[e2e] What should e2e protocols know about lower layers?

[Marcel Waldvogel]

I am not sure that I see the problem. Below are two possible problem 
statements, for which there already seem to be solutions.

If the problem mostly consists of having many short-lived connections to 
a single TCP server,  I would suggest that simply remembering the send 
window of a previous TCP connection to the same host might be a good 
first estimate, instead of using slow start from 0. (I understand there 
are some implementations out there doing that already.) Or for a 
solution at the application layer, switch to a more persistent 
connection (as was done by HTTP).

If the problem relates to having multiple connections to all kinds of 
"local" hosts, then slow-start should take no time. On a Gigabit 
Ethernet, a single TCP connection should saturate the network after 
about 16 RTT (=log_2 (Rate/MSS)). Assuming typical RTT of 0.2ms, this is 
achieved after 3ms, which doesn't look bad to me. For a 10Gbps network, 
it would still be below 4ms to achieve saturation.

Are these not the problems, or do these solutions not solve them 
appropriately?

-Marcel

Christian Huitema wrote:

>It should be pretty obvious that suppressing congestion control based on a naïve test such as "same subnet mask" is BAD. OTOH, developers do this for a reason: they are generally frustrated that TCP does not take full advantage of the capacity of a high speed network, especially in the case of short connections. Make no mistake, the pressure is going to increase with applications such as ISCSI and gigabit networks. 
>
>-- Christian Huitema
>