[e2e] Is a non-TCP solution dead?
Hans Kruse
kruse at ohio.edu
Tue Apr 15 08:07:58 PDT 2003
There is a fundamental disconnect/problem in this discussion, as I see it:
TCP is either very good or a nuisance, DEPENDING ON the assumptions you can
make about the underlying network. Contrary to repeated statements, most
of the current network infrastructure does not do congestion control at
intermediate nodes. An application that is deployed without being able to
make assumptions about the underlying network, and that requires reliable
delivery (i.e. re-transmits), needs to make rate-limit its transmission in
the absence of back-pressure from the network.
IF you can make more specific assumptions about the network with regard to
congestion control, then TCP's action are superfluous and/or a nuisance.
For example, if stations always established an ATM VC before sending the
TCP SYN, TCP would not require slow-start nor congestion control. But that
is a very different network from the one we call the Internet now.
On a side note, TCP's share of the overall network traffic is not a
relevant measure. TCP's share of reliable transports flows is; I would
venture that the vast majority of non-TCP traffic is real-time unreliable
flow, which does not create congestion problems due to retransmissions.
--On Wednesday, April 09, 2003 09:01 -0700 Cannara <cannara at attglobal.net>
wrote:
> Love that touch Lloyd -- it's required on some other lists, believe it or
> not. By the way, you know we can assess how any alternate transport might
> improve over TCP by noting what's been removed -- if slow-start isn't
> there, then it's relatively easy to estimate; if delayed-ack is gone,
> ditto; same for other changes to backoff. In fact, someone could simply
> recompile NS with items commented out, unless it's too spaghetti like. :]
>
> I'll see what I can make of an XCP/FAST comparison, as an exercise for
> students. Might be good.
Hans Kruse, Associate Professor
J. Warren McClure School of Communication Systems Management
Adjunct Associate Professor of Electrical Engineering and Computer Science
Ohio University, Athens, OH, 45701
740-593-4891 voice, 740-593-4889 fax
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