Giving Cisco Telepresence its Own QoS Queue is Some Expensive Real Estate

It's Amazing What You Find in SRNDs

QoS is a tricky beast. In fact, while we are in the midst of WAN Transformation, which puts a lot more VoIP on our new MPLS network, it's become clear that QoS design is the trickiest part of the design. It requires understanding application traffic flow levels, VoIP flows with SIP Trunking, percentage allocations for video, critical applications, regular applications and Internet, and making sure this traffic is all marked properly. And finally, you have to make this all work with what the MPLS service provider offers for QoS, which may not be as flexible as you want it to be. Fortunately, we're moving to a single, global MPLS carrier, so we have at least removed the hassel of making QoS work between two carriers. While WAN Transformation is going on, we are also working on getting our first two Cisco Telepresence systems deployed in our two main corporate offices. While working with a professional services installation firm, we were told something that startled me. Cisco demands (ok, ok, "strongly recommends") that Telepresence get its own QoS queue in the network. Really! That's some expensive QoS real estate to demand your own queue. I checked the Telpresenece SRND and it's noted in several locations. Here's page 6-3 (99 in the PDF): The big problem with this is most MPLS IP VPN service providers will only provide a 4, 5, or 6 queue QoS model. AT&T provides six queues, Verizon provides six. But, two of these queues are already allocated to voice (EF) and default (Internet, backups, etc). Now, according to Cisco, a third queue is dedicated to Telepresence. That only leaves 1-3 queues for everything else. Usually a six queue model includes a scavenger queue which is good for crap, not applications.

  1. Queue #1 - EF - Voice
  2. Queue #2 - CS4 - Telepresence
  3. Queue #3 - CS3 - open
  4. Queue #4 - CS2 - open
  5. Queue #5 - CS1 - scavenger
  6. Queue #6 - default

As you can see, this Telepresence SRND requirement for a separate queue just for Telepresence only leaves two queues for you to do everything else with. What about other video traffic? How do you separate critical applications from interactive traffic from Exchange from corporate bulk data? Where do you fit in cloud based traffic? What if Internet needs to be separate from backup traffic, but Internet can't be allowed to overwhelm corporate applications? Leaving only two queues for all corporate applications is not enough. Sensing this problem, the Telepresence SRND provides a 6-queue service provider model to use with a dedicated Telepresence queue: But this model effectively puts all corporate TCP traffic - critical applications, e-mail, cloud, general TCP traffic, CIFS, etc - into a single queue (SP-Critical 2). Then, all remaining UDP traffic - streaming video, multicast, other video conferencing - falls into the second remaining queue. Sorry, this won't work. TCP applications - which actually make the business work - would start stepping all over each other during congestion. Exchange and CIFS would snuff out Oracle, Siebel, and SAP. Business units would start to scream. I'm all for high quality Telepresence, but this is not viable. Cisco needs to rethink this SRND. It gives too much of a limited resource (QoS queues) to a Cisco specific technology. If Telepresence can't live in a queue with other traffic flows (like other video streams), then the Telepresence protocols needs to be better.

More >From the Field blog entries:

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A Troubleshooting Conference Call on the Weekend - That Hasn't Happened in a While

Facebook-Skype Alliance Could Drive Some Serious Video Bandwidth Usage

We Love Tunnels Too - EoMPLS to Connect Two Data Centers

Positive ROI is What Made WAN Transformation Possible

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