RE: iSCSI: Portal Group clarification

Kevin and Marjorie,

Thanks for pointing that out. When I made the diagram, I didn't really intend to show an object diagram. I intended to show the flow and connecting lines between logical parts.

I'll see if I can make a change that will properly depict the Network Entity.

Eddy

-----Original Message-----
From: KRUEGER,MARJORIE (HP-Roseville,ex1) [mailto:marjorie.krueger@hp.com]
Sent: Thursday, April 03, 2003 6:31 PM
To: 'Kevin Gibbons'; ips@ece.cmu.edu
Subject: RE: iSCSI: Portal Group clarification

The drawing in http://www.haifa.il.ibm.com/satran/ips/EddyQuicksall-iSCSI-in-diagrams/portal_groups.pdf has used the label "network entity" in a manner inconsistent with the usage/intent in the iSCSI protocol specification. A "network entity" is meant to represent a computer system with ethernet egress points. As a computer system, it can contain one iSCSI Node if it's an initiator, and one or more iSCSI Nodes if it's a target. It's not correct to talk about an iSCSI Node "accessing" a network entity, it's a containment relationship.

Portal tags must only be unique within the scope of a single iSCSI target node, and are 16 bit integers. I don't see where you get the UTF-8 out of the examples in (1)? I just see numbers, with no mention of what format they must be exchanged in. Of course, SendTargets commands are character strings, so the exchange of TargetPortalGroupTags are integers represented in character format.

Marjorie Krueger
Networked Storage Architecture
Networked Storage Solutions
Hewlett-Packard

-----Original Message-----
From: Kevin Gibbons [mailto:kgibbons@NishanSystems.com]
Sent: Thursday, April 03, 2003 1:17 PM
To: ips@ece.cmu.edu
Cc: 'John Hufferd'; Eddy Quicksall
Subject: RE: iSCSI: Portal Group clarification

I have been reviewing the iSCSI Model examples on http://www.haifa.il.ibm.com/satran/ips , and am trying to get them straight in my head. I was hoping someone can help.

Network Entity: Can different entities provide access to the same iSCSI Node? In 1) "iSCSI Configuration Examples", http://www.haifa.il.ibm.com/satran/ips/iSCSIConfigurationExamples.pdf, the iSCSI Network Entity contains iSCSI Nodes and Network Portals. Each Network Portal has a TCP/IP network address. This limits access to an iSCSI Node to one Entity, and seems to agree with the architecture model in the iSCSI draft. But 2) "Portal Groups", http://www.haifa.il.ibm.com/satran/ips/EddyQuicksall-iSCSI-in-diagrams/portal_groups.pdf, shows Network Entities that provide access to, but do not contain, Network Portals and iSCSI Nodes. These feed into Portal Groups and then iSCSI Nodes. This would mean multiple Entities can provide access to the same iSCSI Node, and the example (2) shows this. This seems to disagree with (1). I tried but could not map this into the iSCSI draft architecture model.

Portal Tags: Are they uniquely defined using 16 bit integers? In 1) "iSCSI Configuration Examples" figures, the Portal Tags are specified using UTF-8 characters. But the included Send Targets examples use integer values. In 2) "Portal Groups", integer values are used for defining Portal Tags. This seems to agree with the iSCSI draft.

Is there a UML/entity-relationship model for the iSCSI architecture? This would help me a lot. I am aware of one for the iSCSI MIB model, but not the iSCSI Architecture.

Many Regards, Kevin

-----Original Message-----
From: John Hufferd [mailto:hufferd@us.ibm.com]
Sent: Tuesday, April 01, 2003 11:04 PM
To: Eddy Quicksall
Cc: ips@ece.cmu.edu; Kevin Gibbons; owner-ips@ece.cmu.edu
Subject: RE: iSCSI: Portal Group clarification

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
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