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    RE: iSCSI: Login negotiation space



    Julian,
     
    A factor of 10 is way overkill. It isn't just 16 k bytes of extra memory. It is n * 16k where n is the number of simultaneous logins the implementation supports - it adds up. The system vendors we work with want to use the memory to do useful work and demand that driver sizes be kept small -- they want the memory available to do "real" work.
     
    If 2k doesn't leave enough headroom, then we could live with somewhat more like 4k.
     
    If future features added to iSCSI require more space, the drivers that support that can allocate more memory. It is an internal parameter that can be changed when the need arises. There is no future interoperability need to make the buffer oversized in current implementations.
     
    Regards,
    Pat
     
    -----Original Message-----
    From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
    Sent: Tuesday, July 02, 2002 12:10 AM
    To: pat_thaler@agilent.com
    Cc: ips@ece.cmu.edu
    Subject: RE: iSCSI: Login negotiation space


    Pat,

    A factor of 10 over what is needed today is what I would call a conservative design.
    Limiting the support to 2k would be extremely unwise.
    And 16 is a tiny amount of memory - of no concern to software implementation and to most hardware implementations.

    Julo



    pat_thaler@agilent.com

    07/02/2002 01:56 AM
    Please respond to pat_thaler

           
            To:        Julian Satran/Haifa/IBM@IBMIL
            cc:        ips@ece.cmu.edu
            Subject:        RE: iSCSI: Login negotiation space

           


    Julian,

    4.1 contains a requirement that initiators and targets support receiving at least 16384 bytes of key=value data (when not supporting very long authentication items). This is overkill and is making drivers larger than they need to be.

    My calculations are that Security negotiation using the CHAP method (including the Any-stage keys) takes less than 1600 bytes. Operational negotiation requires 1276 bytes (also including the Any-stage keys). All the operational plus security keys are 1911 bytes.

    Therefore an implementation could hold all the necessary keys in 2 Kbytes. And, the implementation doesn't need to keep the security keys after the security negotiation is done so it could clear some of that out to make room for future keys or vendor specific keys. 16 K bytes is about 10 times the necessary storage in that case.

    The number of negotiation bytes that a device is required to support should be reduced substantially - preferably to 2048 bytes.

    Regards,
    Pat


    The numbers:

     43                                  AuthMethod
              CHAP keys
    264                                  Name (no defined size limit - using 255)
     11                                  Algorithm
     11                                  Identifier
    264                                  Challenge
     42                                  Response (for MD5)
    _____
    635 Chap negotiation length
    892 Any-stage keys
    ----
    1527

    Operational negotiation keys
     24                                  HeaderDigest
     24        DataDigest
     49        MaxConnections
    270                                  TargetName* or InitiatorName*
    271                                  TargetAlias* or InitiatorAlias*
    273        TargetAddress*
     55                                  TargetPortalGroupTag*
     15                                  InitialR2T
     19                                  BidiInitialR2T
     18                                  ImmediateData
     34                                  MaxRecvDataSegmentLength
     24                                  MaxBurstLength
     26                                  FirstBurstLength
     24                                  DefaultTime2Wait
     26                                  DefaultTime2Retain
     25                                  MaxOutstandingR2T
     18                                  DataPDUInOrder
     24                                  DataSequenceInOrder
     24                                  ErrorRecoveryLevel
     23                                  SessionType*
    ------
    892 Any-stage keys
    384 Not Any-stage
    ------
    1276 Operational keys









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Last updated: Tue Jul 02 16:18:54 2002
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