Capacity Planning Challenges at Cisco
Capacity planning is facing some significant problems with two new services in the future: high definition desktop/laptop video, and home Telepresence. Video has a significant impact on bandwidth use, and these two services threaten to place new demands on the network.
Home telepresence will place significant load on the Internet and on our enterprise Internet points of presence. Currently our few Internet POPs don’t handle the sort of traffic that will be generated by large numbers of high definition video streams; and in addition to traffic load, we have to maintain strict control over latency and packet drops for real-time video. We are still working on figuring out how to size and architect the Internet POPs to maintain security and still deliver high quality video through the POPs.
High definition desktop / laptop video has the most potential for stressing the network., since the video streams will come from unpredictable locations.. Telepresence video sites on our WAN are fixed in location, but we are about to enable high quality, high definition (and thus higher bandwidth) video from the desktop – both with new IP phones (8900 and 9900), and with HD video cameras for conferencing. We could have a branch office which has one or two TP rooms – but with 50 people we could suddenly have 50 HD additional video streams coming from a single site. The next day that same building could host a meeting where 50 more people come and they could generate another 50 HD video streams from that one site. This could come from any Cisco building at any time. This is a huge difference from the WAN suddenly carrying twice the normal email traffic: video takes more bandwidth, and is very sensitive to latency and packet-loss. This is the major reason for flagging the peak (90%) traffic utilization. We don’t have any other solution to this problem as yet.
Without perfect solutions to these problems, we are looking at a range of other options. For example, today our standard practice is that all voice goes over the WAN. But we are beginning to offload a lot of our outbound voice traffic via SIP trunks to the Internet, and are open to looking at the price of Internet voice traffic vs. the price of added WAN bandwidth. Also, we’re carrying a lot of 1080p HD video, when we could reduce the load considerably by downgrading the video streams to 720p HD. We are working to provide more flexibility in our video services, and would like to be able to drop individual streams from 1080 to 720 intelligently when some portion of the end to end circuit reaches capacity.
We are preparing various options for our business decision makers: supporting video for all users, or supporting video for some, and providing cost information for each option; and we will see what the business would like to support. We are also trying to build additional capacity into our network in the core to support increased traffic demands (see National Lambda Rail blog).