wdiff rfc7794.original rfc7794.txt

Networking Working Group
Internet Engineering Task Force (IETF) L. Ginsberg, Ed.
Internet-Draft
Request for Comments: 7794 Cisco Systems
Intended status:
Category: Standards Track B. Decraene
Expires: July 7, 2016
ISSN: 2070-1721 Orange
S. Previdi
Cisco Systems
X. Xu
Huawei
U. Chunduri
Ericsson
January 4,
February 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 that 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 an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force
(IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list It represents the consensus of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid the IETF community. It has
received public review and has been approved for a maximum publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of six months RFC 5741.

Information about the current status of this document, any errata,
and how to provide feedback on it may be updated, replaced, or obsoleted by other documents obtained 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.
http://www.rfc-editor.org/info/rfc7794.

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
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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. New sub-TLVs Sub-TLVs for Extended Reachability TLVs . . . . . . . . . 3
2.1. IPv4/IPv6 Extended Reachability Attribute Flags . . . . . 3
2.2. IPv4/IPv6 Source Router ID . . . . . . . . . . . . . . . 5 4
2.3. Advertising Router IDs . . . . . . . . . . . . . . . . . 5
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. Contributors References . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.
5.1. Normative References . . . . . . . . . . . . . . . . . . 6
5.2. Informative References . . . . . . . 7
6.1. Normative References . . . . . . . . . . 7
Contributors . . . . . . . . 7
6.2. Informational References . . . . . . . . . . . . . . . . 8 . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8

1. Introduction

IS-IS is a link state 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 or not an advertised prefix is directly
connected to the advertising router or not. router. In the case of [SR] [SR], knowing
whether or not a prefix is directly connected or not determines what action
should be taken as regards processing of labels associated with an
incoming packet.

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 Therefore, a new sub-TLV is
introduced which that allows for the advertisement of attribute flags
associated with prefix advertisements.

In cases where multiple node addresses are advertised by a given
router
router, it is also useful to be able to associate all of these
addresses with a single Router-ID Router ID even when prefixes are advertised
outside of the area in which they are originated. Therefore Therefore, a new
sub-TLV sub-
TLV is introduced to advertise the router-id Router ID of the originator of a
prefix advertisement.

1.1. Requirements Language

2. New sub-TLVs 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 and 237, unless
otherwise stated.

Prefix Attribute Flags
Type: 4 (suggested - to be assigned by IANA)
Length: Number of octets to follow
Value
Value:

(Length * 8) bits.

0 1 2 3 4 5 6 7...
+-+-+-+-+-+-+-+-+...
|X|R|N| ...
+-+-+-+-+-+-+-+-+...

Bits are defined/sent starting with Bit #0 0 defined below. Additional
bit definitions which that may be defined in the future SHOULD be assigned
in ascending bit order so as to minimize the number of bits which that will
need to be transmitted.

Undefined bits MUST be transmitted as 0 and MUST be ignored on
receipt.

Bits which that 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 237 237, 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 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) IPv6), then the flag MUST be ignored. The flag
MUST be preserved when leaked between levels.

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., with the N-flag set in the Extended Reachability Prefix Attribute Flags sub-
TLV as described in the previous section) Section 2.1), it may be useful for other routers
to know the source of the advertisement. The sub-TLVs defined below
provide this that information.

Note that the Router ID advertised is always the Router ID of the IS-
IS instance which that originated the advertisement. This would be true
even if the prefix has had been learned from another protocol (X-flag (i.e., with
the 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 included, the value MUST be identical to the value
advertised in the 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 included, the value MUST be identical to the value
advertised in the IPv6 TE Router ID (TLV 140) defined in [RFC6119].

If present 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 IPv6, respectively. Although both drafts documents discuss the use
of router ID in the context of Traffic Engineering (TE), the
advertisement of router IDs is explicitly allowed for purposes other
than TE. The use of router IDs to identify the source of a prefix
advertisement as defined in the previous section Section 2.2 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, and 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 The registration policy is Expert
Review as defined in [RFC5226]. This registry is to be part of the IS-IS "IS-IS
TLV Codepoints Codepoints" registry. The name of the registry is "Bit values
for Prefix Attribute Flags sub-TLV". Defined The 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:

Clarence Filsfils
Cisco Systems

Email: cf@cisco.com

Stephane Litkowski
Orange Business Service

Email: stephane.litkowski@orange.com

6. References

6.1.

5.1. 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 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>.

[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

5.2. Informative References

[SR] Previdi, S., Ed., 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-06(work Routing", Work in progress)", Progress,
draft-ietf-isis-segment-routing-extensions-06, December
2015.

Contributors

The following people gave a substantial contribution to the content
of this document:

Clarence Filsfils
Cisco Systems

Email: cf@cisco.com

Stephane Litkowski
Orange Business Service

Email: stephane.litkowski@orange.com

Authors' Addresses

Les Ginsberg (editor)
Cisco Systems
510 McCarthy Blvd.
Milpitas, CA 95035
USA
United States

Email: ginsberg@cisco.com

Bruno Decraene
Orange
38 rue du General Leclerc
Issy Moulineaux cedex 9 92794
France

Email: bruno.decraene@orange.com

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