Network Working Group S. Previdi, Ed.
Internet-Draft L. Ginsberg
Intended status: Standards Track C. Filsfils
Expires: May 21, 2016 Cisco Systems, Inc.
November 18, 2015
Segment Routing IPv6 Prefix-SID
draft-previdi-isis-ipv6-prefix-sid-00
Abstract
This document defines the Segment Routing IPv6 Prefix-SID in the
IPv4/IPv6 Extended Reachability Attribute Flags TLV. The new flag is
used for advertising the capability to handle the IPv6 Segment
Routing header for the prefix that has the flag attached.
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
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This Internet-Draft will expire on May 21, 2016.
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. SRv6 Prefix SID . . . . . . . . . . . . . . . . . . . . . . . 2
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 3
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 3
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 3
6.1. Normative References . . . . . . . . . . . . . . . . . . 3
6.2. Informative References . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
With Segment Routing (SR)[I-D.ietf-spring-segment-routing], a node
steers a packet through an ordered list of instructions, called
segments. Segments are identified through Segment Identifiers (SIDs)
that are advertised by routing protocols. The IS-IS extensions for
SR information advertisement are defined in
[I-D.ietf-isis-segment-routing-extensions].
Segment Routing can be directly applied to the IPv6 dataplane through
the use of the Segment Routing Header defined in
[I-D.previdi-6man-segment-routing-header].
2. SRv6 Prefix SID
When SR is applied to the IPv6 dataplane, Segment Identifiers (SIDs)
are regular IPv6 addresses that are advertised in routing protocols.
When SR is used over IPv6 dataplane, it is desirable to identify
which of the prefixes originated by a node can be used as SIDs
compared to any other prefix that the node advertises.
[I-D.ietf-isis-prefix-attributes], defines the IPv4/IPv6 Extended
Reachability Attribute Flags TLV. This document defines the
following new flag:
S6-Flag (bit 3).
SRv6 Prefix-SID flag: when set, the router
indicates that the prefix this flag is attached
to can be used as an IPv6 Prefix-SID.
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The S6-Flag may also be set in conjunction with the Node-Flag (Bit 2)
if the prefix does also identifies the node in the topology.
In the case where the prefix has a shorter mask-length than 128 or
when the prefix does not identify the node (e.g.: assigned to a
physical interface instead of a loopback) the S6-Flag MAY be set and
the N-flag MUST NOT be set.
When a prefix is flagged as a SRv6-Prefix-SID, the originating router
MUST support the IPv6 Segment Routing Header (SRH) and its procedures
described in [I-D.previdi-6man-segment-routing-header]. Therefore
the originating router MUST set the H-flag in the SR-Capability
SubTLV as defined in [I-D.ietf-isis-segment-routing-extensions].
A router receiving the advertisement of the IPv6 prefix with the
S6-Flag set MUST check whether the originator has set the H-flag in
its SR-Capability SubTLV if present in the receiving router link
state database.
The S6-Flag has relevance only for IPv6 prefixes. When processing
IPv4 prefixes, the S6-Flag MUST be ignored.
3. IANA Considerations
This document introduces the SRv6-Prefix-SID flag in the Prefix
Attribute Flags sub-TLV:
Name Bit #
------- -----
S6-Flag 3 (suggested value, to be assigned by IANA)
4. Security Considerations
This document doesn't introduce new security considerations.
5. Acknowledgements
The authors would like to thank Nagendra Kumar for his review of this
document.
6. References
6.1. Normative References
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[I-D.ietf-isis-prefix-attributes]
Ginsberg, L., Decraene, B., Filsfils, C., Litkowski, S.,
Previdi, S., Xu, X., and U. Chunduri, "IS-IS Prefix
Attributes for Extended IP and IPv6 Reachability", draft-
ietf-isis-prefix-attributes-01 (work in progress), June
2015.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
6.2. Informative References
[I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Filsfils, C., Bashandy, A., Gredler, H.,
Litkowski, S., Decraene, B., and J. Tantsura, "IS-IS
Extensions for Segment Routing", draft-ietf-isis-segment-
routing-extensions-05 (work in progress), June 2015.
[I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
and r. rjs@rob.sh, "Segment Routing Architecture", draft-
ietf-spring-segment-routing-06 (work in progress), October
2015.
[]
Previdi, S., Filsfils, C., Field, B., Leung, I., Linkova,
J., Kosugi, T., Vyncke, E., and D. Lebrun, "IPv6 Segment
Routing Header (SRH)", draft-previdi-6man-segment-routing-
header-08 (work in progress), October 2015.
Authors' Addresses
Stefano Previdi (editor)
Cisco Systems, Inc.
Via Del Serafico, 200
Rome 00142
Italy
Email: sprevidi@cisco.com
Les Ginsberg
Cisco Systems, Inc.
US
Email: ginsberg@cisco.com
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Clarence Filsfils
Cisco Systems, Inc.
Brussels
BE
Email: cfilsfil@cisco.com
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