Network Working Group E. Osborne
Internet-Draft Cisco
Intended status: Experimental February 13, 2013
Expires: August 17, 2013
Extended Administrative Groups in MPLS-TE
draft-osborne-mpls-extended-admin-groups-00
Abstract
This document provides additional administrative groups (sometimes
referred to as "link colors") to the IGP extensions for MPLS-TE.
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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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on August 17, 2013.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Extended Administrative Groups sub-TLV . . . . . . . . . . . . 3
2.1. Packet Format . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Admin group numbering . . . . . . . . . . . . . . . . . . . 4
2.3. Backward compatability . . . . . . . . . . . . . . . . . . 4
2.3.1. AG and EAG coexistence . . . . . . . . . . . . . . . . 4
2.3.2. Desire for unadvertised EAG bits . . . . . . . . . . . 4
3. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
6. Normative References . . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 5
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1. Introduction
MPLS-TE advertises 32 administrative groups (commonly referred to as
"colors" or "link colors") using the Administrative Group sub-TLV of
the Link TLV. This is defined for OSPF [RFC3630]and ISIS [RFC5305].
This document adds a sub-TLV to the IGP TE extensions, "Extended
Administrative Group". It
2. Extended Administrative Groups sub-TLV
The Extended Administrative Groups sub-TLV is used in addition to the
Administrative Groups when a device wishes to advertise more than 32
colors for a link. The EAG sub-TLV is optional.
This document uses the term 'colors' as a shorthand to refer to
particular bits with an AG or EAG. The examples in this document use
'red' to represent the least significant bit in the AG (red == 0x1),
'blue' to represent the second bit (blue == 0x2). To say that a link
has a given color or that the specified color is set on the link is
to say that the corresponding bit or bits in the link's AG are set to
1.
2.1. Packet Format
The format of the Extended Administrative Groups sub-TLV is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type: Extended Admin Group | Length: Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value: Extended Admin Group Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ........... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value: Extend Admin Group Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Length is the size of the Extended Admin Group (EAG) value in
octets. The EAG may be of any length, but must be a multiple of 4
octets.
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2.2. Admin group numbering
By convention, the existing Administrative Group TLVs are numbered 0
(LSB) to 31 (MSB). The EAG values pick up where this numbering
scheme leaves off. The LSB in the EAG is 32. If the EAG is 4 bytes
in length, the MSB is 63. If the EAG is 8 bytes in length, the MSB
is 95.
2.3. Backward compatability
There are two things to consider for backward compatibility with
existing AG implementations - how do AG and EAG coexist, and what
happens if a node has matching criteria for unadvertised EAG bits?
2.3.1. AG and EAG coexistence
If a node advertises the EAG sub-TLV it MUST also advertise the
existing Administrative Group (AG) sub-TLV defined in RFCs 3630 and
5305. This ensures that the first bit of the EAG sub-TLV is always
bit 32, and ensures maximum interoperability with legacy
implementations.
2.3.2. Desire for unadvertised EAG bits
The existing AG bits are optional; thus a node may be configured with
a preference to include red or exclude blue, and be faced with a link
that is not advertising a value for either blue or red. What does an
implementation do in this case? It shouldn't assume that red is set,
but it is also arguably incorrect to assume that red is NOT set, as a
bit must first exist before it can be set to 0.
Practically speaking this has not been an issue for deployments, as
many implementations always advertise the AG bits, often with a
default value of 0x00000000. However, this issue may be of more
concern once EAGs are added to the network. EAGs may exist on some
nodes but not others, and the EAG length may be longer for some links
than for others.
Each implementation is free to choose its own method for handling
this question. However, to encourage maximum interoperability an
implementation SHOULD treat specified but unadvertised EAG bits as if
they are set to 0. A node MAY provide other (configurable)
strategies for handling this case.
3. Security Considerations
This extension adds no new security considerations.
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4. IANA Considerations
This document requests a sub-TLV allocation in both OSPF and ISIS.
5. Acknowledgements
Thanks to Santiago Alvarez and Rohit Gupta for their review and
comments.
6. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
September 2003.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, October 2008.
Author's Address
Eric Osborne
Cisco
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