draft-ietf-idr-bgp-prefix-sid-09.txt   draft-ietf-idr-bgp-prefix-sid-10.txt 
IDR S. Previdi, Ed. IDR S. Previdi, Ed.
Internet-Draft C. Filsfils Internet-Draft C. Filsfils
Intended status: Standards Track A. Lindem Intended status: Standards Track A. Lindem
Expires: July 9, 2018 Cisco Systems Expires: July 20, 2018 Cisco Systems
A. Sreekantiah A. Sreekantiah
H. Gredler H. Gredler
RtBrick Inc. RtBrick Inc.
January 5, 2018 January 16, 2018
Segment Routing Prefix SID extensions for BGP Segment Routing Prefix SID extensions for BGP
draft-ietf-idr-bgp-prefix-sid-09 draft-ietf-idr-bgp-prefix-sid-10
Abstract Abstract
Segment Routing (SR) architecture allows a node to steer a packet Segment Routing (SR) architecture allows a node to steer a packet
flow through any topological path and service chain by leveraging flow through any topological path and service chain by leveraging
source routing. The ingress node prepends an SR header to a packet source routing. The ingress node prepends an SR header to a packet
containing a set of segment identifiers (SID). Each SID represents a containing a set of segment identifiers (SID). Each SID represents a
topological or a service-based instruction. Per-flow state is topological or a service-based instruction. Per-flow state is
maintained only on the ingress node of the SR domain. maintained only on the ingress node of the SR domain.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 9, 2018. This Internet-Draft will expire on July 20, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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3.2. IPv6 SID . . . . . . . . . . . . . . . . . . . . . . . . 7 3.2. IPv6 SID . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3. Originator SRGB TLV . . . . . . . . . . . . . . . . . . . 7 3.3. Originator SRGB TLV . . . . . . . . . . . . . . . . . . . 7
4. Receiving BGP Prefix-SID Attribute . . . . . . . . . . . . . 9 4. Receiving BGP Prefix-SID Attribute . . . . . . . . . . . . . 9
4.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 9 4.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 9
4.2. IPv6 Dataplane . . . . . . . . . . . . . . . . . . . . . 10 4.2. IPv6 Dataplane . . . . . . . . . . . . . . . . . . . . . 10
5. Advertising BGP Prefix-SID Attribute . . . . . . . . . . . . 10 5. Advertising BGP Prefix-SID Attribute . . . . . . . . . . . . 10
5.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 11 5.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 11
5.2. IPv6 Dataplane . . . . . . . . . . . . . . . . . . . . . 11 5.2. IPv6 Dataplane . . . . . . . . . . . . . . . . . . . . . 11
6. Error Handling of BGP Prefix-SID Attribute . . . . . . . . . 11 6. Error Handling of BGP Prefix-SID Attribute . . . . . . . . . 11
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
8. Manageability Considerations . . . . . . . . . . . . . . . . 12 8. Manageability Considerations . . . . . . . . . . . . . . . . 13
9. Security Considerations . . . . . . . . . . . . . . . . . . . 13 9. Security Considerations . . . . . . . . . . . . . . . . . . . 13
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 13 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 13
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
12.1. Normative References . . . . . . . . . . . . . . . . . . 14 12.1. Normative References . . . . . . . . . . . . . . . . . . 14
12.2. Informative References . . . . . . . . . . . . . . . . . 15 12.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
Segment Routing (SR) architecture leverages the source routing Segment Routing (SR) architecture leverages the source routing
paradigm. A group of inter-connected nodes that use SR forms an SR paradigm. A group of inter-connected nodes that use SR forms an SR
domain. A segment represents either a topological instruction such domain. A segment represents either a topological instruction such
as "go to prefix P following shortest path" or a service instruction as "go to prefix P following shortest path" or a service instruction
(e.g.: "pass through deep packet inspection"). Other types of (e.g.: "pass through deep packet inspection"). Other types of
segments may be defined in the future. segments may be defined in the future.
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When SR is used over an IPv6 dataplane, the BGP Prefix-SID consists When SR is used over an IPv6 dataplane, the BGP Prefix-SID consists
of an IPv6 address assigned to the BGP speaker. of an IPv6 address assigned to the BGP speaker.
3. BGP Prefix-SID Attribute 3. BGP Prefix-SID Attribute
The BGP Prefix-SID attribute is an optional, transitive BGP path The BGP Prefix-SID attribute is an optional, transitive BGP path
attribute. The attribute type code 40 has been assigned by IANA (see attribute. The attribute type code 40 has been assigned by IANA (see
Section 7). Section 7).
The BGP Prefix-SID attribute is defined here to be a set of elements The BGP Prefix-SID attribute is defined here to be a set of elements
encoded as "Type/Length/Value" tuples (i.e., a set of TLVs). The encoded as "Type/Length/Value" tuples (i.e., a set of TLVs). All BGP
following TLVs are defined: Prefix-SID attribute TLVs will start with a 1-octet type and a
2-octet length. The following TLVs are defined in this document:
o Label-Index TLV o Label-Index TLV
o IPv6 SID TLV o IPv6 SID TLV
o Originator SRGB TLV o Originator SRGB TLV
The Label-Index and Originator SRGB TLVs are used only when SR is The Label-Index and Originator SRGB TLVs are used only when SR is
applied to the MPLS dataplane. applied to the MPLS dataplane.
The IPv6 SID TLV is used only when SR is applied to the IPv6 The IPv6 SID TLV is used only when SR is applied to the IPv6
dataplane. dataplane.
For future extendibility, unknown TLVs are ignored and propagated
unmodified.
3.1. Label-Index TLV 3.1. Label-Index TLV
The Label-Index TLV MUST be present in the BGP Prefix-SID attribute The Label-Index TLV MUST be present in the BGP Prefix-SID attribute
attached to Labeled IPv4/IPv6 unicast prefixes ([RFC8277]). It will attached to Labeled IPv4/IPv6 unicast prefixes ([RFC8277]). It will
be ignored when received for other BGP AFI/SAFI combinations. The be ignored when received for other BGP AFI/SAFI combinations. The
Label-Index TLV has the following format: Label-Index TLV has the following format:
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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which local/incoming label the BGP speaker SHOULD assign. which local/incoming label the BGP speaker SHOULD assign.
4.2. IPv6 Dataplane 4.2. IPv6 Dataplane
When an SR IPv6 BGP speaker receives an IPv6 Unicast BGP Update with When an SR IPv6 BGP speaker receives an IPv6 Unicast BGP Update with
a prefix having the BGP Prefix-SID attribute attached, it checks a prefix having the BGP Prefix-SID attribute attached, it checks
whether the IPv6 SID TLV is present. If present and the chosen as whether the IPv6 SID TLV is present. If present and the chosen as
the best path, the prefix is installed into the Segment Routing IPv6 the best path, the prefix is installed into the Segment Routing IPv6
dataplane as described in [I-D.ietf-spring-segment-routing]. dataplane as described in [I-D.ietf-spring-segment-routing].
The Originator SRGB MUST be ignored on reception. The Label-Index and Originator SRGB TLVs MUST be ignored on
reception. For future extendibility, no TLVs are required for the
BGP IPv6 unicast address family. However, a BGP Prefix-SID attribute
corresponding to the BGP IPv6 address family without an IPv6 SID TLV
will be ignored.
5. Advertising BGP Prefix-SID Attribute 5. Advertising BGP Prefix-SID Attribute
The BGP Prefix-SID attribute MAY be attached to labeled BGP prefixes The BGP Prefix-SID attribute MAY be attached to labeled BGP prefixes
(IPv4/IPv6) [RFC8277] or to IPv6 unicast prefixes [RFC4760]. In (IPv4/IPv6) [RFC8277] or to IPv6 unicast prefixes [RFC4760]. In
order to prevent distribution of the BGP Prefix-SID attribute beyond order to prevent distribution of the BGP Prefix-SID attribute beyond
its intended scope of applicability, attribute filtering SHOULD be its intended scope of applicability, attribute filtering SHOULD be
deployed. deployed.
A BGP speaker that advertises a path received from one of its A BGP speaker that advertises a path received from one of its
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unlabeled IPv6 unicast prefix [RFC4760], it MUST treat the unlabeled IPv6 unicast prefix [RFC4760], it MUST treat the
advertisement as a withdrawal. This is equivalent to the "Treat-as- advertisement as a withdrawal. This is equivalent to the "Treat-as-
withdraw" action specified in [RFC7606]. This action is required withdraw" action specified in [RFC7606]. This action is required
since simply ignoring the BGP Prefix-SID attribute would modify the since simply ignoring the BGP Prefix-SID attribute would modify the
installed path and the "Attribute discard" option is not applicable installed path and the "Attribute discard" option is not applicable
in this case [RFC7606]. When withdrawing the prefix, a BGP speaker in this case [RFC7606]. When withdrawing the prefix, a BGP speaker
SHOULD log an error for further analysis. SHOULD log an error for further analysis.
Consistent with [RFC7606], only the first occurrence of the BGP Consistent with [RFC7606], only the first occurrence of the BGP
Prefix-SID attribute will be considered and subsequent occurrences Prefix-SID attribute will be considered and subsequent occurrences
will be discarded. will be discarded. Similarily, only the first occurrence of a BGP
Prefix-SID attribute TLV of a given TLV type will be considered
unless the specification of that TLV type allows for multiple
occurrences.
For future extendibility, unknown TLVs should be ignored and
propagated unmodified.
7. IANA Considerations 7. IANA Considerations
This document defines a BGP path attribute known as the BGP Prefix- This document defines a BGP path attribute known as the BGP Prefix-
SID attribute. This document requests IANA to assign an attribute SID attribute. This document requests IANA to assign an attribute
code type (suggested value: 40) the BGP Prefix-SID attribute from the code type (suggested value: 40) the BGP Prefix-SID attribute from the
BGP Path Attributes registry. BGP Path Attributes registry.
Currently, IANA temporarily assigned the following: Currently, IANA temporarily assigned the following:
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Email: raysaikat@gmail.com Email: raysaikat@gmail.com
11. Acknowledgements 11. Acknowledgements
The authors would like to thank Satya Mohanty for his contribution to The authors would like to thank Satya Mohanty for his contribution to
this document. this document.
The authors would like to thank Alvaro Retana for substantive The authors would like to thank Alvaro Retana for substantive
comments as part of the Routing AD review. comments as part of the Routing AD review.
The authors would like to thank Shyam Sethuram for comments and
discussion of TLV processing and validation.
12. References 12. References
12.1. Normative References 12.1. Normative References
[I-D.ietf-spring-segment-routing] [I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B., Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing Litkowski, S., and R. Shakir, "Segment Routing
Architecture", draft-ietf-spring-segment-routing-14 (work Architecture", draft-ietf-spring-segment-routing-14 (work
in progress), December 2017. in progress), December 2017.
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