Subject: Re: [tcpm] Is this a problem?

From: MURALI BASHYAM <[email-masked]>
Date: Mon, 5 Nov 2007 16:04:36 -0800 (PST)

Re-posting my response. 

Joe, apologies for mangling your response.

The point is that it can be solved in TCP or at the transport layer
 ALSO. It's as good a place
if not better (from the co-ordination point of view and from the sender
 state visibility points of view). 
Let me ask the question: Can you elaborate the reasons why doing it in
 TCP is not a good idea? 
"A variety of solutions in a variety of places" is not a good position
 to be in, we want the right
solution in the one, correct place, with the least possible disruption
 to the server community.

Murali

----- Original Message ----
From: MURALI BASHYAM <[email-masked]>
To: Joe Touch <[email-masked]>; Lloyd Wood <[email-masked]>
Cc: [email-masked]
Sent: Monday, November 5, 2007 3:14:29 PM
Subject: Re: [tcpm] Is this a problem?

----- Original Message ----
From: Joe Touch <[email-masked]>
To: Lloyd Wood <[email-masked]>
Cc: [email-masked]
Sent: Monday, November 5, 2007 1:27:52 PM
Subject: Re: [tcpm] Is this a problem?

Lloyd Wood wrote:
...
>> Yes, this is a problem for which a variety of solutions exist, and
 for
>> which a coordinated solution would be useful. No, that itself is not
>> justification for assuming TCP is the place to do this.
> 
> try this thought on for size:
> 
> "The need for congestion control is a problem for which a variety of
> solutions exist, and for which a coordinated solution would be
 useful.

I should have said "for which a variety of solutions in a variety of
places - OS, application, API, protocol - exist..."

The primary point is that this isn't owned by communications layers.

Joe

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---

From: Joe Touch <[email-masked]>
Date: Mon, 05 Nov 2007 16:41:47 -0800

MURALI BASHYAM wrote:
>  ALSO. 

It CAN. The question is whether it SHOULD be.

> It's as good a place

Basically because it CAN easily be done somewhere else. The
recommendation (Clark?) is "think twice before modifying TCP, then
don't" comes into play. IMO, that means "don't modify TCP unless you
absolutely have to".

TCP isn't supposed to be a convenient place to do things. It ought to be
lean, so you KNOW it'll work correctly.

> solution in the one, correct place, with the least possible disruption

The right solution in the right place is a good rule too. I don't think
TCP is the right - i.e., best or most appropriate place - to do this.

I've noted in other emails that you're making a huge assumption about
using TCP for this - that all TCP connections are implemented in a
single, shared codebase (i.e., the kernel). They are not; that's not a
requirement of TCP.

I.e., every reason you have for wanting to do this in TCP is a good
reason to do this in the kernel, not TCP.

Joe