the IPv6 data plane
through the use of the Segment Routing Header defined in [RFC8754].
SRv6 refers to this SR instantiation on the IPv6 dataplane.
The network programming paradigm [RFC8986] is central to SRv6. It
describes how any behavior can be bound to a SID and how any network
program can be expressed as a combination of SIDs.
This document specifies IS-IS extensions that allow the IS-IS
protocol to encode some of these SIDs and their behaviors.
Familiarity with the network programming paradigm [RFC8986] is
necessary to understand the extensions specified in this document.
The new SRv6 Locator top level TLV announces SRv6 locators - a form
of summary address for the set of topology/algorithm-specific SIDs
instantiated at the node.
The SRv6 Capabilities sub-TLV announces the ability to support SRv6.
Several new sub-TLVs are defined to advertise various SRv6 Maximum
SID Depths.
The SRv6 End SID sub-TLV, the SRv6 End.X SID sub-TLV, and the SRv6
LAN End.X SID sub-TLV are used to advertise which SIDs are
instantiated at a node and what Endpoint behavior is bound to each
instantiated SID.
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This document updates [RFC7370] by modifying an existing registry
(Section 11.1.2).
2. SRv6 Capabilities sub-TLV
A node indicates that it supports the SR Segment Endpoint Node
functionality as specified in [RFC8754] by advertising a new SRv6
Capabilities sub-TLV of the router capabilities TLV [RFC7981].
The SRv6 Capabilities sub-TLV may contain optional sub-sub-TLVs. No
sub-sub-TLVs are currently defined.
The SRv6 Capabilities sub-TLV has the following format:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| optional sub-sub-TLVs...
Type: 25. Single octet as defined in section 9 of [ISO10589].
Length: Single octet as defined in section 9 of [ISO10589]. The length value is
2 + length of sub-sub-TLVs.
Flags: 2 octets The following flags are defined:
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |O| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
O-flag: If set, the router supports use of the O-bit
in the Segment Routing Header (SRH) as defined in
[I-D.ietf-6man-spring-srv6-oam].
The remaining bits, including bit 0, are reserved for future use. They MUST be
set to zero on transmission and MUST be ignored on receipt.
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3. Advertising Supported Algorithms
An SRv6 capable router indicates supported algorithm(s) by
advertising the Segment Routing Algorithm sub-TLV as defined in
[RFC8667].
4. Advertising Maximum SRv6 SID Depths
[RFC8491] defines the means to advertise node/link specific values
for Maximum SID Depths (MSD) of various types. Node MSDs are
advertised in a sub-TLV of the Router Capabilities TLV [RFC7981].
Link MSDs are advertised in a sub-TLV of TLVs 22, 23, 25, 141, 222,
and 223.
This document defines the relevant SRv6 MSDs and requests MSD type
assignments in the MSD Types registry created by [RFC8491].
4.1. Maximum Segments Left MSD Type
The Maximum Segments Left MSD Type signals the maximum value of the
"Segments Left" field [RFC8754] in the SRH of a received packet
before applying the Endpoint behavior associated with a SID.
SRH Max Segments Left Type: 41
If no value is advertised, the supported value is 0.
4.2. Maximum End Pop MSD Type
The Maximum End Pop MSD Type signals the maximum number of SIDs in
the SRH to which the router can apply "Penultimate Segment Pop of the
SRH" or "Ultimate Segment Pop of the SRH" behavior, as defined in
[RFC8986] flavors.
SRH Max End Pop Type: 42
If the advertised value is zero or no value is advertised,
then the router cannot apply PSP or USP flavors.
4.3. Maximum H.Encaps MSD Type
The Maximum H.Encaps MSD Type signals the maximum number of SIDs that
can be added to the Segment List of an SRH as part of the "H.Encaps"
behavior as defined in [RFC8986].
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SRH Max H.encaps Type: 44
If the advertised value is zero or no value is advertised, then the
headend can apply an SR Policy that only contains one segment, without
inserting any SRH header.
A non-zero SRH Max H.encaps MSD indicates that the headend can insert
an SRH up to the advertised number of SIDs.
4.4. Maximum End D MSD Type
The Maximum End D MSD Type specifies the maximum number of SIDs
present in an SRH when performing decapsulation. As specified in
[RFC8986] the permitted SID types include, but are not limited to
End.DX6, End.DT4, End.DT46, End with USD, End.X with USD.
SRH Max End D Type: 45
If the advertised value is zero or no value is advertised
then the router cannot apply any behavior that results in
decapsulation and forwarding of the inner packet if the
outer IPv6 header contains an SRH.
5. SRv6 SIDs and Reachability
As discussed in [RFC8986], an SRv6 Segment Identifier (SID) is 128
bits and consists of Locator, Function and Argument parts.
A node is provisioned with topology/algorithm specific locators for
each of the topology/algorithm pairs supported by that node. Each
locator is a covering prefix for all SIDs provisioned on that node
which have the matching topology/algorithm.
Locators MUST be advertised in the SRv6 Locator TLV (see
Section 7.1). Forwarding entries for the locators advertised in the
SRv6 Locator TLV MUST be installed in the forwarding plane of
receiving SRv6 capable routers when the associated topology/algorithm
is supported by the receiving node. The processing of the prefix
advertised in the SRv6 Locator TLV, the calculation of its
reachability and the installation in the forwarding plane follows the
process defined for the Prefix Reachability TLV 236 [RFC5308], or TLV
237 [RFC5120].
Locators associated with algorithm 0 and 1 (for all supported
topologies) SHOULD be advertised in a Prefix Reachability TLV (236 or
237) so that legacy routers (i.e., routers which do not support SRv6)
will install a forwarding entry for algorithm 0 and 1 SRv6 traffic.
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In cases where the same prefix, with the same prefix-length, Multi
Topology ID (MT ID), and algorithm is received in both a Prefix
Reachability TLV and an SRv6 Locator TLV, the Prefix Reachability
advertisement MUST be preferred when installing entries in the
forwarding plane. This is to prevent inconsistent forwarding entries
between SRv6 capable and SRv6 incapable routers. Such preference of
Prefix Reachability advertisement does not have any impact on the
rest of the data advertised in the SRv6 Locator TLV.
Locators associated with Flexible Algorithms (see Section 4 of
[I-D.ietf-lsr-flex-algo]) SHOULD NOT be advertised in Prefix
Reachability TLVs (236 or 237). Advertising the Flexible Algorithm
locator in regular Prefix Reachability TLV (236 or 237) would make
the forwarding for it to follow algo 0 path.
SRv6 SIDs are advertised as sub-TLVs in the SRv6 Locator TLV except
for SRv6 SIDs which are associated with a specific Neighbor/Link and
are therefore advertised as sub-TLVs in TLVs 22, 23, 25, 141, 222,
and 223.
SRv6 SIDs received from other nodes are not directly routable and
MUST NOT be installed in the forwarding plane. Reachability to SRv6
SIDs depends upon the existence of a covering locator.
Adherence to the rules defined in this section will assure that SRv6
SIDs associated with a supported topology/algorithm pair will be
forwarded correctly, while SRv6 SIDs associated with an unsupported
topology/algorithm pair will be dropped. NOTE: The drop behavior
depends on the absence of a default/summary route covering a given
locator.
In order for forwarding to work correctly, the locator associated
with SRv6 SID advertisements must be the longest match prefix
installed in the forwarding plane for those SIDs. In order to ensure
correct forwarding, network operators should take steps to make sure
that this requirement is not compromised. For example, the following
situations should be avoided:
o Another locator associated with a different topology/algorithm is
the longest match
o Another prefix advertisement (i.e., from TLV 236 or 237) is the
longest match
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6. Advertising Anycast Property
Both prefixes and SRv6 Locators may be configured as anycast and as
such the same value can be advertised by multiple routers. It is
useful for other routers to know that the advertisement is for an
anycast identifier.
A new flag in Prefix Attribute Flags Sub-TLV [RFC7794] is defined to
advertise the anycast property:
Bit #: 4
Name: Anycast Flag (A-flag)
When the prefix/SRv6 locator is configured as anycast, the A-flag
SHOULD be set. Otherwise, this flag MUST be clear.
The A-flag MUST be preserved when the advertisement is leaked between
levels.
The A-flag and the N-flag MUST NOT both be set. If both N-flag and
A-flag are set in the prefix/SRv6 Locator advertisement, the
receiving routers MUST ignore the N-flag.
The same prefix/SRv6 Locator can be advertised by multiple routers.
If at least one of them sets the A-Flag in its advertisement, the
prefix/SRv6 Locator SHOULD be considered as anycast.
A prefix/SRv6 Locator that is advertised by a single node and without
an A-Flag is considered node specific.
All the nodes advertising the same anycast locator MUST instantiate
the exact same set of SIDs under that anycast locator. Failure to do
so may result in traffic being black-holed or mis-routed.
The Prefix Attribute Flags Sub-TLV can be carried in the SRv6 Locator
TLV as well as the Prefix Reachability TLVs. When a router
originates both the Prefix Reachability TLV and the SRv6 Locator TLV
for a given prefix, and the router is originating the Prefix
Attribute Flags Sub-TLV in one of the TLVs, the router SHOULD
advertise the same flags in the Prefix Attribute Flags Sub-TLV in
both TLVs. However, unlike TLVs 236 [RFC5308] and 237 [RFC5120] the
X-flag in the Prefix Attributes Flags sub-TLV is valid when sent in
the SRv6 Locator TLV. The state of the X-flag in the Prefix
Attributes Flags sub-TLV when included in the Locator TLV MUST match
the setting of the embedded "X-bit" in any advertisement for the same
prefix in TLVs 236 [RFC5308] and 237 [RFC5120]. In case of any
inconsistency between the Prefix Attribute Flags advertised in the
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Locator TLV and in the Prefix Reachability TLV, the ones advertised
in Prefix Reachability TLV MUST be preferred.
7. Advertising Locators and End SIDs
The SRv6 Locator TLV is introduced to advertise SRv6 Locators and End
SIDs associated with each locator.
This new TLV shares the sub-TLV space defined for TLVs 135, 235, 236
and 237.
7.1. SRv6 Locator TLV Format
The SRv6 Locator TLV has the following format:
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 |R|R|R|R| MT ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator Entries . . . |
Type: 27. Single octet as defined in section 9 of [ISO10589].
Length: Single octet as defined in section 9 of [ISO10589]. The
length value is variable.
R bits: reserved for future use. They MUST be set to zero on
transmission and MUST be ignored on receipt.
MT ID: Multitopology Identifier as defined in [RFC5120]. Note
that the value 0 is legal.
Followed by one or more locator entries of the form:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Algorithm | Loc Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Locator (continued, variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLV-len | Sub-TLVs (variable) . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Metric: 4 octets. As described in Section 4 of [RFC5305].
Flags: 1 octet. The following flags are defined:
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|D| Reserved |
+-+-+-+-+-+-+-+-+
D-flag: Same as described in section 4.1. of [RFC5305].
The remaining bits are reserved for future use. They MUST be
set to zero on transmission and MUST be ignored on receipt.
Algorithm: 1 octet. As defined in IGP Algorithm Types registry
[RFC8665].
Loc-Size: 1 octet. Number of bits in the SRv6 Locator field.
MUST be from the range (1 - 128). The TLV MUST be ignored if the
Loc-Size is outside this range.
Locator: 1-16 octets. This field encodes the advertised SRv6
Locator. The Locator is encoded in the minimal number of octets
for the given number of bits. Trailing bits MUST be set to zero
and ignored when received.
Sub-TLV-length: 1 octet. Number of octets used by sub-TLVs.
Optional sub-TLVs: Supported sub-TLVs are specified in
Section 11.1.2. Any Sub-TLV that is not allowed in the SRv6
Locator TLV MUST be ignored.
Prefix Attribute Flags Sub-TLV [RFC7794] SHOULD be included in the
Locator TLV.
Prefix Attribute Flags Sub-TLV MUST be included in the the Locator
TLV when it is leaked upwards in the hierarchy or originated as a
result of the redistribution from another protocol or another ISIS
instance. If the Prefix Attribute Flags Sub-TLV is not included in
these cases, receivers will be unable to determine the correct source
of the advertisement. The receivers will be unable to detect the
violation.
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7.2. SRv6 End SID sub-TLV
The SRv6 End SID sub-TLV is introduced to advertise SRv6 Segment
Identifiers (SID) with Endpoint behaviors which do not require a
particular neighbor in order to be correctly applied. SRv6 SIDs
associated with a neighbor are advertised using the sub-TLVs defined
in Section 8.
Supported behavior values, together with parent TLVs in which they
are advertised, are specified in Section 10 of this document. Please
note that not all behaviors defined in [RFC8986] are defined in this
document, e.g. END.T is not.
This new sub-TLV is advertised in the SRv6 Locator TLV defined in the
previous section. SRv6 End SIDs inherit the topology/algorithm from
the parent locator.
The SRv6 End SID sub-TLV has the following format:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Endpoint Behavior |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (128 bits) . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont . . .) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont . . .) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont . . .) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Sub-sub-TLV-len| Sub-sub-TLVs (variable) . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 5. Single octet as defined in section 9 of [ISO10589].
Length: Single octet as defined in section 9 of [ISO10589]. The
length value is variable.
Flags: 1 octet. No flags are currently defined. All bits are
reserved for future use. They MUST be set to zero on transmission
and MUST be ignored on receipt.
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Endpoint Behavior: 2 octets, as defined in [RFC8986]. Supported
behavior values for this sub-TLV are defined in Section 10 of this
document. Unsupported or unrecognized behavior values are ignored
by the receiver.
SID: 16 octets. This field encodes the advertised SRv6 SID.
Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub-
TLVs.
Optional Sub-sub-TLVs: Supported Sub-sub-TLVs are specified in
Section 11.6. Any Sub-sub-TLV that is not allowed in SRv6 End SID
sub-TLV MUST be ignored.
The SRv6 End SID MUST be allocated from its associated locator. SRv6
End SIDs that are not allocated from the associated locator MUST be
ignored.
Multiple SRv6 End SIDs MAY be associated with the same locator. In
cases where the number of SRv6 End SID sub-TLVs exceeds the capacity
of a single TLV, multiple Locator TLVs for the same locator MAY be
advertised. For a given MTID/Locator the algorithm MUST be the same
in all TLVs. If this restriction is not met all TLVs for that MTID/
Locator MUST be ignored.
8. Advertising SRv6 Adjacency SIDs
Certain SRv6 Endpoint behaviors [RFC8986] are associated with a
particular adjacency.
This document defines two new sub-TLVs of TLV 22, 23, 25, 141, 222,
and 223 - namely "SRv6 End.X SID sub-TLVs" and "SRv6 LAN End.X SID
sub-TLVs".
IS-IS Neighbor advertisements are topology specific - but not
algorithm specific. SIDs advertised in SRv6 End.X SID and SRv6 LAN
End.X SID sub-TLVs therefore inherit the topology from the associated
neighbor advertisement, but the algorithm is specified in the
individual SID.
All SIDs advertised in SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs
MUST be a subnet of a Locator with matching topology and algorithm
which is advertised by the same node in an SRv6 Locator TLV. SIDs
that do not meet this requirement MUST be ignored. This ensures that
the node advertising these SIDs is also advertising its corresponding
Locator with the algorithm that will be used for computing paths
destined to the SID.
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8.1. SRv6 End.X SID sub-TLV
This sub-TLV is used to advertise an SRv6 SID associated with a point
to point adjacency. Multiple SRv6 End.X SID sub-TLVs MAY be
associated with the same adjacency.
The SRv6 End.X SID sub-TLV has the following format:
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 | Algorithm |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Weight | Endpoint Behavior |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (128 bits) . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont . . .) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont . . .) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont . . .) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Sub-sub-tlv-len| Sub-sub-TLVs (variable) . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 43. Single octet as defined in section 9 of [ISO10589].
Length: Single octet as defined in section 9 of [ISO10589]. The
length value is variable.
Flags: 1 octet.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|B|S|P|Reserved |
+-+-+-+-+-+-+-+-+
where:
B-Flag: Backup flag. If set, the SID is eligible for
protection, e.g., using IP Fast Re-route (IPFRR) [RFC5286], as
described in [RFC8355].
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S-Flag. Set flag. When set, the S-Flag indicates that the SID
refers to a set of adjacencies (and therefore MAY be assigned
to other adjacencies as well).
P-Flag. Persistent flag. When set, the P-Flag indicates that
the SID is persistently allocated, i.e., the SID value remains
consistent across router restart and/or interface flap.
Reserved bits: MUST be zero when originated and MUST be ignored
when received.
Algorithm: 1 octet. As defined in IGP Algorithm Types registry
[RFC8665].
Weight: 1 octet. The value represents the weight of the SID for
the purpose of load balancing. The use of the weight is defined
in [RFC8402].
Endpoint Behavior: 2 octets. As defined in [RFC8986]. Supported
behavior values for this sub-TLV are defined in Section 10 of this
document. Unsupported or unrecognized behavior values are ignored
by the receiver.
SID: 16 octets. This field encodes the advertised SRv6 SID.
Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub-
TLVs.
Optional Sub-sub-TLVs: Supported Sub-sub-TLVs are specified in
Section 11.6. Any Sub-sub-TLV that is not allowed in SRv6 End.X
SID sub-TLV MUST be ignored.
Note that multiple TLVs for the same neighbor may be required in
order to advertise all the SRv6 SIDs associated with that neighbor.
8.2. SRv6 LAN End.X SID sub-TLV
This sub-TLV is used to advertise an SRv6 SID associated with a LAN
adjacency. Since the parent TLV is advertising an adjacency to the
Designated Intermediate System (DIS) for the LAN, it is necessary to
include the System ID of the physical neighbor on the LAN with which
the SRv6 SID is associated. Given that many neighbors may exist on a
given LAN, multiple SRv6 LAN END.X SID sub-TLVs may be associated
with the same LAN. Note that multiple TLVs for the same DIS neighbor
may be required in order to advertise all the SRv6 SIDs associated
with that neighbor.
The SRv6 LAN End.X SID sub-TLV has the following format:
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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 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| Neighbor System-ID (ID length octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Algorithm | Weight |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Endpoint Behavior |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (128 bits) . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont . . .) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont . . .) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont . . .) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Sub-sub-TLV-len| sub-sub-TLVs (variable) . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 44. Single octet as defined in section 9 of [ISO10589].
Length: Single octet as defined in section 9 of [ISO10589]. The
length value is variable.
Neighbor System-ID: IS-IS System-ID of length "ID Length" as
defined in [ISO10589].
Flags: 1 octet.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|B|S|P|Reserved |
+-+-+-+-+-+-+-+-+
where B,S, and P flags are as described in Section 8.1.
Reserved bits MUST be zero when originated and MUST be ignored
when received.
Algorithm: 1 octet. As defined in IGP Algorithm Types registry
[RFC8665].
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Weight: 1 octet. The value represents the weight of the SID for
the purpose of load balancing. The use of the weight is defined
in [RFC8402].
Endpoint Behavior: 2 octets. As defined in [RFC8986]. Supported
behavior values for this sub-TLV are defined in Section 10 of this
document. Unsupported or unrecognized behavior values are ignored
by the receiver.
SID: 16 octets. This field encodes the advertised SRv6 SID.
Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub-
TLVs.
Optional Sub-sub-TLVs: Supported Sub-sub-TLVs are specified in
Section 11.6. Any Sub-sub-TLV that is not allowed in SRv6 LAN
End.X SID sub-TLV MUST be ignored.
Note that multiple TLVs for the same neighbor, on the same LAN, may
be required in order to advertise all the SRv6 SIDs associated with
that neighbor.
9. SRv6 SID Structure Sub-Sub-TLV
SRv6 SID Structure Sub-Sub-TLV is an optional Sub-Sub-TLV of:
SRv6 End SID Sub-TLV (Section 7.2)
SRv6 End.X SID Sub-TLV (Section 8.1)
SRv6 LAN End.X SID Sub-TLV (Section 8.2)
SRv6 SID Structure Sub-Sub-TLV is used to advertise the structure of
the SRv6 SID as defined in [RFC8986]. It has the following format:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LB Length | LN Length | Fun. Length | Arg. Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Type: 1. Single octet as defined in section 9 of [ISO10589].
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Length: Single octet as defined in section 9 of [ISO10589]. The
length value is 4 octets.
LB Length: 1 octet. SRv6 SID Locator Block length in bits.
LN Length: 1 octet. SRv6 SID Locator Node length in bits.
Fun. Length: 1 octet. SRv6 SID Function length in bits.
Arg. Length: 1 octet. SRv6 SID Arguments length in bits.
ISIS SRv6 SID Structure Sub-Sub-TLV MUST NOT appear more than once in
its parent Sub-TLV. If it appears more than once in its parent Sub-
TLV, the parent Sub-TLV MUST be ignored by the receiver.
The sum of all four sizes advertised in ISIS SRv6 SID Structure Sub-
Sub-TLV MUST be less than or equal to 128 bits. If the sum of all
four sizes advertised in the ISIS SRv6 SID Structure Sub-Sub-TLV is
larger than 128 bits, the parent Sub-TLV MUST be ignored by the
receiver.
The SRv6 SID Structure Sub-Sub-TLV is intended for informational use
by the control and management planes. It MUST NOT be used at a
transit node (as defined in [RFC8754]) for forwarding packets. As an
example, this information could be used for:
o validation of SRv6 SIDs being instantiated in the network and
advertised via ISIS. These can be learnt by controllers via BGP-
LS and then be monitored for conformance to the SRv6 SID
allocation scheme chosen by the operator as described in
Section 3.2 of [RFC8986].
o verification and the automation for securing the SRv6 domain by
provisioning filtering rules at SR domain boundaries as described
in Section 5 of [RFC8754].
The details of these potential applications are outside the scope of
this document.
10. Advertising Endpoint Behaviors
Endpoint behaviors are defined in [RFC8986]. The codepoints for the
Endpoint behaviors are defined in the "SRv6 Endpoint Behaviors"
registry defined in [RFC8986]. If a behavior is advertised it MUST
only be advertised in the TLV[s] marked with "Y" in the table below,
and MUST NOT be advertised in the TLV[s] marked with "N" in the table
below.
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Endpoint |Endpoint | End | End.X | Lan End.X |
Behavior |Behavior Codepoint| SID | SID | SID |
----------------------|------------------|-----|-------|-----------|
End (PSP, USP, USD)| 1-4, 28-31 | Y | N | N |
----------------------|------------------|-----|-------|-----------|
End.X (PSP, USP, USD)| 5-8, 32-35 | N | Y | Y |
----------------------|------------------|-----|-------|-----------|
End.DX6 | 16 | N | Y | Y |
----------------------|------------------|-----|-------|-----------|
End.DX4 | 17 | N | Y | Y |
----------------------|------------------|-----|-------|-----------|
End.DT6 | 18 | Y | N | N |
----------------------|------------------|-----|-------|-----------|
End.DT4 | 19 | Y | N | N |
----------------------|------------------|-----|-------|-----------|
End.DT46 | 20 | Y | N | N |
11. IANA Considerations
This document requests allocation for the following TLVs, sub-TLVs,
and sub-sub-TLVs as well as updating the ISIS TLV registry and
defining new registries.
11.1. SRv6 Locator TLV
This document makes the following registrations in the IS-IS TLV
Codepoints registry.
Type Description IIH LSP SNP Purge
---- --------------------- --- --- --- -----
27 SRv6 Locator TLV n y n n
11.1.1. SRv6 End SID sub-TLV
The SRv6 Locator TLV shares sub-TLV space with TLVs 135, 235, 236 and
237. This document updates the "Sub-TLVs for TLVs 135, 235, 236, and
237 (Extended IP reachability, MT IP. Reach, IPv6 IP. Reach, and MT
IPv6 IP. Reach TLVs)" registry defined in [RFC7370]. IANA is
requested to update the name of the "Sub-TLVs for TLVs 135, 235, 236,
and 237 (Extended IP reachability, MT IP. Reach, IPv6 IP. Reach,
and MT IPv6 IP. Reach TLVs)" registry to "Sub-TLVs for TLVs 27, 135,
235, 236, and 237 (SRv6 Locator, Extended IP reachability, MT IP.
Reach, IPv6 IP. Reach, and MT IPv6 IP. Reach TLVs)".
IANA is asked to add this document as a reference to (renamed) "Sub-
TLVs for TLVs 27, 135, 235, 236, and 237 (SRv6 Locator, Extended IP
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reachability, MT IP. Reach, IPv6 IP. Reach, and MT IPv6 IP. Reach
TLVs)" registry.
This document makes the following registrations in the (renamed)
"Sub-TLVs for TLVs 27, 135, 235, 236, and 237 (SRv6 Locator, Extended
IP reachability, MT IP. Reach, IPv6 IP. Reach, and MT IPv6 IP.
Reach TLVs)" registry:
Type: 5
Description: SRv6 End SID sub-TLV.
Reference: This document (Section 7.2).
11.1.2. Revised sub-TLV table
The revised table of sub-TLVs for the (renamed) "Sub-TLVs for TLVs
27, 135, 235, 236, and 237 (SRv6 Locator, Extended IP reachability,
MT IP. Reach, IPv6 IP. Reach, and MT IPv6 IP. Reach TLVs)"
registry is shown below:
Type 27 135 235 236 237
1 y y y y y
2 y y y y y
3 n y y y y
4 y y y y y
5 y n n n n
6 n y y y y
11 y y y y y
12 y y y y y
32 n y y y y
11.2. SRv6 Capabilities sub-TLV
This document makes the following registrations in the "Sub-TLVs for
TLV 242 (IS-IS Router CAPABILITY TLV)":
Type: 25
Description: SRv6 Capabilities sub-TLV.
Reference: This document (Section 2).
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11.3. Sub-Sub-TLVs of the SRv6 Capability sub-TLV
This document requests a new IANA registry be created under the IS-IS
TLV Codepoints Registry to control the assignment of sub-TLV types
for the SRv6 Capability sub-TLV specified in this document -
Section 2. The suggested name of the new registry is "sub-sub-TLVs
of the SRv6 Capability sub-TLV". The registration procedure is
"Expert Review" as defined in [RFC8126]. Guidance for the Designated
Experts is provided in the [RFC7370]. No sub-sub-TLVs are defined by
this document except for the reserved type 0.
Type Description Encoding
Reference
---------------------------------------------------------
0 Reserved
1-255 Unassigned
11.4. SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs
This document makes the following registrations in the "Sub-TLVs for
TLVs 22, 23, 25, 141, 222, and 223 (Extended IS reachability, IS
Neighbor Attribute, L2 Bundle Member Attributes, inter-AS
reachability information, MT-ISN, and MT IS Neighbor Attribute TLVs)"
registry:
Type: 43
Description: SRv6 End.X SID sub-TLV.
Reference: This document (Section 8.1).
Type: 44
Description: SRv6 LAN End.X SID sub-TLV.
Reference: This document (Section 8.2).
Type 22 23 25 141 222 223
43 y y y y y y
44 y y y y y y
11.5. MSD Types
This document makes the following registrations in the IGP MSD-Types
registry:
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Value Name Reference
------------------
41 SRH Max SL [This Document]
42 SRH Max End Pop [This Document]
44 SRH Max H.encaps [This Document]
45 SRH Max End D [This Document]
11.6. Sub-Sub-TLVs for SID Sub-TLVs
This document requests a new IANA registry be created under the IS-IS
TLV Codepoints Registry to control the assignment of sub-TLV types
for the SID Sub-TLVs specified in this document - Section 7.2,
Section 8.1, Section 8.2. The suggested name of the new registry is
"sub-sub-TLVs for SRv6 End SID and SRv6 End.X SID". The registration
procedure is "Expert Review" as defined in [RFC8126]. Guidance for
the Designated Experts is provided in [RFC7370]. The following
assignments are made by this document:
Type Description Encoding
Reference
---------------------------------------------------------
0 Reserved
1 SRv6 SID Structure Sub-Sub-TLV [This Document]
2-255 Unassigned
Type 5 43 44
1 y y y
11.7. Prefix Attribute Flags Sub-TLV
This document adds a new bit in the "Bit Values for Prefix Attribute
Flags Sub-TLV" registry:
Bit #: 4
Description: Anycast Flag (A-flag)
Reference: This document (Section 6).
11.8. ISIS SRv6 Capabilities sub-TLV Flags Registry
This document requests a new IANA registry be created under the IS-IS
TLV Codepoints Registry to control the assignment of bits 0 to 15 in
the Flags field of the ISIS SRv6 Capabilities sub-TLV specified in
this document (Section 2). The suggested name of the new registry is
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"ISIS SRv6 Capabilities sub-TLV Flags". The registration procedure
is "Expert Review" as defined in [RFC8126]. Guidance for the
Designated Experts is provided in [RFC7370]. The following
assignments are made by this document:
Bit #: 1
Description: O-flag
Reference: This document (Section 2).
Bit #: 0, 2-7
Description: Unassigned
11.9. ISIS SRv6 Locator TLV Flags Registry
This document requests a new IANA registry be created under the IS-IS
TLV Codepoints Registry to control the assignment of bits 0 to 7 in
the Flags field of the ISIS SRv6 Locator TLV specified in this
document (Section 7.1). The suggested name of the new registry is
"ISIS SRv6 Locator TLV Flags". The registration procedure is "Expert
Review" as defined in [RFC8126]. Guidance for the Designated Experts
is provided in [RFC7370]. The following assignments are made by this
document:
Bit #: 0
Description: D-flag
Reference: This document (Section 7.1).
Bit #: 1-7
Description: Unassigned
11.10. ISIS SRv6 End SID sub-TLV Flags Registry
This document requests a new IANA registry be created under the IS-IS
TLV Codepoints Registry to control the assignment of bits 0 to 7 in
the Flags field of the ISIS SRv6 End SID sub-TLV specified in this
document (Section 7.2). The suggested name of the new registry is
"ISIS SRv6 End SID sub-TLV Flags". The registration procedure is
"Expert Review" as defined in [RFC8126]. Guidance for the Designated
Experts is provided in [RFC7370]. No assignments are made by this
document.
Bit #: 0-7
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Description: Unassigned
11.11. ISIS SRv6 End.X SID and LAN End.X SID sub-TLVs Flags Registry
This document requests a new IANA registry be created under the IS-IS
TLV Codepoints Registry to control the assignment of bits 0 to 7 in
the Flags field of the ISIS SRv6 End.X SID and LAN End.X SID sub-TLVs
(Section 8.1 and Section 8.2). The suggested name of the new
registry is "ISIS SRv6 End.X SID and LAN End.X SID sub-TLVs Flags".
The registration procedure is "Expert Review" as defined in
[RFC8126]. Guidance for the Designated Experts is provided in
[RFC7370]. The following assignments are made by this document:
Bit #: 0
Description: B-flag
Reference: This document (Section 8.1).
Bit #: 1
Description: S-flag
Reference: This document (Section 8.1).
Bit #: 2
Description: P-flag
Reference: This document (Section 8.1).
Bit #: 3-7
Description: Unassigned
12. Security Considerations
Security concerns for IS-IS are addressed in [ISO10589], [RFC5304],
and [RFC5310]. While IS-IS is deployed under a single administrative
domain, there can be deployments where potential attackers have
access to one or more networks in the IS-IS routing domain. In these
deployments, the stronger authentication mechanisms defined in the
aforementioned documents SHOULD be used.
This document describes the IS-IS extensions required to support
Segment Routing over an IPv6 data plane. The security considerations
for Segment Routing are discussed in [RFC8402]. [RFC8986] defines
the SRv6 Network Programming concept and specifies the main Segment
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Routing behaviors to enable the creation of interoperable overlays;
the security considerations from that document apply too.
The advertisement for an incorrect MSD value may have negative
consequences, see [RFC8491] for additional considerations.
Security concerns associated with the setting of the O-flag are
described in [I-D.ietf-6man-spring-srv6-oam].
Security concerns associated with the usage of Flex-Algorithms are
described in [I-D.ietf-lsr-flex-algo]).
13. Contributors
The following people gave a substantial contribution to the content
of this document and should be considered as co-authors:
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Stefano Previdi
Huawei Technologies
Email: stefano@previdi.net
Paul Wells
Cisco Systems
Saint Paul,
Minnesota
United States
Email: pauwells@cisco.com
Daniel Voyer
Email: daniel.voyer@bell.ca
Satoru Matsushima
Email: satoru.matsushima@g.softbank.co.jp
Bart Peirens
Email: bart.peirens@proximus.com
Hani Elmalky
Email: hani.elmalky@ericsson.com
Prem Jonnalagadda
Email: prem@barefootnetworks.com
Milad Sharif
Email: msharif@barefootnetworks.com>
Robert Hanzl
Cisco Systems
Millenium Plaza Building, V Celnici 10, Prague 1,
Prague, Czech Republic
Email rhanzl@cisco.com
Ketan Talaulikar
Cisco Systems, Inc.
Email: ketant@cisco.com
14. Acknowledgments
Thanks to Christian Hopps for his review comments and shepherd work.
Thanks to Alvaro Retana and John Scudder for AD review and comments.
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15. References
15.1. Normative References
[I-D.ietf-6man-spring-srv6-oam]
Ali, Z., Filsfils, C., Matsushima, S., Voyer, D., and M.
Chen, "Operations, Administration, and Maintenance (OAM)
in Segment Routing Networks with IPv6 Data plane (SRv6)",
draft-ietf-6man-spring-srv6-oam-11 (work in progress),
June 2021.
[I-D.ietf-lsr-flex-algo]
Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex-
algo-17 (work in progress), July 2021.
[ISO10589]
International Organization for Standardization,
"Intermediate system to Intermediate system intra-domain
routeing information exchange protocol for use in
conjunction with the protocol for providing the
connectionless-mode Network Service (ISO 8473)", Nov 2002.
[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>.
[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120,
DOI 10.17487/RFC5120, February 2008,
<https://www.rfc-editor.org/info/rfc5120>.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, DOI 10.17487/RFC5305, October
2008, <https://www.rfc-editor.org/info/rfc5305>.
[RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308,
DOI 10.17487/RFC5308, October 2008,
<https://www.rfc-editor.org/info/rfc5308>.
[RFC7370] Ginsberg, L., "Updates to the IS-IS TLV Codepoints
Registry", RFC 7370, DOI 10.17487/RFC7370, September 2014,
<https://www.rfc-editor.org/info/rfc7370>.
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[RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and
U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4
and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794,
March 2016, <https://www.rfc-editor.org/info/rfc7794>.
[RFC7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions
for Advertising Router Information", RFC 7981,
DOI 10.17487/RFC7981, October 2016,
<https://www.rfc-editor.org/info/rfc7981>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[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>.
[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>.
[RFC8491] Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg,
"Signaling Maximum SID Depth (MSD) Using IS-IS", RFC 8491,
DOI 10.17487/RFC8491, November 2018,
<https://www.rfc-editor.org/info/rfc8491>.
[RFC8665] Psenak, P., Ed., Previdi, S., Ed., Filsfils, C., Gredler,
H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", RFC 8665,
DOI 10.17487/RFC8665, December 2019,
<https://www.rfc-editor.org/info/rfc8665>.
[RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C.,
Bashandy, A., Gredler, H., and B. Decraene, "IS-IS
Extensions for Segment Routing", RFC 8667,
DOI 10.17487/RFC8667, December 2019,
<https://www.rfc-editor.org/info/rfc8667>.
[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
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[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021,
<https://www.rfc-editor.org/info/rfc8986>.
15.2. Informative References
[RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for
IP Fast Reroute: Loop-Free Alternates", RFC 5286,
DOI 10.17487/RFC5286, September 2008,
<https://www.rfc-editor.org/info/rfc5286>.
[RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
Authentication", RFC 5304, DOI 10.17487/RFC5304, October
2008, <https://www.rfc-editor.org/info/rfc5304>.
[RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic
Authentication", RFC 5310, DOI 10.17487/RFC5310, February
2009, <https://www.rfc-editor.org/info/rfc5310>.
[RFC8355] Filsfils, C., Ed., Previdi, S., Ed., Decraene, B., and R.
Shakir, "Resiliency Use Cases in Source Packet Routing in
Networking (SPRING) Networks", RFC 8355,
DOI 10.17487/RFC8355, March 2018,
<https://www.rfc-editor.org/info/rfc8355>.
Authors' Addresses
Peter Psenak (editor)
Cisco Systems
Pribinova Street 10
Bratislava 81109
Slovakia
Email: ppsenak@cisco.com
Clarence Filsfils
Cisco Systems
Brussels
Belgium
Email: cfilsfil@cisco.com
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Ahmed Bashandy
Individual
Email: abashandy.ietf@gmail.com
Bruno Decraene
Orange
Issy-les-Moulineaux
France
Email: bruno.decraene@orange.com
Zhibo Hu
Huawei Technologies
Email: huzhibo@huawei.com
Psenak, et al. Expires April 23, 2022 [Page 29]
