Re: iSCSI/iWARP drafts and flow control

[Caitlin Bestler <cait@asomi.com>]

On Thursday, August 7, 2003, at 12:52 PM, Mike Ko wrote:

> Caitlin, since MaxCmdSN is used by the target to limit the number of
> commands it can receive from the initiator, your suggestion would work 
> for
> limiting the number of "fringe" messages the initiator can send to the
> target.  However, for "fringe" messages from the target to the 
> initiator,
> such as the Aysnchronous Message, the target cannot simply raise 
> MaxCmdSN
> and expect the initiator to increase the number of receive buffers for
> "fringe" messages correspondingly.
>
> Mallikarjun is correct in pointing out that some form of new wire 
> protocol
> for flow control is required if we need to flow control the messages 
> not
> regulated by CmdSN.
>

The target may always send untagged messages when they are
a response to an initiator request. Additionally the target
may have N extra outstanding untagged messages, where N is
a protocol constant or negotiated for the session.

A non-responding target message is "outstanding" until
one of the following occurs:

	The initiator responds to a "Nop Out Request".

	The initiator sends a command with CmdSN that
	was only enabled after the non-responding target
	message.

The fact that a prior non-responding target untagged
message is no longer "outstanding" merely means that
whatever buffers are allocated for this purpose have
been replaced. It does not guarantee that the initiator
has completed any associated processing, that logic
is left totally to the ULP.