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    RE: Towards Consensus on TCP Connections



    David,
    
    Thank you for your calming words.
    
    At present, all the disk arrays that attach
    using Fibre Channel use exactly the same protocol that is used
    by the individual disk drives, i.e. FCP (or FCP-2).  Some optional
    choices may be different (e.g., if more than one disk drive is
    attached, it is likely to use FC-AL-2 instead of the point-to-point
    FC transfer rules), but the protocol is identical.  Disk arrays may have
    a slightly larger command set, including portions of SSC-2 and
    SES.  Both devices may have out-of-band command capability as well,
    including SFF-8067 for disk drives and various management interfaces
    for RAID boxes.  But the protocol is the same (FCP).  Disk drives
    tend to have symmetrical behaviors across their multiple ports, while
    RAID boxes may have either symmetrical or asymmetrical behaviors.  The
    protocol is still the same.  Tape drives and storage subsystems may
    have ordering requirements.  The protocol is still the same.  The splendor
    of this is that it does not matter whether you are controller attached, bridge attached, or directly attached, no changes need to be made
    in the protocol.
    
    Similar behavior is true of parallel SCSI RAID boxes and disk drives.
    
    For this and a bunch of other reasons, we have been encouraging the
    use of the common packet structure and architecture implemented 
    by packetized parallel SCSI, SBP-2, SSA, and FCP in the iSCSI.
    
    Bob
    
    Bob Snively
    Brocade Communications           Phone  408 487 8135
    1901 Guadalupe Parkway
    San Jose, CA 95131               Email   rsnively@brocade.com
    
    
    >  -----Original Message-----
    >  From: Black_David@emc.com [mailto:Black_David@emc.com]
    >  Sent: Friday, August 11, 2000 6:08 PM
    >  To: ips@ece.cmu.edu
    >  Subject: RE: Towards Consensus on TCP Connections
    >  
    >  
    >  > I do not think that such contentious statements are useful.
    >  
    >  Can we calm down a bit -- or at least leave refereeing attempts
    >  to folks like the co-chairs and ADs?  Thanks in advance.
    >  
    >  It is the case that Douglas Otis's statement to which John Hufferd
    >  objected is seriously at odds with industry practice --
    >  
    >  > If you wish to use this interface at a controller, it should
    >  > assume an identical role to a device.
    >  
    >  Even disk arrays that are all-Fibre Channel are often using FC-SW
    >  (switched) to talk to servers and FC-AL (arbitrated loop) to 
    >  talk to drives.
    >  There are disk array products with Fibre Channel interfaces 
    >  to servers
    >  that use SCSI and even SSA drives.  Most mainframes still use ESCON
    >  as their storage interface, even though there hasn't been an ESCON
    >  disk drive produced for many years.
    >  
    >  So, I think the onus is on Douglas to explain why uniformity 
    >  of controller
    >  and drive interfaces should be required, given the large 
    >  number of product
    >  engineering decisions that have gone in the other direction. 
    >   After all,
    >  this
    >  is the Internet *Engineering* Task Force :-).
    >  
    >  The overall discussion of whether the iSCSI protocol 
    >  specification should
    >  include both arrays and individual drives is definitely 
    >  germane and in
    >  scope for this list - there are words in the draft charter 
    >  to that effect.
    >  
    >  --David  
    >  
    >  ---------------------------------------------------
    >  David L. Black, Senior Technologist
    >  EMC Corporation, 42 South St., Hopkinton, MA  01748
    >  +1 (508) 435-1000 x75140, FAX: +1 (508) 497-6909
    >  black_david@emc.com  Cellular: +1 (978) 394-7754
    >  ---------------------------------------------------
    >  
    >  
    


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Last updated: Tue Sep 04 01:07:52 2001
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