Performance Based Routing: not necessarily good for real time audio and video


At first read performance based routing sounds great. The network automatically choosing the best route based on the performance of the routes and being able to make automatic adjustments without admin intervention.

However if the network doesn’t converge quickly after the route is changed it can adversely affect real time audio and video. At my customer we use both Skype and ACANO/CISCO VTC. The network is stretched across the globe but mostly across the greatest country in the world, you guessed it “the United States of America”.

Several of our field sites were having issues when using real time audio and video. Their Lync clients would disconnect constantly during A/V conferences and peer to peer sessions with users at other locations, the Video would freeze and the Audio drop. Needless to say the users at these locations were very unhappy with Microsoft and ACANO.

After many times of providing metrics, pulled from the Skype monitoring reports I was finally able to get the networking team to take notice and monitor the network for one of the remote locations for more than a 30 second snap shot. What they found was that every few minutes routing loops would form and it would take about 30 seconds before things went back to normal.

Another indicator was that performing tracert’s you could see the routes changing frequently.

The network engineer, we’ll call him Bob, determined that this was one of the remote locations where Performance Based Routing had been Piloted. For some reason the route was constantly changing and when it did it would take the network up to 30 seconds to converge.

30 seconds is a life time for Skype.

After removing the performance based routing we held a 30 minute A/V conference with several sites, including the affected site and the experience was as expected. The users at the location were extremely happy. Of course they all asked me what I had fixed in Skype and the ACANO. Luckily for me the network engineer is a standup guy and explained in detail about the issue.

Of course now we are fighting the battle with the manager who championed performance based routing as the magical thing that would fix all of our networking issues. No one wants to hear that their baby is ugly.

Performance Based Routing:

http://www.cisco.com/c/en/us/products/ios-nx-os-software/performance-routing-pfr/index.html

http://docwiki.cisco.com/wiki/Performance_Routing_FAQs

 


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