Subject: Re: CM related

From: Hari Balakrishnan <[email-masked]>
Date: Tue, 11 Apr 2000 18:41:17 -0400

On Tue, 29 Feb 2000 11:36:24 PST, you wrote:

> how would the CM based protocols perform if the receiver
> feedback is zero ?  If one were to deploy a CM based approach
> but cannot expect any feeback from the receiver, in terms of
> response to CM probes,etc could the CM extract more information per flow
> then the existing TCP stack.
> 
> thanks,
> jayanth

Jayanth,

Catching up on old old mail...

To do (feedback-based) congestion control, you need some form of feedback.  :)  
In the absence of changes to receiver operating systems or protocol stacks, 
this feedback needs to come from applications.

The reason you need feedback for congestion management is to figure out whether 
in the past round-trip, your transmissions reached successfully or encountered 
congestion.

The comparison to an existing TCP stack that you make isn't clear to me.  If 
you're running TCPs over CM, the corresponding ACK feedback is all that's 
needed for the CM to work.  The advantage the CM provides in this case is 
two-fold:
	1. Treats the ensemble of TCPs (in the same macroflow) as one congestion group
	2. Allows the sending app or system admin to decide how to partition the 
"pipe" amongst the connections in the ensemble.

The CM (according to the IETF draft) doesn't send any explicit probe messages.

Does this clarify things?

Hari