On Thu, Feb 08, 2007 at 10:44:41PM +0000, Michael Rogers wrote: > > > 52 = 5% * 1000. The probability of a packet being dropped is less than > > 5% on most useful links. > > Sorry, I don't see how the loss rate of the link is relevant - I'm > talking about the overhead of sending an ack straight away (52 bytes) > versus the overhead of retransmitting a packet unnecessarily (1000 > bytes). Unnecessary retransmissions happen when the RTT variance is > high, which it is at the moment because acks are held for anywhere > between 0 and 100ms. Currently we retransmit a packet if it hasn't been > acked for 4 * RTT + MAX_DELAY, but we don't know what fraction of acks > arrive after 4 * RTT + MAX_DELAY. If it's more than 5% then it would be > cheaper to send the acks straight away.
Simulations maybe? Most packets are less than 1000 bytes in practice. What exactly does TCP do? I thought it combined ack's with data in order to minimize overhead. > > Cheers, > Michael
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