Internet DRAFT - draft-ietf-isis-prefix-attributes
draft-ietf-isis-prefix-attributes
Networking Working Group L. Ginsberg, Ed.
Internet-Draft Cisco Systems
Intended status: Standards Track B. Decraene
Expires: July 7, 2016 Orange
S. Previdi
Cisco Systems
X. Xu
Huawei
U. Chunduri
Ericsson
January 4, 2016
IS-IS Prefix Attributes for Extended IP and IPv6 Reachability
draft-ietf-isis-prefix-attributes-04.txt
Abstract
This document introduces new sub-TLVs to support advertisement of IP
and IPv6 prefix attribute flags and the source router ID of the
router which originated a prefix advertisement.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://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 July 7, 2016.
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Copyright Notice
Copyright (c) 2016 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. New sub-TLVs for Extended Reachability TLVs . . . . . . . . . 3
2.1. IPv4/IPv6 Extended Reachability Attribute Flags . . . . . 3
2.2. IPv4/IPv6 Source Router ID . . . . . . . . . . . . . . . 5
2.3. Advertising Router IDs . . . . . . . . . . . . . . . . . 5
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.1. Normative References . . . . . . . . . . . . . . . . . . 7
6.2. Informational References . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
IS-IS is a link state routing protocol defined in [ISO10589] and
[RFC1195]. Extensions in support of advertising new forms of IP/IPv6
prefix reachability are defined in [RFC5305], [RFC5308], and
[RFC5120].
There are existing use cases in which knowing additional attributes
of a prefix is useful.
It is useful to know whether an advertised prefix is directly
connected to the advertising router or not. In the case of [SR]
knowing whether a prefix is directly connected or not determines what
action should be taken as regards processing of labels associated
with an incoming packet.
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It is useful to know what addresses can be used as addresses of the
node in support of services (e.g., Remote Loop Free Alternate (RLFA)
endpoint).
Current formats of the Extended Reachability TLVs for both IP and
IPv6 are fixed and do not allow the introduction of additional flags
without backwards compatibility issues. Therefore a new sub-TLV is
introduced which allows for the advertisement of attribute flags
associated with prefix advertisements.
In cases where multiple node addresses are advertised by a given
router it is also useful to be able to associate all of these
addresses with a single Router-ID even when prefixes are advertised
outside of the area in which they are originated. Therefore a new
sub-TLV is introduced to advertise the router-id of the originator of
a prefix advertisement.
2. New sub-TLVs for Extended Reachability TLVs
The following new sub-TLVs are introduced:
o IPv4/IPv6 Extended Reachability Attributes
o IPv4 Source Router ID
o IPv6 Source Router ID
All sub-TLVs are applicable to TLVs 135, 235, 236, and/or 237.
2.1. IPv4/IPv6 Extended Reachability Attribute Flags
This sub-TLV supports the advertisement of additional flags
associated with a given prefix advertisement. The behavior of each
flag when a prefix advertisement is leaked from one level to another
(upwards or downwards) is explicitly defined below.
All flags are applicable to TLVs 135, 235, 236, 237 unless otherwise
stated.
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Prefix Attribute Flags
Type: 4 (suggested - to be assigned by IANA)
Length: Number of octets to follow
Value
(Length * 8) bits.
0 1 2 3 4 5 6 7...
+-+-+-+-+-+-+-+-+...
|X|R|N| ...
+-+-+-+-+-+-+-+-+...
Bits are defined/sent starting with Bit #0 defined below. Additional
bit definitions which may be defined in the future SHOULD be assigned
in ascending bit order so as to minimize the number of bits which
will need to be transmitted.
Undefined bits MUST be transmitted as 0 and MUST be
ignored on receipt.
Bits which are NOT transmitted MUST be treated as if they are
set to 0 on receipt.
X-Flag: External Prefix Flag (Bit 0)
Set if the prefix has been redistributed from another protocol.
This includes the case where multiple virtual routers are
supported and the source of the redistributed prefix is another
IS-IS instance.
The flag MUST be preserved when leaked between levels.
In TLVs 236 and 237 this flag SHOULD always be sent as 0 and
MUST be ignored on receipt. This is because there is an existing
X flag defined in the fixed format of these TLVs as specified in
[RFC5308] and [RFC5120].
R-Flag: Re-advertisement Flag (Bit 1)
Set when the prefix has been leaked from one level to another
(upwards or downwards).
N-flag: Node Flag (Bit 2)
Set when the prefix identifies the advertising router i.e., the
prefix is a host prefix advertising a globally reachable address
typically associated with a loopback address.
The advertising router MAY choose to NOT set this flag even when
the above conditions are met.
If the flag is set and the prefix length is NOT a host prefix
(/32 for IPV4, /128 for IPv6) then the flag MUST be ignored.
The flag MUST be preserved when leaked between levels.
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2.2. IPv4/IPv6 Source Router ID
When a reachability advertisement is leaked from one level to
another, the source of the original advertisement is unknown. In
cases where the advertisement is an identifier for the advertising
router (e.g., N-flag set in the Extended Reachability Attribute sub-
TLV as described in the previous section) it may be useful for other
routers to know the source of the advertisement. The sub-TLVs
defined below provide this information.
Note that the Router ID advertised is always the Router ID of the IS-
IS instance which originated the advertisement. This would be true
even if the prefix has been learned from another protocol (X-flag set
as defined in Section 2.1).
IPv4 Source Router ID
Type: 11 (suggested - to be assigned by IANA)
Length: 4
Value: IPv4 Router ID of the source of the advertisement
Inclusion of this TLV is optional and MAY occur in TLVs
135, 235, 236, or 237. When included the value MUST be
identical to the value advertised in Traffic Engineering
router ID (TLV 134) defined in [RFC5305].
If present the sub-TLV MUST be included when the prefix
advertisement is leaked to another level.
IPv6 Source Router ID
Type: 12 (suggested - to be assigned by IANA)
Length: 16
Value: IPv6 Router ID of the source of the advertisement
Inclusion of this TLV is optional and MAY occur in TLVs
135, 235, 236, or 237. When included the value MUST be
identical to the value advertised in IPv6 TE Router ID
(TLV 140) defined in [RFC6119].
If present the sub-TLV MUST be included when the prefix
advertisement is leaked to another level.
2.3. Advertising Router IDs
[RFC5305] and [RFC6119] define the advertisement of router IDs for
IPv4 and IPv6 respectively. Although both drafts discuss the use of
router ID in the context of Traffic Engineering (TE), the
advertisement of router IDs is explicitly allowed for purposes other
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than TE. The use of router IDs to identify the source of a prefix
advertisement as defined in the previous section is one such use
case. Therefore, whenever the source router ID sub-TLVs defined in
the previous section are used, the originating router SHOULD also
advertise the corresponding address-family specific router ID TLV(s).
3. IANA Considerations
This document adds the following new sub-TLVs to the registry of sub-
TLVs for TLVs 135, 235, 236, 237.
Value: 4 (suggested - to be assigned by IANA)
Name: Prefix Attribute Flags
Value: 11 (suggested - to be assigned by IANA)
Name: IPv4 Source Router ID
Value: 12 (suggested - to be assigned by IANA)
Name: IPv6 Source Router ID
This document also introduces a new registry for bit values in the
Prefix Attribute Flags sub-TLV. Registration policy is Expert Review
as defined in [RFC5226]. This registry is to be part of the IS-IS
TLV Codepoints registry. The name of the registry is "Bit values for
Prefix Attribute Flags sub-TLV". Defined values are:
Bit # Name
----- ------------------------
0 External Prefix Flag (X-flag)
1 Re-advertisement Flag (R-flag)
2 Node Flag (N-flag)
4. Security Considerations
Security concerns for IS-IS are addressed in [RFC5304] and [RFC5310].
Advertisement of the additional information defined in this document
introduces no new security concerns.
5. Contributors
The following people gave a substantial contribution to the content
of this document and should be considered as co-authors:
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Clarence Filsfils
Cisco Systems
Email: cf@cisco.com
Stephane Litkowski
Orange Business Service
Email: stephane.litkowski@orange.com
6. References
6.1. Normative References
[ISO10589]
International Organization for Standardization,
"Intermediate system to Intermediate system intra-domain
routeing information exchange protocol for use in
conjunction with the protocol for providing the
connectionless-mode Network Service (ISO 8473)", ISO/
IEC 10589:2002, Second Edition, Nov 2002.
[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
dual environments", RFC 1195, DOI 10.17487/RFC1195,
December 1990, <http://www.rfc-editor.org/info/rfc1195>.
[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>.
[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120,
DOI 10.17487/RFC5120, February 2008,
<http://www.rfc-editor.org/info/rfc5120>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
Authentication", RFC 5304, DOI 10.17487/RFC5304, October
2008, <http://www.rfc-editor.org/info/rfc5304>.
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[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, DOI 10.17487/RFC5305, October
2008, <http://www.rfc-editor.org/info/rfc5305>.
[RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308,
DOI 10.17487/RFC5308, October 2008,
<http://www.rfc-editor.org/info/rfc5308>.
[RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic
Authentication", RFC 5310, DOI 10.17487/RFC5310, February
2009, <http://www.rfc-editor.org/info/rfc5310>.
[RFC6119] Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic
Engineering in IS-IS", RFC 6119, DOI 10.17487/RFC6119,
February 2011, <http://www.rfc-editor.org/info/rfc6119>.
6.2. Informational References
[SR] "IS-IS Extensions for Segment Routing, draft-ietf-isis-
segment-routing-extensions-06(work in progress)", December
2015.
Authors' Addresses
Les Ginsberg (editor)
Cisco Systems
510 McCarthy Blvd.
Milpitas, CA 95035
USA
Email: ginsberg@cisco.com
Bruno Decraene
Orange
38 rue du General Leclerc
Issy Moulineaux cedex 9 92794
France
Email: bruno.decraene@orange.com
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Stefano Previdi
Cisco Systems
Via Del Serafico 200
Rome 0144
Italy
Email: sprevidi@cisco.com
Xiaohu Xu
Huawei
Email: xuxiaohu@huawei.com
Uma Chunduri
Ericsson
Email: uma.chunduri@ericsson.com
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