Re: [storm] MPA Draft - Review

<david.black@emc.com> Thu, 31 March 2011 14:48 UTC

Return-Path: <david.black@emc.com>
X-Original-To: storm@core3.amsl.com
Delivered-To: storm@core3.amsl.com
Received: from localhost (localhost [127.0.0.1]) by core3.amsl.com (Postfix) with ESMTP id B753F28C11D for <storm@core3.amsl.com>; Thu, 31 Mar 2011 07:48:51 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -106.579
X-Spam-Level:
X-Spam-Status: No, score=-106.579 tagged_above=-999 required=5 tests=[AWL=0.020, BAYES_00=-2.599, RCVD_IN_DNSWL_MED=-4, USER_IN_WHITELIST=-100]
Received: from mail.ietf.org ([64.170.98.32]) by localhost (core3.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 1k3U9b5Gtzzr for <storm@core3.amsl.com>; Thu, 31 Mar 2011 07:48:50 -0700 (PDT)
Received: from mexforward.lss.emc.com (mexforward.lss.emc.com [128.222.32.20]) by core3.amsl.com (Postfix) with ESMTP id 5300728C107 for <storm@ietf.org>; Thu, 31 Mar 2011 07:48:50 -0700 (PDT)
Received: from hop04-l1d11-si01.isus.emc.com (HOP04-L1D11-SI01.isus.emc.com [10.254.111.54]) by mexforward.lss.emc.com (Switch-3.4.3/Switch-3.4.3) with ESMTP id p2VEoTTs010605 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for <storm@ietf.org>; Thu, 31 Mar 2011 10:50:29 -0400
Received: from mailhub.lss.emc.com (mailhubhoprd01.lss.emc.com [10.254.221.251]) by hop04-l1d11-si01.isus.emc.com (RSA Interceptor) for <storm@ietf.org>; Thu, 31 Mar 2011 10:50:23 -0400
Received: from mxhub21.corp.emc.com (mxhub21.corp.emc.com [128.221.56.107]) by mailhub.lss.emc.com (Switch-3.4.3/Switch-3.4.3) with ESMTP id p2VEmRpB002340 for <storm@ietf.org>; Thu, 31 Mar 2011 10:48:27 -0400
Received: from mx14a.corp.emc.com ([169.254.1.143]) by mxhub21.corp.emc.com ([128.221.56.107]) with mapi; Thu, 31 Mar 2011 10:48:26 -0400
From: <david.black@emc.com>
To: <storm@ietf.org>
Importance: high
X-Priority: 1
Date: Thu, 31 Mar 2011 10:48:23 -0400
Thread-Topic: MPA Draft - Review
Thread-Index: AcuiSMs9BaSwGO4cTKyXNsSoFs8erRNZ1Z5A
Message-ID: <7C4DFCE962635144B8FAE8CA11D0BF1E03E5E9530C@MX14A.corp.emc.com>
References: <7C4DFCE962635144B8FAE8CA11D0BF1E03D74C7183@MX14A.corp.emc.com>
In-Reply-To: <7C4DFCE962635144B8FAE8CA11D0BF1E03D74C7183@MX14A.corp.emc.com>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
acceptlanguage: en-US
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-EMM-MHVC: 1
Subject: Re: [storm] MPA Draft - Review
X-BeenThere: storm@ietf.org
X-Mailman-Version: 2.1.9
Precedence: list
List-Id: Storage Maintenance WG <storm.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/listinfo/storm>, <mailto:storm-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/storm>
List-Post: <mailto:storm@ietf.org>
List-Help: <mailto:storm-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/storm>, <mailto:storm-request@ietf.org?subject=subscribe>
X-List-Received-Date: Thu, 31 Mar 2011 14:48:51 -0000

The -03 version of the MPA draft has addressed all of the issues from my review, and .  Unfortunately, I need some minor edits for clarity before I can send this on to our AD with a publication request.  Would the authors please submit a -04 version with the following two changes quickly.

Section 9 (end)

OLD

   The peer-to-peer negotiation for the RTR message follows the	
   following order:	
				
   Initiator -->: Sets Control Flags it is capable to send for RTR	
				
   Responder <--: Sets Control Flags it is capable to receive for RTR	
				
   Initiator -->: The first message send MUST be a negotiated RTR

NEW

   The peer-to-peer negotiation for the RTR message follows the	
   following order:	
				
   Initiator -->: Sets Control Flags to indicate Initiator-supported forms of RTR	
				
   Responder <--: Sets Control Flags to indicate Responder-supported forms of RTR	
				
   Initiator -->: If at least one form of RTR is supported by both Initiator and
	Responder, then the first message sent MUST be an RTR using a form supported
	by both the Initiator and Responder.

Section 10

OLD
      In
      this case initiator CAN attempt to establish RDMA connection using
      unenhanced MPA protocol as defined in [RFC5044] and let ULP deal
      with ORD and IRD, and peer-to-peer negotiations.

NEW

      In
      this case initiator MAY attempt to establish RDMA connection using
------------------------->^^^
      unenhanced MPA protocol as defined in [RFC5044] if this protocol is
	compatible with the application, and let ULP deal with ORD and IRD,
      and peer-to-peer negotiations.

Ordinarily, I'd write an RFC Editor Note for small changes like these, but they're sufficiently critical to interoperability that I'd prefer to have a new draft version that contains them.

Thanks,
--David


> -----Original Message-----
> From: Black, David
> Sent: Wednesday, December 22, 2010 9:26 PM
> To: storm@ietf.org
> Cc: Black, David
> Subject: MPA Draft - Review
> 
> WG Last Call on this draft has run its course:
> 
>                  Enhanced RDMA Connection Establishment
>                   draft-ietf-storm-mpa-peer-connect-02
> 
> I've done my review as a WG chair (and the person who will be shepherding this draft to the ADs and
> IESG):
> 
> - This draft is on the right track, but has open issues.
> - Another version of the draft will be needed.
> 
> Also, it would be greatly appreciated if a few people other than the authors could take a look at
> this draft.  We have a very good author team on this draft, whose expertise is beyond doubt, but
> more eyes on this draft would help.
> 
> [1] My primary concern is that Section 9 on interoperability is inadequate:
> 
>    An initiator SHOULD NOT use the Enhanced DDP Connection Establishment
>    formats or function codes when no enhanced functionality is desired.
> 
>    A responder SHOULD continue to accept the unenhanced connection
>    requests.
> 
> The good news is that the first sentence is ok.
> The bad news is that the second sentence has significant problems:
> 	- It uses SHOULD instead of MUST.
> 	- It doesn't lay out behavior for initiator and responder
> 		Revision mixes.
> IETF interoperability requirements are usually expressed with MUST, including backwards
> compatibility.  If interop with unenhanced implementations is only a SHOULD, that will need a
> convincing explanation.
> 
> There are 3 Initiator/Responder cases that need attention (New/Old, Old/New and New/New).  I think
> they lead to roughly the following:
> 
> New/Old:
> - Explain error or failure that the New Initiator will see because the Old responder
> 	doesn't support Revision 2 of the MPA protocol.
> - Explain what the Initiator does when it sees that error or failure.  The
> 	easiest approach is to always retry with Revision 1, but that won't work
> 	if the Initiator has to send an RTR (that's the "convincing explanation"
> 	for why backwards compatibility is not always possible).  The result
> 	might be two requirements:
> 	- If the Initiator has data to send, it MUST retry with Revision 1.
> 	- If the Initiator has no data to send, and hence has to send an RTR,
> 		the connection setup fails, the TCP connection closes and that
> 		failure MUST to be reported to the application.
> 
> Old/New:
> - If a responder receives a Revision 1 message, it MUST respond with a Revision 1 message.
> 
> New/New:
> - If a responder receives a Revision 2 message, it MUST respond with a Revision 2 message.
> 
> I found a few other concerns:
> 
> [B]In Section 7, we need to get the listing of all the SCTP function codes into one place.  Either
> repeat the definitions of codes 1-4 from RFC 5043, or create an IANA registry in Section 10 and list
> all 7 codes as its initial contents.
> 
> [C] In Section 8, what happens if the responder sends an IRD or ORD value that's different from the
> corresponding initiator value?  Is the responder allowed to increase the value that was sent?  An
> important case to cover is that the initiator sends a valid value (e.g., 0x2000) but the responder
> returns the 0x3FFF value indicating that negotiation is not supported.  Also, what is the behavior
> of an IRD or ORD that is set to 0x0000?
> 
> [D] In contrast, the Section 8 discussion of Control Flag functionality is in better shape.  It
> would be helpful to add a sentence or two indicating when the RTR occurs (Request ->, <- Reply, RTR
> ->), even though that is discussed earlier in the draft.  Also, it's necessary to state whether
> negotiation of RTR functionality commits the Initiator to using an RTR (e.g., suppose the initiator
> negotiates control flags to allow an RTR and instead sends an FULPDU with payload data after
> receiving the Reply - is that ok or is it an error?).
> 
> [E] Nit: In the definition of Control Flag A: ULPDU -> FULPDU
> 
> Thanks,
> --David
> ----------------------------------------------------
> David L. Black, Distinguished Engineer
> EMC Corporation, 176 South St., Hopkinton, MA  01748
> +1 (508) 293-7953             FAX: +1 (508) 293-7786
> david.black@emc.com        Mobile: +1 (978) 394-7754
> ----------------------------------------------------