Quote:
Originally Posted by Ignitionnet
There is no requirement to ack every single packet, I'm not sure where this comes from. TCP does, by default, do cumulative acknowledgement - an ack implicitly acknowledges every transmitted packet up until the sequence number the acknowledgement is supplied for.
The exception to this is misconfigured TCP stacks.
If one is acknowledging every single packet 100Mbit requires 3.6Mbit of upstream as a bare minimum, which would, yes, mean that 1.75Mbit is not enough for the 53Mbit downstream on the 50M.
HTH.
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TCP stacks *used* to acknowledge every packet. These days, almost all TCP stacks implement delayed ACK which will (as the name suggests) delay ACKs, but SHOULD send at least one for every two packets. You therefore need approximately 1.8Mbps (by your calculation) for a 100Mbps downstream. It's probably possible to configure delayed ACK to acknowledge less often, but the default is always one ACK per two packets received.
http://freesoft.org/CIE/RFC/1122/110.htm
That said, it's assuming you're downloading efficiently with a 1500 btye MTU. As an example, my firewall pegs the TCP MSS to 1300 for various reasons, so in my case I'd need a little more upstream for my ACKs.
I'd also quite like to use the downstream while backing up my computer to Mozy!