Subject: iSCSI: use of Text/Login with no data segment

From: [email-masked]
Date: Fri, 14 Jun 2002 15:51:28 -0600

Julian,

4.2 (page 72) of iSCSI-13 says:
A target or initiator SHOULD NOT use a Text/Login Response or Text/
Login Request with no data segment (DataSegmentLength 0) unless
responding to a Text/Login Request respective Text/Login Response
with the C bit set to 1.

"SHOULD NOT" is too strong here as there are times when one must send a
Text/Login Response or Request with no data segment if one is to complete
the login.

For example, a Target might send a Login response with the T=0 and C=0. If
the initiator doesn't have an keys it wants to send, then the initiator will
have to send a Login Request with no data segment if the login is to
complete.

Also, wrt grammar, "respective" is not a conjunction so the normal way to
use it would be "... A or B ... C or D, respectively, ...." At least that is
the usage that I have seen and what the dictionary at hand supports.

If one wants to retain the idea of not sending empty PDUs when you do have
something to say, one could put in:
A target or initiator SHOULD NOT use a Text/Login Response or Text/
Login Request with no data segment (DataSegmentLength 0) unless
responding to a Text/Login Request or Text/Login Response, respectively,
with the T bit set to 0 while the node has no keys to send or with the C bit
set to 1.

Pat

---

From: Martins Krikis <[email-masked]>
Date: Fri, 14 Jun 2002 16:32:09 -0700 (PDT)

> to send or with the C bit

I don't see a problem with an implementation that
deliberately sends an empty PDU to let the other 
side "speak" first. Doing this back-and-forth would 
not be a great situation, but IMHO it suffices to
simply discourage such behavior, without resorting
to "SHOULD NOT"-s.

So, how about this instead?

  A target or initiator is discouraged from
  sending Text/Login Response or Text/Login Request
  with no data segment (DataSegmentLength 0) unless
  responding to a Text/Login Request or Text/Login
  Response, respectively, with the C bit set to 1,
  or the F/T bit set to 0 while having no keys to
  send.

Or, let's just skip such restrictions/discouragements
entirely.

Martins Krikis, Intel Corp.

Disclaimer: these opinions are mine and may not
            be those of my employer.

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