Understanding Peer-to-Peer Systems

Although I had a basic understanding of how peer-to-peer (P2P) systems worked (thanks to a little application known as BitTorrent), reading about how a P2P system is designed helped me better understand the nuances associated with creating a P2P application. In particular, the distributed lookup protocol I studied was entitled "Chord." Unlike many other networking protocol names, this wasn't an acronym for anything special.

The main problem Chord is trying to solve is the problem of efficiently locating a node that stores a particular data item. Chord is impressive in its running time, taking only O(logN), where N is the number of nodes, to maintain routing information and resolve lookups, and also in its robustness, updating routing information for leaving and joining in O(log^2(n)) time.

More importantly, Chord showed me that in order to effectively create a P2P application we need to look at several aspects of P2P. Firstly, Chord implements consistent hashing and stabilization in order to allow for nodes to join and leave. Successfully allowing for users to be able to enter or drop out at any time without disturbing the distributed network is an important aspect of P2P applications. If this aspect of P2P is not handled correctly and efficiently, then the application will essentially fail.

Next, Chord is also scalable, which essentially means it is a feasible protocol for the existing internet architecture. Unlike the other architectures I have studied, Chord is a protocol that is implemented on the application layer, which is much easier to manipulate than the underlying architecture of the internet. Chord not only solves a problem in existing P2P protocols, but it does so in a way that is actual usable, which is an important aspect of research that I haven't seen a lot of in networking (at least in research on internet architecture).

Overall, I found this particular paper very useful, because I feel that understanding these basic ideas of P2P networks and protocols will better prepare me for the next paper I will read for my networking class, a paper on matchmaking for online games, which I am very excited to read.