We recently had a customer complaining that performance from their remote site to our home office here was bad. Investigation with Iperf and Wireshark showed a massive number of retrans and dupe acks. In chasing the circuit back to the home office we found out that the circuit provider had put a rate limit of 15 Mbps on their Foundry router in between us. When they took off the limit the circuit tested clean.
I've heard of some network devices simply dropping the packets when the limit is reached which, I guess, is why we saw this result. I have a hard time believing that all rate limit devices are this crude. Are there other methods or is this pretty much what I'm going to see in terms of symptoms?
asked 01 Apr '11, 08:19
I can't speak for "real" routers, but FreeBSD's traffic shaper (see the ipfw man page) allows you to limit traffic to a given speed but it also allows you to control the queue size of the "pipe" (see the 'bandwidth' and 'queue' parameters). I would (possibly naively) think that "real" routers would have similar mechanisms.
answered 01 Apr '11, 11:09