[e2e] Why do we need TCP flow control (rwnd)?

[Abraham Matta]

Sure -- just making the point of explicit feedback... 

-----Original Message-----
From: detlef.bosau at web.de [mailto:detlef.bosau at web.de] 
Sent: Monday, June 30, 2008 6:24 PM
To: e2e
Cc: Abraham Matta
Subject: Re: [e2e] Why do we need TCP flow control (rwnd)?

Abraham Matta wrote:
>> isn't it up to the sending side to decide when to stop probing the 
>> network?
>>     
>
> I don't see a good reason for the sender *not* to stop probing the 
> network if it is told *explicitly* by the receiver about the rate at 
> which the sender should send?
>
> Ideally, if the network *explicitly* tells the sender about a (fair or
> not) rate at which the sender should send, then no probing by the 
> sender is needed (similar to the good old ATM explicit rate control ;)
>   
However: TCP does not probe for a "rate" but it probes for _storage_
capacity.
The "rate" is a result of selfclocking: A TCP sender is clocked / paced
by ACK packets.

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