Re: [storm] iSER draft
Tom Talpey <ttalpey@microsoft.com> Fri, 15 July 2011 18:16 UTC
Return-Path: <ttalpey@microsoft.com>
X-Original-To: storm@ietfa.amsl.com
Delivered-To: storm@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id EFF8221F8B61 for <storm@ietfa.amsl.com>; Fri, 15 Jul 2011 11:16:45 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -110.298
X-Spam-Level:
X-Spam-Status: No, score=-110.298 tagged_above=-999 required=5 tests=[AWL=-0.300, BAYES_00=-2.599, HTML_MESSAGE=0.001, J_CHICKENPOX_46=0.6, RCVD_IN_DNSWL_HI=-8, USER_IN_WHITELIST=-100]
Received: from mail.ietf.org ([64.170.98.30]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id nG-sOhmy4rRr for <storm@ietfa.amsl.com>; Fri, 15 Jul 2011 11:16:39 -0700 (PDT)
Received: from smtp.microsoft.com (smtp.microsoft.com [131.107.115.215]) by ietfa.amsl.com (Postfix) with ESMTP id 5366021F8B44 for <storm@ietf.org>; Fri, 15 Jul 2011 11:16:39 -0700 (PDT)
Received: from TK5EX14HUBC102.redmond.corp.microsoft.com (157.54.7.154) by TK5-EXGWY-E802.partners.extranet.microsoft.com (10.251.56.168) with Microsoft SMTP Server (TLS) id 8.2.176.0; Fri, 15 Jul 2011 11:16:38 -0700
Received: from TK5EX14MBXC111.redmond.corp.microsoft.com ([169.254.2.64]) by TK5EX14HUBC102.redmond.corp.microsoft.com ([157.54.7.154]) with mapi id 14.01.0323.002; Fri, 15 Jul 2011 11:16:38 -0700
From: Tom Talpey <ttalpey@microsoft.com>
To: Michael Ko <Michael@huaweisymantec.com>, Mallikarjun Chadalapaka <cbm@chadalapaka.com>, 'Caitlin Bestler' <cait@asomi.com>
Thread-Topic: [storm] iSER draft
Thread-Index: AQHMNlPpov6tD7xTq0WTfzkPhGmP2JTUcDZAgABph/mAAdAuAIATxsXggAFa2ACAAHJheIAAD/iAgAAmeC+AALC4gP//kWlMgAEM23A=
Date: Fri, 15 Jul 2011 18:16:38 +0000
Message-ID: <F83812DF4B59B9499C1BC978336D91745EE03EAD@TK5EX14MBXC111.redmond.corp.microsoft.com>
References: <BANLkTi=GVHUBdsZiwsRXxETd_rU=F8f85w@mail.gmail.com> <F83812DF4B59B9499C1BC978336D91745EDE207F@TK5EX14MBXC118.redmond.corp.microsoft.com> <971779FD6B314A40B1A3658E521C0D4A@china.huawei.com> <BANLkTik0rG2=orD0S0L3s62gBSJsLapA+w@mail.gmail.com> <F83812DF4B59B9499C1BC978336D91745EE0279D@TK5EX14MBXC111.redmond.corp.microsoft.com> <B443B9D1-754C-4D74-B43A-858A6031850A@asomi.com> <1680F0051D794095A86AF16343CAD400@china.huawei.com> <F83812DF4B59B9499C1BC978336D91745EE039F9@TK5EX14MBXC111.redmond.corp.microsoft.com> <70CC5C8CCDD74EA0A9CEFF6DDC8145ED@china.huawei.com> <SNT131-ds105B54D3D6E874C31C27A9A0490@phx.gbl> <D74343B13CC640229AB1AFCDEE9F9883@china.huawei.com>
In-Reply-To: <D74343B13CC640229AB1AFCDEE9F9883@china.huawei.com>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-originating-ip: [157.54.51.36]
Content-Type: multipart/alternative; boundary="_000_F83812DF4B59B9499C1BC978336D91745EE03EADTK5EX14MBXC111r_"
MIME-Version: 1.0
Cc: "storm@ietf.org" <storm@ietf.org>
Subject: Re: [storm] iSER draft
X-BeenThere: storm@ietf.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: Storage Maintenance WG <storm.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/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: Fri, 15 Jul 2011 18:16:46 -0000
This discussion is starting to fork, but I'll do my best to reply to the top of the thread. I'm glad we're making progress, but I don't think we're on the same page yet. In particular, I disagree with your statement that "for iWARP, the Steering Address is set to zero." The choice of addressing mode is not made on a per-protocol basis, it is a local issue on the initiator. If ZBVA mode is used, then the addressing mode is zero-based. However local verbs support several other modes, and the "steering address" is not at all constrained to be an "address". Depending on several factors, it can be a virtual address, a physical address, or a completely arbitrary value. To my reading, the new draft is proposing that an additional value be sent in the Control PDU header, to be added to the BufferOffset of the individual SCSI control PDU payload when the target performs RDMA Read or RDMA Write. To me, this value is not an address, and has no semantics beyond being an initiator-provided value needed to direct the expected RDMA, when it is performed by the target. Personally, I think it would be better defined as a "Base Offset", or "Tagged Base Offset", to which the BufferOffset is added to form the resulting TaggedOffset. There's no further requirement than to have the two values to add together. I think that any proposed addition of a connection attribute for "iWARP" or "offset" to the normative discussion is incorrect, for the reasons above. While it's true that iWARP may support addressing modes that another RDMA protocol may not, it's neither necessary or desirable to require iSER or iSCSI to change behavior depending on the lower RDMA layer. iSER is appropriately a transport adaptation layer, and should be defined in such a way as to be agnostic to the needs of the lower layer. So again, I would like to see: - Virtual Address renamed to agnostic term (perhaps) Base Offset - Clearly stated processing at the target to compute the necessary TaggedOffset - Avoidance of discussion of addressing mode requirements or local verb semantics. From: Michael Ko [mailto:Michael@huaweisymantec.com] Sent: Thursday, July 14, 2011 9:50 PM To: Mallikarjun Chadalapaka; Tom Talpey; 'Caitlin Bestler' Cc: storm@ietf.org Subject: Re: [storm] iSER draft Mallikarjun, Nice to hear from you! I have embedded my comments in your response. Mike ----- Original Message ----- From: Mallikarjun Chadalapaka<mailto:cbm@chadalapaka.com> To: 'Michael Ko'<mailto:Michael@huaweisymantec.com> ; Tom Talpey<mailto:ttalpey@microsoft.com> ; 'Caitlin Bestler'<mailto:cait@asomi.com> Cc: storm@ietf.org<mailto:storm@ietf.org> Sent: Thursday, July 14, 2011 6:26 PM Subject: RE: [storm] iSER draft I suggest we have to be explicit about the responsibilities of each protocol layer because the phrase "initiator side needs to translate the Tagged Offset" sounds vague to me. [mk] That statement is only meant to convey what would be done by the initiator if it uses address for referencing the buffer rather than using buffer offset to reference the buffer, and the Steering Address is not sent to the target as currently defined in RFC 5046. It does not appear in the spec. Also, it may be worth formalizing the notion of "if Virtual Address was used for this command" via a negotiated connection attribute. [mk] The use of the Steering Address is up to the RCaP. For iWARP, the Steering Address is set to zero. By adding the explanation (as I indicated in my previous note) on how the Tagged Offset is computed from the Steering Address and the Buffer Offset, it is up to the RCaP to determine what they want to do. If I followed this thread right, it seems like we are talking roughly about the following: 1) A shared iSCSI/iSER-level connection attribute (connection-scoped text key?) that indicates whether Steering Address ("Address") or Tagged Offset ("Offset") is required by the RCaP in the RDMA requests on the wire for that connection. How the RCaP API exposes this capability to its local iSER layer is implementation-dependent, and we do not need spec it. [mk] Both the Steering Address and the Tagged Offset will be required. When the Steering Address is set to zero, we have the iWARP mode of behavior as defined in RFC 5046. 2) If the connection attribute = "Offset:, [mk] I don't think a new connection attribute is needed. The RCaP just needs to set the Steering Address to the appropriate value. So for iWARP, set the Steering Address to zero. a) the semantic requirement on the RCaP layer on the initiator is that it treats the incoming RDMA memory references as offsets, and does the appropriate base+offset local translation for RDMA Reads and RDMA Writes. b) The initiator iSER layer must only use ZB-VA, and must set the Steering Address to 0 in appropriate control-type PDUs. c) The target iSER layer must assume that zero TO for the advertised STag points to the beginning of the initiator I/O Buffer in all the RDMA Writes and RDMA Reads that it issues (same as now). 3) If the connection attribute = "Address": a) the semantic requirement on the RCaP layer on the initiator is that it treats incoming RDMA memory references as complete Steering Addresses in RDMA Reads and RDMA Writes. b) The initiator iSER layer must use non-ZB-VA, and must set the Steering Address to the RCaP-API-returned Virtual Address in appropriate control-type PDUs. c) The target iSER layer must assume that the Steering Address for the advertised STag points to the beginning of the initiator I/O Buffer, and compute the Tagged Offset in all the RDMA Writes and RDMA Reads that it issues by adding the Steering Address to the Buffer Offset received from the Data_Descriptor of Datamover API. Mallikarjun From: storm-bounces@ietf.org<mailto:storm-bounces@ietf.org> [mailto:storm-bounces@ietf.org]<mailto:[mailto:storm-bounces@ietf.org]> On Behalf Of Michael Ko Sent: Thursday, July 14, 2011 1:53 PM To: Tom Talpey; Caitlin Bestler Cc: storm@ietf.org<mailto:storm@ietf.org> Subject: Re: [storm] iSER draft For clarity, I need to update in the next revision of the spec everywhere where "Tagged Offset", "Steering Tag", etc. are mentioned to specify how the Tagged Offset is computed from the "Steering Address" and the buffer offset. So for example, in the example you cited in section 7.3.5, the target computes the Tagged Offset using the Steering Address and the Buffer Offset. For iWARP, the Steering Address is zero, and so the Tagged Offset is the Buffer Offset in the SCSI Data-in PDU as defined in RFC 5046. Mike ----- Original Message ----- From: Tom Talpey To: Michael Ko ; Caitlin Bestler Cc: Alexander Nezhinsky ; storm@ietf.org<mailto:storm@ietf.org> Sent: Thursday, July 14, 2011 1:16 PM Subject: RE: [storm] iSER draft Changing the name doesn't address the core issues here. There are no processing rules defined in the draft to support the arithmetic you describe below, or even to use the Steering/Virtual Address. For example, section 7.3.5 states the target MUST use the Buffer Offset of the Data-In PDU as the Tagged Offset of an RDMA Write. Where does the new Steering Address in the control PDU header get folded into the Tagged Offset? And what protocol state would trigger the target to do so, including perform the arithmetic? Same question for several other sections. From: Michael Ko [mailto:Michael@huaweisymantec.com]<mailto:[mailto:Michael@huaweisymantec.com]> Sent: Thursday, July 14, 2011 2:39 PM To: Caitlin Bestler; Tom Talpey Cc: Alexander Nezhinsky; storm@ietf.org<mailto:storm@ietf.org> Subject: Re: [storm] iSER draft When "Virtual Address" is not used, as in iWARP, the initiator side needs to translate the "Tagged Offset" which is just the offset into the buffer, into a usable address by adding it to the starting base address of the buffer. If the starting base address is communicated to the target side, as is done in some RCaPs, then the "Tagged Offset" is the usable address itself at the initiator where data is to be fetched or stored. Alex suggested that perhaps we can change the name "Virtual Address" to "Steering Address". Then it can be defined in the glossary without tripping over the common term "virtual address". Mike ----- Original Message ----- From: Caitlin Bestler To: Tom Talpey Cc: Alexander Nezhinsky ; Michael Ko ; storm@ietf.org<mailto:storm@ietf.org> Sent: Wednesday, July 13, 2011 9:49 PM Subject: Re: [storm] iSER draft On Jul 13, 2011, at 8:12 AM, Tom Talpey wrote: > Yes, understood on the ZBVA/Infiniband issue. Regarding the VA term's presence in an earlier draft, I did not see it in RFC5046 and I did not review the expired draft, so consider these comments to be on the overall change, not the last revision. > > Let me try a different approach to perhaps make myself clearer. > > First, it seems to me that a "virtual address" has no real meaning to the network protocol. It begins, perhaps, as some value in an address space on the initiator, but it's not meaningful on the target in this way, it's only used to request that the remote RNIC perform a transfer to that originally registered remote address. So calling it a Virtual Address as an iSER protocol object seems, to me, an artificial and somewhat leading convention. > > Second, the Virtual Address goes out from the initiator to the target in a Control PDU, but where does it come back? The RDMA Read or Write as depicted in (xx) shows only a Tagged Offset. So, it's not clear what its protocol meaning is. > > Third, I don't ever see a Tagged Buffer described by a fully qualified four-tuple. I see it appearing as either { Stag, TO, length } or { Stag, VA, length }, depending on the addressing mode. > > I think the non-ZBVA mode is really just a special case of the existing one, but where the meaning of TO has changed from a small offset to some other token, generated and managed only at the initiator. So, it seems artificial to define it as distinct, and document it as possessing some new properties. Isn't it just a Target Offset, still? > > Tom. > > I agree, so far we have not seen a protocol justification for the need to add "Virtual Address" to the glossary as something distinct from Target Offset for the purpose of defining an IETF protocol. I am sympathetic to the interoperability issues raised, but I don't think those can justify something that has *no* justification in the protocol. If someone could site a class of implementation where there is a real need for this distinction in an iSER adapter, but as far as I can see the adapters have to be able to translate to TO *anyway* in order to use an RDMA Write or RDMA Read. Local Interface compatibility with IB can make a *lot* of sense, but why does it have to make its way into the *wire* protocol? -- Caitlin Bestler cait@asomi.com<mailto:cait@asomi.com> http://www.asomi.com/CaitlinBestlerResume.html
- [storm] iSER draft Alexander Nezhinsky
- Re: [storm] iSER draft Tom Talpey
- Re: [storm] iSER draft Michael Ko
- Re: [storm] iSER draft Caitlin Bestler
- Re: [storm] iSER draft Michael Ko
- Re: [storm] iSER draft Alexander Nezhinsky
- Re: [storm] iSER draft Tom Talpey
- Re: [storm] iSER draft Caitlin Bestler
- Re: [storm] iSER draft Michael Ko
- Re: [storm] iSER draft Tom Talpey
- Re: [storm] iSER draft Michael Ko
- Re: [storm] iSER draft Mallikarjun Chadalapaka
- Re: [storm] iSER draft Michael Ko
- Re: [storm] iSER draft Tom Talpey
- Re: [storm] iSER draft Mallikarjun Chadalapaka