Routing with a clue

Yehuda Afek*, Anat Bremler-Barr, Sariel Har-Peled

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

We suggest a new simple forwarding technique to speed up IP destination address lookup. The technique is a natural extension of IP, requires 5 bits in the IP header (IPv4, 7 in IPv6), and performs IP lookup nearly as fast as IP/Tag switching but with a smaller memory requirement and a much simpler protocol. The basic idea is that each router adds a "clue" to each packet, telling its downstream router where it ended the IP lookup. Since the forwarding tables of neighboring routers are similar, the clue either directly determines the best prefix match for the downstream router, or provides the downstream router with a good point to start its IP lookup. The new scheme thus prevents repeated computations and distributes the lookup process across the routers along the packet path. Each router starts the lookup computation at the point its upstream neighbor has finished. Furthermore, the new scheme is easily assimilated into heterogeneous IP networks, does not require routers coordination, and requires no setup time. Even a flow of one packet enjoys the benefits of the scheme without any additional overhead. The speedup we achieve is about 10 times faster than current standard techniques. In a sense, this paper shows that the current routers employed in the Internet are clue-less; namely, it is possible to speed up the IP lookup by an order of magnitude without any major changes to the existing protocols.

Original languageEnglish
Pages (from-to)693-705
Number of pages13
JournalIEEE/ACM Transactions on Networking
Volume9
Issue number6
DOIs
StatePublished - Dec 2001

Keywords

  • Best matching prefix
  • IP forwarding
  • IP lookup
  • IP routing
  • MPLS

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