Subject: [Ips] Login Phase in iSER over IB

From: "Alex Nezhinsky" <[email-masked]>
Date: Mon, 15 Aug 2005 21:20:03 +0300

I would like to propose some changes for the "iSER over IB" draft
(http://www.ietf.org/internet-drafts/draft-hufferd-iser-ib-00.txt). The
changes being proposed address a group of statements regarding possible
mechanisms of message exchange during the iSER Login Phase in protocols
such as IB. 

The following statement is an example (section 3.1.6): "For LLPs that
have message delivery capability such as [IB], the iSCSI Layer may use
that messaging capability immediately after connection establishment
before enabling iSER-assisted mode."

Because IB as such does not provide streaming capability equivalent to
the plain (not RDMA-enabled) TCP mode in iWARP, a substitute for it
should be found elsewhere. One option is to use the messaging
capabilities provided by the transport layer itself. This is a valid
option because the Login phase exchange is carried out in half-duplex
mode. It can be understood from the previous statement that using two
separate connections for the iSCSI Login and iSER Full-Feature phases is
also allowed. For example, the Login phase is carried out using an IPoIB
connection, while the iSER part is carried out using a separate IB RC
connection. 

In order to clarify that only using a single transport connection is
mandated, the following changes are proposed:

1) In 3.1.6 the third paragraph is to be replaced with:

"And in that same section (4.1) the next to last * paragraph is hereby
replaced with the following: 

    * For a transport layer that operates in stream mode such as TCP,
the RDMA-Capable Protocol implementation supports the enabling of the
RDMA mode after Connection establishment and the exchange of Login
parameters in stream mode. For a transport layer that provides message
delivery capability, such as [IB], the RDMA-Capable Protocol
implementation supports the use of this messaging capability by the
iSCSI Layer directly for the Login phase after connection establishment
before enabling iSER-assisted mode."

2) In 3.1.6.1 the first paragraph is to be repaced with:

"For a transport layer that provides message delivery capability, such
as [IB], the iSCSI Layer MUST interact with the transport layer directly
to use the messaging capability for exchanging the iSCSI Login Request
and Login Response PDUs. The method for establishing the actual
connection is protocol specific and outside the scope of this
specification. The same connection MUST be used for both the iSCSI Login
phase and the subsequent iSER-supported Full-Feature phase.

Alexander Nezhinsky

Software Engineer
Infiniband Storage Solutions
www.voltaire.com <http://www.voltaire.com/> 
9 Ha-Menofim, Herzelya 46725 Israel
tel: +972- 9- 9717637
fax: +972- 9- 9717660
mobile: +972-50-7504376
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From: "Mallikarjun C." <[email-masked]>
Date: Tue, 23 Aug 2005 13:52:47 -0700

I can understand the desire to permit iSCSI Login on IB RCs.  I can also 
see why a message delivery-capable transport (say, MDT for short) 
naturally aligns with iSCSI Login needs.  However, note that iSER draft 
itself does not specify "iSCSI login on MDT" for good reasons.  iSER 
draft assumes that iSCSI login phase mechanics are defined elsewhere, 
and so simply imposes certain key negotiation semantics on a known 
mechanism (and of course defines the FFP behavior).

Having said that, I readily agree that the iSER draft should not 
disallow such an eventuality.  I do not however think that iSER draft 
should explicitly sanction a new iSCSI/MDT login mechanism now unless it 
can reference at least one standard that defines such a login mechanism. 
  My concern with such a reference would be the normative dependency and 
the potential delay.

My apologies if these details were already discussed in the Paris 
meeting, I missed it.

Mallikarjun

Mallikarjun Chadalapaka
Networked Storage Architecture
StorageWorks Division
Hewlett-Packard MS 5668
Roseville CA 95747
cbm [at] rose.hp.com

Alex Nezhinsky wrote:
> have message delivery capability such as [IB], the iSCSI Layer *may* use 
> separate connections for the iSCSI Login and iSER Full-Feature phases 
> is also allowed. For example, the Login phase is carried out using an 
> IPoIB connection, while the iSER part is carried out using a separate IB 
> RC connection.
> 
> *"And in that same section (4.1) the next to last * paragraph is hereby 
> replaced with the following: *
> 
> *     * For a transport layer that operates in stream mode such as TCP, 
> before enabling iSER-assisted mode." *
> 
> *"For a transport layer that provides message delivery capability, such 
> phase and the subsequent iSER-supported Full-Feature phase.*
> 
> Alexander Nezhinsky
> 
> Software Engineer
> ------------------------------------------------------------------------
>