North American Network Operators Group|
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Re: TCP congestion
On 12-jul-2007, at 22:27, Philip Lavine wrote:
I just don't understand how if there is 1 segment that gets lost how this could translate to such a catastrophic long period of slow- start. How can I minimize the impact of the inevitable segment loss/out of order over a WAN. Is QoS the only option?
Is there perhaps a firewall somewhere in the communication path? In that case' it's entirely possible that packets that use certain TCP options are filtered because the firewall doesn't implement these options.
For instance, if there are selective acknowledgements, the firewall may not like that.
Also, if you use the window scale option the firewall probably doesn't understand that and may easily conclude that a packet which is in-window with the scale factor applied is out-of-window because the scale factor _isn't_ applied and drop it, so that you miss the packet with byte 1, then get the ones with everything upto 65535 and the rest is dropped, and so many dropped packets will stop TCP dead in its tracks.
Also note that minimal amounts of cell loss on ATM create huge amounts of packet loss at the IP layer.