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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: iSCSI: NOP-Out closing the command windowMark, 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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