[G4] Broadband Speed Liar's Poker

[Robert A. Rosenberg]

At 09:10 -0500 on 12/14/2003, sr ferenczy wrote about Re: [G4] 
Broadband Speed  Liar's Poker:

>that doesnt really sound that great to me though. i would much rather
>have them raise the upstream rates-or maybe give us cheaper symmetrical
>service. i would rather have 1.5 Mbps/1.5 Mbps than 4 Mbps/128 Kbps
>..... but that may just be me.

Even worse, given the way TCP/IP works, a 128Kbps Uplink may not be 
enough bandwidth to support a 4Mbps downlink. Each packet received 
must be acknowledged and due to the size of the packets, you can run 
out of available bandwidth at 128Kbps without playing games. Email is 
normally sent one line per packet (ie: an maximum of about 80 
charters per line/packet) and each line is supposed to get 
acknowledged (ACK) with a separate (I got it, send the next line) 
reply before the next one is sent. Thus you get a situation where you 
can not keep sending the "I got it" packets fast enough on a 128Kbs 
uplink to saturate the full 4Mbps downlink. There are ways to pack 
more than one line in a packet (so as to compensate for the 
packet-overhead) as well as keep the number of ACKs down by sending 
not sending one ACK per received packet but only periodic ones that 
say "I got all the packets up to Packet#x" (thus ACKing all the "in 
flight" packets at once instead of going Lock-Step 
(Send/ACK/Send/ACK/etc).