RE: iscsi: Data PDU in two Sequence multiplexing issue

["Rod Harrison" <rod.harrison@windriver.com>]

Agreed, if the R2Ts ask for all the data sent in both PDUs 1 & 2.
i.e. The amount of data solicited by the R2Ts is sent in two PDUs
1 and 2.

Do you agree the examples I gave where A1, B1, A2, B2 is valid
are correct given the conditions I specified?

- Rod

-----Original Message-----
From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu]On
Behalf Of
Eddy Quicksall
Sent: Friday, June 06, 2003 8:44 PM
To: Rod Harrison; ips@ece.cmu.edu
Subject: RE: iscsi: Data PDU in two Sequence multiplexing issue


I think the word "fulfilled" in 10.8 is the same as saying
"completed".

T->I R2T-A
T->I R2T-B

So PDU 1 of A  -> PDU 1 of B -> PDU2 of A -> PDU2 of B would be
illegal
because sequence A is not fulfilled before sequence B begins.

Do you agree with that?

Eddy


-----Original Message-----
From: Rod Harrison [mailto:rod.harrison@windriver.com]
Sent: Friday, June 06, 2003 8:52 PM
To: Sanjay Goyal; ips@ece.cmu.edu
Subject: RE: iscsi: Data PDU in two Sequence multiplexing issue


That depends on why the initiator is sending the data. If we are
talking solely about unsolicited data then you are correct, all
the unsolicited data for command N must be sent before any
unsolicited data for command N+1. In your example we must see A1,
A2, B1, B2.

However, your second sequence can be valid if there are solicited
data involved. There are at least two valid scenarios for A1, B1,
A2, B2:

First A1 and B1 are unsolicited data and are FirstBurstSize big.
The initiator would then have to see R2T-A2 and R2T-B2 in that
order. Where R2T-A2 means the R2T requesting PDU A2.

Alternatively all the data could be solicited and A1 and B1
satisfy R2T-A1 and R2T-B1 respectively.

What 3.2.4.1 is telling you is that the target can not assume the
PDU following a command PDU is the corresponding unsolicited
data. In fact pretty much any PDU can come next, the only thing
that is guaranteed is that the next unsolicited DATA-OUT PDU will
be for command in question.

- Rod

-----Original Message-----
From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu]On
Behalf Of
Sanjay Goyal
Sent: Friday, June 06, 2003 12:58 PM
To: ips@ece.cmu.edu
Subject: iscsi: Data PDU in two Sequence multiplexing issue


Hi,
Can somebody please comment,

This is what I am not very clear about, from the specification.
-----------------
10.8 says: Within a connection, outstanding R2Ts MUST be
fulfilled by the initiator in the order in which they were
received.

3.2.4.1 says: When unsolicited data is used, the order of the
unsolicited
data on each connection MUST match the order in which the
commands
on that connection are sent. Command and unsolicited data PDUs
may
be interleaved on a single connection as long as the ordering
requirements of each are maintained (e.g., command N+1 MAY be
sent
before the unsolicited Data-Out PDUs for command N, but the
unsolicited Data-Out PDUs for command N MUST precede the
unsolicited
Data-Out PDUs of command N+1).
------------------


if we have two Data-out sequences A and B of 2 pdus each, to be
sent on the
same connection.
this is how I think they will be sent
PDU 1 of A -> PDU2 of A  -> PDU1 of B -> PDU2 of B
  What I am trying to verify is that the below sequence is valid
or not.
PDU 1 of A  -> PDU 1 of B -> PDU2 of A -> PDU2 of B

Regards
Sanjay Goyal