Subject: Re: FW: ssthressh

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Thu, 14 Jul 2005 13:01:46 -0600

Janardhan,

On Thu, 14 Jul 2005, Janardhan Iyengar wrote:

> [Folks on the Cc list: Let me know if I should trim you off the list]
> 
> Brian,
> 
> I was tied up in other things for a little while, so seem to have missed 
> this discussion.
> 
> I am not sure what _you mean_ by "CMT". I thought I understood at first, 
> but now, I am convinced that I do not. A couple of years ago, we 
> introduced the term CMT as Concurrent Multipath Transfer - sending new 
> data concurrently to the multiple destination addresses of a multihomed 
> receiver.

Well, if you want to define CMT as something else, go ahead.  But, what
I'm doing is transmitting to multiple destinations to achieve efficient
load balancing over multiple destinations in contrast to the stock
RFC 2960 primary/alternate approach.

> 
> You have written (several times) about how you schedule data to the 
> multiple destination addresses. That is only a part of the CMT-SCTP 
> problem, not all of it. Please look at 
> http://www.cis.udel.edu/~iyengar/publications for the rest.

Yes, I looked at these last year.  It has taken your research some time
to catch up with practice.  Look at my last note to Randall to see the
two little other things that I do to get rid of those effects.

> 
> The experiments you point to assume several things; a significant one 
> being that the bandwidth and delay on the two paths used are the same. 
> These results cannot be generalized.

As I said, tests were also performed in competition with TCP, which results
in paths that do not have the same bandwidth-delay product.  The same
performance is achieved.

> 
> Although I am not entirely clear on its impact, the problem Randy points 
> out is a very pertinent problem, which certainly cannot be solved by your 
> sending algorithm, because to the extent that I understand your algo, it 
> does not really apply to CMT (as I understand CMT).

But in testing it demonstrates that it does solve the problem.

> 
> It would really help if you could present your algo to the list. Even I 
> have only a vague memory of what it is. If you are interested, we could 
> take the discussion from there.

Check with Armando, I have sent it to him many times, starting in 2001.  I
have been sending it to you for 4 years now...

You can download the entire implementation (including all the points that
I mentioned to Randall and provide the performance posted) from

	http://www.openss7.org/download.html

On my latest version I will add automated test scripts that will recreate
the test results for independent corroboration.

--brian