RE: iSCSI: advancing CmdSN after a command retry rule

[pat_thaler@agilent.com]

Julian,

 

Thanks. That still leaves the problem that there is no definition of when a connection is "operational" but that could be added to the last call issues.

 

Pat

 

-----Original Message-----
From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
Sent: Saturday, June 15, 2002 9:27 AM
To: THALER,PAT (A-Roseville,ex1)
Cc: ips@ece.cmu.edu
Subject: Re: iSCSI: advancing CmdSN after a command retry rule

Pat, 

If the connection went through a "restart" 
(login with the same CID) then the "cleaning" is also not needed. 
Your text modified as follows is 
acceptable: 

If an initiator 
issues a command retry for a command with CmdSN R on 
a connection when the session CmdSN register is Q, it 
MUST NOT advance the CmdSN past R + 2**31 -1 unless the connection is no longer 
operational, or the connection has been reinstated (see Section 4.3.4 Connection 
reinstatement), or a non-immediate command with CmdSN equal or greater than Q 
was issued on the same connection and the reception of the command is 
acknowledged by the target (see Section 8.4 Command Retry and Cleaning Old 
Command Instances). 

Thanks, 
Julo

"THALER,PAT (A-Roseville,ex1)" <pat_thaler@agilent.com> 06/15/2002 03:39 AM Please respond to "THALER,PAT (A-Roseville,ex1)"

To:        Julian Satran/Haifa/IBM@IBMIL, ips@ece.cmu.edu         cc:                 Subject:        iSCSI: advancing CmdSN after a command retry rule

Julian,

I'm having a little trouble understanding this text near 
the end of 2.2.2.1:

If an initiator issues a command retry for a command 
with CmdSN R on
a connection when the session CmdSN register is Q, it MUST 
NOT
advance the CmdSN past R + 2**31 -1 unless a different 
non-immediate
command with CmdSN equal or greater than Q was issued on the 
same
connection if the connection is still operational, and the 
reception
of the command is acknowledged by the target (see Section 8.4 
Command
Retry and Cleaning Old Command Instances). The second 
non-immediate
command when sent, MUST be sent in-order after the 
retried
command on the same connection.

What does "different" mean in 
a different non-immediate command with CmdSN equal or greater than Q"? Isn't any 
command with a new CmdSN because it has a new CmdSN? 

What is the purpose 
of "if the connection is still operational"? If a new command is issued on the 
connection it must still be operational. Perhaps it was intended to mean that if 
the connection was not operational then CmdSN can be advanced past the limit 
without this requirement being met. 

There doesn't seem to be any 
definition of when a connection is "operational". Does the connection leave the 
operational state when it leaves S5 or is it when it has returned to 
S1?

Does "second non-immediate command" mean the command sent on this 
connection with CmdSN equal or greater than Q? Other commands with Q <= CmdSN 
< R + 2**31 - 1 may be sent on other connections, so the second command is 
the second command on this connection, right?

It isn't clear what the 
last sentence was intended to do since any command sent before the retry would 
advance Q so inherently any command sent after the retry with a new CmdSN must 
be in-order after the retry. 

I suggest the following text plus 
clarification of the meaning of operational for a connection:
"If an 
initiator issues a command retry for a command with CmdSN R on
a connection 
when the session CmdSN register is Q, it MUST NOT
advance the CmdSN past R + 
2**31 -1 unless the connection is no longer operational or a non-immediate 
command with CmdSN equal or greater than Q was issued on the same
connection 
and the reception of the command is acknowledged by the target (see Section 8.4 
Command Retry and Cleaning Old Command Instances). 

Pat