Re: iSCSI/iWARP drafts and flow control

On Wednesday, July 30, 2003, at 07:49 PM, Mallikarjun C. wrote:

>
>> There is an identical flow control issue for
>> RDMA Reads.
>
> Not true.  There's a built-in credit renewal in an RDMA Read.
> The Peer issuing the RDMA Read knows it can reuse the
> Read credit when it receives an RDMA Read Response.
> Send Messages carrying the "fringe" iSCSI PDUs need both
> new wire protocol and cross-layer chit-chat within an end-node
> between iSCSI and iSER - in order to renew credits.

No new wire protocol is required.

Restoration of no-CmdSNs credits could be piggy-backed on top
of the existing CmdSN credit system.

Basically each Cmd reply restores one "Cmd Credit". It could
also restore an implicit number of "NoCmd" credits. Basically
if Cmd X had been proceeded by Y "NoCmd" messages, then the
reply to Cmd X would restore Y "NoCmd" credits.

It is simple credit counting, suitable for implementation in
hardware or software at any number of layers, and requires
no additional wire messages or even fields.