RFC 2682 (rfc2682) - Page 1 of 12

Performance Issues in VC-Merge Capable ATM LSRs

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Network Working Group                                         I. Widjaja
Request For Comments: 2682                Fujitsu Network Communications
Category: Informational                                       A. Elwalid
                                          Bell Labs, Lucent Technologies
                                                          September 1999


            Performance Issues in VC-Merge Capable ATM LSRs

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 (1999).  All Rights Reserved.

Abstract

   VC merging allows many routes to be mapped to the same VC label,
   thereby providing a scalable mapping method that can support
   thousands of edge routers. VC merging requires reassembly buffers so
   that cells belonging to different packets intended for the same
   destination do not interleave with each other.  This document
   investigates the impact of VC merging on the additional buffer
   required for the reassembly buffers and other buffers.  The main
   result indicates that VC merging incurs a minimal overhead compared
   to non-VC merging in terms of additional buffering. Moreover, the
   overhead decreases as utilization increases, or as the traffic
   becomes more bursty.

1.0 Introduction

   Recently some radical proposals to overhaul the legacy router
   architectures have been presented by several organizations, notably
   the Ipsilon's IP switching [1], Cisco's Tag switching [2], Toshiba's
   CSR [3], IBM's ARIS [4], and IETF's MPLS [5].  Although the details
   of their implementations vary, there is one fundamental concept that
   is shared by all these proposals: map the route information to short
   fixed-length labels so that next-hop routers can be determined by
   direct indexing.

   Although any layer 2 switching mechanism can in principle be applied,
   the use of ATM switches in the backbone network is believed to be a
   very attractive solution since ATM hardware switches have been
   extensively studied and are widely available in many different



Widjaja & Elwalid            Informational
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