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The Importance Of Correcting Packet Loss In VDI

Recently, on the LinkedIN WAN optimization professionals group, I participated in a conversation around whether virtual desktop infrastructure (VDI) is ready for the WAN. Face it, delivering responsive VDI over the WAN is going to be a challenge. One of the interesting points that came up was the importance of correcting for packet loss when considering WAN optimizers.

In all my conversations, I heard a fairly consistent story. My sources hadn't noted any significant packet loss on their private networks. As for the public Internet, NTT aside, packet loss for the most part within a network had been very low--sub 1 percent. NTT has shown packet loss at times close to 5 percent, likely because of the events in Japan. (It's a wonder actually that packet loss wasn't higher.)

The bigger challenge came at the exchanges, where providers buffer incoming traffic for insertion into their own networks. Packet loss at these exchanges can be significantly higher, reaching above 1 percent and peaking over 5 percent. As of this time, Cogent-to-AT&T, for example, shows packet loss rates of 1.32 percent.

To put this in context, though, many voice codecs today include error correction and jitter compensation technologies so they work on even lossier networks. "Any decent system will tolerate a 5 percent loss with no issues," says Cullen Jennings a distinguished engineer at Cisco systems who's been heavily involved in Cisco's VoIP and video communication standardization effort.

At first glance, these numbers would appear to support Mr. Smoot's conclusion that special packet loss compensation technology should not be a factor when selecting a WAN optimizer. If organizations can keep their offices on a single backbone, average packet loss would not seem to be an issue.

But enterprises often aren't able to locate all of their offices on a single provider, especially when those offices are located around the world. IT managers need the freedom to choose a local provider right for them--not just for technical reasons, but also for fiscal and operational reasons. "Packet loss rates differ from region to region," notes David Schwartz, CTO of XConnect, a neutral provider of Interconnect 2.0 services. "For instance, loss rates are probably lower in Japan and Korea than in U.S."

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