Subject: [Ips] iSCSI Names and Addresses

From: [email-masked]
Date: Mon, 24 Oct 2005 14:24:47 -0400

I have a novice question.

When rfc3721 says that iscsi names are associated with iscsi nodes (relevant
portion at the end), what does that mean exactly for a host with multiple
network adapter cards ?

For example, a Win2K03 host might have an initiator named

- iqn.1991-05.com.microsoft:hosta

- if there are two network adapters, say, 172.20.4.67 and 172.21.4.67

How would/should the two paths be represented and/or utilized by the
'outside' world ?
I do not see how the single initiator name is sufficient for what is
described in 3721.

Thanks in advance,
Steve

[portion of 3721 follows]

RFC 3721 iSCSI Naming and Discovery April 2004

1. iSCSI Names and Addresses

The main addressable, discoverable entity in iSCSI is an iSCSI Node.
An iSCSI node can be either an initiator, a target, or both. The
rules for constructing an iSCSI name are specified in [RFC3720].
This document provides examples of name construction that might be
used by a naming authority.

Both targets and initiators require names for the purpose of
identification, so that iSCSI storage resources can be managed
regardless of location (address). An iSCSI name is the unique
identifier for an iSCSI node, and is also the SCSI device name [SAM2]
of an iSCSI device. The iSCSI name is the principal object used in
authentication of targets to initiators and initiators to targets.
This name is also used to identify and manage iSCSI storage
resources.

Furthermore, iSCSI names are associated with iSCSI nodes instead of
with network adapter cards to ensure the free movement of network
HBAs between hosts without loss of SCSI state information
(reservations, mode page settings etc) and authorization
configuration.

An iSCSI node also has one or more addresses. An iSCSI address
specifies a single path to an iSCSI node and consists of the iSCSI
name, plus a transport (TCP) address which uses the following format:
<domain-name>[:<port>]
Where <domain-name> is one of:
- IPv4 address, in dotted decimal notation. Assumed if the name
contains exactly four numbers, separated by dots (.), where each
number is in the range 0..255.
- IPv6 address, in colon-separated hexadecimal notation, as
specified in [RFC3513] and enclosed in "[" and "]" characters, as
specified in [RFC2732].
- Fully Qualified Domain Name (host name). Assumed if the <domainname>
is neither an IPv4 nor an IPv6 address.
For iSCSI targets, the <port> in the address is optional; if
specified, it is the TCP port on which the target is listening for
connections. If the <port> is not specified, the default port 3260,
assigned by IANA, will be assumed. For iSCSI initiators, the <port>
is omitted.

Bakke, et al. Informational [Page 3]

Steve Yackey
EMC2 Corporation
1401 Main Street, Suite 350
Columbia, SC 29201
803-231-2632

Steve Yackey
EMC2 Corporation
1401 Main Street, Suite 350
Columbia, SC 29201
803-231-2632

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---

From: William Studenmund <[email-masked]>
Date: Mon, 24 Oct 2005 13:26:13 -0700

On Oct 24, 2005, at 11:24 AM, [email-masked] wrote:

> When rfc3721 says that iscsi names are associated with iscsi nodes 
> (relevant portion at the end), what does that mean exactly for a host 
> with multiple network adapter cards ?
>

Paths and TCP connections, which involve IP addresses, are different 
from sessions, which involve initiator names. Yes, multiple connections 
can make up a session, but connections are a TCP thing and sessions are 
a SCSI thing (the I_T nexus from SAM).

I think part of the problem is that you are asking about the source 
ports for a TCP connection. They really aren't used much outside of the 
box. The only standard way a target would care about them is if an AUTH 
entry were limited to being used only from certain source port ranges.

It would be quite reasonable for one iSCSI session to be handled by 
connections coming from both of the addresses you list above. That 
would give you a measure of multipath support.

Take care,

Bill