TCP RDMA option to accelerate NFS, CIFS, SCSI, etc.

[Costa Sapuntzakis <csapuntz@cisco.com>]

The TCP RDMA option reduces the overhead of receiving data over
TCP-based protocols such as NFS and HTTP.  

It enables the construction of a simple hardware accelerator that
copies data directly from the incoming packet into application
buffers, avoiding expensive copies in the protocol stack.  Even
without hardware acceleration, the option enables the protocol stack
to decrease the number of copies it must do.

The TCP RDMA option is an annotation and requires no modifications to
higher layer protocols. It can be used with popular protocols such as 
HTTP, NFS, and CIFS, along with new protocols.

The TCP option also provides a bit to indicate application-level
message boundaries. The bit enables out-of-order processing of the TCP
receive queue, potentially decreasing service times in the presence of
packet drops and improving performance on parallel systems.

A draft describing the TCP RDMA option can be found at:
ftp://ftpeng.cisco.com/pub/rdma/draft-csapuntz-tcprdma-00.txt

-Costa