Advertising Per-node Admin Tags in IS-IS
draft-psarkar-isis-node-admin-tag-01

Abstract

This document describes an extension to IS-IS protocol [ISO10589], [RFC1195] to add an optional operational capability, that allows tagging and grouping ofthe nodes in an IS-IS domain. This allows simple management and easy control over route and path selection, based on local configured policies.

This document describes the protocol extensions to disseminate per-node admin-tags in IS-IS protocols.

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.

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This Internet-Draft will expire on August 18, 2014.

Copyright Notice

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Table of Contents

• 1. Introduction
• 2. Administrative Tag
• 3. TLV format
• 3.1. Per-node Admin Tag sub-TLV
• 3.2. Ordering of tags
• 4. Applications
• 5. Security Considerations
• 6. IANA Considerations
• 7. Acknowledgments
• 8. References
• 8.1. Normative References
• 8.2. Informative References
• Authors' Addresses

1. Introduction

This document provides mechanisms to advertise per-node administrative tags in the IS-IS Link State PDU [RFC1195]. In certain path-selection applications like for example in traffic-engineering or LFA [RFC5286] selection there is a need to tag the nodes based on their roles in the network and have policies to prefer or prune a certain group of nodes.

2. Administrative Tag

For the purpose of advertising per-node administrative tags within IS-IS, a new sub-TLV to the IS-IS Router Capability TLV-242 that is defined in [RFC4971] is proposed. Because path selection is a functional set which applies both to TE and non-TE applications the same has not added as a new sub-TLV in the Traffic Engingineering TLVs [RFC5305].

An administrative Tag is a 32-bit integer value that can be used to identify a group of nodes in the IS-IS domain. The new sub-TLV specifies one or more administrative tag values. An IS-IS node advertises the set of groups it is part of in the specific IS-IS level. As an example, all PE-nodes may be configured with certain tag value, whereas all P-nodes are configured with a different tag value in.

The new sub-TLV defined will be carried inside the IS-IS Router Capability TLV-242 (defined in [RFC4971]) in the Link State PDUs originated by the router. Link State PDUs [ISO10589] has level-wise (i.e. L1 or L2) flooding scope. Choosing the flooding scope to flood the group tags are defined by the policies and is a local matter. Once a group tag is decided in a specific level the same will be inserted in the administrative tag sub-TLV in the Link State PDU for the same level. Implementations should allow configuring both a 'global' and 'per-level' admin tag. In the absence of a specific admin tag configuration for a specific level the global admin tag should be copied in to the LSP PDU for the same level.

3. TLV format

3.1. Per-node Admin Tag sub-TLV

The new Administrative Tag sub-TLV, like other ISIS Capability sub-TLVs, is formatted as Type/Length/Value (TLV)triplets. Figure 1 below shows the format of the new sub-TLV.

  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      |    Length     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   Administrative Tag #1                       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   Administrative Tag #2                       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //                                                             //
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   Administrative Tag #N                       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 Type :  TBA

 Length: A 8-bit field that indicates the length of the value
         portion in octets and will be a multiple of 4 octets
         dependent on the number of tags advertised.

 Value:  A sequence of multiple 4 octets defining the
         administrative tags.