Forwarding Requests among Reverse Proxies

Limin Wang$^{\dagger}$ - Fred Douglis$^{\star}$ - Michael Rabinovich$^{\star}$ -
$^{\dagger}$Department of Computer Science
Princeton University
Princeton, NJ 08544
lmwang@cs.princeton.edu -
$^{\star}$AT&T Labs-Research
180 Park Avenue
Florham Park, NJ 07932-0971
{douglis,misha}@research.att.com

Date:

Abstract:

Reverse proxy caching is a technology deployed by many ISPs at the border routers of their backbones to improve performance of their Web hosting services. Currently, cooperation among reverse proxies (if any) is limited to sharing each other's cache copies. In this paper, we propose to extend the cooperation by forwarding requests among cooperating reverse proxies. Instead of fetching objects from remote proxies, a proxy in this mechanism forwards requests to other proxies and tells them to send the objects directly to clients. The resulting ``circular communication'' (client$\rightarrow$proxy$\rightarrow$remote proxy$\rightarrow$client) can be implemented in practice with a TCP hand-off among proxies.

Request forwarding has serveral potential benefits: first, it can get the heavy traffic off an ISP's own backbone quickly and make more backbone bandwidth available to accommodate more customers; second, it can offload busy proxies and achieve some load balancing; finally, by observing network delay of their previous interactions with clients, reverse proxies can use request forwarding to improve client-proxy network proximity and avoid congested networks. Using trace-driven simulations, we evaluated the first benefit by studying two policies. Preliminary results show a 13-35% backbone bandwidth reduction and the benefit of maintaining a dedicated output link at the content server.