Question on SBP-2 Reconnection

PJohansson PJohansson at
Wed Apr 1 20:54:20 PST 1998

* From the T10 (formerly SCSI) Reflector (t10 at, posted by:
* PJohansson <PJohansson at>
In a message dated 98-03-31 18:45:02 EST, srao at writes:

<<SBP-2 Standard in section 6.3 mentions

"An Initiator may signal a request by means of an 8-byte block write
transaction that specifies the address of the request. If the management agent
is busy with another request, the block write shall be rejected with a
response of

Is the management is considered busy until Managment Agent writes into Status
FIFO of Access Orbs ( Login, Logout, Reconnect etc.. )?>>

Whether or not the MANAGEMENT_AGENT responds with conflict error while the
target is occupied with a *single* management request is an implementation. It
is easy to imagine implementations that might buffer N management requests
before a write to the MANAGEMENT_AGENT register would yield

<<If so, how do we handle the following:

There is a possiblity that more than one login sessions are possible to the
same unit in the target ( Due to multiple logins to different LUNs in one unit
Or multiple logins to same LUN ). If more than one logins sessions are present
and bus reset happens at that time,then all initiators try to reconnect to the
target. Since all of these sessions are to the same unit, these reconnect ORBs
are addressed to the same Managment Agent register.

In this case, except for one, all reconnection process will fail with
'resource conflict error'.

What should be the initiator behaviour in the failed case? Does it need to
retry after backing off for some random amount of time.>>

IEEE Std 1394-1995 describes conflict error as a problem that may be transient
and may succeed if retried. If the initiator is at all interested in
reconnecting, it should retry---and retry within the reconnect time-out

If a target has M logical units each of which can support N concurrent logins
by different initiators, it might add value to the device and enhance its
competitive appeal if the MANAGEMENT_AGENT register were designed to support M
* N outstanding management requests.


Peter Johansson

Congruent Software, Inc.
3998 Whittle Avenue
Oakland, CA  94602

(510) 531-5472
(510) 531-2942 FAX

pjohansson at
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