RE: iSCSI: Flow Control

["Douglas Otis" <dotis@sanlight.net>]

Michael,

The present scheme used by iSCSI limits commands as a indirect means of
controlling traffic.  This provides the dynamic element per response in that
even if the initiator wished to send data that might be discarded, it would
need an opportunity in terms of the command window.  If you detect traffic
between devices unrelated to this flow control method, your methods of
allowing internal bandwidth would still be to stop incoming commands as the
dynamic method of control at this time- capping maximum commands across the
medium becoming congested.

Doug

> -----Original Message-----
> From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu]On Behalf Of
> Michael Krause
> Sent: Wednesday, October 04, 2000 1:44 PM
> To: IPS@ece.cmu.edu
> Subject: RE: iSCSI: Flow Control
>
>
> At 12:34 PM 10/4/00 -0700, John Hufferd/San Jose/IBM wrote:
>
> >Michael Krause,
> >First, a session usually lasts from Boot Time till it is Booted again or
> >stopped.  The variant to this is a Storage Device being used in a manor
> >like a Mount or Map done with NAS.  Even then, most folks, have
> that setup
> >so the Mounting and Mapping is done at bring up, though it is sometimes
> >done at other times, but even then it is left around.  So I
> think the thing
> >you can say about Session Time as the term is used in the iSCSI
> context is
> >that it is LONG.
> >
> >I do not think we have consensus about the notification of available
> >buffers.  With the way many systems work, is (as stated above),
> all devices
> >are set up at startup of the Host, and the Session is kept around by the
> >Host, even if there hasn't been anything which use that device all
> >day/week, etc.  So I am not sure if having a certain amount of
> buffer space
> >reserved for each Host (which could be 100s-1000s) would be an especially
> >good idea.
>
> I believe we are in agreement both in terms of duration and the need to
> have dynamic buffer management.  I will clarify that there will also be
> sessions that are not host focused, e.g. the peer-to-peer direction of a
> storage object to another device, e.g. multi-media streaming and these
> sessions will be shorter lived - possibly on a per transaction
> basis where
> a transaction is something of reasonably large in value (e.g.
> 100's MBs of
> data movement).
>
> Mike
>