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Old 15-12-2010, 12:59   #106
Ignitionnet
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Join Date: Jun 2008
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Re: Terrible performance Leicester (LE3)

Quote:
Originally Posted by qasdfdsaq View Post
That's interesting because I seem to have observed VM's network/equipment appear to have two operating "modes" - one with low latency, high speeds, and considerable packet loss just as you describe, and the other one with moderate latency, moderate speeds, and zero packet loss.
The different hardware does handle congestion differently.

CMTS can respond to upstream congestion in one of two ways, they can either ignore the excess requests and force the modems to re-request and they drop traffic, or they can give them zero-length grants which tell them to wait and buffer the data they have to transmit.

The first scheme causes packet loss and a touch of jitter, the second latency and considerable jitter.

The first scheme can be overcome to an extent by transport level protocols so download speeds aren't necessary too badly affected, the second not so much.
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