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    RE: iSCSI: No Framing

    Dear Colleagues,
    PART 1 of 3 : 
    The pertinent points that "I" see in Jim's email are:
    A. Need to hear from iSCSI chip implementers ...
       The issues that you raise for e.g. in #2&#4 are simply
       circumstantial( See PART 2 ). Answers to those questions 
       unnecessarily call for data flows and implementation 
       details that silicon vendors are not allowed to share 
       in public. While I do not know of many silicon vendors 
       in the multi gig space, clearly one of the competitions 
       I respect, namely Trebia, point to FIM as well. Granted, 
       no matter what, we are going to see several 
       trebia-on-the-other-end and adaptec-on-the-other-end 
       type of cost optimizations.
    B. The iWARP/TUF/SCTP under-current ...
       The "only" message of significance in Jim's email is #5. 
       It seems like the iWARP/SCTP/TUF enthusiasts somehow feel
       threatened that FIM-iSCSI will dilute the perceived value 
       proposition of iWARP :-) I for one am an enthusiast of 
       iWARP ideals myself, barring the proposed mechanics. I 
       would love to make a buck or two along with you in 
       building iWARP NICs, "at the right time". In the 
       meanwhile, iSCSI is the flag ship effort that has the 
       unique opportunity to make a dent in enabling IP Storage 
       visions. ( See PART 3 )
    My assertions are :
        i) TUF/SCTP/iWARP is ruled out in the near term. The 
           mechanics are unclear as hell.
        ii) FIM is the least intrusive, TCP transparent, means for
           enabling low-cost(power,b/w,latency,memory,space,CPU) 
           RDMA transport of bulk data. 
        iii) I do not see significant technical reasons that 
           merit major changes to the iSCSI draft at this late 
        iii) Making it OPTIONAL to use, and SHOULD only on send 
           provides a graceful and incremental deployment path 
           for "real":-) providers and users to succeed.
    I have personally contributed nothing to the iSCSI effort 
    and do applaud the pains that several of you are taking to 
    pull it all together. In that very same spirit, I respect
    David's decision w.r.t. consensus, whatever that turns out 
    to be.
    -Shridhar Mukund + Todd Sperry, Siva Munnangi, Dev ...
    PART 2 of 3 : MUST delete, SHOULD read
    Dear Jim,
    Congratulations Jim! Seems like when you bowl, pins 
    roll, unintentional as they may be. You make a "seemingly" 
    well balanced set of arguments and "tactfully" tilt the 
    balance towards your chosen side. I would love to be on 
    your side ... maybe in another effort :-)
    I would like to introduce you to my respectable friend, 
    who "vehemently" contradicts you on all accounts. One of 
    his numerous quotes goes as follows:
    "Much of today's usage of the Internet and IP networks
    is for buffer-to-buffer data transfers, often in the 
    form of bulk data ... Gigabit and faster network transfers
    incur 'heavy' system resource costs, including both CPU
    use and system bus bandwidth, particularly on the
    receiving side ... The costs incurred on hosts for protocol
    processing and management has 'inhibited' the use of IP
    in the high speed bulk data domain. ... Bulk data transfer
    is dominated by the costs of copying and validating 
    incoming data in order to place it at its ultimate 
    The good friend I quote above is none other than Jim 
    Wendt himself!!! I REST MY CASE.
    -Shridhar Mukund
    PART 3 of 3: MUST delete, OPTIONAL read
    On the lighter side ... since the opponents have "no" technical 
    arguments whatsoever against FIM and it is all turning out to 
    be a pure political gimmick, I will put on my rusting tin 
    politician hat :-)
    My dear fellow iSCSI country (wo)men: If our goals are anything 
    short of enabling the HP's, Cisco's, uSoft's, IBM's and EMC's of 
    the world in globalization of storage for McDonald's and Macy's 
    from Kabul to Somalia, via iSCSI, we have lost our identity! 
    ( \insert APPLAUSE for 13 seconds )We are no more protected by 
    the vast oceans between us and other Storage efforts. The 
    freedom of iSCSI America is threatened from within by elements 
    who will not blink twice when it comes to using the world's most 
    potent BOO-bombs ... and grinnn while we end up sifting through 
    the rubbles for iSCSI, youSCSI and theySCSI. 
    ( \insert APPLAUSE for 11 seconds ) Beware of the elements that
    sleep with "our" very ideals in their privacy(burkha clad 
    though) and yet attempt to destabilize us, only to accomplish 
    their mutated agenda.( \insert APPLAUSE for 57 seconds )
    No offense folks. I respect each and every one of you and 
    especially Jim. I think that he was only attempting to 
    question, "are we sure ... should we commit ...". 
    I disagree with him anyway!
    - the running(actually limping) mate :-) :-) :-)
    -----Original Message-----
    From: WENDT,JIM (HP-Roseville,ex1) []
    Sent: Tuesday, January 29, 2002 10:47 PM
    Subject: iSCSI: No Framing
    Perhaps we should discuss the possibility of not 
    specifying any framing mechanism (FIM or COWS) in the 
    first version of iSCSI.
    The arguments for not specifying framing include 
    (there may be others as well):
    1) The brute force approach of putting TCP receiver 
    reassembly memory on the iSCSI NIC will work for both 
    1Gbps and 10Gbps. Cost is incurred for memory chips, 
    ASIC pins, power, and board space. But, it is a 
    feasible approach.
    2) I/O bus latency (or bandwidth limitations) could 
    mandate inbound buffering (as a 'smoothing' buffer) 
    from the iSCSI NIC to the host system. If this buffer 
    memory is large enough to have to be off-chip, then 
    it will require some minimum number of memory chips 
    to provide the necessary bandwidth, and the 
    memory/pins/power/space costs will be incurred 
    3) Very large receive buffering on the NIC is only 
    required for high-bandwidth links traversing large 
    geographic distances (which may not be the 
    predominate case). These specialized implementations 
    can cost more (e.g. more memory/power/pins/etc) and 
    customers will likely be willing to pay accordingly.
    4) Many NICs will likely aspire to be combo 
    iSCSI+TOE+Ethernet NICs allowing the host system to 
    use a single Ethernet port for all of its network 
    communications. The TOE function on this combo NIC 
    will already require TCP receive buffering and off-
    chip buffer memory to support the existing sockets 
    interface receive model.  More importantly, to allow 
    senders to assume ownership of the buffer upon return 
    from a socket send call, the TOE NIC would need to 
    copy application send buffers into NIC memory as 
    5) The framing/marker mechanism will be an iSCSI-only 
    solution. It is quite possible that the problem will 
    be solved via a different, and hopefully more 
    general, mechanism for other ULPs.
    6) Both FIM and COWS are poor solutions for software 
    implementation. COWS requires, at a minimum, the 
    sender to read every word in the buffer. FIM either 
    imposes additional sender gather processing (iovecs) 
    or requires a data buffer copy (on systems that don't 
    support HW gather on sends).
    7) Unless all senders thoroughly test framing/markers 
    now (i.e. unless the framing method is a MUST 
    implement), there is potential for future 
    interoperability problems as framing/marker receivers 
    are deployed in the future.
    8) Neither FIM nor COWS is an elegant solution. Are 
    we comfortable with the legacy we are creating under 
    the umbrella of state-of-the-art IP networked 
    9) Is it essential to build in forward compatibility 
    now, or will there be a different solution in the 
    10Gbps or 40Gbps timeframe - perhaps involving iSCSI-
    2?  Will it be reasonable to update or bridge initial 
    1Gbps deployments?
    So, it would be good to hear from several iSCSI 
    NIC/chip implementors who:
    - have or plan to implement FIM or COWS (or some 
    other framing mechanism) and take advantage of it to 
    minimize demands on on-NIC buffer memory 
    - believe that all-buffers-on-chip solutions are 
    feasible and valid (wrt the points above, including 
    - can quantify the memory/pin/power/space cost 
    savings for all-buffers-on-chip solutions


Last updated: Fri Feb 01 23:17:57 2002
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