Performance Issues in VC-Merge Capable ATM LSRs (RFC2682)
Original Publication Date: 1999-Sep-01
Included in the Prior Art Database: 2019-Feb-11
Internet Society Requests For Comment (RFCs)
I. Widjaja: AUTHOR [+1]
This document investigates the impact of VC merging on the additional buffer required for the reassembly buffers and other buffers. This memo provides information for the Internet community.
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 (C) The Internet Society (1999). All Rights Reserved.
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.
Recently some radical proposals to overhaul the legacy router architectures have been presented by several organizations, notably the Ipsilon’s IP switching , Cisco’s Tag switching , Toshiba’s CSR , IBM’s ARIS , and IETF’s MPLS . 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 [Page 1]
RFC 2682 Issues in VC Merge Capable ATM LSRs September 1999
architectures. In this document, we will assume that layer 2 switching uses ATM technology. In this case, each IP packet may be segmented to multiple 53-byte cells before being switched. Traditionally, AAL 5 has been used as the encapsulation method in data communications since it is simple, efficient, and has a powerful error detection mechanism. For the ATM switch to forward incoming cells to the correct outputs, the IP route information needs to be mapped to ATM labels which are kept in the VPI or/and VCI fields. The relevant route information that is stored semi-permanently in the IP routing table contains the tuple (destination, next-hop router). The route information changes when the network state changes and this typically occurs slowly, except during transient cases. The word "destination" typically refers to the destination network (or CIDR prefix), but can be readily generalized to (destination network, QoS), (destination host, QoS), or many other granula...