Internet DRAFT - draft-chen-idr-mbinding
draft-chen-idr-mbinding
Network Working Group H. Chen
Internet-Draft Futurewei
Intended status: Standards Track B. Decraene
Expires: 18 October 2023 Orange
G. Mishra
Verizon
Y. Fan
Casa Systems
A. Wang
China Telecom
X. Liu
IBM Corporation
16 April 2023
BGP for Mirror Binding
draft-chen-idr-mbinding-01
Abstract
BGP is used to distribute a binding to a node. The binding includes
a binding SID and a path represented by a list of SIDs. This
document describes extensions to BGP for distributing the information
about the binding to a protecting node. For an SR path via the node
with the binding SID, when the node fails, the protecting node such
as the upstream neighbor on the path uses the information to protect
the binding SID of the failed node.
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.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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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 18 October 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 (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Extensions to BGP . . . . . . . . . . . . . . . . . . . . . . 3
3. Procedure for Updating Information . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
6.1. Normative References . . . . . . . . . . . . . . . . . . 5
6.2. Informative References . . . . . . . . . . . . . . . . . 6
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
[I-D.ietf-idr-segment-routing-te-policy] specifies how BGP may be
used to distribute a Segment Routing (SR) Policy to a node in a
network. An SR Policy may contain a binding, which includes a
binding SID and a path represented by a list of SIDs.
After a BGP as a controller distributes the binding to the node, the
node forwards the packet with the binding SID according to the first
SID in the list. It replaces the binding SID in the packet with the
list of SIDs and forwards the packet using the FIB entry for the top
SID (i.e., the first SID) in the packet.
When the node fails, suppose that the upstream neighbor (as PLR) of
the node has the corresponding binding protection information for
protecting the binding SID of the node. The information includes the
binding SID, the list of SIDs and an identifier of the node. After
the upstream neighbor as PLR detects the failure of the node, for a
packet with the node SID of the failed node received, it protects the
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binding SID of the failed node. It pops the node SID, replaces the
binding SID in the packet with the list of SIDs, forwards the packet
without going through the failed node towards the top SID (i.e., the
first SID, assuming it is a node SID for simplicity here). How a
upstream node protect the binding SID of the failed node is out of
scope of this document and described in
[I-D.ietf-spring-segment-protection-sr-te-paths] and
[I-D.hu-spring-segment-routing-proxy-forwarding]. (Note: the second
reference will be removed after the first one includes enough text
for protecting binding SIDs of a node).
This document proposes some procedures and extensions to BGP for
distributing the information to each of the nodes that may protect
the failed node.
2. Extensions to BGP
This section defines a new Binding Protection sub-TLV under a Tunnel
Encapsulation Attribute TLV of type 15 (i.e., SR Policy TLV). A
Tunnel Encapsulation Attribute contains a Tunnel Encapsulation
Attribute TLV. The structure containing a Binding Protection sub-TLV
is shown below.
Attributes:
Tunnel Encapsulation Attribute (23)
Tunnel Type (15): SR Policy TLV
Preference sub-TLV
Binding SID sub-TLV
SRv6 Binding SID sub-TLV
Explicit NULL Label Policy (ENLP) sub-TLV
Priority sub-TLV
Policy Candidate Path Name sub-TLV
Policy Name sub-TLV
Binding Protection sub-TLV
Segment List sub-TLV
Weight sub-TLV
Segment sub-TLV
Segment sub-TLV
...
...
The format of a Binding Protection sub-TLV is illustrated below.
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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 (TBD1) | Length | Flags | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-TLVs |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Binding Protection sub-TLV Format
Type: Its value (TBD1) is to be assigned by IANA.
Length: It is variable.
Flags: 1 octet of flags. No flags is defined now. MUST be set to
zero by the sender and MUST be ignored by the receiver.
sub-TLVs: This field contains the sub-TLV below to indicate the node
to be protected (i.e., the protected node).
o Protected Node ID sub-TLV indicating the ID of the Protected
Node.
When an SR Policy (i.e., SR Policy TLV) contains a binding SID and a
path with a protected node, the SR policy is for distributing the
binding protection information. The binding SID is encoded by a
Binding SID sub-TLV or SRv6 Binding SID sub-TLV, the path is encoded
by a Segment List Sub-TLV, and the node is encoded by a Binding
Protection sub-TLV.
When an SR Policy contains a binding SID and a path without a
protected node, the SR policy is for replacing the Binding SID with
the path (i.e., the list of SIDs) when the node receives a packet
with the Binding SID.
The format of Protected Node ID sub-TLV is illustrated 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 (1) | Length (4) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protected Node ID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Protected Node ID sub-TLV Format
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Type: Its value (1) indicates the type of Protected Node ID sub-TLV.
Length: Its value (4) indicates the length of the value field of the
sub-TLV is 4.
Protected Node ID: 4-octet field contains the identifier (ID) of the
Protected Node.
3. Procedure for Updating Information
When a BGP sends a binding to node N in a first Update message, the
BGP distributes the corresponding binding protection information to
the possible protecting nodes such as neighbors of node N in a second
Update message. The first message contains a first SR Policy. The
first SR Policy includes a binding SID and a path but does not
include node N as a protected node. The second message contains a
second SR Policy. The second SR Policy includes the binding SID, the
path and node N as a protected node.
After sending the binding to node N and distributing the
corresponding binding protection information to the protecting nodes,
if BGP removes the binding from node N, it removes the corresponding
binding protection information from the protecting nodes. If BGP
changes the binding in node N, it changes the corresponding binding
protection information in the protecting nodes.
4. Security Considerations
Protocol extensions defined in this document do not affect the BGP
security other than those as discussed in the Security Considerations
section of [RFC9012].
5. IANA Considerations
This document requests assigning a new sub-TLV in the registry "BGP
Tunnel Encapsulation Attribute sub-TLVs" as follows:
+------------+--------------------+-------------+
| Code Point | Description | Reference |
+------------+--------------------+-------------+
| TBD1 | Binding Protection |This document|
+------------+--------------------+-------------+
6. References
6.1. Normative References
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[I-D.ietf-spring-segment-protection-sr-te-paths]
Hegde, S., Bowers, C., Litkowski, S., Xu, X., and F. Xu,
"Segment Protection for SR-TE Paths", Work in Progress,
Internet-Draft, draft-ietf-spring-segment-protection-sr-
te-paths-04, 10 March 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-spring-
segment-protection-sr-te-paths-04>.
[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>.
[RFC9012] Patel, K., Van de Velde, G., Sangli, S., and J. Scudder,
"The BGP Tunnel Encapsulation Attribute", RFC 9012,
DOI 10.17487/RFC9012, April 2021,
<https://www.rfc-editor.org/info/rfc9012>.
6.2. Informative References
[I-D.hu-spring-segment-routing-proxy-forwarding]
Hu, Z., Chen, H., Yao, J., Bowers, C., Zhu, Y., and Y.
Liu, "SR-TE Path Midpoint Restoration", Work in Progress,
Internet-Draft, draft-hu-spring-segment-routing-proxy-
forwarding-23, 21 February 2023,
<https://datatracker.ietf.org/doc/html/draft-hu-spring-
segment-routing-proxy-forwarding-23>.
[I-D.ietf-idr-segment-routing-te-policy]
Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P.,
Jain, D., and S. Lin, "Advertising Segment Routing
Policies in BGP", Work in Progress, Internet-Draft, draft-
ietf-idr-segment-routing-te-policy-20, 27 July 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-
segment-routing-te-policy-20>.
Acknowledgments
The authors would like to thank Andrew Stone, Robert Raszuk and Ketan
Talaulikar for their comments to this work.
Authors' Addresses
Huaimo Chen
Futurewei
Boston, MA,
United States of America
Email: huaimo.chen@futurewei.com
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Bruno Decraene
Orange
France
Email: bruno.decraene@orange.com
Gyan S. Mishra
Verizon
13101 Columbia Pike
Silver Spring, MD 20904
United States of America
Phone: 301 502-1347
Email: gyan.s.mishra@verizon.com
Yanhe Fan
Casa Systems
United States of America
Email: yfan@casa-systems.com
Aijun Wang
China Telecom
Beiqijia Town, Changping District
Beijing
102209
China
Email: wangaj3@chinatelecom.cn
Xufeng Liu
IBM Corporation
United States of America
Email: xufeng.liu.ietf@gmail.com
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