Network Hierarchy and Multilayer Survivability
RFC 3386

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• 01

Network Working Group                                        W. Lai, Ed.
Request for Comments: 3386                                          AT&T
Category: Informational                                  D. McDysan, Ed.
                                                                WorldCom
                                                           November 2002

            Network Hierarchy and Multilayer Survivability

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   This document presents a proposal of the near-term and practical
   requirements for network survivability and hierarchy in current
   service provider environments.

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, RFC 2119 [2].

Lai, et. al.                 Informational                      [Page 1]
RFC 3386          Hierarchy & Multilayer Survivability     November 2002

Table of Contents

   1. Introduction..............................................2
   2. Terminology and Concepts..................................5
   2.1 Hierarchy................................................6
   2.1.1 Vertical Hierarchy.....................................5
   2.1.2 Horizontal Hierarchy...................................6
   2.2 Survivability Terminology................................6
   2.2.1 Survivability..........................................7
   2.2.2 Generic Operations.....................................7
   2.2.3 Survivability Techniques...............................8
   2.2.4 Survivability Performance..............................9
   2.3 Survivability Mechanisms: Comparison....................10
   3. Survivability............................................11
   3.1 Scope...................................................11
   3.2 Required initial set of survivability mechanisms........12
   3.2.1 1:1 Path Protection with Pre-Established Capacity.....12
   3.2.2 1:1 Path Protection with Pre-Planned Capacity.........13
   3.2.3 Local Restoration.....................................13
   3.2.4 Path Restoration......................................14
   3.3 Applications Supported..................................14
   3.4 Timing Bounds for Survivability Mechanisms..............15
   3.5 Coordination Among Layers...............................16
   3.6 Evolution Toward IP Over Optical........................17
   4. Hierarchy Requirements...................................17
   4.1 Historical Context......................................17
   4.2 Applications for Horizontal Hierarchy...................18
   4.3 Horizontal Hierarchy Requirements.......................19
   5. Survivability and Hierarchy..............................19
   6. Security Considerations..................................20
   7. References...............................................21
   8. Acknowledgments..........................................22
   9. Contributing Authors.....................................22
   Appendix A: Questions used to help develop requirements.....23
   Editors' Addresses..........................................26
   Full Copyright Statement....................................27

1. Introduction

   This document is the result of the Network Hierarchy and
   Survivability Techniques Design Team established within the Traffic
   Engineering Working Group.  This team collected and documented
   current and near term requirements for survivability and hierarchy in
   service provider environments.  For clarity, an expanded set of
   definitions is included.  The team determined that there appears to
   be a need to define a small set of interoperable survivability
   approaches in packet and non-packet networks.  Suggested approaches
   include path-based as well as one that repairs connections in

Lai, et. al.                 Informational                      [Page 2]
RFC 3386          Hierarchy & Multilayer Survivability     November 2002

   proximity to the network fault.  They operate primarily at a single
   network layer.  For hierarchy, there did not appear to be a driving
   near-term need for work on "vertical hierarchy," defined as
   communication between network layers such as Time Division
   Multiplexed (TDM)/optical and Multi-Protocol Label Switching (MPLS).
   In particular, instead of direct exchange of signaling and routing
   between vertical layers, some looser form of coordination and
   communication, such as the specification of hold-off timers, is a
   nearer term need.  For "horizontal hierarchy" in data networks, there
   are several pressing needs.  The requirement is to be able to set up