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NAT444 or ?

>> However these are with a very high address-sharing ratio (several 
>> thousands users per address). Using a sparser density (<= 64 users per 
>> address) is likely to show much less dramatic user impacts. 
> 
> I think you have the numbers off, he started with 1000 users sharing 
> the same IP, since you can only do 62k sessions or so 

These numbers were not off. From page 19: "...we should assign at least 
1000 [..] ports per customer to assure good performance of IPv4 
applications"
"At least 1000 ports per customers" is roughly the same than "less than 
64 users per address" as I stated above. 

Btw, 90% of subscribers have less than 100 active connections at any time, 

if I read these tiny graphs correctly: 
http://www.wand.net.nz/~salcock/pam2009_final.pdf

> and with a "normal" timeout on those sessions you ran into issues 
quickly.

Agreed for UDP, but most of these sessions are TCP, which arguably time 
out 
rather rapidly after a FIN and an extra hold time. Normal duration of a 
TCP 
session is usually under a few seconds. 

This study saw an average connection time of 8 seconds for DSL, but it's 
from 2004. 
http://www.google.com/#q=A+Comparative+Study+of+TCP/IP+Traffic+Behavior+in+Broadband+Access+Networks


/JF