Caching P2P traffic: What are the benefits for an ISP?

Caching P2P content could be an effective way of alleviating network usage, thereby reducing operation costs for operators. However, cache performances are affected by a lot of factors related to the cache itself, but also to the properties of the P2P overlay, the P2P contents, and the cache deployment location. In order to evaluate the potential usefulness of P2P caches, we have setup a large-scale experiment for monitoring traffic of a popular P2P application in the operational network of France Telecom. After gaining some insights on the characteristics of the P2P traffic, we simulate a cache based on data contained in our trace. We are then able to evaluate cache performances in terms of the bandwidth that could have been saved if a cache was really in the network during our measurements. Additionally, the paper studies the impact of various factors on performance, such as cache properties and more importantly the number of customers served by the cache. The results show that the bandwidth gain can reach 23% of P2P traffic with a passive cache.