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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: iSCSI: NOP-Out closing the command windowJulian Satran wrote: > > Sandeep, > > They are 3 distinguishing elements P and the ITT+TTT. > > Julo > I believe you are commenting on my question about the validity about the 2nd sequence.. correct ? But this 2nd sequence isn't documented in Sec 2.12 or 2.13. Incidentally, there is a similar ping type mentioned in Sec 2.13.1 and its used to test the connection from the target end. Could you please say what the response would be : T->I NOP +P=0 T=ff I=ff I->T < response or it none ? > And I still prefer that the ping response from the initiator *not* have a valid ITT/cmdSN. A 3-way ping looks forbidding and may open up new problems. -Sandeep > Sandeep Joshi <sandeepj@research.bell-labs.com> on 27-07-2001 18:53:20 > > Please respond to Sandeep Joshi <sandeepj@research.bell-labs.com> > > To: ips@ece.cmu.edu > cc: > Subject: Re: iSCSI: NOP-Out closing the command window > > If the NOP-Out does not have the ping-bit set, then it is a > ping response and *not* a new command being issued by the > initiator. > > Hence, it seems that the NOP-OUT with P=0 need not carry a > new cmdSN (Mark's 2nd option). > > Btw, I did not know the 2nd sequence (P=0 from initiator?) > below was valid > > I->T NOP +P=0 +I=x+ Data > > T->I NOP +P=0 +I=x > > -Sandeep > > Julian Satran wrote: > > > > Mark, > > > > Definitely a problem . How about stating (the obvious) that NOP as any > > thing carying an ITT expectes an answer > > wheter it carries an echo (P=1) or not (P=0). > > > > If it does not carry an ITT it does not. > > > > We can have the following sequences all valid: > > > > I->T NOP +P=1 +I=x+ Data > > T->I NOP +P=0 + Data > > > > I->T NOP +P=0 +I=x+ Data > > T->I NOP +P=0 +I=x > > > > T->I NOP +P=1 +TTT > > I->T NOP +P=0 I=1 + TTT (no ITT) > > > > All would be permitted today if we remove the tie between ITT and P say > > that NOP must have an ITT if issued at initiators initiative. > > > > We might add as valid (today it is not, it is explicitly forbidden): > > > > T->I NOP +P=1 +TTT > > I->T NOP +P=1+ I= 1 TTT + ITT + Data > > T->I NOP +P=0 +ITT + Data > > > > The last requires us to "tweak" the termination rule (a target is > forbiden > > to answer a P=1 with a P=1 > > > > comments? > > Julo > > > > Mark Bakke <mbakke@cisco.com> on 27-07-2001 16:25:20 > > > > Please respond to Mark Bakke <mbakke@cisco.com> > > > > To: IPS <ips@ece.cmu.edu> > > cc: > > Subject: iSCSI: NOP-Out closing the command window > > > > When sending a NOP-Out without the P bit set, there's > > no response to update ExpCmdSN to keep the window open. > > > > On an otherwise idle session, sending a long enough > > sequence of these NOP-Outs can close the command window > > permanently. > > > > In case of a stuck command window, please break glass... > > > > The easy solution is to turn on the P bit, and get the > > responses to update the window, but that defaults the > > purpose of allowing the P bit to not be set in the first > > place. > > > > Another easy solution (but I almost hate to mention it) > > is not to have NOP-Out update the CmdSN. This seems to > > have the possibility of breaking other things. > > > > I suppose we could come up with a more complicated rule, > > like "if the NOP-Out's CmdSN would be the last (or perhaps > > penultimate) CmdSN allowed by the current window, it MUST > > set the P bit." Or something like that. > > > > Anyway, I see three possible solutions. Any thoughts? > > > > -- > > Mark A. Bakke > > Cisco Systems > > mbakke@cisco.com > > 763.398.1054
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