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    RE: iSCSI Framing Formats



    Hello All,
    
    I've had the same thoughts after reading the spec. Pardon my lack of
    knowledge as to the previous discussions, but why not use a framing bit
    pattern as a marker? Pick some 32 bit number, anything but all zeros or
    ones would work, and prefix each header with it. If there is a packet
    loss then the receiver can scan for the next "possible" marker. Once a
    marker pattern is found the receiver then does a sanity check on the
    header. If it passes then the receiver is re-synced. If not then the
    search continues until a valid marker & header is found.
    
    Mike Parkhurst
    
    -----Original Message-----
    From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu] On Behalf Of
    Trang Nguyen
    Sent: Monday, July 09, 2001 1:44 PM
    To: ips@ece.cmu.edu; julian_satran@il.ibm.com; steph@cs.uchicago.edu
    Cc: Trang Nguyen
    Subject: iSCSI Framing Formats
    
    Hello everyone,
    
    I've read your discussion about how to find iSCSI PDU header from the
    TCP
    stream at the receiving end.  There are 2 different approaches with
    various
    ways:
    
    1.  TCP unaware approach suggests: periodic marker, fixed length
    messages,
    byte stuffing, chunks.
    2.  TCP aware approach suggests: Urgent pointer, and PSH bit.
    
    I found that there are some objections about using Urgent point and PSH
    bit
    because the TCP has to be modified.  The iSCSI internet draft suggests
    the
    use of periodic marker.  The problem with the periodic marker in the
    iSCSI
    I-D is that both initiator and target have to agree on the marker.  "In
    certain environments a sender not willing to supply markers to a
    receiver
    willing to accept marker MAY suffer from a considerable performance
    degradation."  (draft-ietf-ips-iscsi-06.txt).
    
    I am just wondering if any method of iSCSI framing has been finalized
    yet?
    What is the status of this issue?  Will the next version of iSCSI I-D
    have
    more information about it?
    
    Thank you in advance for your reply,
    
    
    Trang Nguyen
    
    
    


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Last updated: Tue Sep 04 01:04:20 2001
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