Skype's Journey from P2P

Bruce Lowekamp (Principal Architect for Skype’s Cloud Infrastructure) did a talk yesterday on Skype’s migration from P2P to a centrally-stored service.

If you’re at all interested in how Skype P2P worked, or how they completely changed the service without any interruption, it’s definitely worth a watch/listen. Also there’s discussion about how they experiment with everyone using Skype and how that data is interpreted and used.

Here are a few notes I made:

  • The old Skype P2P network is still up, but will be shutdown in Fall 2018.
  • The old Skype P2P clients could operate on their own after login. If they wanted to upgrade the Skype backend database, they would shut it down for 20 minutes as the clients could operate without it. I think I remember experiencing this more than once myself.
  • The migration of Skype chat’s protocols are: P2P -> P2P + Griffin -> Messenger -> New Chat Service
    For those who were claiming the MSNP is going to continue, I really doubt “New Chat Service” is that.
  • The migration of Skype contacts backends are: CBL -> JCS -> ABCH -> PCS -> EXO.
    CBL/JCS is Skype’s own contacts, ABCH was the Messenger/Hotmail contacts store. Apparently when they were “75% done” with the ABCH, Microsoft elected to shut it down, and EXO (Exchange Online, the current one) was not ready, so they created PCS.
  • There are “thousands” of configuration options that Skype will configure specifically for your client when you connect.
    The idea is that they can experiment with users to determine what settings work best in what configurations, and then after a successful experiment, they can deploy that change to everyone.

It’s honestly pretty cool to see how Skype managed this P2P thing and the caveats and benefits it brought up, like the whole thing about users lagging behind on the latest version of Skype as the P2P infrastructure affected little on how the Skype clients talked to each other, and also how they could upgrade the DB infrastructure without users experiencing downtime also due to the P2P infrastructure not relying on servers. Oh, how you can’t get away with things like that now, as P2P is apparently dead in the modern age due to mobile phones still rising in popularity, plus the fact that companies are basically forced to eye on everything their users do, so it’s HTTPS and JSON that can be easily logged for everyone. :stuck_out_tongue:

When I heard that Skype used ABCH, I immediately thought Skype at one point used SOAP for that. Must be all the MSN I’ve been indulging myself in that made me think that. :stuck_out_tongue:

It will suck that Skype’s P2P service will be shut down this Fall, and I’m unsure of if it’ll affect Skype 7 or older clients that use MSNP24, but companies gotta do what they gotta do: push users to use the latest version of their software, which isn’t the best in Skype’s case. But I think it’ll leave a legacy of an innovative technology that got cut short, P2P messaging. I wish I cared enough to use Skype back then, because it could’ve been cool to talk to people without big wigs snooping on my messages lol. :stuck_out_tongue:

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