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Skype brief post-mortem

skype.com

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Re: Skype brief post-mortem

#11
post #6

Earlier quoted context omitted.

Why is it a problem to bring supernode back online?

I can imagine it would self-DDoS from lack of peer supernodes to share the load.

That can be avoided by altering the logic by which supernodes are queried. Not all nodes must try all supernodes.

Re: Skype brief post-mortem

#12

does anyone know why skype picked German as the only translation of this message?

Obvious possibilities include German being the most used non-English language for Skype users, or that they're going to be adding other languages but their translators haven't yet written them.

The only guess I have that isn't from an obvious reason is that Skype HQ is in Luxembourg, a small country right next to Germany. One of the three official languages there is German, and the other is Luxembourgish, which is closely related to German.

Re: Skype brief post-mortem

#13
post #6

Earlier quoted context omitted.

I can imagine it would self-DDoS from lack of peer supernodes to share the load.

But at least it would successfully reply to at least some of requests, right? And would still keep trying to serve the requests, right? So if sufficient number of supernodes is brought back online then the problems should disappear.

When this happens to our websites (when all servers go down), we need to rate limit and/or shut down traffic at the load balancer level as we bring things back online, otherwise everything just continues to get swamped and goes right back down. This would be nearly impossible in a P2P network and coordinating it between locations would be an even bigger nightmare. I imagine this is why turning on an entirely new network is a more viable option for them.

Re: Skype brief post-mortem

#14
Does anybody know if these supernodes are paid for by Skype or they're simply users' computers being commandeered by Skype (after getting click-through permission).

The explanation doesn't ring true to me because AFAIK supernodes are used only if a direct P2P path cannot be established between caller and callee.

What we're observing is the inability to sign in and see contacts' status. I always thought that was centralized. Are supernodes involved in signin?

Re: Skype brief post-mortem

#15
post #11
post #6

Earlier quoted context omitted.

I can imagine it would self-DDoS from lack of peer supernodes to share the load.

That can be avoided by altering the logic by which supernodes are queried. Not all nodes must try all supernodes.

Since it seems a good chunk of the super nodes went down, I imagine every running unconnected Skype instance is checking all of the super nodes it can find (or actively searching for them). Changing the logic at this point isn't really an option for them.

Re: Skype brief post-mortem

#17

"Our engineers are creating new ‘mega-supernodes’ as fast as they can" What a brilliant solution.

Yea, see the above comments. Bringing up individual nodes isn't an option as they would likely be overwhelmed and rate limiting traffic from all of the running instances in a P2P network would be near impossible. Bringing up an entirely new super node network, while insane, is probably their best option right now.

Edit: I initially read your post as sarcastic, but I realize now it may not have been. It's definitely outside-the-box thinking and after considering their options, this certainly seems the most viable.

Re: Skype brief post-mortem

#18
post #11

Earlier quoted context omitted.

That can be avoided by altering the logic by which supernodes are queried. Not all nodes must try all supernodes.

Since it seems a good chunk of the super nodes went down, I imagine every running unconnected Skype instance is checking all of the super nodes it can find (or actively searching for them). Changing the logic at this point isn't really an option for them.

Well, even if we were to talk about this point, it actually might be. I have no knowledge of Skype architecture, so I'm totally guessing here. But, those unconnected Skype instances have to have some kind of directory of supernodes: either dynamic or static. If it's dynamic, that is from Skype's servers, it can be affected.

Re: Skype brief post-mortem

#19

Earlier quoted context omitted.

But at least it would successfully reply to at least some of requests, right? And would still keep trying to serve the requests, right? So if sufficient number of supernodes is brought back online then the problems should disappear.

When this happens to our websites (when all servers go down), we need to rate limit and/or shut down traffic at the load balancer level as we bring things back online, otherwise everything just continues to get swamped and goes right back down. This would be nearly impossible in a P2P network and coordinating it between locations would be an even bigger nightmare. I imagine this is why turning on an entirely new netw…

Why would overloaded server go down? Shouldn't it simply stop serving incoming requests if it's overloaded?
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