RE: a vote for asymmetric connections in a session

[Joshua Tseng <jtseng@NishanSystems.com>]

John,

TCP provides congestion management for the network.  The command windowing
mechanism is supposed to provide congestion management for the target's
command
queue, I presume.  Another way to describe it is command flow control. Well,
TCP will NOT fulfill this role unless iSCSI can actively tell TCP to halt
ACK
responses for TCP segments.  Now, I don't think anybody is advocating this
(right???).

I do not know if a command flow control mechanism is necessary, but I do
believe that the existing sliding window mechanism is a whole lot of work to
do something that can be accomplished more easily by other means.

Josh

-----Original Message-----
From: John Hufferd/San Jose/IBM [mailto:hufferd@us.ibm.com]
Sent: Thursday, September 07, 2000 4:29 PM
To: ips@ece.cmu.edu
Subject: Re: a vote for asymmetric connections in a session


Folks,
Matt and Julian are correct.  The sliding window was put in for a
completely different reason then is currently being discussed.  I suggest
that we all  look at it only as it was originally intended and then see if
something else needs to be done, or not.  TCP/IP probably handles all the
other issues (well enough).


.
.
.
John L. Hufferd



"Matt Wakeley" <matt_wakeley@agilent.com>@ece.cmu.edu on 09/07/2000
03:46:53 PM

Please respond to Matt Wakeley <matt_wakeley@agilent.com>

Sent by:  owner-ips@ece.cmu.edu


To:   ips@ece.cmu.edu
cc:
Subject:  Re: a vote for asymmetric connections in a session



As Julian has stated in a different thread, the purpose of the "sliding
windows" in iSCSI is not for congestion management.  It is simply there to
handle the case where if a connection goes down in a multiple connection
session, it prevents the remaining connections from overwhelming the target
with new commands that it can't process due to missing commands that where
on
the broken connection.

Since all of this runs on top of TCP, and TCP performs congestion
management,
why must iSCSI perform congestion management on top of TCP?

-Matt Wakeley
Agilent Technologies

Scott Bradner wrote:

> > Implementing sliding windows is not that hard
>
> note that the issue is not "just" sliding windows - ips also has to deal
> with congestion TCP-friendly way - that can get quite complicated
>
> Scott