Subject: Re: [Ips] Targets that don't want to support discovery

From: "Eddy Quicksall" <[email-masked]>
Date: Thu, 11 May 2006 09:56:17 -0400

I can't find anything in the spec that says a discovery session can't be redirected. I know that it is logical that redirection would require a TargetName but I don't see that in the spec either.

(but I may be missing those parts so please point out the reference).

Eddy
  ----- Original Message ----- 
  From: William Studenmund 
  To: Eddy Quicksall 
  Cc: [email-masked] 
  Sent: Thursday, April 27, 2006 7:09 PM
  Subject: Re: [Ips] Targets that don't want to support discovery

  On Apr 27, 2006, at 11:50 AM, Eddy Quicksall wrote:

    Appendix D says:
       A system that contains targets MUST support discovery sessions on
       each of its iSCSI IP address-port pairs, and MUST support the
       SendTargets command on the discovery session

    Suppose I have targets A, B and C. I want target A to be the only target that can support discovery. Login to targets B and C will be redirected by A.

    This is fine except for the fact that once the redirection occurs the initiator has the address of B and C and could open a discovery session to B or C.

    I'm thinking that I could have B and C redirect to A for any discovery session hence A would become the only target to support discovery (but that would "break the law").

    I'm wondering how the community thinks this should be handled.

  I have a feeling that that'd be breaking the rules.

  Why do you want to do this?

  Another option is that while ports B and C should support discovery sessions, they don't have to do it very efficiently. It's fine if they use some sort of proxy to internally route the commands to A for processing. So only A is very smart, but discovery works everywhere.

  Take care,

  Bill

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From: "John Hufferd" <[email-masked]>
Date: Thu, 11 May 2006 10:43:23 -0700

The whole issue here was that when we created the discovery stuff we
wanted the host system to be able to start their discovery with any
portal that they knew about.  I am not sure that we would want to
prevent what you are suggesting, and I do not think there is any
prohibition against it. Especially since the initiator can still start
at any known portal.

In fact since one of the reasons we created redirection was to permit
maintenance to be applied to the targets; this capability may actually
be appropriate. The intention was that with some implementations you can
have just enough capabilities at the portal to permit the redirection
but nothing else while maintenance for the target controller board is
being applied.

So I would think, therefore, that redirection in the discovery process
would be permitted.

The issue for any product that uses this approach is: will the iSCSI
initiators actually permit this, or will they be surprised by the action
and fail in some manner.  You may then be technically correct that the
initiator has a bug, but this may impact your product schedules as you
attempt to get the initiators fixed.  You might want to test it first
before you bet any development dollars on this.  

.

.

.

John L Hufferd

Sr. Executive Director of Technology

Brocade Communications Systems, Inc

[email-masked]

Office Phone: (408) 333-5244; eFAX: (408) 904-4688

Alt Office Phone: (408) 997-6136; Cell: (408) 627-9606

  _____  

From: Eddy Quicksall [mailto:[email-masked]] 
Sent: Thursday, May 11, 2006 6:56 AM
To: William Studenmund
Cc: [email-masked]
Subject: Re: [Ips] Targets that don't want to support discovery

I can't find anything in the spec that says a discovery session can't be
redirected. I know that it is logical that redirection would require a
TargetName but I don't see that in the spec either.

Eddy

	----- Original Message ----- 

	From: William Studenmund <mailto:[email-masked]>  

	To: Eddy Quicksall
<mailto:[email-masked]>  

	Cc: [email-masked] 

	

	Appendix D says:

	   A system that contains targets MUST support discovery
sessions on
	   each of its iSCSI IP address-port pairs, and MUST support the
	   SendTargets command on the discovery session

	Suppose I have targets A, B and C. I want target A to be the
only target that can support discovery. Login to targets B and C will be
redirected by A.

	This is fine except for the fact that once the redirection
occurs the initiator has the address of B and C and could open a
discovery session to B or C.

	I'm thinking that I could have B and C redirect to A for any
discovery session hence A would become the only target to support
discovery (but that would "break the law").

	Another option is that while ports B and C should support
discovery sessions, they don't have to do it very efficiently. It's fine
if they use some sort of proxy to internally route the commands to A for
processing. So only A is very smart, but discovery works everywhere.

	Take care,

	Bill

  _____