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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: is TargetName always mandatory or not?John, Section 3.12.9 of the spec reads: The TSID is the target assigned tag for a session with a specific named initiator that, together with the ISID uniquely identifies a session with that initiator. So according to that, TSID + ISID + InitiatorName must be enough information for a target to uniquely idenfity a session, so mapping TSID to target portal group ID won't always work (see my other note addressed to Jim for an example of where it won't). After thinking about this for a while, I've come to the same conclusion as you (that a target should compare ISID + InitiatorName + TargetName + target portal group to uniquely identify a session), but from a different angle. My reasoning: Since there is a 1-1 correspondence between an I_T nexus and a session, if you can identify the nexus, you've identified the session, and vice versa. Since 3.12.9 says that TSID + ISID + InitiatorName must uniquely identify a session, then TSID must be an alias for TargetName + target portal group ID, since (ISID + InitiatorName + TargetName + portal group ID) uniquely identifies a nexus. In my opinion, that aliasing only complicates (and confuses!) the protocol and should be done away with. If TargetName were required on every initial login request, then the target could compare (ISID + InitiatorName + TargetName + portal group) to determine a session match, and forget about TSID entirely. In that case, there is no need for TSID, except to flag whether the login request is to create a new session or to add a new connection to an existing session (i.e. indicate leading login), in which case it could be dropped and replaced with a single bit. To eliminate TSID, I believe the following changes would be needed: - Eliminate TSID from login request and login response - Use one of the bits in byte 1 of login request to indicate a leading login, and update any text that refers to TSID=0 to refer to this bit - Define session to be equivalent to I_T nexus (not "loosely equivalent to") - Define SSID/session ID to be the same as the I_T nexus identifier - Remove the "LO" from TargetName - If it hasn't already been done, remove the "LO" from InitiatorName Comments? Andre Asselin IBM ServeRAID Software Development Research Triangle Park, NC John Hufferd To: Andre Asselin/Raleigh/IBM 10/31/2001 cc: ips@ece.cmu.edu 06:32 PM From: John Hufferd/San Jose/IBM@IBMUS Subject: Re: is TargetName always mandatory or not?(Document link: Andre Asselin) Andre, TSID, and therefore SSID is a handle that can be use to queue stuff within the scope of the Initiator Node and Target Node. The target can use what ever it wants in this field. Some Folks might want to use the TSID to be the Portal Group Tag and I think then it might be unique. But even then only within the InitiatorName+ISID Space. Anyway, you need to think of it only as a handle. Also since most folks will not have 64k Sessions into their box, some (most?) implementations might find it unique. But it is not unique in the Architecture. Now the important thing is that, as things stand now, the Login needs the InitiatorName, and the TargetName on the Initial Login of ALL Connections in order to uniquely identify secondary Connections to the Original Connection of the Session. Does that seem correct to you and others on the Reflector? . . . John L. Hufferd Senior Technical Staff Member (STSM) IBM/SSG San Jose Ca Main Office (408) 256-0403, Tie: 276-0403, eFax: (408) 904-4688 Home Office (408) 997-6136 Internet address: hufferd@us.ibm.com Andre Asselin 10/31/2001 03:00 PM To: John Hufferd/San Jose/IBM@IBMUS cc: ips@ece.cmu.edu From: Andre Asselin/Raleigh/IBM@IBMUS Subject: Re: is TargetName always mandatory or not? (Document link: John Hufferd) John, WHOOPS! I was wrong; you are absolutely right that the spec says "TargetName" and not "TSID". When I was reading through it, I saw "TargetName", but read to myself "TSID". Apologies... In my defense (confusion?), however, 3.12.9 says TSID rather than TargetName is used to uniquely identify a session. Going by that, SSID + InitiatorName must be enough to uniquely identify a session. Jim Hafner pointed out to me that the I_T nexus is identified by one thing and the session is identified by another. If the two must have a 1-1 mapping in iSCSI, why are there two different identifiers? Why not just use the current definition of the I_T nexus to uniquely identify both the nexus and session (i.e. get rid of TSID)? Andre Asselin IBM ServeRAID Software Development Research Triangle Park, NC John Hufferd To: Andre Asselin/Raleigh/IBM@IBMUS 10/31/2001 cc: ips@ece.cmu.edu 04:42 PM From: John Hufferd/San Jose/IBM@IBMUS Subject: Re: is TargetName always mandatory or not?(Document link: Andre Asselin) Andre, I looked again through the document and No where could I find a statement that you claimed as "a nexus, and therefore an iSCSI session, is uniquely identified by the InitiatorName, ISID, TSID, and portal group tag". It is the InitiatorName, ISID, TSID, with the TargetName and PortalGroup. Please point out to me in the Spec (8 or above), where I can find your statement on I_T Nexus. I did find the following (please ignore for this conversation the "i" and 't" stuff): "- Session: The group of TCP connections that link an initiator with a target, form a session (loosely equivalent to a SCSI I-T nexus). TCP connections can be added and removed from a session. Across all connections within a session, an initiator sees one "target image". " " - I_T nexus: According to [SAM2], the I_T nexus is a relationship between a SCSI Initiator Port and a SCSI Target Port. For iSCSI, this relationship is a session, defined as a relationship between an iSCSI Initiator's end of the session (SCSI Initiator Port) and the iSCSI Target's Portal Group. The I_T nexus can be identified by the conjunction of the SCSI port names; that is, the I_T nexus identifier is the tuple (iSCSI Initiator Name + 'i'+ ISID, iSCSI Target Name + 't'+ Portal Group Tag). NOTE: The I_T nexus identifier is not equal to the session identifier (SSID). " I have not found a place where Session ID is tied to the TSID. Hence my comment that we also need to have the TargetName in the Initial Login on all Connections. . . . John L. Hufferd Senior Technical Staff Member (STSM) IBM/SSG San Jose Ca Main Office (408) 256-0403, Tie: 276-0403, eFax: (408) 904-4688 Home Office (408) 997-6136 Internet address: hufferd@us.ibm.com Andre Asselin/Raleigh/IBM@IBMUS@ece.cmu.edu on 10/31/2001 10:40:55 AM Sent by: owner-ips@ece.cmu.edu To: ips@ece.cmu.edu cc: John Hufferd/San Jose/IBM@IBMUS Subject: Re: is TargetName always mandatory or not? John & Julian, How about this for the section 5 text: The initial Login request of the first connection of a session (leading login) MUST include the InitiatorName key=value pair. The initial login request of the leading Login MAY also include the SessionType key=value pair, in which case if the SessionType is not "discovery", then the initial login request MUST also include the key=value pair TargetName. John, I disagree with your second statement: I don't see any way you could have 2 different sessions established within the same portal group with the same InitiatorName, ISID, and TSID. The spec. says that a nexus, and therefore an iSCSI session, is uniquely identified by the InitiatorName, ISID, TSID, and portal group tag. There is no mention of TargetName contributing to the identificaiton of a session. In my opinion, a non-leading connection should NOT have the TargetName, since it doesn't contribute anything. Andre Asselin IBM ServeRAID Software Development Research Triangle Park, NC John Hufferd/San To: Julian Satran/Haifa/IBM@IBMIL Jose/IBM@IBMUS cc: ips@ece.cmu.edu Sent by: Subject: Re: is TargetName always mandatory or not? owner-ips@ece. cmu.edu 10/31/2001 04:20 AM Julian, I think the TargetName should be included on the Initial Login Request on the Leading Login. It seem strange to permit the Authentication functions to proceed if perhaps the intended Target is different then the one doing the Authentication. The way it currently is written, you could pass all the Security test and then find out just before going into Full Function Phase, that it was intended for some other Target. Seems like a waste. My I think that TargetName should also be on all connections on the Initial Login Request. Here is my thinking: The SSID (ISID+TSID) is unique only with regards to a Specific Initiator and Target Node Pair. It is therefore not clear that just knowing the SSID and InitiatorName is enough to understand what session the subsequent connections are being attached to. And it is possible that the CID could be also overlapped with another session. Therefore, I think it make since to determine all this on the initial Login on every Connection, so you know at the beginning what values can be negotiated, or that are being set to the right Session. . . . John L. Hufferd Senior Technical Staff Member (STSM) IBM/SSG San Jose Ca Main Office (408) 256-0403, Tie: 276-0403, eFax: (408) 904-4688 Home Office (408) 997-6136 Internet address: hufferd@us.ibm.com Julian Satran/Haifa/IBM@IBMIL@ece.cmu.edu on 10/30/2001 11:33:50 PM Sent by: owner-ips@ece.cmu.edu To: ips@ece.cmu.edu cc: Subject: Re: is TargetName always mandatory or not? It is the leading login: The section 5 paragraph will read: The initial Login request of the first connection of a session (leading login) MUST include the InitiatorName key=value pair. The leading Login request MAY also include the SessionType key=value pair in which case if the SessionType is not "discovery" then the leading Login Request MUST also include the key=value pair TargetName. Julo Andre Asselin/Raleigh/IBM@IBMUS Sent by: owner-ips@ece.cmu.edu 31-10-01 02:08 Please respond to Andre Asselin To: "IPS Reflector (E-mail)" <ips@ece.cmu.edu> cc: Subject: is TargetName always mandatory or not? In section 5 of the spec, it says "If the SessionType is not "discovery" then the initial Login Request MUST also include the key=value pair TargetName.". However, in Appendix D, the description for TargetName says it is Leading Only. Should TargetName not be Leading Only, or should the text in section 5 say that TargetName must be in the initial Login Request of a leading connection? Andre Asselin IBM ServeRAID Software Development Research Triangle Park, NC
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