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This is a sub-selection from Not much improvement over docsis 2.0


Suffern, NY
reply to cdru

Re: Not much improvement over docsis 2.0

said by cdru:

said by jadebangle:

Its always 10/1, 20/2, 30/3 massive on the download side, pathetic on the upload side
Please give an example where 2 or 3mbit upload isn't adequate for a residential connection.
TCP/IP is a handshake protocol. This means that the receiver must tell the sender that the data has arrived successfully arrived and to send more data. Until the sender has been informed of the arrival (at the receiver) of what it has sent, it can/will not send more data. Thus depending on how fast the downlink is at the receiving side, the uplink side (and the actual receiver->sender speed of the connection between the receiver and the sender) must be fast enough to keep the downlink end saturated (ignoring the issue of the need to resend due to receive errors or dropped packets) or the downlink is going to be throttled due to the sender not being told to send more data soon enough. As you increase the download speed, you must increase the upload speed to keep pace or you will be unable to use all of the download speed capability.



There's not really much of an issue in TCP/IP
with respect to throttled upload speeds impairing
download speeds to due the need for ACKs from
the receiver. In older TCP/IP implementations
this was indeed the case but modern mechanisms
like cumulative and selective ACKs (in which
you send a single ACK indicating the receipt
of a large window of packets) have dramatically
reduced the impact.