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An Analysis of the Skype Protocol
zib writes "Ever felt a need to peek under the hood of your Skype client? This paper (PDF) explains all the details. Among other issues, it focuses on the NAT capabilities of Skype and audio compression."
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What is the deal with supernodes, isn't there a peer to peer protocol that doesn't revolve around supernodes?
Because this type of tiered network is what works and scales well to thousands and millions of clients. The original Gnutella protocol was designed not to use "supernodes" or a tiered network structure and it was a miserable failure. The bandwidth and large latency required for all of the clients to communicate with each other (especially ones using 56K modems) easily overcame the usefulness of the network. The current Gnutella protocol now uses a tiered (layered) network where clients can become supernodes and this version actually works with tens to hundreds of thousands of people connected.
When creating a large, scalable network this type of protocol is what has been proven to work.
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I checked out Skype's EULA as found on their website.
The only thing relating to third party software that I found was this:
2.4 Third Parties. You acknowledge and agree that the Skype Software may be incorporated into, and may incorporate itself, software and other technology owned and controlled by third parties. Skype emphasizes that it will only incorporate such third party software or technology for the purpose of (a) adding new or additional functionality or (b) improving the technical performance of the Skype Software. Any such third party software or technology that is incorporated in the Skype Software falls under the scope of this Agreement. Any and all other third party software or technology that may be distributed together with the Skype Software will be subject to you explicitly accepting a license agreement with that third party. You acknowledge and agree that you will not enter into a contractual relationship with Skype or its Affiliates regarding such third party software or technology and you will look solely to the applicable third party and not to Skype or its Affiliates to enforce any of your rights.
Basically, you have to explicitly accept a license agreement with the third party. They say nothing in here about installing and using 3rd party software on your computer without your consent.
There are other solutions which'll do essentially what you want. One option is to have connections rotate round-robin style, rather than by bandwidth. That way, if you can go by 5 paths, each path gets 1/5th of the traffic, making it much harder for evesdroppers.
A second option is to use kernel or userland IPSec, so that all connections are secure. IPSec is pretty solid and it is doubtful anyone would be able to break into such traffic.
Supernodes are just a load-balancing mechanism. Not a very good one, because it's a two-state system, but it works. Networks have developed routing and QoS protocols to handle exactly the kind of information P2P is approximating with the supernode scheme. It would seem to make much more sense to use mechanisms people have worked on for much longer to get right.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
FYI, if you want to look at the "registry" info for Skype on Linux, it's in $HOME/.Skype/shared.xml.
If you run Skype on Linux or Mac OS X, it is reduced to using high ports anyway, so it's easy to block. An example iptables command line would be
(Caveat: Check your local servers, use passive FTP, modify this if you actually want to use P2P, etc.)