Nathan Stratton <nathan@netrail.net> writes:

This is what I beleave sprint is doing. They are using the new Cisco 12000 GSR with external router servers. It is a smart way of patching the problem. If you need more CPU or memory you can just add a bigger box and more RAM.

The GSRs are to move bits fast. They are not to act as route servers. Sprint recently announced that they are deploying 622Mbps POS cross-country links, and the GSRs are the only things you can put on the ends of such beasts that are available today. (Someone may point out that it may not be the only choice for very long, however, it's the only one whose design I know and have had any influence upon, and is therefore frankly the only one I trust, although I don't expect the people building the competing box will ship anything but a good product even if they are now rather deeply in bed with the cell-heads and about as transparent to most observers as the Kremlin during the cold war... The box being built by someone who actually worked very close to the Kremlin during the cold war is also something I don't know enough about, however that is much more due to my neglect than due to organizational attitude.) Remember that a current snapshot is not a good indicator of future health. Sure the processing demands of routing are such that the GSR's main CPU is largely idle after converging with its neighbours, however there is still a CPU spike during convergence and the processing load is non-zero. If you increase the growth curve of the number of prefixes, you increase the CPU demands during large-scale convergence. You also statistically increase the CPU demand after convergence unless you reduce the probability of any given prefix transitioning from up to down or vice versa over time. If you have a growth curve where the processing load during large-scale convergence and the processing load to handle background noise increases beyond processing capacity faster than processing capacity can be increased, you lose, no matter how crunchy your box is today relative to today's processing demands. In other words, removing the feedback mechanisms on the growth of the number of globally-visible prefixes and on prefix instability is probably a really bad idea. Sean.