Re: Possible New iNID
08-31-2010 07:41:16 AM
Yeah, but I thought you need the upload speed to be able to handle the higher download speeds due to the fact that you have to factor in the standard TCP/IP handshake in which if you don't have enough upstream your downstream is limited because ACK packets aren't getting to the endpoint fast enough.
That's not really a bandwidth issue, but more of a latency issue.
For 1500 byte download IP packets, the ACK is only 64 bytes. That's over a 20:1 ratio, meaning you only need 1/20th the bandwidth in the upload direction. For an 18 Mbps download, that translates to only about 900 kbps in the upload direction.
But if the end-point to end-point latency is high, then the TCP window has to expand in order for the sender to utilize the full bandwidth. Vista and 7 handle this well, XP only does so with some TCP/IP stack tweaking.