RE: iSCSI: Portal Group clarification

[John Hufferd <hufferd@us.ibm.com>]

Eddy,
Your point is exactly correct!

The key point that was being missed was the words at the bottom of the figure on page 40 which says "(within Network Entity, not shown)".

When one has more than one target (node) within a Network Entity, the portal (IP Address:Port) can be part of any of the enclosed Targets.  That is because the path to the Target is defined by the portal (IP Address:Port) and the Target Name.  This is reasonable since nothing is ambiguous about the description of the path that is intended.  

Having said that, there is also NO requirement that all portals need be connectable to all targets within the Network Entity.  This is an implementation decision.  (Just thought I would through that in.)

Your point is also supported by the figure in section 3.4  and also the following example that describes what is returned by SendTargets for a Network Entity that has two iSCSI targets:

- iSCSI Draft20 Appendix D : SendTargets Operation 
  "The next example has two internal iSCSI targets, each accessible via
   two different ports with different IP addresses.  The following is
   the text response:

         TargetName=iqn.1993-11.com.example:diskarray.sn.8675309
         TargetAddress=10.1.0.45:3000,1
         TargetAddress=10.1.1.45:3000,2
         TargetName=iqn.1993-11.com.example:diskarray.sn.1234567
         TargetAddress=10.1.0.45:3000,1
         TargetAddress=10.1.1.45:3000,2   "
       

.
.
John L. Hufferd
Senior Technical Staff Member (STSM)
IBM/System Group, San Jose CA
Main Office: (408) 256-0403, Tie: 276-0403, eFax: (408) 904-4688
Home Office: (408) 997-6136, Cell: (408) 499-9702
Internet Address: hufferd@us.ibm.com

Eddy Quicksall <eddy_quicksall@ivivity.com> Sent by: owner-ips@ece.cmu.edu 04/01/2003 05:13 PM

To:        Kevin Gibbons <kgibbons@NishanSystems.com>, ips@ece.cmu.edu         cc:                 Subject:        RE: iSCSI: Portal Group clarification

Yes.

Note however that a Network Portal can belong to more than one Target Portal
Group but only one Target Portal Group within a single node (which is a
target in this context).

Eddy

-----Original Message-----
From: Kevin Gibbons [mailto:kgibbons@NishanSystems.com] 
Sent: Tuesday, April 01, 2003 6:39 PM
To: ips@ece.cmu.edu
Subject: iSCSI: Portal Group clarification

Hi, I would like to make sure I understand the iSCSI model correctly.  Can
anyone confirm that a Portal, providing access to a target, is part of
exactly one Portal Group at a time?  My reading of the spec indicates this
is true.  That each Portal has a 16 bit Portal Group tag.  But I would like
to make sure.

I believe that in iSCSI draft 20, it states that a Portal can be part of
exactly one Portal Group.  Please see page 15:

   - Portal Groups: iSCSI supports multiple connections within the same
   session; some implementations will have the ability to combine
   connections in a session across multiple Network Portals. A Portal
   Group defines a set of Network Portals within an iSCSI Network
   Entity that collectively supports the capability of coordinating a
   session with connections spanning these portals. Not all Network
   Portals within a Portal Group need participate in every session
   connected through that Portal Group. One or more Portal Groups may
   provide access to an iSCSI Node. Each Network Portal, as utilized by
   a given iSCSI Node, belongs to exactly one portal group within that
   node.

                 Also, please see page 39 for similar wording.  There is also a
figure on page 40:

     ----------------------------IP Network---------------------
            |               |                    |
       +----|---------------|-----+         +----|---------+
       | +---------+  +---------+ |         | +---------+  |
       | | Network |  | Network | |         | | Network |  |
       | | Portal  |  | Portal  | |         | | Portal  |  |
       | +--|------+  +---------+ |         | +---------+  |
       |    |               |     |         |    |         |
       |    |    Portal     |     |         |    | Portal  |
       |    |    Group 1    |     |         |    | Group 2 |
       +--------------------------+         +--------------+
            |               |                    |
   +--------|---------------|--------------------|--------------------+
   |        |               |                    |                    |
   |  +----------------------------+  +-----------------------------+ |
   |  | iSCSI Session (Target side)|  | iSCSI Session (Target side) | |
   |  |                            |  |                             | |
   |  |       (TSIH = 56)          |  |       (TSIH = 48)           | |
   |  +----------------------------+  +-----------------------------+ |
   |                                                                  |
   |                     iSCSI Target Node                            |
   |             (within Network Entity, not shown)                   |
   +------------------------------------------------------------------+


Please let me know if I am in error.
                 Thanks very much! Kevin

-------------------------------------------------
Kevin Gibbons
Nishan Systems, Inc.
kgibbons@NishanSystems.com
(408) 519-3756
-------------------------------------------------