RE: Framing Discussion

[JP Raghavendra Rao <Jp.Raghavendra@EBay.Sun.COM>]

>> The design goal behind the framing discussion
>> is avoidance of that copy.  In contrast to the
>> typical case for NICs and TCP/IP, read data
>> buffers for SCSI data are usually *not*
>> interchangeable.
>> 
>Why are they not interchangeable ? This is an
>assumption not stated anywhere.  Is there
>a list of other assumptions that is documented ?
>

Typically, the original data buffer is with the application that
made the SCSI READ request - and this buffer may not have been
allocated with the constraints that should be ready for a simple
swapping. Assuming that the constraints are met, it would require
VM page flipping, which is considered to be an implementation hack.

A protocol level solution to locate the buffer and its offset for
the incoming TCP segment is probably a better thing to have.

-JP