Skype to Users: Microsoft Good, My Bad, We Fixed, All Better Now

Skype to Users: Microsoft Good, My Bad, We Fixed, All Better Now

Problems with popular P2P VoIP phone purveyor Skype caused problems for millions of users last week. They couldn't connect to the service to phone home, work, or anyplace else. Skype's initial posting at its Heartbeat blog seemed to suggest that the fault was partially Microsoft's, but in its latest posting, Skype puts the blame squarely on itself. Selections from the full posting follow (ellipses [...] indicate omitted sections):

1. Are we blaming Microsoft for what happened?

We don’t blame anyone but ourselves. The Microsoft Update patches were merely a catalyst — a trigger — for a series of events that led to the disruption of Skype, not the root cause of it. And Microsoft has been very helpful and supportive throughout.[...]

2. What was different about this set of Microsoft update patches?

In short – there was nothing different about this set of Microsoft patches. During a joint call soon after problems were detected, Skype and Microsoft engineers went through the list of patches that had been pushed out. We ruled each one out as a possible cause for Skype’s problems.[...]

3. How come previous Microsoft update patches didn’t cause disruption?

That’s because the update patches were not the cause of the disruption.[...]

4. Has the bug been fixed? Should Skype users worry about future Microsoft Update patches and reboots?

Yes, the bug has been squashed. The parameters of the P2P network have been tuned to be smarter about how similar situations should be handled. Once we found the algorithmic fix to ensure continued operation in the face of high numbers of client reboots, the efforts focused squarely on stabilising the P2P core. The fix means that we’ve tuned Skype’s P2P core so that it can cope with simultaneous P2P network load and core size changes similar to those that occurred on August 16. We’d like to reassure our users across the globe that we’ve done everything we need to do to make sure this doesn’t happen again. We’ve already introduced a number of improvements to our software to ensure our users will not be similarly affected – in the unlikely possibility of this combination of events recurring.[...]

So, let's sum up. In short, Skype is saying 'Don't blame Microsoft, blame us. We found the problem and fixed it.'  Read the whole post.

Is That All There Is? A Closer Look at How Skype Works 

Even after Skype's second post, lots of people have been wondering if that's all there is to it. After all, in the past, Skype's had no problems handling lots of login requests triggered by past Windows Update or other reboots, but this time, its self-healing mechanism didn't work properly. What went wrong this time?

According to Skype, there was a "previously unseen fault in the P2P network resource allocation algorithm Skype used. Consequently, the P2P network’s self-healing function didn’t work quickly enough. Skype’s peer-to-peer core was not properly tuned to cope with the load and core size changes that occurred on August 16. The reboots resulting from software patching merely served as a catalyst. This combination of factors created a situation where the self-healing needed outside intervention and assistance by our engineers."

First of all, let's make it clear: Microsoft (and Windows Update) did not cause Skype to fail. Period. So, if Windows Update merely exposed a problem (rather than causing it), exactly what is it about Skype's P2P design that helped the failure to take place? To understand that, it's time to learn about Supernodes.



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Would Putting a linux Skype server in the routers DMZ allow it to work as a supernode or does NAT problems still apply
I Thought A Trojan Protects Me!



A resource for VOIP is at VoIP Service Provider



Maybe i am misunderstanding the function of a "supernode".
is the suppernode just a linking relay (user "A" at address "X" connect to user "B" at address "Y")or a traffic relay for the packets?
if it is a traffic relay don't "supernode" users run the risk of getting shut down by their ISP for excessive traffic- the current favorite thing they are doing. ISPs argue you pay for 5 mega bits per second but if you use that for more than short bursts during a month you are using excessively. Won't being a supernode blow your usage outta the water like being a P2P super sharing site would also?
again maybe I am just dumb and that is not how it works at all.
feel free to correct me.



Supernodes are used as linking relays, and use a small amount of bandwidth, rather than the large amounts needed by a typical P2P file sharing client. See this study, performed in 2006, for details:

Here's part of the summary at the end of the study:

"From the empirical data we have gathered, it is clear that Skype differs significantly from other peer-to-peer file-sharing networks in several respects. Active clients show diurnal and work-week behavior analogous to web-browsing rather than file-sharing. Stability of the supernode population tends to mitigate churn in the network. Supernodes typically use little bandwidth even though they relay VoIP and file-transfer traffic in certain cases."

So, Skype supernodes don't chew up a lot of bandwidth, and aren't likely to cause an ISP to lower the boom.
It's amazing how illogical a business built on binary logic can be.



Thanks for the piece Mark. I believe that Skype is going to have to re-think their software functionality in order to insure this doesn't happen again. With more people utilizing firewalls every day there is no way Skype can count on these idle unprotected drones to continue to power their service.

But there is a larger concern here - security. Do I really want my private conversations to be flowing through a network of insecure computers? No, no I don't. And just what did Skype "fix" to prevent this from happening next time? Perhaps they have altered the software to create MORE supernodes.

Shame on Skype for not making their network functionality more public (I've been using Skype since it launched and never knew about the supernodes), and double shame(?) on them for not making it secure. Triple shame(!) on Skype for calling a distributed network a P2P network.

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