North American Network Operators Group|
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Re: BBN peering, a technical issue
Jerry - The problem boils down to making traffic move the right way, and making sure the traffic is well-behaved. The biggest problem with using MEDs to attract traffic to the right places, in your model, is simply route aggregation. The next-biggest -- and less immediately soluble -- problem is policing the MEDs. How do you tell whether your rival is obeying your MED announcements faithfully, and what do you do when they don't? (Conversely, how can you tell if the MEDs are being fair to you?) There are other small issues involving what happens in the face of failures -- peering routers crash, peering infrastructure fails, people mess up configurations, etc. In other words, even if you design for traffic going the right way, sometimes it doesn't. What do you do then? Finally, my own concern is what happens if the big colo site ends up playing with devices which deliberately over-ack -- adding fractional ACKs into the stream coming back from web browsers -- and other techniques for opening the congestion window larger or faster than it should be opened, or otherwise sending traffic that does not back off in the face of congestion in your network. It would be ironic if a business race was triggered by people deliberately breaking congestion-avoidance. "Come buy colo from us -- your web pages will seem faster even than web pages on our peers' networks!" would be pretty bad. I say bad not for business reasons, but because TCP's timers and other congestion-avoiding mechanisms are *THE* key mechanism for stability in the Internet. Classic congestion collapse would not be nice for anyone. Sean.