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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Fw: Re: iSCSI Marker questions----- Forwarded by Julian Satran/Haifa/IBM on 12-12-01 02:39 -----
Dean, owner-ips@ece.cmu.edu wrote on 11-12-2001 03:09:11: > The iSCSI Draft 9 Appendix C makes the following statements about > Markers and the Initial Marker-less Interval: > > "The offset to the next iSCSI PDU header is counted in terms > of the TCP stream data. Anything counted in the TCP > sequence-number is counted for the offset. Specifically this > includes any bytes "inserted" in the TCP stream by an UFL and > it excludes any other markers inserted between the one we are > examining and the next PDU header."... > > "To enable the connection setup including the login phase > negotiation, marking (if any) is started only at the first > marker interval after the end of the login phase." > > I understand that markers are not inserted until after login phase. > Am I correct to assume that the placement of the first marker > determined by the TCP sequence numbers on the final Login Request/ > Response PDUs, or is initial marker position determined by the > TCP sequence numbers at connection establishment? > > Assume the following interaction: > > I-> SYN (TCP sequenceNum=1000) -- irrelevant to this discussion? > > T-> SYN-ACK (TCP sequenceNum=2000) -- irrelevant to this discussion? > > I-> Login Request PDU, T=0,CSG=1,NSG=0: > InitiatorName=xxx > TargetName=yyy > SessionType=normal > ... > FMarker=send-receive > RFMarkInt=512,1024 > > T-> Login Response PDU, T=0,CSG=1,NSG=0: > ... > FMarker=send-receive > SFMarkInt=1024 > RFMarkInt=1024 > > I-> Login Request PDU, T=1,CSG=1,NSG=3: > SFMarkInt=1024 > (64-byte PDU... TCP sequenceNum=1301-1364) > > T-> Login Response PDU, T=1,CSG=1,NSG=3: > (48-byte PDU... TCP sequenceNum=2201-2248) > > The above interaction designates a 1024 x 4 = 4096-byte marker > interval in both directions. The first PDU byte sent by the > intitiator in full-feature mode will have sequenceNum=1365, and > the first byte sent by the target will have sequenceNum=2249. > > Assuming the markerless interval starts at the end of login > phase, the first two markers in each direction will have the > following TCP sequence numbers: > > TCP SeqNum of TCP SeqNum of > First Marker Second Marker > ------------ ------------- > Initiator: 5461-5468 9565-9572 > Target: 6345-6352 10449-10456 > No - the correct numbers are dependent only on the marker interval (not the length of the login phase) and are: Initiator 5096-5103 9200-9201 Target 6096-6103 10200-10201 > Is this the correct interpretation of marker usage in iSCSI > Draft 9, or does marker placement depend on the connection's > initial sequence numbers? > > Also, is "RFMarkInt=..." always considered an offer, and "SFMarkInt=" > considered a reply to that offer? If an offer is sent with "FMarker=..." > and "RFMarkInt=...", MUST the reply contain either "FMarker=no" or > BOTH "FMarker=yes" and "SFMarkInt=..."? > Fmarker is not boolean - legal values are no, send, receive, send-receive The sender and receiver must set the interval it wants/is ready to use otherwise the responder can't answer. I assume a normal dialogue may go like: I->FMarker=send-receive,RFMarkInt=1,4,SFMarkInt=1,512 T->FMarker=send-receive,RFMarkInt=8, SFMarkInt=2 Please observe that target answers with RFMarkInt to the initiators SFMarkInt and viceversa. I will attempt an example in draft 10 (last?). > Thanks, > Dean Scoville > QLogic Corp.
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