This much we know: Skypes two-day outage was triggered after its peer-to-peer network became disrupted following a massive restart of its users computers as they rebooted after receiving a routine set of patches through Windows Update.
The blitzkrieg of restarts caused a flood of log-in requests, which led to a global bog down in service. In the course of the outage, Skype engineers discovered a software bug within the network resource allocation algorithm that prevented the service from righting itself.
So, is it Skypes fault or are the routine Microsoft Windows Update patches to blame? VOIP (voice over IP) experts believe Microsoft cant be blamed because service providers are supposed to be prepared for the regular updates the software power automatically deploys.
IDC analyst Rebecca Swensen said the fault was only indirectly related to the Microsoft updates.
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"It basically had to do with a bug in Skypes P2P network algorithms," Swensen said. "They hadnt found the bug in their code until this huge Microsoft update. The way that Skype built their network they relied heavily on these super nodes [clients] and because so many of them went down, that put a lot of strain on the network. Usually, they have a failover, which would allow their servers to pick up the slack, so I guess thats where the bug was."
Swensen said its indicative of how different a VOIP network is from PTSN (Public Telephone Switched Networks), which rarely go down and dont typically go down for two days the way the Skype network did.
"Over time, service providers will continue to learn how to make sure that a VOIP service is more reliable. Inherently a VOIP network is less reliable than a PTSN."
Forrester Research analyst Sally Cohen said that its Skypes responsibility to not just know how Microsoft does its updates but also be aware about the software bug before it can cause an outage.
"For all they know they were fixing the bug and this just came at a really bad time," Cohen said. "As far as Skype is concerned, I guess they might not have foreseen millions of people signing on at the same time but ... there is no excuse."
Regardless of the what, where, why and how, Cohen called the outage a black eye on Skypes service. Cohen said some user groups will look for a new service.
"Up until last week, a lot of businesses had shown significant interest in Skype or similar services," Cohen said. "The fact that the service was down for so long shows that these services—Skype and their competitors—are not a viable option if you want to run a business."
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