Modelling P2P Networks

Nathan Kennedy writes: "Mihajlo A. Jovanovic did his Master's project at the University of Cincinnati on modelling P2P networks with Gnutella as a case study. You view his project along with source code, stunningly pretty pictures, an applet and a paper on scalability."

Comments

Interesting...

[ZigMonty]

The pictures are cool but wouldn't one of the Fasttrack based P2P networks be a better example? I've got nothing against Gnutella but Morpheus and co seem to have scaled better. Is it because Gnutella is easier to test, its protocol more open, etc? Can anyone enlighten me as to why Gnutella would be better? Not trying to be a troll, just curious.

Re:Interesting...

[jilles]

Morpheus is apparently going to switch to gnutella in their next version of their client. Due to the unexpected exclusion of their existing client of the fasttrack network the release will probably be in a couple of days.

The Gnutella protocol and the fasttrack protocol are actually very similar since limewire added superpeers. In a couple of days (when morpheus releases their gnutella stuff), gnutella will be put to the test. Theoretically it should scale at least as well as fasttrack.

Gnutella has a few advantages over fasttrack:
- Gnutella is an open, simple to implement protocol. Fasttrack is a propietary implementation of a propietary protocol. Non authorized implementations are being banned from the network.
- there are implementations of Gnutella in various languages for various platforms. The best are free (both in terms of speech and beer).
- shutting down one gnutella client doesn't affect other clients. So if bearshare is shut down you just switch to limewire or something else and connect to the same gnutella network.
- unlike fasttrack, gnutella has no dependencies on a central server. It only needs the ip of one other client in the network to connect itself. Typically clients contact a webserver to get a list of such clients, however this is optional.
- It's theoretically just as scalable and potentially even more scalable (due to future innovations in clients).
- Most of the clients are stable and will survive more than a few searches (morpheus consistently crashes on me)

However there are disadvantages:
- Gnutella doesn't specify how to handle queries. Consequently some clients are better at this than others and you may get crappy search results. Limewire has metasearch abilities in the works which could potentially be just as good as morpheus (or better). However, until all (or most clients) on the network support this, this will be relatively useless.
- The gnutella network is smaller (typically around 50000 hosts at the moment) than fasttrack at the moment.

If you want to give gnutella a try and don't want the spyware, I recommend that you don't download the windows installer but the installer for "other" platforms instead. This will get you nice Java only version without all the crap (except for ads). Also be sure to run it using the latest jdk (1.4.0) as it is somewhat faster than previous versions.

Gnutella Ultrapeers

[chrohrs]

One problem I see with this study is it doesn't account for ultrapeers, technology that was released by LimeWire in early January. Ultrapeers increase scalability by offloading most of the bandwidth burden to dynamically-elected high-speed hosts. Unlike Fasttrack, ultrapeers use an open protocol with open-source implementations. I believe BearShare is also adding ultrapeer support.

One problem with LimeWire's initial implementation is that ultrapeers didn't respond to "crawler pings" with "leaf pongs". (We've since changed that.) So as pretty as these pictures are, they're probably not accurate. I would love to see updated results that accounted for ultrapeers.

The Gnutella network is evolving rapidly, and it would be great if academic papers considered these changes. The Gnutella Developer Forum (GDF) is the primary location for protocol development.

Christopher Rohrs
Sr. Software Engineer
LimeWire