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Title: Message
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
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
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
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| 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
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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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Last updated: Thu Apr 03 19:19:15 2003
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