RFC 3386 (rfc3386) - Page 3 of 27
Network Hierarchy and Multilayer Survivability
Alternative Format: Original Text Document
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 many Label Switched Paths (LSPs) in a service provider network with hierarchical Interior Gateway Protocol (IGP). This is necessary to support layer 2 and layer 3 Virtual Private Network (VPN) services that require edge-to-edge signaling across a core network. This document presents a proposal of the near-term and practical requirements for network survivability and hierarchy in current service provider environments. With feedback from the working group solicited, the objective is to help focus the work that is being addressed in the TEWG (Traffic Engineering Working Group), CCAMP (Common Control and Measurement Plane Working Group), and other working groups. A main goal of this work is to provide some expedience for required functionality in multi-vendor service provider networks. The initial focus is primarily on intra-domain operations. However, to maintain consistency in the provision of end-to-end service in a multi-provider environment, rules governing the operations of survivability mechanisms at domain boundaries must also be specified. While such issues are raised and discussed, where appropriate, they will not be treated in depth in the initial release of this document. The document first develops a set of definitions to be used later in this document and potentially in other documents as well. It then addresses the requirements and issues associated with service restoration, hierarchy, and finally a short discussion of survivability in hierarchical context. Here is a summary of the findings: A. Survivability Requirements o need to define a small set of interoperable survivability approaches in packet and non-packet networks o suggested survivability mechanisms include - 1:1 path protection with pre-established backup capacity (non- shared) - 1:1 path protection with pre-planned backup capacity (shared) Lai, et. al. Informational
