[e2e] TCP and MAC layer

[Joe Touch]

Lloyd Wood wrote:

> On Tue, 30 Oct 2001 Gregory.Maman at space.alcatel.fr wrote:
> 
> 
>>Following your intersting discussion : "What should e2e protocols know about
>>lower layers?",
>>
>>I would have more information about the messages that could be exchange between
>>MAC layer and higher layers (TCP or Application).
>>
>>For example, we can imagine that MAC layer indicates to TCP the available
>>bandwidth allocated for the connection (information available at the MAC layer
>>of a satellite terminal) and will allow  TCP to auto-tune his Initial Window.
>>
> 
> I suspect knowing the latency of the path is more useful than the
> next-hop link capacity in this instance. High latency -> larger
> initial window to reduce round-trip time opening window. The question
> is whether you can safely reuse such knowledge from previous
> connections, and generally you can't.


Whether you can or not depends on whether you have data that is a 
reasonable predictor. For the average net-connected system, this may not 
be true, but for systems on the terminus of a satellite link, this may 
be just fine.

Joe