Segment Routing BGP Egress Peer Engineering over Layer 2 Bundle
draft-lin-idr-sr-epe-over-l2bundle-01
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Active".
|
|
|---|---|---|---|
| Authors | Changwang Lin , Mengxiao Chen , Hao Li | ||
| Last updated | 2023-03-12 | ||
| RFC stream | (None) | ||
| Formats | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-lin-idr-sr-epe-over-l2bundle-01
Network Working Group C. Lin
Internet Draft M. Chen
Intended status: Standards Track H. Li
Expires: September 13, 2023 New H3C Technologies
March 13, 2023
Segment Routing BGP Egress Peer Engineering over Layer 2 Bundle
draft-lin-idr-sr-epe-over-l2bundle-01
Abstract
There are deployments where the Layer 3 interface on which a BGP
peer session is established is a Layer 2 interface bundle. In order
to allow BGP-EPE to control traffic flows on individual member links
of the underlying Layer 2 bundle, BGP Peering SIDs need to be
allocated to individual bundle member links, and advertisement of
such BGP Peering SIDs in BGP-LS is also required. This document
describes how to support Segment Routing BGP Egress Peer Engineering
over Layer 2 bundle.
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 September 13, 2023.
Copyright Notice
Copyright (c) 2023 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
(http://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
Lin, et al. Expire September 13, 2023 [Page 1]
Internet-Draft SR BGP EPE over L2 Bundle March 2023
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...................................................2
1.1. Requirements Language.....................................3
2. Problem Statement..............................................3
3. Peer Adjacency Segment for L2 Bundle Member Link...............4
3.1. Advertising in BGP-LS.....................................4
3.2. Example...................................................5
4. Considerations of Defining New Types of BGP Peering Segments...7
5. Security Considerations........................................7
6. IANA Considerations............................................8
7. References.....................................................8
7.1. Normative References......................................8
7.2. Informative References....................................8
Authors' Addresses...............................................10
1. Introduction
Segment Routing (SR) leverages the source routing paradigm. A node
steers a packet through an ordered list of instructions called
"segments". Segment Routing can be instantiated on both MPLS and
IPv6 data planes, which are referred to as MPLS-SR and SRv6.
BGP Egress Peer Engineering (BGP-EPE) allows an ingress Provider
Edge (PE) router within the domain to use a specific egress PE and a
specific external interface/neighbor to reach a particular
destination.
The SR architecture [RFC8402] defines three types of BGP Peering
Segments that may be instantiated at a BGP node:
o Peer Node Segment (PeerNode SID): instruction to steer to a
specific peer node
o Peer Adjacency Segment (PeerAdj SID): instruction to steer over a
specific local interface towards a specific peer node
o Peer Set Segment (PeerSet SID): instruction to load-balance to a
set of specific peer nodes
[RFC9087] illustrates a centralized controller-based BGP-EPE
solution involving SR path computation using the BGP Peering
Segments. A centralized controller learns the BGP Peering SIDs via
Lin, et al. Expires September 13, 2023 [Page 2]
Internet-Draft SR BGP EPE over L2 Bundle March 2023
Border Gateway Protocol - Link State (BGP-LS) and then uses this
information to program a BGP-EPE policy. [RFC9086] defines the
extension to BGP-LS for advertisement of BGP Peering Segments along
with their BGP peering node information.
There are deployments where the Layer 3 interface on which a BGP
peer session is established is a Layer 2 interface bundle (L2
Bundle), for instance, a Link Aggregation Group (LAG) [IEEE802.1AX].
BGP-EPE may wish to control traffic flows on individual member links
of the underlying Layer 2 bundle. In order to do so, BGP Peering
SIDs need to be allocated to individual bundle member links, and
advertisement of such BGP Peering SIDs in BGP-LS is also required.
This document describes how to support Segment Routing BGP Egress
Peer Engineering over Layer 2 bundle.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Problem Statement
In the network depicted in Figure 1, B and C establish BGP peer
session on a Layer 2 bundle. Assume that, the link delays of the
members are different because they are over different transport
paths, and member link 1 has the lowest delay.
The operator of AS1 wishes to apply a BGP-EPE policy to steer the
time-sensitive traffic from AS1 to AS2 via member link 1 of the
Layer 2 bundle.
Lin, et al. Expires September 13, 2023 [Page 3]
Internet-Draft SR BGP EPE over L2 Bundle March 2023
L2 Bundle +--------+
/---member 1---\ | |
--+---member 2---+--C AS2 |
+--------+ / \---member 3---/ | |
| |/ +--------+
A AS1 B
| |\ +--------+
+--------+ \ | |
--------------------D AS3 |
| |
+--------+
Figure 1: BGP-EPE over L2 Bundle
The existing PeerAdj SID can be allocated to the Layer 3 interface
between B and C, which is a Layer 2 interface bundle. If steered by
that PeerAdj SID, the traffic will be forwarded by load balancing
among all the bundle member links. So, the existing mechanism cannot
meet the requirement of steering traffic flows via individual member
link.
3. Peer Adjacency Segment for L2 Bundle Member Link
This document extends Peer Adjacency Segments to be allocated to the
individual member links of the Layer 2 interface bundle.
The semantics of a Peer Adjacency Segment for L2 Bundle Member Link
are:
o SR operation: NEXT.
o Next-Hop: forwarding across the bundle member link, which the
segment is associated with, to the peer connected through the
parent L3 interface.
On the MPLS-SR data plane, Peer Adjacency Segments for L2 Bundle
Member Links are instantiated as MPLS labels. On the SRv6 data
plane, Peer Adjacency Segments for L2 Bunlde Members are
instantiated as SRv6 End.X SIDs.
3.1. Advertising in BGP-LS
BGP peering segments are generally advertised in BGP-LS from a BGP
node along with its peering topology information, in order to enable
computation of efficient BGP-EPE policies and strategies.
When advertising Peer Adjacency Segments for L2 Bunlde Member Links
in BGP-LS, they can be carried in the sub-TLVs of L2 Bundle Member
Lin, et al. Expires September 13, 2023 [Page 4]
Internet-Draft SR BGP EPE over L2 Bundle March 2023
Attributes TLVs [RFC9085]. Derived from IS-IS advertisements of L2
Bundle [RFC8668], each L2 Bundle Member Attributes TLV identifies an
L2 Bundle Member link, which in turn is associated with a parent L3
link. The L3 link is described by the Link NLRI, and the L2 Bundle
Member Attributes TLV is associated with the Link NLRI. The L2
Bundle Member Attributes TLV MAY include sub-TLVs that describe
attributes associated with the bundle member.
In order to advertise Peer Adjacency Segments for L2 Bundle Member
Links in BGP-LS, a BGP-LS Link NLRI is advertised to describe the
parent L3 link to the BGP peer, which is similar with advertising a
PeerAdj SID for the parent L3 link as specified in Section 5.2 of
[RFC9086]. Then, multiple L2 Bundle Member Attributes TLVs are
included in the Link Attribute TLVs associated with the parent L3
link, each identifying an L2 Bundle member link. The L2 Bundle
Member Attributes TLV MAY carry the following sub-TLVs:
o PeerAdj SID TLV (Type-1102) [RFC9086] contains a Peer Adjacency
Segment for the associated L2 Bundle member link on MPLS-SR data
plane.
o SRv6 End.X SID TLV (Type-1106) [I-D.ietf-idr-bgpls-srv6-ext]
contains a Peer Adjacency Segment for the associated L2 Bundle
member link on SRv6 data plane.
o Other BGP-LS Attribute TLVs used to describe the associated L2
Bundle member link [RFC9085], such as administrative group
(color), link bandwidth, and link delay.
3.2. Example
Take the allocating and advertising of Peer Adjacency Segments on
Node B in Figure 1 as an example.
B allocates a PeerAdj SID for the Layer 2 interface bundle to peer
C, along with a PeerAdj SID for each member link. B programs its
forwarding table accordingly:
Lin, et al. Expires September 13, 2023 [Page 5]
Internet-Draft SR BGP EPE over L2 Bundle March 2023
+===============================+====================+
| PeerAdj SID | Outgoing Interface |
+---------------+---------------+ |
| IF on MPLS-SR | IF on SRv6 | |
| Data Plane | Data Plane | |
+===============+===============+====================+
| 1010 | A::A0 | L2 Bundle to C |
+---------------+---------------+--------------------+
| 1011 | A::A1 | Member link 1 to C |
+---------------+---------------+--------------------+
| 1012 | A::A2 | Member link 2 to C |
+---------------+---------------+--------------------+
| 1013 | A::A3 | Member link 3 to C |
+---------------+---------------+--------------------+
B signals the related BGP-LS NLRI to the BGP-EPE controller, which
is described in the following.
Descriptors:
o Local Node Descriptors (B's router-ID, ASN-AS1)
o Remote Node Descriptors (C's router-ID, ASN-AS2)
o Link Descriptors (Link Local/Remote Identifiers describing the
Layer 2 bundle, IPv4 or IPv6 Interface Address, IPv4 or IPv6
Neighbor Address)
Attributes (MPLS-SR data plane):
o PeerAdj SID TLV (Label-1010)
o L2 Bundle Member Attribute TLV (Link Local Identifier describing
the member link 1)
* PeerAdj SID TLV (Label-1011)
* Min/Max Unidirectional Link Delay TLV (Delay of member link 1)
o L2 Bundle Member Attribute TLV (Link Local Identifier describing
the member link 2)
* PeerAdj SID TLV (Label-1012)
* Min/Max Unidirectional Link Delay TLV (Delay of member link 2)
o L2 Bundle Member Attribute TLV (Link Local Identifier describing
the member link 3)
Lin, et al. Expires September 13, 2023 [Page 6]
Internet-Draft SR BGP EPE over L2 Bundle March 2023
* PeerAdj SID TLV (Label-1013)
* Min/Max Unidirectional Link Delay TLV (Delay of member link 3)
Attributes (SRv6 data plane):
o SRv6 End.X SID TLV (SID-A::A0)
o L2 Bundle Member Attribute TLV (Link Local Identifier describing
the member link 1)
* SRv6 End.X SID TLV (SID-A::A1)
* Min/Max Unidirectional Link Delay TLV (Delay of member link 1)
o L2 Bundle Member Attribute TLV (Link Local Identifier describing
the member link 2)
* SRv6 End.X SID TLV (SID-A::A2)
* Min/Max Unidirectional Link Delay TLV (Delay of member link 2)
o L2 Bundle Member Attribute TLV (Link Local Identifier describing
the member link 3)
* SRv6 End.X SID TLV (SID-A::A3)
* Min/Max Unidirectional Link Delay TLV (Delay of member link 3)
4. Considerations of Defining New Types of BGP Peering Segments
The solution in Section 3 reuses the existing Peer Adjacency
Segments. It may also be possible to define a new type of BGP
Peering Segments for L2 Bundle member links. Then, a new type of BGP
Peering SIDs TLV is required, having the same format as described in
Figure 2 of [RFC9086].
One of the main advantages of reusing Peer Adjacency Segments is
that, no new BGP-LS TLVs is introduced. This mechanism is similar
with the BGP-LS advertisements of IGP Adj-SIDs for an L2 Bundle and
its member links [RFC9085] [I-D.ietf-idr-bgpls-srv6-ext].
5. Security Considerations
TBD
Lin, et al. Expires September 13, 2023 [Page 7]
Internet-Draft SR BGP EPE over L2 Bundle March 2023
6. IANA Considerations
TBD
7. References
7.1. 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>.
[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>.
[RFC9085] Previdi, S., Talaulikar, K., Ed., Filsfils, C., Gredler,
H., and M. Chen, "Border Gateway Protocol - Link State
(BGP-LS) Extensions for Segment Routing", RFC 9085, DOI
10.17487/RFC9085, August 2021, <https://www.rfc-
editor.org/info/rfc9085>.
[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>.
[I-D.ietf-idr-bgpls-srv6-ext] Dawra, G., Filsfils, C., Talaulikar,
K., Chen, M., Bernier, D., and B. Decraene, "BGP Link
State Extensions for SRv6", Work in Progress, Internet-
Draft, draft-ietf-idr-bgpls-srv6-ext-14, 17 February 2023,
<https://www.ietf.org/archive/id/draft-ietf-idr-bgpls-
srv6-ext-14.txt>.
7.2. Informative References
[IEEE802.1AX] IEEE, "IEEE Standard for Local and metropolitan area
networks -- Link Aggregation", IEEE 802.1AX,
<https://ieeexplore.ieee.org/document/7055197>.
Lin, et al. Expires September 13, 2023 [Page 8]
Internet-Draft SR BGP EPE over L2 Bundle March 2023
[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>.
[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>.
Lin, et al. Expires September 13, 2023 [Page 9]
Internet-Draft SR BGP EPE over L2 Bundle March 2023
Authors' Addresses
Changwang Lin
New H3C Technologies
China
Email: linchangwang.04414@h3c.com
Mengxiao Chen
New H3C Technologies
China
Email: chen.mengxiao@h3c.com
Hao Li
New H3C Technologies
China
Email: lihao@h3c.com
Lin, et al. Expires September 13, 2023 [Page 10]