A Policy Control Mechanism in IS-IS Using Administrative Tags
draft-ietf-isis-admin-tags-04
The information below is for an old version of the document that is already published as an RFC.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 5130.
|
|
|---|---|---|---|
| Authors | Mike Shand , Stefano Previdi , Christian Martin | ||
| Last updated | 2015-10-14 (Latest revision 2007-11-19) | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | Proposed Standard | ||
| Formats | |||
| Reviews | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | (None) | |
| Document shepherd | (None) | ||
| IESG | IESG state | Became RFC 5130 (Proposed Standard) | |
| Action Holders |
(None)
|
||
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | Ross Callon | ||
| Send notices to | (None) |
draft-ietf-isis-admin-tags-04
Network Working Group S. Previdi
Internet-Draft M. Shand, Ed.
Intended status: Standards Track Cisco Systems
Expires: May 22, 2008 C. Martin
Verizon
B. Neal
Broadwing Communications
November 19, 2007
A Policy Control Mechanism in IS-IS Using Administrative Tags
draft-ietf-isis-admin-tags-04.txt
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Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This document describes an extension to the IS-IS protocol to add
operational capabilities that allow for ease of management and
control over IP prefix distribution within an IS-IS domain. This
document enhances the IS-IS protocol by extending the information
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that adraft-ietf-isis-wg-multi-topology Intermediate System (IS)
[router] can place in Link State Protocol Data Units (LSPs) for
policy use. This extension will provide operators with a mechanism
to control IP prefix distribution throughout multi-level IS-IS
domains.
Table of Contents
1. Conventions used in this Document . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Sub-TLV Additions . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. 32-bit Administrative Tag Sub-TLV 1 . . . . . . . . . . . . 4
3.2. 64-bit Administrative Tag Sub-TLV 2 . . . . . . . . . . . . 4
4. Ordering of Tags . . . . . . . . . . . . . . . . . . . . . . . 4
5. Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . 5
6. Operations . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
9. Manageability Considerations . . . . . . . . . . . . . . . . . 7
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
11.1. Normative References . . . . . . . . . . . . . . . . . . . 7
11.2. Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . . . 9
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1. Conventions used in this Document
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 BCP 14, [RFC2119].
2. Introduction
As defined in [RFC1195] and extended in [RFC3784], the IS-IS protocol
[ISO10589] may be used to distribute IPv4 prefix reachability
information throughout an IS-IS domain. In addition, thanks to
extensions made in [I-D.ietf-isis-wg-multi-topology] and
[I-D.ietf-isis-ipv6], IS-IS may be used to distribute IPv6
reachability information.
The IPv4 prefix information is encoded as TLV type 128 and 130 in
[RFC1195], with additional information carried in TLV 135 as
specified in [RFC3784] and TLV 235 as defined in
[I-D.ietf-isis-wg-multi-topology]. In particular, the extended IP
Reachability TLV (TLV 135) contains support for a larger metric
space, an up/down bit to indicate redistribution between different
levels in the hierarchy, an IP prefix, and one or more sub-TLVs that
can be used to carry specific information about the prefix. TLV 235
is a derivative of TLV 135, with the addition of Multi-Topology
membership information [I-D.ietf-isis-wg-multi-topology]. The IPv6
prefix information is encoded as TLV 236 in [I-D.ietf-isis-ipv6] and
TLV 237 in [I-D.ietf-isis-wg-multi-topology].
This draft proposes 2 new sub-TLVs for TLV 135, TLV 235, TLV 236 and
TLV 237 that may be used to carry administrative information about an
IP prefix.
3. Sub-TLV Additions
This draft proposes 2 new "Administrative Tag" sub-TLVs to be added
to TLV 135, TLV 235, TLV 236 and TLV 237. These TLVs specify one or
more 32 or 64 bit unsigned integers that may be associated with an IP
prefix. Example uses of these tags include controlling
redistribution between levels and areas, different routing protocols,
or multiple instances of IS-IS running on the same router, or
carrying BGP standard or extended communities.
The methods for which their use is employed is beyond the scope of
this document and left to the implementer and/or operator.
The encoding of the sub-TLV(s) is discussed in the following
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subsections.
3.1. 32-bit Administrative Tag Sub-TLV 1
The Administrative Tag SHALL be encoded as one or more 4 octet
unsigned integers using Sub-TLV 1 in TLV-135 [RFC3784], TLV 235
[I-D.ietf-isis-wg-multi-topology], TLV 236 [I-D.ietf-isis-ipv6] and
TLV 237 [I-D.ietf-isis-wg-multi-topology]. The Administrative Tag
Sub-TLV has following structure:
o 1 octet of type (value: 1)
o 1 octet of length (value: multiple of 4)
o one or more instances of 4 octets of administrative tag
On receipt, an implementation MAY consider only one encoded tag, in
which case the first encoded tag MUST be considered and any
additional tags ignored. A tag value of zero is reserved and SHOULD
be treated as "no tag".
3.2. 64-bit Administrative Tag Sub-TLV 2
The Administrative Tag SHALL be encoded as one or more 8 octet
unsigned integers using Sub-TLV 2 in TLV-135 [RFC3784], TLV 235
[I-D.ietf-isis-wg-multi-topology], TLV 236 [I-D.ietf-isis-ipv6] and
TLV 237 [I-D.ietf-isis-wg-multi-topology]. The 64-bit Administrative
Tag Sub-TLV has following structure:
o 1 octet of type (value: 2)
o 1 octet of length (value: multiple of 8)
o one or more instances of 8 octets of administrative tag
On receipt, an implementation MAY consider only one encoded tag, in
which case the first encoded tag MUST be considered and any
additional tags ignored. A tag value of zero is reserved and SHOULD
be treated as "no tag".
4. Ordering of Tags
The semantics of the tag order are implementation-dependent. That
is, there is no implied meaning to the ordering of the tags that
indicates a certain operation or set of operations need be performed
based on the order of the tags. Each tag SHOULD be treated as an
autonomous identifier that MAY be used in policy to perform a policy
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action. Whether or not tag A precedes or succeeds tag B SHOULD not
change the meaning of the tag set. However, when propagating TLVs
containing multiple tags between levels, an implementation SHOULD
preserve the ordering such that the first tag remains the first tag,
so that implementations which only recognise a single tag will have a
consistent view across levels.
Each IS that receives an LSP with TLV(s) 135 and/or 235 and/or 236
and/or 237, that have associated SubTLV(s) 1 and/or 2, MAY operate on
the tag values as warranted by the implementation. If an
implementation needs to change tag values, for example, when
propagating TLVs between levels at an area boundary, then the TLV(s)
SHOULD be copied to the newly generated Level-1 or Level-2 LSP at
which point, the contents of the SubTLV(s) MAY change as dictated by
the policy action. In the event that no change is required, the
SubTLV(s) SHOULD be copied in order into the new LSP, such that
ordering is preserved.
5. Compliance
A compliant IS-IS implementation MUST be able to assign one tag to
any IP prefix in any of the following TLVs: TLV 135, TLV 235, TLV
236, TLV 237. It MUST be able to interpret a single tag present in
the sub-TLV, or the first tag where there is more than one tag
present in the sub-TLV
A compliant IS-IS implementation MAY be able to assign more than one
tag to any IP prefix in any of the following TLVs: TLV 135, TLV 235,
TLV 236, TLV 237. It MAY be able to interpret the second and
subsequent tags where more than one tag is present in the sub-TLV
A compliant IS-IS implementation MAY be able to rewrite or remove one
or more tags associated with a prefix in any of the following TLVs:
TLV 135, TLV 235, TLV 236, TLV 237 when propagating TLVs between
levels.
6. Operations
An administrator associates an Administrative Tag value with some
interesting property. When IS-IS advertises reachability for some IP
prefix that has that property, it adds the Administrative Tag to the
IP reachability information TLV for that prefix, and the tag "sticks"
to the prefix as it is flooded throughout the routing domain.
Consider the network in Figure 1. We wish to "leak" L1 prefixes
[RFC2966] with some property, A, from L2 to the L1 router R1.
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Without policy- groups, there is no way for R2 to know property A
prefixes from property B prefixes.
R2--------R3--------R4
L2 / \
- - - /- - - - - - - - - - - - - -
L1 / \
R1----1.1.1.0/24 (A) R5
|
|
1.1.2.0/24 (B)
Figure 1: Example of usage
We associate Administrative Tag 100 with property A, and have R5
attach that value to the IP extended reachability information TLV for
prefix 1.1.2.0/24. R2 has a policy in place to "match prefixes with
Administrative Tag 100, and leak to L1."
The previous example is rather simplistic; it seems that it would be
just as easy for R2 simply to match the prefix 1.1.2.0/24. However,
if there are a large number of routers that need to apply some policy
according to property A and large number of "A" prefixes, this
mechanism can be quite helpful.
Implementations which support only a single tag and those which
support multiple tags may co-exist in the same IS-IS domain. An
implementatation supporting multiple tags SHOULD therefor assign any
tag which is required to be interpretted by all systems as the first
tag in any set of multiple tags.
7. Security Considerations
This document raises no new security issues for IS-IS, as any
annotations to IP prefixes should not pass outside the administrative
control of the network operator of the IS-IS domain. Such an
allowance would violate the spirit of Interior Gateway Protocols in
general and IS-IS in particular
8. IANA Considerations
The authors have chosen "1" as the type code of the 32-bits
Administrative Tag Sub-TLV and "2" as the type code of the 64-bits
Administrative Tag Sub-TLV. These values must be allocated by IANA.
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9. Manageability Considerations
These extensions which have been designed, developed and deployed for
many years do not have any new impact on management and operation of
the ISIS protocol via this standardization process.
10. Acknowledgements
The authors would like to thank Henk Smit for clarifying the best
place to describe this new information, Tony Li and Tony Przygienda
for useful comments on this draft, Danny McPherson for some much
needed formatting assistance.
11. References
11.1. 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, December 1990.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
11.2. Informative References
[I-D.ietf-isis-ipv6]
Hopps, C., "Routing IPv6 with IS-IS",
draft-ietf-isis-ipv6-07 (work in progress), October 2007.
[I-D.ietf-isis-wg-multi-topology]
Przygienda, T., "M-ISIS: Multi Topology (MT) Routing in
IS-IS", draft-ietf-isis-wg-multi-topology-12 (work in
progress), November 2007.
[RFC2966] Li, T., Przygienda, T., and H. Smit, "Domain-wide Prefix
Distribution with Two-Level IS-IS", RFC 2966,
October 2000.
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[RFC3784] Smit, H. and T. Li, "Intermediate System to Intermediate
System (IS-IS) Extensions for Traffic Engineering (TE)",
RFC 3784, June 2004.
Authors' Addresses
Stefano Previdi
Cisco Systems
Via Del Serafico, 200
00142 Rome,
Italy
Email: sprevidi@cisco.com
Mike Shand (editor)
Cisco Systems
250, Longwater Avenue.
Reading, Berks RG2 6GB
UK
Phone: +44 208 824 8690
Email: mshand@cisco.com
Christian Martin
Verizon
1880 Campus Commons Dr
Reston, VA 20191
USA
Email: cmartin@verizon.com
Brad Neal
Broadwing Communications
1835 Kramer Lane - Suite 100
Austin, TX 78758
USA
Email: bneal@broadwing.com
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