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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: iSCSI: enquiry keyBob, "Robert D. Russell" <rdr@io.iol.unh.edu> wrote on 20-12-2001 12:48:31: > Julian: > > A few questions: > > 1. Does the value of MaxOutstandingR2T include the implied initial R2T > when operating in unsolicited mode (as described in 2.2.5)? > > I believe the answer is "no", but would suggest a minor rewording > in Appendix D item 29 to remove any doubt: > "Initiator and target negotiate the maximum number of outstanding R2Ts > per task, excluding any implied initial R2T that might be part of that > task." > OK > > 2. I believe the upper limit for MaxRecvPDULength should be 2**24-1, > not 2**24 as is currently shown in Appendix D item 24. > The reason is that the Data Segment Length field in the header is only > 24 bits, so 2**24-1 is the largest number that can be stored in it > (i.e., a PDU with 2**24 bytes of data could never be sent). > To be consistent, if the limit for MaxRecvPDULength is changed to be > 2**24-1, perhaps we should also change the limit for MaxBurstSize and > FirstBurstSize to be the same 2**24-1. > OK > > 3. In section 2.2.4 it says: The value "?" with any key has the meaning > of enquiry and should be answered with the current value of > "NotUnderstood." > > 3a.It is not clear what this means when keys are "one-way". For example, > assume the initiator sends the target "MaxRecvPDULength=?". Should the > target send back the maximum PDU length it (the target) expects to > receive from the initiator, or should the target send back the maximum > PDU length it (the target) will ever send to the initiator? > The same question applies to "FMarker=?" and "RFMarkInt=?" and > "SFMarkInt=?". Regardless of what the answer to this question is, > another question immediately arises -- how does one side ask for the > other value? > Yes - I will clarify that both values have to sent and state how > 3b.It is not clear if the usual restrictions to LO, IO, and FFPO > should apply to these enquiries. For example, during a login for a > second (third, fourth, ...) connection in a session, can one side > send "MaxBurstSize=?" to the other side to obtain the current value > for the session, even though MaxBurstSize is an LO parameter and can > not be negotiated for the second (third, fourth, ...) connection? > Or in another example, can a text request from the initiator include > "MaxBurstSize=?" even though MaxBurstSize cannot be negotiated or > changed after the Leading Login? > will clarify > If the answer to these examples is "yes", then further clarification in > the standard is necessary to indicate that the "key=?" can be sent > at any time and is not restricted by the LO, IO, and FFPO labels. > > In the "yes" case, we also need to clarify whether it is possible to > send "key=?" enquiries for operational keys during security negotiation, > and vice versa. > > If the answer to these examples is "no", then the value of an enquiry > appears to be marginal, and I would suggest that it be eliminated > from the spec (when can it be used to any benefit?). > > My personal opinion is that "key=?" seems fairly useless -- if they are > to operate correctly, both sides of a connection really have to know the > values of all the keys at all times, and the rules for negotiation make > it clear how and when these values change. The only real "enquiry" > situation is when an initiator is attempting to discover targets, and > this is handled completely differently by the use of "SendTargets". > So when is there a use for either side to send "key=?". Unless there > is a clear example where this is useful, we should eliminate it and thus > remove another special case during parameter processing. > I am not sure that we have all the use scenarios to afford removing it > > Bob Russell > InterOperability Lab > University of New Hampshire > rdr@iol.unh.edu > 603-862-3774 >
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