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On Jun 16, 2006, at 5:37 AM, Praveen Madhavan wrote:
Hi Folks,
Can any one point me the frame format of bidirectional command in
case of iSCSI & FCP ?.. I was trying to route bidirectional command
recv'd from iSCSI initiator to FC Target..
Here is the iSCSI PDU format for bi-direct command recv from initiator
----------------------------------------------------------------------
--------------------------
| BHS
(48bytes)
|
| R & W bit set to
ONE, |
| Expected xfer len =
0x200 |
| Total AHS Length = 2
(8bytes) |
| SCSI CDB = Write(10) Transfer length = 00 01 ( 512 bytes) |
----------------------------------------------------------------------
--------------------------|
| AHS ( 8
bytes)
|
| Expected Read data length = 0x200(512
bytes) |
----------------------------------------------------------------------
----------------------------
Here is the FCP format for bi-direct command that i frame for
sending it to target.
----------------------------------------------------------------------
--------------------------
| FC-Header
(24bytes) |
|---------------------------------------------------------------------
---------------------------
| FCP-Header(36
bytes) |
| R & W bit set to
ONE, |
| Additional CDB length =
0 |
| SCSI CDB = Write(10) Transfer length = 00 01 ( 512
bytes) |
| FCP_DL = 0x200 ( 512
bytes) |
| FCP_BIDIRECTIONAL_READ_DL = 0x200(512) |
----------------------------------------------------------------------
---------------------------|
Well, I am not quite sure about the CDB values in case Bidir
commands..
Will Bi directional cmds use Write CDB(10) or Read CDB (10) ? ..
No. Read and Write in normal sizes (6, 10, 12, 16) are unidirectional.
Each specific command has either no data phase (test unit ready),
has at most a data-out phase (Write for instance), at most a
data-in phase (Read), or is bidirectional.
How can i control following bidi- operation in case of iSCSI & FCP ?
1.bidirectional command with read before write operation
2.bidirectional command with write before read operation
You really don't need to do anything different for BiDi commands,
other than be able to keep both a Write and a Read residual. As you
note, the SCSI Command Request will indicate what data phases the
initiator expects, you need only map them along.
How does the target announce/control data flow in FCP? You need only
pass that information on to the iSCSI layer. If the FCP target sends
you data, then you send the initiator a bunch of Data-In PDUs.
However it is that FCP controls data openings translates into R2Ts
to the iSCSI initiator.
Take care,
Bill
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