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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: iSCSI: draft 7: remove S bit and Status field from the Data-iI am sure we don't want to enter this. The sequencing rules are there to asure: that there is no deadlock (order of data must follow the order of commands) that the target command buffer does not overflow (MaxCmdSN) - this will eliminate an "unlimited number of immediate" Any additional rules will interfere with performance, multiplexing policy etc. and I see no great value in enforcing them (and enforcing means checking and that means expense). Julo Sandeep Joshi <sandeepj@research.bell-labs.com>@ece.cmu.edu on 26-08-2001 00:11:39 Please respond to Sandeep Joshi <sandeepj@research.bell-labs.com> Sent by: owner-ips@ece.cmu.edu To: Dave Sheehy <dbs@acropora.rose.agilent.com> cc: IETF IP SAN Reflector <ips@ece.cmu.edu> Subject: Re: iSCSI: draft 7: remove S bit and Status field from the Data-i Julian, I wonder if Dave's last paragraph in this email has been considered. Here it is again.. > This does help some. It eliminates the situation where a target can receive > an essentially unlimited number of immediate data commands prior to receiving > *any* data PDUs. in reference to Section 1.2.5 > Unsolicited data MUST be sent on > every connection in the same order in which commands were sent. The draft currently allows c-1,c-2,c-3, (SEP-1-1),(SEP-1-2),(SEP-2-1,SEP-2-2),.. where c-N = command {N} and SEP-N-M = unsolicited (non-immediate) PDU number {M} for command {N} It would be simplify target login (ITT lookup) if we only permitted this sequence. c-1, SEP-1-1, SEP-1-2, c-2, SEP-2-1, SEP-2-2,.. -Sandeep Dave Sheehy wrote: > > David, > > > I think you've taken a wrong turn. > > I think John hit the nail on the head. > > > > Second, thoughts of removing the immediate data seem not to be > > > simplification, since all the information to tie the data to the command > > is > > > right there with the command. That has got to be easier than matching up > > > separate PDUs of data with the appropriate commands. > > > > Actually, that was the point, since the logic for "matching up separate > > PDUs of data with the appropriate commands" has to exist for inbound > > Data PDUs already. > > Except that there is a target context present in the solicited case to route > the data. That doesn't exist in the unsolicited case. > > > The slide I presented in London was about replacing > > immediate data with an unsolicited data PDU immediately following the > > command, thus removing the immediate data case in favor of reusing the > > logic for dealing with separate Data PDUs. Remember that this was presented > > as a simplification possibility. > > This does help some. It eliminates the situation where a target can receive > an essentially unlimited number of immediate data commands prior to receiving > *any* data PDUs. > > But, do you mean to say that *one* unsolicited data PDU would follow the > command? Wouldn't that be unnecessarily restrictive if the PDU size is small? > Simply guaranteeing that the data PDUs will immediately follow the command > seems like an adequate improvement. > > Dave Sheehy
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