RE: Framing Discussion

["Y P Cheng" <ycheng@advansys.com>]

> >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.

I think you are mixing TCP and SCSI implementations.  The SCSI semantic
requires the buffers of a READ pre-allocated and locked.  For TCP, the
incoming byte stream enters a socket can be buffered waiting for a READ
command.

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

I guess by protocol you are referring to the TCP/RDMA or iSCSI framing that
allow the iSCSI data in a TCP segment to be quickly moved to the application
buffers, PRE-ALLOCATED, without in-order arriving.

Y.P. Cheng, Connectcom Solutions.