LSR Routing Working Group J. Dong
Internet-Draft Z. Hu
Intended status: Standards Track Huawei Technologies
Expires: August 24, 2021 February 20, 2021
Advertising SRv6 SIDs for Layer 2 Bundle Member Links in IGP
draft-dong-lsr-l2bundle-srv6-00
Abstract
There are deployments where the Layer-3 interface on which IGP
operates is a Layer-2 interface bundle. Existing IGP advertisements
only support advertising link attributes of the Layer-3 interface.
If entities external to IGP wish to control traffic flows on the
individual physical links that comprise the Layer-2 interface bundle,
link attribute information about the bundle members is advertised by
IGP extensions for Layer-2 (L2) bundle.
When Segment Routing over IPv6 (SRv6) is used with Layer-2 interface
bundle to control traffic flows on the individual member links, the
SRv6 SIDs which represent the Layer 2 member links of the L2 bundle
needs to be advertised in IGP.
This document proposes the IGP extensions to advertise the SRv6 SIDs
of the Layer 2 (L2) bundle member links.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on August 24, 2021.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. SRv6 Function for L2 Bundle Member Links . . . . . . . . . . 3
4. Advertising SRv6 SIDs for L2 Bundle Members . . . . . . . . . 3
4.1. SRv6 SIDs Encodings for IS-IS L2 Bundle . . . . . . . . . 3
4.1.1. L2 Bundle Member SRv6 End.XU SID Sub-TLV . . . . . . 4
4.1.2. L2 Bundle Member SRv6 LAN End.XU SID Sub-TLV . . . . 5
4.2. SRv6 SIDs Encodings for OSPF L2 Bundle . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
There are deployments where the Layer-3 interface on which an IGP
adjacency is established is a Layer-2 interface bundle, for instance,
a Link Aggregation Group (LAG) [IEEE802.1AX]. This reduces the
number of adjacencies that need to be maintained by the routing
protocol in cases where there are parallel links between the
neighbors. Entities external to IS-IS such as Path Computation
Elements (PCEs) [RFC4655] may wish to control traffic flows on
individual members of the underlying Layer-2 bundle. In order to do
so, link attribute information about individual bundle members is
required.
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[RFC8668] and [I-D.ietf-lsr-ospf-l2bundles] specify the IGP
extensions to advertise link attribute information for each of the L2
Bundle members which comprise the Layer-3 interface, in which the
encoding and advertisement of SR-MPLS adjacency SIDs of each bundle
member link is defined. When SRv6 is used with Layer-2 interface
bundle, to control traffic flows on the individual member links, the
SRv6 SIDs which represent the Layer-2 member links of the L2 bundle
needs to be advertised.
This document proposes the IGP extensions to advertise the SRv6 SIDs
of the Layer-2 (L2) bundle member links.
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
BCP14 RFC 2119 [RFC2119] RFC 8174 [RFC8174] when, and only when, they
appear in all capitals, as shown here.
3. SRv6 Function for L2 Bundle Member Links
As defined in [I-D.ietf-spring-srv6-network-programming], the SRv6
End.X behavior means "Endpoint with cross-connect to an array of
layer-3 adjacencies". An SRv6 SID associated with a Layer 2 bundle
member link of an L3 adjacency is considered a variant of the End.X
behavior. In order to distinguish it from the SIDs associated with a
L3 adjacency, it is considered that a different type of SRv6 function
needs to be used.
[I-D.dong-spring-srv6-inter-layer-programming] defines a new End.XU
function which means "Endpoint with cross-connect to an underlay
interface", this function can be used for the L2 bundle member links.
4. Advertising SRv6 SIDs for L2 Bundle Members
4.1. SRv6 SIDs Encodings for IS-IS L2 Bundle
This section defines the IS-IS sub-TLVs to advertise SRv6 SIDs for L2
Bundle Members. Following the encoding mechanism used in [RFC8668]
for the advertisement of SR-MPLS adj-SIDs for L2 Bundle Members, this
allows the advertisement of a set of SRv6 SIDs (one per L2 Bundle
Member) in a single sub-TLV.
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4.1.1. L2 Bundle Member SRv6 End.XU SID Sub-TLV
[I-D.ietf-lsr-isis-srv6-extensions] defines the SRv6 End.X SID sub-
TLV to advertise an SRv6 SID associated with a point to point
adjacency. This document defines a new sub-TLV of called "L2 Bundle
Member SRv6 End.XU SIDs" to advertise the SRv6 End.XU SIDs for the L2
Bundle Members. This sub-TLV is allowed to be carried in TLV 25 "L2
Bundle Member Attributes" only. The format of the sub-TLV is as
below:
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 #1 (128 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID #2 (128 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID #n (128 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Sub-sub-tlv-len| Sub-sub-TLVs (variable) . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where:
o Type: TBA.
o Length: Variable.
o Flags: 1 octet. The format is the same as the Flags field in the
SRv6 End.X SID sub-TLV as defined in
[I-D.ietf-lsr-isis-srv6-extensions].
o Algorithm: 1 octet. The algorithm values are defined in the IGP
Algorithm Type registry.
o Weight: 1 octet. The value represents the weight of the SID for
the purpose of load balancing.
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o Endpoint Behavior: 2 octets. It SHOULD be set to the Endpoint
functions as defined in
[I-D.dong-spring-srv6-inter-layer-programming].
o SIDs. One or multiple 16-octet SRv6 SIDs. The number of the SIDs
is determined by the "Number of L2 Bundle Member Descriptors"
field as defined in [RFC8668].
o Sub-sub-tlv-length: 1 octet. Number of octets used by sub-sub-
TLVs.
4.1.2. L2 Bundle Member SRv6 LAN End.XU SID Sub-TLV
[I-D.ietf-lsr-isis-srv6-extensions] defines the SRv6 LAN End.X SID
sub-TLV to advertise an SRv6 SID associated with a LAN adjacency.
This document defines a new sub-TLV called "L2 Bundle Member SRv6 LAN
End.XU SIDs" to advertise the SRv6 LAN End.XU SIDs for the L2 Bundle
Members. The format of the sub-TLV is as below:
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 #1 (128 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID #2 (128 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID #n (128 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Sub-sub-tlv-len| Sub-sub-TLVs (variable) . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where:
o Type: TBA.
o Length: Variable.
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o Neighbor System-ID: IS-IS System-ID of length "ID Length" as
defined in [ISO10589].
o Flags: 1 octet, the format is the same as the Flags field in the
SRv6 End.X SID sub-TLV as defined in
[I-D.ietf-lsr-isis-srv6-extensions].
o Algorithm: 1 octet. The algorithm values are defined in the IGP
Algorithm Type registry.
o Weight: 1 octet. The value represents the weight of the End.X SID
for the purpose of load balancing.
o Endpoint Behavior: 2 octets. It SHOULD be set to the Endpoint
functions as defined in
[I-D.dong-spring-srv6-inter-layer-programming].
o SIDs. One or multiple 16-octet SRv6 SIDs. The number of the SIDs
is determined by the "Number of L2 Bundle Member Descriptors"
field as defined in [RFC8668].
o Sub-sub-tlv-length: 1 octet. Number of octets used by sub-sub-
TLVs.
4.2. SRv6 SIDs Encodings for OSPF L2 Bundle
This section defines the mechanism to advertise SRv6 SIDs for L2
Bundle Members. In [I-D.ietf-lsr-ospf-l2bundles], the SR-MPLS
Adjacency SID sub-TLVs for the L3 adjacency is reused for the
advertisement of Adjacency SIDs of L2 Bundle Members. For SRv6 data
plane , the SRv6 End.X SID sub-TLV and SRv6 LAN End.X SID Sub-TLV as
defined in [I-D.ietf-lsr-ospfv3-srv6-extensions] are reused for the
advertisement of SRv6 End.XU SIDs of L2 Bundle Members, the Endpoint
Behavior in the sub-TLV SHOULD be set to the Endpoint functions as
defined in [I-D.dong-spring-srv6-inter-layer-programming].
5. IANA Considerations
IANA is requested to assign two new code points from the IS-IS "Sub-
TLVs for TLVs 22, 23, 25, 141, 222, and 223" registry.
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+------+--------------------------+----+----+----+-----+-----+-----+
| Type | Description | 22 | 23 | 25 | 141 | 222 | 223 |
+======+==========================+====+====+====+=====+=====+=====+
| TBD | L2 Bundle Member SRv6 | n | n | y | n | n | n |
| | End.XU SID | | | | | | |
+------+--------------------------+----+----+----+-----+-----+-----+
| TBD | L2 Bundle Member SRv6 | n | n | y | n | n | n |
| | LAN End.XU SID | | | | | | |
+------+--------------------------+----+----+----+-----+-----+-----+
6. Security Considerations
The security considerations in [RFC8668] and
[I-D.ietf-lsr-ospf-l2bundles] apply. This document introduces no
additional security vulnerabilities to IS-IS and OSPF.
7. Acknowledgements
The authors would like to thank Zhenbin Li for the review and
discussion of this document.
8. References
8.1. Normative References
[I-D.ietf-lsr-isis-srv6-extensions]
Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and
Z. Hu, "IS-IS Extension to Support Segment Routing over
IPv6 Dataplane", draft-ietf-lsr-isis-srv6-extensions-11
(work in progress), October 2020.
[I-D.ietf-lsr-ospf-l2bundles]
Talaulikar, K. and P. Psenak, "Advertising L2 Bundle
Member Link Attributes in OSPF", draft-ietf-lsr-ospf-
l2bundles-00 (work in progress), October 2020.
[I-D.ietf-lsr-ospfv3-srv6-extensions]
Li, Z., Hu, Z., Cheng, D., Talaulikar, K., and P. Psenak,
"OSPFv3 Extensions for SRv6", draft-ietf-lsr-
ospfv3-srv6-extensions-01 (work in progress), August 2020.
[IEEE802.1AX]
IEEE, "IEEE Standard for Local and metropolitan area
networks -- Link Aggregation", 2016,
<https://ieeexplore.ieee.org/document/7055197>.
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[ISO10589]
ISO, "Information technology -- Telecommunications and
information exchange between systems -- Intermediate
System to Intermediate System intra-domain routing
information exchange protocol for use in conjunction with
the protocol for providing the connectionless-mode network
service (ISO 8473)", November 2002,
<https://ieeexplore.ieee.org/document/7055197>.
[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>.
[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>.
[RFC8668] Ginsberg, L., Ed., Bashandy, A., Filsfils, C., Nanduri,
M., and E. Aries, "Advertising Layer 2 Bundle Member Link
Attributes in IS-IS", RFC 8668, DOI 10.17487/RFC8668,
December 2019, <https://www.rfc-editor.org/info/rfc8668>.
8.2. Informative References
[I-D.dong-spring-srv6-inter-layer-programming]
Dong, J. and Z. Du, "SRv6 for Inter-Layer Network
Programming", draft-dong-spring-srv6-inter-layer-
programming-01 (work in progress), October 2020.
[I-D.ietf-spring-srv6-network-programming]
Filsfils, C., Camarillo, P., Leddy, J., Voyer, D.,
Matsushima, S., and Z. Li, "SRv6 Network Programming",
draft-ietf-spring-srv6-network-programming-28 (work in
progress), December 2020.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>.
Authors' Addresses
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Jie Dong
Huawei Technologies
Huawei Campus, No. 156 Beiqing Road
Beijing 100095
China
Email: jie.dong@huawei.com
Zhibo Hu
Huawei Technologies
Huawei Campus, No. 156 Beiqing Road
Beijing 100095
China
Email: huzhibo@huawei.com
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