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I'm looking at purchasing a network switch, and the only spec I'm not sure of is one specifying "buffer memory" per port. What is that used for?

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It is used to buffer packets in a store-and-forward switch. More buffers are not neccesarily better, and can even make things worse. See the Buffer Bloat phenomenon. Cut-through switches provide much lower latency and do not use buffers.

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Note though that for some workloads, larger port buffers can offer significant performance improvements. iSCSI SAN traffic, for example. –  Chris Thorpe Sep 30 '11 at 14:52
    
So I should just ignore that particular spec? –  Billy ONeal Sep 30 '11 at 15:00
    
@Chris Thorpe, it shouldn't help at all, and due to the buffer bloat problem, could make things worse. More buffered packets leads to more latency. –  psusi Sep 30 '11 at 15:02
    
@Billy ONeal, I would look for cut-through switches that don't use buffers. –  psusi Sep 30 '11 at 15:03
    
@psusi: Hmmm... I don't see anything like that available anywhere. Then again, I'm talking about a small (~8 port) switch. Everything available seems to be store-and-forward. –  Billy ONeal Sep 30 '11 at 15:23
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