Peer-to-Peer Caching Schemes to Address Flashing Crowds

Tyron Stading, Petros Maniatis, Mary Baker
IPTPS '02: 1st International Peer To Peer Systems Workshop

Overview

This paper introduces a system, Backslash, to address flash crowds. As long as a server is capable of serving all requests it does not use the Backslash system and continues to serve its own content. Once a Backslash node perceives an increased load switch to either pre-overload mode or overload mode, depending on load thresholds. In pre-overload mode the server is still capable of serving all requests but it sees a very high load. In overload mode the server is nearly overrun with requests.

To divert subsequent requests an overloaded backslash node uses URL rewriting: embedded URLs of a document (e.g. images) are rewritten such that requests are send other Backslash nodes.

Resources are placed and located by a distributed hash table. The storage space of a node is split in two categories: replica space and temporary cache. Objects in the replica space are guaranteed to be where they were place, these objects are the result of insertions in the distributed hash table. Temporary cached objects are placed opportunistically to speed up subsequent retrievals.