INTERNET DRAFT Mallikarjun Chadalapaka draft-chadalapaka-iwarp-da-02.txt HP John Hufferd IBM Julian Satran IBM Hemal Shah Intel Expires January 2005 Datamover Architecture for iSCSI (DA) 1 Status of this Memo By submitting this Internet-Draft, we certify that any applicable patent or other IPR claims of which we are aware have been disclosed, or will be disclosed, and any of which we become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than a "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. ^Chadalapaka et al. Expires January, 2005 [Page 1] ^Internet-Draft DA 16 July 2004 2 Abstract iSCSI is a SCSI transport protocol that maps the SCSI family of application protocols onto TCP/IP. The Datamover Architecture for iSCSI (DA) defines an abstract model in which the movement of data between iSCSI end nodes is logically separated from the rest of the iSCSI protocol in order to allow iSCSI to adapt to innovations available in new IP transports. The new Datamover protocol provides a reliable transport for all iSCSI PDUs, but actually moves the data required for certain iSCSI PDUs without involving the remote iSCSI layer itself. This document begins with an introduction of a few new abstractions, defines a layered architecture for iSCSI and Datamover protocols, and then models the interactions within an iSCSI end node between the iSCSI layer and the Datamover layer that happen in order to transparently perform remote data movement within an IP fabric. It is intended that this definition would help map iSCSI to generic RDMA-capable IP fabrics in the future comprising TCP, SCTP, and possibly other underlying network transport layers. ^Chadalapaka et al. Expires January, 2005 [Page 2] ^Internet-Draft DA 16 July 2004 Table of Contents 1 Status of this Memo ....................................1 2 Abstract ...............................................2 3 Definitions and acronyms ...............................6 3.1 Definitions ............................................6 3.2 Acronyms ...............................................6 4 Motivation .............................................8 5 Architectural layering of iSCSI and Datamover layers ..10 6 Design Overview .......................................12 7 Architectural Concepts ................................14 7.1 iSCSI PDU types .......................................14 7.1.1 iSCSI data-type PDUs.................................14 7.1.2 iSCSI control-type PDUs..............................15 7.2 Data_Descriptor .......................................15 7.3 Connection_Handle .....................................15 7.4 Operational Primitive .................................16 7.5 Transport Connection ..................................16 8 Datamover layer and Datamover protocol ................17 9 Operational Primitives provided by the Datamover layer 19 9.1 Send_Control ..........................................19 9.2 Put_Data ..............................................20 9.3 Get_Data ..............................................20 9.4 Allocate_Connection_Resources .........................21 9.5 Deallocate_Connection_Resources .......................22 9.6 Enable_Datamover ......................................23 9.7 Connection_Terminate ..................................23 9.8 Notice_Key_Values .....................................24 9.9 Deallocate_Task_Resources .............................24 10 Operational Primitives provided by the iSCSI layer ....25 10.1 Control_Notify.......................................25 10.2 Connection_Terminate_Notify..........................26 10.3 Data_Completion_Notify...............................26 10.4 Data_ACK_Notify......................................27 11 Datamover Interface (DI) ..............................29 11.1 Overview.............................................29 11.2 Interactions for handling asynchronous notifications.29 11.2.1 Connection termination .............................29 11.2.2 Data transfer completion ...........................29 11.2.3 Data acknowledgement ...............................30 11.3 Interactions for sending an iSCSI PDU................31 11.3.1 SCSI Command .......................................31 11.3.2 SCSI Response ......................................32 11.3.3 Task Management Function Request ...................32 11.3.4 Task Management Function Response ..................32 11.3.5 SCSI Data-out & SCSI Data-in .......................33 11.3.6 Ready To Transfer (R2T) ............................33 11.3.7 Asynchronous Message ...............................34 11.3.8 Text Request .......................................34 11.3.9 Text Response ......................................34 ^Chadalapaka et al. Expires January, 2005 [Page 3] ^Internet-Draft DA 16 July 2004 11.3.10 Login Request ....................................34 11.3.11 Login Response ...................................35 11.3.12 Logout Command ...................................36 11.3.13 Logout Response ..................................36 11.3.14 SNACK Request ....................................36 11.3.15 Reject ...........................................36 11.3.16 NOP-Out ..........................................37 11.3.17 NOP-In ...........................................37 11.4 Interactions for receiving an iSCSI PDU..............37 11.4.1 SCSI Command .......................................37 11.4.2 SCSI Response ......................................38 11.4.3 Task Management Function Request ...................38 11.4.4 Task Management Function Response ..................38 11.4.5 SCSI Data-out & SCSI Data-in .......................38 11.4.6 Ready To Transfer (R2T) ............................39 11.4.7 Asynchronous Message ...............................39 11.4.8 Text Request .......................................39 11.4.9 Text Response ......................................40 11.4.10 Login Request ....................................40 11.4.11 Login Response ...................................40 11.4.12 Logout Command ...................................40 11.4.13 Logout Response ..................................41 11.4.14 SNACK Request ....................................41 11.4.15 Reject ...........................................41 11.4.16 NOP-Out ..........................................41 11.4.17 NOP-In ...........................................41 12 Security Considerations ...............................42 13 IANA Considerations ...................................43 14 References and Bibliography ...........................44 14.1 Normative References.................................44 14.2 Informative References...............................44 15 Authors' Addresses ....................................45 16 Acknowledgements ......................................46 17 Appendix ..............................................50 17.1 Design considerations for a Datamover protocol.......50 17.2 Examples of Datamover interactions...................51 18 Full Copyright Statement ..............................61 19 Intellectual Property Statement .......................62 Table of Figures Figure 1 Datamover Architecture diagram, with the RDMAP example.....................................................10 Figure 2 A successful iSCSI login on initiator..............52 Figure 3 A successful iSCSI login on target.................52 Figure 4 A failed iSCSI login on initiator..................53 Figure 5 A failed iSCSI login on target.....................53 Figure 6 iSCSI does not enable the Datamover................54 Figure 7 A normal iSCSI connection termination..............55 ^Chadalapaka et al. Expires January, 2005 [Page 4] ^Internet-Draft DA 16 July 2004 Figure 8 An abnormal iSCSI connection termination...........55 Figure 9 A SCSI Write data transfer.........................57 Figure 10 A SCSI Read data transfer.........................58 Figure 11 A SCSI Read data acknowledgement..................59 Figure 12 Task resource cleanup on abort...................60 ^Chadalapaka et al. Expires January, 2005 [Page 5] ^Internet-Draft DA 16 July 2004 2 Definitions and acronyms 2.1 Definitions I/O Buffer ¡ A buffer that is used in a SCSI Read or Write operation so SCSI data may be sent from or received into that buffer. Datamover protocol ¡ A Datamover protocol is a data transfer wire protocol for iSCSI that meets the requirements stated in section 7. Datamover layer ¡ A Datamover layer is a protocol layer within an end node that implements the Datamover protocol. Datamover-assisted - An iSCSI connection is said to be "Datamover-assisted" when a Datamover layer is enabled for moving control and data information on that connection. 2.2 Acronyms Acronym Definition ------------------------------------------------------------- - DA Datamover Architecture DDP Direct Data Placement Protocol DI Datamover Interface IANA Internet Assigned Numbers Authority IETF Internet Engineering Task Force I/O Input - Output IP Internet Protocol iSCSI Internet SCSI iSER iSCSI Extensions for RDMA ITT Initiator Task Tag ^Chadalapaka et al. Expires January, 2005 [Page 6] ^Internet-Draft DA 16 July 2004 LO Leading Only MPA Marker PDU Aligned Framing for TCP PDU Protocol Data Unit RDDP Remote Direct Data Placement RDMA Remote Direct Memory Access R2T Ready To Transfer R2TSN Ready To Transfer Sequence Number RDMA Remote Direct Memory Access RDMAP Remote Direct Memory Access Protocol RFC Request For Comments SAM SCSI Architecture Model SCSI Small Computer Systems Interface SN Sequence Number SNACK Selective Negative Acknowledgment - also Sequence Number Acknowledgement for data TCP Transmission Control Protocol TTT Target Transfer Tag ^Chadalapaka et al. Expires January, 2005 [Page 7] ^Internet-Draft DA 16 July 2004 3 Motivation There are new industry and standards initiatives to develop Remote Direct Memory Access (RDMA) and Remote Direct Data Placement (RDDP) technologies to work over IP fabrics. The principal value proposition of these technologies is that they enable one end node to place data in the final intended buffer on the remote end node, thus eliminating the data copy that traditionally happens in the receive path to move the data to the final buffer. The data copy avoidance in turn eliminates unnecessary memory bandwidth consumption, substan- tially decreases the reassembly buffer size requirements, and preserves CPU cycles that would otherwise be spent in copying. The iSCSI specification ([RFC3720]) defines a very detailed data transfer model that employs SCSI Data-In PDUs, SCSI Data-Out PDUs, and R2T PDUs, in addition to the SCSI Command and SCSI Response PDUs that respectively create and conclude the task context for the data transfer. In the traditional iSCSI model, the iSCSI protocol layer plays the central role in pacing the data transfer and carrying out the ensuing data transfer itself. An alternative architecture would be for iSCSI to delegate a large part of this data transfer role to a separate protocol layer exclusively designed to move data, which in turn is possibly aided by a data movement and placement technology such as RDMA. If iSCSI were operating in such RDMA environments, iSCSI would be shielded from the low-level data transfer mechanics but would only be privy to the conclusion of the requested data transfer Thus, there would be an effective "off- loading" of the work that an iSCSI protocol layer is expected to perform, compared to today's iSCSI end nodes. For such RDMA environments, it is highly desirable that there be a standard architecture to separate the data movement part of the iSCSI protocol definition from the rest of the iSCSI functionality. This architecture precisely defines what a Datamover layer is and also describes the model of interactions between the iSCSI layer and the Datamover layer (section 7). In order to satisfy this need, this document presents a Datamover Architecture (DA) and also summarizes a reasonable model for interactions between the iSCSI layer and the Datamover layer for each of the iSCSI PDUs that are defined in [RFC3720]. Note that while DA is motivated by the advent of RDMA over TCP/IP technology, the architecture is ^Chadalapaka et al. Expires January, 2005 [Page 8] ^Internet-Draft DA 16 July 2004 not dependent on RDMA in its design. DA is intended to be a generic architectural framework for allowing different types of Datamovers based on different types of RDMA and transport protocols. Adoption of this model will help iSCSI proliferate into more environments. ^Chadalapaka et al. Expires January, 2005 [Page 9] ^Internet-Draft DA 16 July 2004 4 Architectural layering of iSCSI and Datamover layers Figure 1 illustrates an example of the architectural layering of iSCSI and Datamover layers, in conjunction with a TCP/IP implementation of RDMAP/DDP layers in an iSCSI end node. Note that RDMAP/DDP/MPA, and TCP protocol layers are shown here only as an example and in reality, DA is completely oblivious to protocol layers below the Datamover layer. The RDMAP/DDP/MPA protocol stack provides a generic transport service with direct data placement. There is no need to tailor the implementation of this protocol stack to the specific ULP to benefit from these services. Initiator stack Target stack +----------------+ SCSI application +----------------+ | SCSI Layer | protocols | SCSI Layer | +----------------+ +----------------+ ^ ^ | | v v +----------------+ iSCSI protocol +----------------+ | iSCSI Layer | (excluding data | iSCSI Layer | +----------------+ movement) +----------------+ ^ ^ -- ---+-- ---- ---- -- DI -- ---- ---- ----+--- ---- v v +----------------+ a Datamover +----------------+ | Datamover Layer| protocol | Datamover Layer| +----------------+ +----------------+ ^ ^ +-------+----------+ +---------+-----------+ | v | | v | |+---------------+ | | +-----------------+ | || RDMAP/DDP/MPA | | RDMAP/DDP/MPA | | RDMAP/DDP/MPA | | || Layers | | protocols | | Layers | | |+---------------+ | | +-----------------+ | | ^ | | ^ | | | network | | | network | | | transport| | | transport | | v | | v | |+---------------+ | | +----------------+ | || TCP Layer | | TCP protocol | | TCP Layer | | |+---------------+ | | +----------------+ | | ^ | | ^ | +-------+----------+ +---------+-----------+ +------------------------------------------+ Figure 1 Datamover Architecture diagram, with the RDMAP example ^Chadalapaka et al. Expires January, 2005 [Page 10] ^Internet-Draft DA 16 July 2004 The scope of this document is limited to: 1. Defining the notion of a Datamover layer and a Datamover protocol (section 7), 2. Defining the functionality distribution between the iSCSI layer and the Datamover layer along with the communication model between the two (Operational Primitives), and, 3. Modeling the interactions between the blocks labeled as "iSCSI Layer" and "Datamover Layer" in Figure 1 ¡ i.e. defining the interface labeled as "DI" in the figure - for each defined iSCSI PDU, based on the Operational Primitives. ^Chadalapaka et al. Expires January, 2005 [Page 11] ^Internet-Draft DA 16 July 2004 6 Design Overview This document discusses and defines a model for interactions between the iSCSI layer and a "Datamover layer" (see section 7) operating within an iSCSI end node, presumably communicating with one or more iSCSI end nodes with similar layering. The model for interactions for handling different iSCSI operations is called the "Datamover Interface" (DI, section 10), while the architecture itself is called "Datamover Architecture" (DA). It is likely that the architecture will have implications on the Datamover wire protocols as DA places certain requirements and functionality expectations on the Datamover layer. However, this document itself neither defines any new wire protocol for the Datamover layer, nor any potential modifications to the iSCSI wire protocol to employ the Datamover layer. The scope of this document is strictly limited to specifying the architectural framework and the minimally required interactions that happen within an iSCSI end node to leverage the Datamover layer. The design ideas behind DA can be summarized thus ¡ 1) DA defines an abstract procedural interface definition of iSCSI layer's interactions with a Datamover layer below ¡ i.e. DA models the interactions between the logical "bottom" interface of iSCSI and the logical "top" interface of a Datamover. 2) DA guides the wire protocol for a Datamover layer by defining the iSCSI knowledge that the Datamover layer may utilize in its protocol definition (as an example, this draft completely limits the notion of "iSCSI session" to the iSCSI layer). 3) DA is designed to allow implementing the Datamover layer either in hardware or in software. 4) DA is not a wire protocol spec, but an architecture that also models the interactions between iSCSI and Datamover layers operating within an iSCSI end node. 5) DA by design seeks to model the iSCSI-Datamover interactions in a way that the modeling is independent of the specifics of either a particular iSCSI revision, or a specific instantiation of a Datamover layer. ^Chadalapaka et al. Expires January, 2005 [Page 12] ^Internet-Draft DA 16 July 2004 6) DA introduces and relies on the notion of a defined set of Operational Primitives (could be seen as entry point definitions in implementation terms) provided by each layer to the other to carry out the request-response interactions. 7) DA is intended to allow Datamover protocol definitions with minimal changes to existing iSCSI implementations. 8) DA is designed to allow the iSCSI layer to completely rely on the Datamover layer for all the data transport needs. 9) DA models the architecturally required minimal interactions between an operational iSCSI layer and a Datamover layer to realize the iSCSI-transparent data movement. There may be several other interactions in a typical implementation in order to bootstrap a Datamover layer (or an iSCSI layer) into operation, and they are outside the scope of this document. Note that in summary, DA is architected to support many different Datamover protocols operating under the iSCSI layer. One such example of a Datamover protocol is iSER ([iSER]). ^Chadalapaka et al. Expires January, 2005 [Page 13] ^Internet-Draft DA 16 July 2004 7 Architectural Concepts 7.1 iSCSI PDU types This section defines the iSCSI PDU classification terminology, as defined and used in this document. Out of the set of legal iSCSI PDUs defined in [RFC3720], as we will see in section 6.1.1, the iSCSI layer does not request a SCSI Data-Out PDU carrying solicited data for transmission across the Datamover Interface per this architecture. For this reason, the SCSI Data-Out PDU carrying solicited data is excluded in the iSCSI PDU classification we introduce in this section. The rest of the legal iSCSI PDUs that may be exchanged across the Datamover Interface are defined to consist of two classes: 1) iSCSI data-type PDUs 2) iSCSI control-type PDUs 7.1.1 iSCSI data-type PDUs An iSCSI data-type PDU is defined as an iSCSI PDU that causes data transfer, transparent to the remote iSCSI layer, to take place between the peer iSCSI nodes on a full feature phase iSCSI connection. A data-type PDU, when requested for transmission by the sender iSCSI layer, results in the associated data transfer without the participation of the remote iSCSI layer, i.e. the PDU itself is not delivered as- is to the remote iSCSI layer. The following iSCSI PDUs constitute the set of iSCSI data-type PDUs ¡ 1) SCSI Data-In PDU 2) R2T PDU In an iSCSI end node structured as an iSCSI layer and a Datamover layer as defined in this document, the solicitation for Data-out (i.e. R2T PDU) is not delivered to the initiator iSCSI layer, per the definition of an iSCSI data-type PDU. The data transfer is instead performed via the mechanisms known to the Datamover layer (e.g. RDMA Read). This in turn implies that a SCSI Data-Out PDU for solicited data is never requested for transmission across the Datamover Interface at the initiator. ^Chadalapaka et al. Expires January, 2005 [Page 14] ^Internet-Draft DA 16 July 2004 7.1.2 iSCSI control-type PDUs Any iSCSI PDU that is not an iSCSI data-type PDU and also not a solicited SCSI Data-out PDU is defined as an iSCSI control- type PDU. Specifically, it is to be noted that SCSI Data-Out PDUs for unsolicited Data are defined as iSCSI control-type PDUs. 7.2 Data_Descriptor A Data_Descriptor is an information element that describes an iSCSI/SCSI data buffer, provided by the iSCSI layer to its local Datamover layer or by the Datamover layer to its local iSCSI layer for identifying the data associated respectively with the requested or completed operation. In implementation terms, a Data_Descriptor may be a scatter- gather list describing a local buffer, the exact structure of which is subject to the constraints imposed by the operating environment on the local iSCSI node. 7.3 Connection_Handle A Connection_Handle is an information element that identifies the particular iSCSI connection for which an inbound or outbound iSCSI PDU is intended. A connection handle is unique for a given pair of an iSCSI layer instance and a Datamover layer instance. The Connection_Handle qualifier is used in all invocations of any Operational Primitive for connection identification. Note that the Connection_Handle is conceptually different from the Connection Identifier (CID) defined by the iSCSI specification. While the CID is a unique identifier of an iSCSI connection within an iSCSI session, the uniqueness of the Connection_Handle extends to the entire iSCSI layer instance coupled with the Datamover layer instance, across possibly multiple iSCSI sessions. ^Chadalapaka et al. Expires January, 2005 [Page 15] ^Internet-Draft DA 16 July 2004 In implementation terms, a Connection_Handle could be an opaque identifier exchanged between the iSCSI layer and the Datamover layer at the connection login time. One may also consider it to be similar in scope of uniqueness to a socket identifier. The exact structure and modalities of exchange of a Connection_Handle between the two layers is implementation-specific. 7.4 Operational Primitive An Operational Primitive, in this document, is an abstract functional interface procedure that requests another layer to perform a specific action on the requestor's behalf or notifies the other layer of some event. The Datamover Interface between an iSCSI layer instance and a Datamover layer instance within an iSCSI end node uses a set of Operational Primitives to define the functional interface between the two layers. Note that not every invocation of an Operational Primitive may elicit a response from the requested layer. This document describes the types of Operational Primitives that are implicitly required and provided by the iSCSI protocol layer as defined in [RFC3720], and the semantics of these Primitives. Note that ownership of buffers and data structures is likely to be exchanged between the iSCSI layer and its local Datamover layer in invoking the Operational Primitives defined in this architecture. The buffer management details, including how buffers are allocated and released, are implementation-specific and thus are outside the scope of this document. 7.5 Transport Connection The term "Transport Connection" is used in this document as a generic term to represent the end-to-end logical connection as defined by the underlying reliable transport protocol. For this revision of this document, a Transport Connection means only a TCP connection. ^Chadalapaka et al. Expires January, 2005 [Page 16] ^Internet-Draft DA 16 July 2004 8 Datamover layer and Datamover protocol This section introduces the notion of a "Datamover layer" and "Datamover protocol" as meant in this document, and defines the requirements on a Datamover protocol. A Datamover layer is the implementation component that realizes a Datamover protocol functionality in an iSCSI- capable end node, in communicating with other iSCSI end nodes with similar capabilities. More specifically, a "Datamover layer" MUST provide the following functionality and the "Datamover protocol" MUST consist of the wire protocol required to realize the following functionality ¡ 1) guarantee that all the necessary data transfers take place when the local iSCSI layer requests transmitting a command (in order to complete a SCSI command, for an initiator),or sending/receiving an iSCSI data sequence (in order to complete part of a SCSI command, for a target). 2) transport an iSCSI control-type PDU as-is to the peer Datamover layer when requested to do so by the local iSCSI layer. 3) provide notification and delivery to the iSCSI layer upon arrival of an iSCSI control-type PDU. 4) provide an end-to-end data acknowledgement of SCSI read data to the target iSCSI layer, when requested. 5) provide an asynchronous notification upon completion of a requested data transfer operation that moved data without involving the iSCSI layer. 6) place the SCSI data into the I/O buffers or pick up the SCSI data for transmission out of the data buffers that the iSCSI layer had requested to be used for a SCSI I/O. 7) guarantee an error-free (i.e. must have at least the same level of assurance of data integrity as the CRC32C iSCSI data digest), reliable, in-order delivery transport mechanism over IP fabrics in performing the data transfer, and asynchronously notify the iSCSI layer upon iSCSI connection termination. ^Chadalapaka et al. Expires January, 2005 [Page 17] ^Internet-Draft DA 16 July 2004 Note that this architecture expects that each compliant Datamover protocol will define the precise means of satisfying the requirements specified in this section. ^Chadalapaka et al. Expires January, 2005 [Page 18] ^Internet-Draft DA 16 July 2004 9 Operational Primitives provided by the Datamover layer While the iSCSI specification itself does not have a notion of Operational Primitives, any iSCSI layer implementing the iSCSI specification functionally requires the following Operational Primitives from its Datamover layer. These Operational Primitives are invoked by the iSCSI layer as appropriate. Unless otherwise stated, all the following Operational Primitives may be used both on the initiator side and the target side. In general programming terminology, this set of Operational Primitives may be construed as "down calls". 1) Send_Control 2) Put_Data 3) Get_Data 4) Allocate_Connection_Resources 5) Deallocate_Connection_Resources 6) Enable_Datamover 7) Connection_Terminate 8) Notice_Key_Values 9) Deallocate_Task_Resources 9.1 Send_Control Input qualifiers: Connection_Handle, iSCSI PDU-specific qualifiers Return Results: Not specified. An iSCSI layer requests its local Datamover layer to transmit an iSCSI control-type PDU to the peer iSCSI layer operating in the remote iSCSI node by this Operational Primitive. The Datamover layer performs the requested operation, and may add its own protocol headers in doing so. The iSCSI layer MUST NOT invoke the Send_Control Operational Primitive on an iSCSI connection that is not yet Datamover-assisted. ^Chadalapaka et al. Expires January, 2005 [Page 19] ^Internet-Draft DA 16 July 2004 An initiator iSCSI layer requesting the transfer of a SCSI command PDU or a target iSCSI layer requesting the transfer of a SCSI response PDU are examples of invoking the Send_Control Operational Primitive. 9.2 Put_Data Input qualifiers: Connection_Handle, contents of a SCSI Data- In PDU header, Data_Descriptor, Notify_Enable Return Results: Not specified. An iSCSI layer requests its local Datamover layer to transmit the data identified by the Data_Descriptor for the SCSI Data- In PDU to the peer iSCSI layer on the remote iSCSI node by this Operational Primitive. The Datamover layer performs the operation by using its own protocol means, completely transparent to the remote iSCSI layer. The iSCSI layer MUST NOT invoke the Put_Data Operational Primitive on an iSCSI connection that is not yet Datamover-assisted. The Notify_Enable qualifier is used to request the local Datamover layer to generate or to not generate the eventual local completion notification to the iSCSI layer for this Put_Data invocation. For detailed semantics of this qualifier, see section 9.3. A Put_Data Primitive may only be invoked by an iSCSI layer on the target to its local Datamover layer. A target iSCSI layer requesting the transfer of an iSCSI read data sequence (also known as a read burst) is an example of invoking the Put_Data Operational Primitive. 9.3 Get_Data Input qualifiers: Connection_Handle, contents of an R2T PDU, Data_Descriptor, Notify_Enable ^Chadalapaka et al. Expires January, 2005 [Page 20] ^Internet-Draft DA 16 July 2004 Return Results: Not specified. An iSCSI layer requests its local Datamover layer to retrieve certain data identified by the R2T PDU from the peer iSCSI layer on the remote iSCSI node into the buffer identified by the Data_Descriptor by invoking this Operational Primitive. The Datamover layer performs the operation by using its own protocol means, completely transparent to the remote iSCSI layer. The iSCSI layer MUST NOT invoke the Get_Data Operational Primitive on an iSCSI connection that is not yet Datamover-assisted. The Notify_Enable qualifier is used to request the local Datamover layer to generate or to not generate the eventual local completion notification to the iSCSI layer for this Get_Data invocation. For detailed semantics of this qualifier, see section 9.3. A Get_Data Primitive may only be invoked by an iSCSI layer on the target to its local Datamover layer. A target iSCSI layer requesting the transfer of an iSCSI write data sequence (also known as a write burst) is an example of invoking the Get_Data Operational Primitive. 9.4 Allocate_Connection_Resources Input qualifiers: Connection_Handle[, Resource_Descriptor ] Return Results: Status. By invoking this Operational Primitive, an iSCSI layer requests its local Datamover layer to perform all the Datamover-specific resource allocations required for the full feature phase of an iSCSI connection. The Connection_Handle identifies the connection the iSCSI layer is requesting the resource allocation for in order to eventually transition the connection to be a Datamover-assisted iSCSI connection. Note that the Datamover layer however does not allocate any Datamover-specific task-level resources upon invocation of this Primitive. ^Chadalapaka et al. Expires January, 2005 [Page 21] ^Internet-Draft DA 16 July 2004 An iSCSI layer, in addition, optionally specifies the implementation-specific resource requirements for the iSCSI connection to the Datamover layer, by passing an input qualifier called Resource_Descriptor. The exact structure of a Resource_Descriptor is implementation-dependent, and hence structurally opaque to DA. A return result of Status=success means that the Allocate_Connection_Resources invocation corresponding to that Connection_Handle succeeded. If an Allocate_Connection_Resources invocation is made for a Connection_Handle for which an earlier invocation succeeded, the return Status must be success and the request will be ignored by the Datamover layer. A return result of Status=failure means that the Allocate_Connection_Resources invocation corresponding to that Connection_Handle failed. There MUST NOT be more than one Allocate_Connection_Resources Primitive invocation outstanding for a given Connection_Handle at any time. The iSCSI layer must invoke the Allocate_Connection_Resources Primitive before the invocation of the Enable_Datamover Primitive. 9.5 Deallocate_Connection_Resources Input qualifiers: Connection_Handle Return Results: Not specified. By invoking this Operational Primitive, an iSCSI layer requests its local Datamover layer to deallocate all the Datamover-specific resources that may have been allocated earlier for the Transport Connection identified by the Connection_Handle. The iSCSI layer may invoke this Operational Primitive when the Datamover-specific resources associated with the Connection_Handle are no longer necessary (such as the Login failure of the corresponding iSCSI connection). ^Chadalapaka et al. Expires January, 2005 [Page 22] ^Internet-Draft DA 16 July 2004 9.6 Enable_Datamover Input qualifiers: Connection_Handle, Transport_Connection_Descriptor [, Final_Login_Response_PDU] Return Results: Not specified. By invoking this Operational Primitive, an iSCSI layer requests its local Datamover layer to assist all further iSCSI exchanges on the iSCSI connection (i.e. to make the connection Datamover-assisted) identified by the Connection_Handle, for which the Datamover-specific resource allocation was earlier made. The iSCSI layer MUST NOT invoke the Enable_Datamover Operational Primitive for an iSCSI connection unless there was a corresponding prior resource allocation. The Final_Login_Response_PDU input qualifier is applicable only for a target, and contains the final Login Response that concludes the iSCSI Login phase and which must be sent as a byte stream as expected by the initiator iSCSI layer. When this qualifier is used, the target-Datamover layer MUST transmit this final Login Response before Datamover assistance is enabled for the Transport Connection. The iSCSI layer identifies the specific Transport Connection associated with the Connection_Handle to the Datamover layer by specifying the Transport_Connection_Descriptor. The exact structure of this Descriptor is implementation-dependent. 9.7 Connection_Terminate Input qualifiers: Connection_Handle Return Results: Not specified. By invoking this Operational Primitive, an iSCSI layer requests its local Datamover layer to terminate the Transport Connection and deallocate all the connection and task resources associated with the Connection_Handle. When this Operational Primitive invocation returns to the iSCSI layer, the iSCSI layer may assume the full ownership of all the iSCSI-level resources, e.g. I/O Buffers, associated with the connection. This Operational Primitive may be invoked only ^Chadalapaka et al. Expires January, 2005 [Page 23] ^Internet-Draft DA 16 July 2004 with a valid Connection_Handle and the Transport Connection associated with the Connection_Handle must already be Datamover-assisted. 9.8 Notice_Key_Values Input qualifiers: Connection_Handle, Number of keys, a list of Key-Value pairs Return Results: Not specified. By invoking this Operational Primitive, an iSCSI layer requests its local Datamover layer to take note of the negotiated values of the listed keys for the Transport Connection. This Operational Primitive may be invoked only with a valid Connection_Handle and the Key-Value pairs MUST be the current values that were successfully agreed upon by the iSCSI peers for the connection. The Datamover layer may use the values of the keys to aid the Datamover operation as it deems appropriate. The specific keys to be passed in as input qualifiers and the point(s) in time this Operational Primitive is invoked are implementation-dependent. 9.9 Deallocate_Task_Resources Input qualifiers: Connection_Handle, ITT Return Results: Not specified. By invoking this Operational Primitive, an iSCSI layer requests its local Datamover Layer to deallocate all Datamover-specific resources that earlier may have been allocated for the task identified by the ITT qualifier. The iSCSI layer uses this Operational Primitive during exception processing when one or more active tasks are to be terminated without corresponding SCSI Response PDUs. This Primitive MUST be invoked for each active task terminated without a SCSI Response PDU. This Primitive MUST NOT be invoked by the iSCSI layer when a SCSI Response PDU normally concludes a task. When a SCSI Response PDU normally concludes a task (even if the SCSI Status was not a success), the Datamover layer is assumed to have automatically deallocated all Datamover-specific task resources for that task. ^Chadalapaka et al. Expires January, 2005 [Page 24] ^Internet-Draft DA 16 July 2004 10 Operational Primitives provided by the iSCSI layer While the iSCSI specification itself does not have a notion of Operational Primitives, any iSCSI layer implementing the iSCSI specification would have to provide the following Operational Primitives to its local Datamover layer. These Operational Primitives are invoked by the Datamover layer as appropriate and when the iSCSI connection is Datamover- assisted. Unless otherwise stated, all the following Operational Primitives may be used both on the initiator side and the target side. In general programming terminology, this set of Operational Primitives may be construed as "up calls". 1) Control_Notify 2) Connection_Terminate_Notify 3) Data_Completion_Notify 4) Data_ACK_Notify 10.1 Control_Notify Input qualifiers: Connection_Handle, an iSCSI control-type PDU. Return Results: Not specified. A Datamover layer notifies its local iSCSI layer, via this Operational Primitive, of the arrival of an iSCSI control- type PDU from the peer Datamover layer on the remote iSCSI node. The iSCSI layer processes the control-type PDU as defined in [RFC3720]. A target iSCSI layer being notified of the arrival of a SCSI Command is an example of invoking the Control_Notify Operational Primitive. Note that implementations may choose to describe the "iSCSI control-type PDU" qualifier in this notification using a ^Chadalapaka et al. Expires January, 2005 [Page 25] ^Internet-Draft DA 16 July 2004 Data_Descriptor (section 6.2) and not necessarily one contiguous buffer. 10.2 Connection_Terminate_Notify Input qualifiers: Connection_Handle Return Results: Not specified. A Datamover layer notifies its local iSCSI layer on an unsolicited termination or failure of an iSCSI connection providing the Connection_Handle associated with the iSCSI Connection. The iSCSI Layer MUST consider the Connection_Handle to be invalid upon being so notified. The iSCSI layer processes the connection termination as defined in [RFC3720]. The Datamover layer MUST deallocate the connection and task resources associated with the terminated connection before notifying the iSCSI layer of the termination via this Operational Primitive. A target iSCSI layer being notified of the arrival of TCP RESET is an example of when the Connection_Terminate_Notify Operational Primitive is invoked. 10.3 Data_Completion_Notify Input qualifiers: Connection_Handle, ITT, SN Return Results: Not specified. A Datamover layer notifies its local iSCSI layer on completing the retrieval of the data or upon sending the data, as requested in a prior iSCSI data-type PDU, from/to the peer Datamover layer on the remote iSCSI node via this Operational Primitive. The iSCSI layer processes the operation as defined in [RFC3720]. SN may be either the DataSN associated with the SCSI Data-In PDU or R2TSN associated with the R2T PDU depending on the SCSI operation. Note that, for targets, a TTT (see [RFC3720]) could have been specified instead of an SN. However, the considered choice was to leave the SN to be the ^Chadalapaka et al. Expires January, 2005 [Page 26] ^Internet-Draft DA 16 July 2004 qualifier for two reasons ¡ a) it is generic and applicable to initiators and targets as well as Data-in and Data-out, and b) having both SN and TTT qualifiers for the notification was considered onerous on the Datamover layer, in terms of state maintenance for each completion notification. The implication of this choice is that iSCSI target implementations will have to adapt to using the ITT-SN tuple in associating the solicited data to the appropriate task, rather than the ITT-TTT tuple for doing the same. If Notify_Enable was set in either a Put_Data or a Get_Data invocation, the Datamover layer MUST invoke the Data_Completion_Notify Operational Primitive upon completing that requested data transfer. If the Notify_Enable was cleared in either a Put_Data or a Get_Data invocation, the Datamover layer MUST NOT invoke the Data_Completion_Notify Operational Primitive upon completing that requested data transfer. A Data_Completion_Notify invocation serves to notify the iSCSI layer of the Put_Data or Get_Data completion respectively. As earlier noted in sections 8.2 and 8.3, specific Datamover protocol definitions may restrict the usage scope of Put_Data and Get_Data, and thus implicitly the usage scope of Data_Completion_Notify. A target iSCSI layer being notified of the retrieval of a write data sequence is an example of invoking the Data_Completion_Notify Operational Primitive. 10.4 Data_ACK_Notify Input qualifiers: Connection_Handle, ITT, DataSN Return Results: Not specified. A target Datamover layer notifies its local iSCSI layer of the arrival of a previously requested data acknowledgement from the peer Datamover layer on the remote (initiator) iSCSI node via this Operational Primitive. The iSCSI layer processes the data acknowledgement notification as defined in [RFC3720]. ^Chadalapaka et al. Expires January, 2005 [Page 27] ^Internet-Draft DA 16 July 2004 A target iSCSI layer being notified of the arrival of a data acknowledgement for a certain SCSI Read data PDU is the only example of invoking the Data_ACK_Notify Operational Primitive. ^Chadalapaka et al. Expires January, 2005 [Page 28] ^Internet-Draft DA 16 July 2004 11 Datamover Interface (DI) 11.1 Overview This chapter describes the interactions model between iSCSI and Datamover layers when the iSCSI connection is Datamover- assisted so the iSCSI layer may carry out the following - - send iSCSI data-type PDUs and exchange iSCSI control-type PDUs, and - handle asynchronous notifications such as completion of data sequence transfer, and connection failure. This chapter relies on the notion of Operational Primitives (section 6.4) to define DI. 11.2 Interactions for handling asynchronous notifications 11.2.1 Connection termination As stated in section 9.2, the Datamover layer notifies the iSCSI layer of a failed or terminated connection via the Connection_Terminate_Notify Operational Primitive. The iSCSI layer MUST consider the connection as unusable upon the invocation of this Primitive and handle the connection termination as specified in [RFC3720]. 11.2.2 Data transfer completion As stated in section 9.3, the Datamover layer notifies the iSCSI layer of a completed data transfer operation via the Data_Completion_Notify Operational Primitive. The iSCSI layer processes the transfer completion as specified in [RFC3720]. 11.2.2.1 Completion of a requested SCSI Data transfer The Datamover layer, to notify the iSCSI layer of the completion of a requested iSCSI data-type PDU transfer, uses the Data_Completion_Notify Operational Primitive with the following input qualifiers. a) Connection_Handle ^Chadalapaka et al. Expires January, 2005 [Page 29] ^Internet-Draft DA 16 July 2004 b) ITT: Initiator Task Tag semantics as defined in [RFC3720] c) SN: DataSN for a SCSI Data-in/Data-out PDU, and R2TSN for an iSCSI R2T PDU. The semantics for both types of sequence numbers are as defined in [RFC3720]. The rationale for choosing SN is explained in section 9.3. Every invocation of the Data_Completion_Notify Operational Primitive MUST be preceded by an invocation of the Put_Data or Get_Data Operational Primitive with the Notify_Enable qualifier set by the iSCSI layer at an earlier point in time. 11.2.3 Data acknowledgement [RFC3720] allows the iSCSI targets to optionally solicit data acknowledgement from the initiator for one or more Data-in PDUs, via setting of the A-bit on a Data-in PDU. The Data_ACK_Notify Operational Primitive with the following input qualifiers is used by the target Datamover layer to notify the local iSCSI layer of the arrival of data acknowledgement of a previously solicited iSCSI read data acknowledgement. This Operational Primitive thus is appli- cable only to iSCSI targets. a) Connection_Handle b) ITT: Initiator Task Tag semantics as defined in [RFC3720] c) DataSN: of the next SCSI Data-in PDU which immediately follows the SCSI Data-in PDU with the A-bit set to which this notification corresponds, with semantics as defined in [RFC3720]. Every invocation of the Data_ACK_Notify Operational Primitive MUST be preceded by an invocation of the Put_Data Operational Primitive by the iSCSI target layer with the A-bit set to 1 at an earlier point in time. ^Chadalapaka et al. Expires January, 2005 [Page 30] ^Internet-Draft DA 16 July 2004 11.3 Interactions for sending an iSCSI PDU This section discusses the interactions model for sending each of the iSCSI PDUs defined in [RFC3720]. A Connection_Handle (see section 6.3) is assumed to qualify each of these interactions so that the Datamover layer can route it to the appropriate Transport Connection. The qualifying Connection_Handle is not explicitly listed in the subsequent sections. 11.3.1 SCSI Command The Send_Control Operational Primitive with the following input qualifiers is used for requesting the transmission of a SCSI Command PDU. a) BHS and AHS, if any, of the SCSI Command PDU as defined in [RFC3720] b) DataDescriptorOut: that defines the I/O Buffer meant for Data-out for the entire command, in the case of a write or bidirectional command c) DataDescriptorIn: that defines the I/O Buffer meant for Data-in for the entire command, in the case of a read or bidirectional command d) ImmediateDataSize: that defines the number of octets of immediate unsolicited data for a write/bidirectional command e) UnsolicitedDataSize: that defines the number of octets of immediate and non-immediate unsolicited data for a write/bidirectional command. Note that some implementations may choose to ascertain the ImmediateDataSize input qualifier from the DataSegmentLength field of the SCSI Command PDU. The defined list of input qualifiers represents the semantically required set for the Datamover layer to consider in implementing the Primitive. ^Chadalapaka et al. Expires January, 2005 [Page 31] ^Internet-Draft DA 16 July 2004 11.3.2 SCSI Response The Send_Control Operational Primitive with the following input qualifiers is used for requesting the transmission of a SCSI Response PDU. a) BHS of the SCSI Response PDU as defined in [RFC3720] b) DataDescriptorStatus: that defines the iSCSI buffer which contains the sense and response information for the command 11.3.3 Task Management Function Request The Send_Control Operational Primitive with the following input qualifiers is used for requesting the transmission of a Task Management Function Request PDU. a) BHS of the Task Management Function Request PDU as defined in [RFC3720] b) DataDescriptorOut: that defines the I/O Buffer meant for Data-out for the entire command, in the case of a write or bidirectional command (Only valid if Function="TASK REASSIGN" ¡ [RFC3720] ] c) DataDescriptorIn: that defines the I/O Buffer meant for Data-in for the entire command, in the case of a read or bidirectional command (Only valid if Function="TASK REASSIGN" - [RFC3720] ) 11.3.4 Task Management Function Response The Send_Control Operational Primitive with the following input qualifier is used for requesting the transmission of a Task Management Function Response PDU. a) BHS of the Task Management Function Response PDU as defined in [RFC3720] ^Chadalapaka et al. Expires January, 2005 [Page 32] ^Internet-Draft DA 16 July 2004 11.3.5 SCSI Data-out & SCSI Data-in 11.3.5.1 SCSI Data-out The Send_Control Operational Primitive with the following input qualifiers is used by the initiator iSCSI layer for requesting the transmission of a SCSI Data-out PDU carrying the non-immediate unsolicited data. a) BHS of the SCSI Data-out PDU as defined in [RFC3720] b) DataDescriptorOut: that defines the I/O Buffer with the Data-out to be carried in the iSCSI data segment of the PDU 11.3.5.2 SCSI Data-in The Put_Data Operational Primitive with the following input qualifiers is used by the target iSCSI layer for requesting the transmission of the data carried by a SCSI Data-in PDU. a) BHS of the SCSI Data-in PDU as defined in [RFC3720] b) DataDescriptorIn: that defines the I/O Buffer with the Data-in being requested for transmission 11.3.6 Ready To Transfer (R2T) The Get_Data Operational Primitive with the following input qualifiers is used by the target iSCSI layer for requesting the retrieval of the data as specified by the semantic content of an R2T PDU. a) BHS of the Ready To Transfer PDU as defined in [RFC3720] b) DataDescriptorOut: that defines the I/O Buffer for the Data-out being requested for retrieval ^Chadalapaka et al. Expires January, 2005 [Page 33] ^Internet-Draft DA 16 July 2004 11.3.7 Asynchronous Message The Send_Control Operational Primitive with the following input qualifiers is used for requesting the transmission of an Asynchronous Message PDU. a) BHS of the Asynchronous Message PDU as defined in [RFC3720] b) DataDescriptorSense: that defines an iSCSI buffer which contains the sense and iSCSI Event information. 11.3.8 Text Request The Send_Control Operational Primitive with the following input qualifiers is used for requesting the transmission of a Text Request PDU. a) BHS of the Text Request PDU as defined in [RFC3720] b) DataDescriptorTextOut: that defines the iSCSI Text Request buffer 11.3.9 Text Response The Send_Control Operational Primitive with the following input qualifiers is used for requesting the transmission of a Text Response PDU. a) BHS of the Text Response PDU as defined in [RFC3720] b) DataDescriptorTextIn: that defines the iSCSI Text Response buffer 11.3.10 Login Request The Send_Control Operational Primitive with the following input qualifiers is used for requesting the transmission of a Login Request PDU. ^Chadalapaka et al. Expires January, 2005 [Page 34] ^Internet-Draft DA 16 July 2004 a) BHS of the Login Request PDU as defined in [RFC3720] b) DataDescriptorLoginRequest: that defines the iSCSI Login Request buffer Note that specific Datamover protocols may choose to disallow the standard DA Primitives from being used for the iSCSI Login phase. When used in conjunction with such Datamover protocols, an attempt to send a Login Request via the Send_Control Operational Primitive invocation is clearly an error scenario, as the Login Request PDU is being sent while the connection is in the iSCSI full feature phase. It is outside the scope of this document to specify the resulting implementation behavior in this case - [RFC3720] already defines the error handling for this error scenario. 11.3.11 Login Response The Send_Control Operational Primitive with the following input qualifiers is used for requesting the transmission of a Login Response PDU. a) BHS of the Login Response PDU as defined in [RFC3720] b) DataDescriptorLoginResponse: that defines the iSCSI Login Response buffer Note that specific Datamover protocols may choose to disallow the standard DA Primitives from being used for the iSCSI Login phase. When used in conjunction with such Datamover protocols, an attempt to send a Login Response via the Send_Control Operational Primitive invocation is clearly an error scenario, as the Login Response PDU is being sent while in the iSCSI full feature phase. It is outside the scope of this document to specify the resulting implementation behavior in this case - [RFC3720] already defines the error handling for this error scenario. ^Chadalapaka et al. Expires January, 2005 [Page 35] ^Internet-Draft DA 16 July 2004 11.3.12 Logout Command The Send_Control Operational Primitive with the following input qualifier is used for requesting the transmission of a Logout Command PDU. a) BHS of the Logout Command PDU as defined in [RFC3720] 11.3.13 Logout Response The Send_Control Operational Primitive with the following input qualifier is used for requesting the transmission of a Logout Response PDU. a) BHS of the Logout Response PDU as defined in [RFC3720] 11.3.14 SNACK Request The Send_Control Operational Primitive with the following input qualifier is used for requesting the transmission of a SNACK Request PDU. a) BHS of the SNACK Request PDU as defined in [RFC3720] 11.3.15 Reject The Send_Control Operational Primitive with the following input qualifiers is used for requesting the transmission of a Reject PDU. a) BHS of the Reject PDU as defined in [RFC3720] b) DataDescriptorReject: that defines the iSCSI Reject buffer ^Chadalapaka et al. Expires January, 2005 [Page 36] ^Internet-Draft DA 16 July 2004 11.3.16 NOP-Out The Send_Control Operational Primitive with the following input qualifiers is used for requesting the transmission of a NOP-Out PDU. a) BHS of the NOP-Out PDU as defined in [RFC3720] b) DataDescriptorNOPOut: that defines the iSCSI Ping data buffer 11.3.17 NOP-In The Send_Control Operational Primitive with the following input qualifiers is used for requesting the transmission of a NOP-In PDU. a) BHS of the NOP-In PDU as defined in [RFC3720] b) DataDescriptorNOPIn: that defines the iSCSI Return Ping data buffer 11.4 Interactions for receiving an iSCSI PDU The only PDUs that are received by an iSCSI layer operating on a Datamover layer are the iSCSI control-type PDUs. The Datamover layer delivers the iSCSI control-type PDUs as they arrive, qualifying each with the Connection_Handle (see section 6.3) that identifies the iSCSI connection the PDU is meant for. The subsequent processing of the iSCSI control- type PDUs proceeds as defined in [RFC3720]. 11.4.1 SCSI Command The Control_Notify Operational Primitive is used for notifying the arrival of a SCSI Command PDU. ^Chadalapaka et al. Expires January, 2005 [Page 37] ^Internet-Draft DA 16 July 2004 11.4.2 SCSI Response The Control_Notify Operational Primitive is used for notifying the arrival of a SCSI Response PDU. 11.4.3 Task Management Function Request The Control_Notify Operational Primitive is used for notifying the arrival of a Task Management Function Request PDU. 11.4.4 Task Management Function Response The Control_Notify Operational Primitive is used for notifying the arrival of a Task Management Function Response PDU. 11.4.5 SCSI Data-out & SCSI Data-in 11.4.5.1 SCSI Data-out The Control_Notify Operational Primitive is used for notifying the iSCSI layer of the arrival of a SCSI Data-out PDU carrying the non-immediate unsolicited data. Note however that the solicited SCSI Data-out arriving on the target is not notified to the iSCSI layer using the Control_Notify Primitive because the solicited SCSI Data-out was not sent by the initiator iSCSI layer as control-type PDUs. 11.4.5.2 SCSI Data-in The arrival of the SCSI Data-in is not notified to the iSCSI layer by the Datamover layer at the initiator, because SCSI Data-in is an iSCSI data-type PDU (see section 6.1). The iSCSI layer at the initiator however may infer the arrival of the SCSI Data-in when it receives a subsequent notification of the SCSI Response PDU via a Control_Notify invocation. ^Chadalapaka et al. Expires January, 2005 [Page 38] ^Internet-Draft DA 16 July 2004 While this document does not contemplate the possibility of a Data-in PDU being received at the initiator iSCSI layer, specific Datamover protocols may define how to deal with an unexpected inbound SCSI Data-in PDU that may result in the initiator iSCSI layer receiving the Data-in PDU. This document leaves the details of handling this error scenario to the specific Datamover protocols, so each may define the appropriate error handling specific to the Datamover environment. 11.4.6 Ready To Transfer (R2T) Because an R2T PDU is an iSCSI data-type PDU (see section 6.1) that is not delivered as-is to the initiator iSCSI layer, the arrival of an R2T PDU is not notified to the iSCSI layer by the Datamover layer. When an iSCSI node sends an R2T PDU to its local Datamover layer, the local and remote Datamover layers transparently bring about the data transfer requested by the R2T PDU. While this document does not contemplate the possibility of an R2T PDU being received at the initiator iSCSI layer, specific Datamover protocols may define how to deal with an unexpected inbound R2T PDU that may result in the initiator iSCSI layer receiving the R2T PDU. This document leaves the details of handling this error scenario to the specific Datamover protocols, so each may define the appropriate error handling specific to the Datamover environment. 11.4.7 Asynchronous Message The Control_Notify Operational Primitive is used for notifying the arrival of an Asynchronous Message PDU. 11.4.8 Text Request The Control_Notify Operational Primitive is used for notifying the arrival of a Text Request PDU. ^Chadalapaka et al. Expires January, 2005 [Page 39] ^Internet-Draft DA 16 July 2004 11.4.9 Text Response The Control_Notify Operational Primitive is used for notifying the arrival of a Text Response PDU. 11.4.10 Login Request The Control_Notify Operational Primitive is used for notifying the target iSCSI layer of the arrival of a Login Request PDU. Note that specific Datamover protocols may choose to disallow the standard DA Primitives from being used for the iSCSI Login phase. When used in conjunction with such Datamover protocols, the arrival of a Login Request necessitating the Control_Notify Operational Primitive invocation is clearly an error scenario, as the Login Request PDU is arriving in the iSCSI full feature phase. It is outside the scope of this document to specify the resulting implementation behavior in this case - [RFC3720] already defines the error handling in this error scenario. 11.4.11 Login Response The Control_Notify Operational Primitive is used for notifying the initiator iSCSI layer of the arrival of a Login Response PDU. Note that specific Datamover protocols may choose to disallow the standard DA Primitives from being used for the iSCSI Login phase. When used in conjunction with such Datamover protocols, the arrival of a Login Response necessitating the Control_Notify Operational Primitive invocation is clearly an error scenario, as the Login Response PDU is arriving in the iSCSI full feature phase. It is outside the scope of this document to specify the resulting implementation behavior in this case - [RFC3720] already defines the error handling in this error scenario. 11.4.12 Logout Command The Control_Notify Operational Primitive is used for notifying the arrival of a Logout Command PDU. ^Chadalapaka et al. Expires January, 2005 [Page 40] ^Internet-Draft DA 16 July 2004 11.4.13 Logout Response The Control_Notify Operational Primitive is used for notifying the arrival of a Logout Response PDU. 11.4.14 SNACK Request The Control_Notify Operational Primitive is used for notifying the arrival of a SNACK Request PDU. 11.4.15 Reject The Control_Notify Operational Primitive is used for notifying the arrival of a Reject PDU. 11.4.16 NOP-Out The Control_Notify Operational Primitive is used for notifying the arrival of a NOP-Out PDU. 11.4.17 NOP-In The Control_Notify Operational Primitive is used for notifying the arrival of a NOP-In PDU. ^Chadalapaka et al. Expires January, 2005 [Page 41] ^Internet-Draft DA 16 July 2004 12 Security Considerations In view of the fact that DA does not define any new wire protocol nor propose modifications to the existing protocols, there are no additional security considerations in employing DA, in addition to that of using the iSCSI protocol itself. Any additional security considerations resulting from the use of any Datamover protocol must be identified by the specific Datamover protocol specification as appropriate. ^Chadalapaka et al. Expires January, 2005 [Page 42] ^Internet-Draft DA 16 July 2004 13 IANA Considerations If a well-known port is chosen as the mechanism to identify a Datamover protocol on TCP, the well-known port must be registered with IANA. Because the use of the well-known port is specific to the Datamover protocol in such a case, the resulting IANA considerations from such use must be specified by the specific Datamover protocol. DA itself does not have any specific IANA considerations. ^Chadalapaka et al. Expires January, 2005 [Page 43] ^Internet-Draft DA 16 July 2004 14 References and Bibliography 14.1 Normative References [RFC3720] J. Satran, K. Meth, C. Sapuntzakis, M. Chadalapaka, E. Zeidner, "Internet Small Computer Systems Interface (iSCSI)", RFC 3720, April 2004. [SAM2] T10/1157D, SCSI Architecture Model - 2 (SAM-2). [SPC]T10/1416-D, SCSI-3 Primary Commands. 14.2 Informative References [DDP] H. Shah et al., "Direct Data Placement over Reliable Transports", IETF Internet Draft draft-ietf-rddp-ddp- 00.txt (work in progress), February 2003. [iSER] M. Ko et al., "iSCSI Extensions for RDMA", IETF Internet Draft draft-ko-iwarp-iser-02.txt (work in progress), July 2004. [MPA] P. Culley et al., "Marker PDU Aligned Framing for TCP Specification", IETF Internet Draft draft-culley-iwarp- mpa-02.txt (work in progress), February 2003. [RDMAP] R. Recio et al., "An RDMA Protocol Specification", IETF Internet Draft draft-ietf-rddp-rdmap-00.txt (work in progress), February 2003. [RFC2119] Bradner, S. "Key Words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [SAM] ANSI X3.270-1998, SCSI-3 Architecture Model (SAM). [SCTP] R. Stewart et al., "Stream Control Transmission Protocol", RFC 2960, October 2000. [SPC3]T10/1416-D, SCSI Primary Commands-3. ^Chadalapaka et al. Expires January, 2005 [Page 44] ^Internet-Draft DA 16 July 2004 15 Authors' Addresses Mallikarjun Chadalapaka Hewlett-Packard Company 8000 Foothills Blvd. Roseville, CA 95747-5668, USA Phone: +1-916-785-5621 E-mail: cbm@rose.hp.com John L. Hufferd IBM San Jose CA, USA Phone: +1-408-256-0403 E-mail: hufferd@us.ibm.com Julian Satran IBM, Haifa Research Lab Haifa University Campus - Mount Carmel Haifa 31905, Israel Phone +972-4-829-6264 E-mail: Julian_Satran@il.ibm.com Hemal Shah Intel Corporation MS PTL1 1501 South Mopac Expressway, #400 Austin, TX 78746 USA Phone: +1 (512) 732-3963 Email: hemal.shah@intel.com Comments may be sent to Mallikarjun Chadalapaka. ^Chadalapaka et al. Expires January, 2005 [Page 45] ^Internet-Draft DA 16 July 2004 16 Acknowledgements The IPS Working group in the Transport Area of IETF is responsible for defining the iSCSI protocol (apart from a host of other relevant IP Storage protocols). The authors are grateful to the entire working group, whose work allowed this document to build on the concepts and details of the iSCSI protocol. In addition, the following individuals had reviewed and contributed to the improvement of this document. The authors are grateful for their contribution. John Carrier Adaptec, Inc. 691 S. Milpitas Blvd. Milpitas, CA 95035 USA Phone: +1 (360) 378-8526 Email: john_carrier@adaptec.com Hari Ghadia Adaptec, Inc. 691 S. Milpitas Blvd., Milpitas, CA 95035 USA Phone: +1 (408) 957-5608 Email: hari_ghadia@adaptec.com Hari Mudaliar Adaptec, Inc. 691 S. Milpitas Blvd., Milpitas, CA 95035 USA Phone: +1 (408) 957-6012 Email: hari_mudaliar@adaptec.com Patricia Thaler Agilent Technologies, Inc. 1101 Creekside Ridge Drive, #100 M/S-RG10 Roseville, CA 95678 Phone: +1-916-788-5662 ^Chadalapaka et al. Expires January, 2005 [Page 46] ^Internet-Draft DA 16 July 2004 email: pat_thaler@agilent.com Uri Elzur Broadcom Corporation 16215 Alton Parkway Irvine, California 92619-7013 USA Phone: +1 (949) 585-6432 Email: Uri@Broadcom.com Mike Penna Broadcom Corporation 16215 Alton Parkway Irvine, California 92619-7013 USA Phone: +1 (949) 926-7149 Email: MPenna@Broadcom.com Ted Compton EMC Corporation Research Triangle Park, NC 27709, USA Phone: 919-248-6075 Email: compton_ted@emc.com Dwight Barron Hewlett-Packard Company 20555 SH 249 Houston, TX 77070-2698 USA Phone: +1 (281) 514-2769 Email: Dwight.Barron@Hp.com Paul R. Culley Hewlett-Packard Company 20555 SH 249 Houston, TX 77070-2698 USA Phone: +1 (281) 514-5543 Email: paul.culley@hp.com Dave Garcia Hewlett-Packard Company 19333 Vallco Parkway Cupertino, Ca. 95014 USA ^Chadalapaka et al. Expires January, 2005 [Page 47] ^Internet-Draft DA 16 July 2004 Phone: +1 (408) 285-6116 Email: dave.garcia@hp.com Randy Haagens Hewlett-Packard Company 8000 Foothills Blvd, MS 5668 Roseville CA Phone: +1-916-785-4578 email: randy_haagens@hp.com Jeff Hilland Hewlett-Packard Company 20555 SH 249 Houston, Tx. 77070-2698 USA Phone: +1 (281) 514-9489 Email: jeff.hilland@hp.com Mike Krause Hewlett-Packard Company, 43LN 19410 Homestead Road Cupertino, CA 95014 USA Phone: +1 (408) 447-3191 Email: krause@cup.hp.com Jim Wendt Hewlett-Packard Company 8000 Foothills Blvd, MS 5668 Roseville CA Phone: +1-916-785-5198 email: jim_wendt@hp.com Mike Ko IBM 650 Harry Rd. San Jose, CA 95120 Phone: +1 (408) 927-2085 Email: mako@us.ibm.com ^Chadalapaka et al. Expires January, 2005 [Page 48] ^Internet-Draft DA 16 July 2004 Renato Recio IBM Corporation 11501 Burnett Road Austin, TX 78758 USA Phone: +1 (512) 838-1365 Email: recio@us.ibm.com Howard C. Herbert Intel Corporation MS CH7-404 5000 West Chandler Blvd. Chandler, AZ 85226 USA Phone: +1 (480) 554-3116 Email: howard.c.herbert@intel.com Dave Minturn Intel Corporation MS JF1-210 5200 North East Elam Young Parkway Hillsboro, OR 97124 USA Phone: +1 (503) 712-4106 Email: dave.b.minturn@intel.com James Pinkerton Microsoft Corporation One Microsoft Way Redmond, WA 98052 USA Phone: +1 (425) 705-5442 Email: jpink@microsoft.com Tom Talpey Network Appliance 375 Totten Pond Road Waltham, MA 02451 USA Phone: +1 (781) 768-5329 EMail: thomas.talpey@netapp.com ^Chadalapaka et al. Expires January, 2005 [Page 49] ^Internet-Draft DA 16 July 2004 17 Appendix 17.1 Design considerations for a Datamover protocol This section discusses the specific considerations for RDMA- based and RDDP-based Datamover protocols, and is only informational. a) Note that the modeling of interactions for SCSI Data-Out (section 10.3.5.1) is only used for unsolicited data transfer. b) The modeling of interactions for SNACK (section 10.3.14, and section 10.4.14) is not expected to be used given that one of the design requirements on the Datamover is that it "guarantees an error-free, reliable, in-order transport mechanism" (section 7). The interactions for sending and receiving a SNACK are nevertheless modeled in this document because the receiving iSCSI layer can deterministically deal with an inadvertent SNACK. This also shows the DA designers' intent that DI is not meant to filter certain types of PDUs. c) The onus is on a reliable Datamover (per requirements stated in section 7) to realize end-to-end data acknowledgements via Datamover-specific means. In view of this, even data-ACK-type SNACKs are unnecessary to be used. Consequently, an initiator may never request sending a SNACK Request in this model assuming that the proactive (timeout-driven) SNACK functionality is turned off in the legacy iSCSI code. d) Note that the current DA model for bootstrapping a Connection_Handle into service ¡ i.e. associating a new iSCSI connection with a Connection_Handle ¡ clearly implies that the iSCSI connection must already be in full feature phase when the Datamover layer comes into the stack. This further implies that the iSCSI login phase must be carried out in the traditional "Byte streaming mode" with no assistance or involvement from the Datamover layer. ^Chadalapaka et al. Expires January, 2005 [Page 50] ^Internet-Draft DA 16 July 2004 17.2 Examples of Datamover interactions The figures described in this section provide some examples of the usage of Operational Primitives in interactions between the iSCSI layer and the Datamover layer. The following abbreviations are used in this section. Avail ¡ Available Buf ¡ I/O Buffer Cmd ¡ Command Compl ¡ Complete Conn - Connection Ctrl_Notify ¡ Control_Notify Dal_Tsk_Res ¡ Deallocate_Task_Resources Data_Cmp_Nfy ¡ Data_Completion_Notify Data_ACK_Nfy ¡ Data_ACK_Notify DM ¡ Datamover Imm - Immediate Snd_Ctrl ¡ Send_Control Msg ¡ Message Resp ¡ Response Sol ¡ Solicited TMF Req ¡ Task Management Function Request TMF Res ¡ Task Management Function Response Trans ¡ Transfer Unsol ¡ Unsolicited ^Chadalapaka et al. Expires January, 2005 [Page 51] ^Internet-Draft DA 16 July 2004 | | Allocate_Connection_Resources | D | ^ | |------------------------------->| a | | | | Connection resources are | t | | | i | successfully allocated | a | | iSCSI | S | | m | | Login | C | | o | | Phase | S | | v | | | I | | e | | | | | r | | Login Phase | L | Final Login Response (success) v succeeds | a |<----------------------------------------^ | y | | L | | iSCSI | e | Enable_Datamover | a | | Full | r |------------------------------->| y | | Feature | | Datamover is enabled | e | | Phase | | | r | | | | Full Feature Phase | | | | | control and data Transfer | | v Figure 2 A successful iSCSI login on initiator | | Notice_Key_Values | | | | |------------------------------->| | | | | Datamover layer is notified | | | | | of the negotiated key values | | | | | | | | | | Allocate_Connection_Resources | | | | |------------------------------->| D | | | | Connection resources are | a | | | i | successfully allocated | t | | iSCSI | S | | a | | Login | C | | m |Final | Phase | S | | o |Login | | I |Enable_Datamover(Login Response)| v |Resp | | |------------------------------->| e |---->vLogin Phase | L | Datamover is enabled | r | ^ succeeds | a | | | | | y | | L | | iSCSI | e | | a | | Full | r | | y | | Feature | | | e | | Phase | | Full Feature Phase | r | | | | control and data Transfer | | | | | | | v Figure 3 A successful iSCSI login on target ^Chadalapaka et al. Expires January, 2005 [Page 52] ^Internet-Draft DA 16 July 2004 | | Allocate_Connection_Resources | D | ^ | |------------------------------->| a | | | | Connection resources are | t | | | i | successfully allocated | a | | iSCSI | S | | m | | Login | C | | o | | Phase | S | | v | | | I | | e | | | | | r | | Login | | | | | Phase | L | Final Login Response (failure) v fails | a |<------------------------------------------ | y | | L | | e | Deallocate_Connection_Resources| a | | r |------------------------------->| y | | | Datamover-specific | e | | | connection resources freed | r | | | | | | | | | Connection terminated by standard means | |---------------------------------------------> Figure 4 A failed iSCSI login on initiator | | Allocate_Connection_Resources | D | ^ | |------------------------------->| a | | | | Connection resources are | t | | | i | successfully allocated | a | | iSCSI | S | | m | | Login | C | | o | | Phase | S | | v | | | I | | e | | | | | r | | Login | | | | | Phase | L | Final Login Response (failure) v fails | a |----------------------------------------------> | y | | L | | e | Deallocate_Connection_Resources| a | | r |------------------------------->| y | | | Datamover-specific | e | | | connection resources freed | r | | | | | | | | | Connection terminated by standard means | |--------------------------------------------> Figure 5 A failed iSCSI login on target ^Chadalapaka et al. Expires January, 2005 [Page 53] ^Internet-Draft DA 16 July 2004 | | Allocate_Connection_Resources | D | ^ | |------------------------------->| a | | | | Connection resources are | t | | | i | successfully allocated | a | | iSCSI | S | | m | | Login | C | | o | | Phase | S | | v | | | I | | e | | | | | r | | | L | Login non-Final Request/Response | | a |<-----------------------------------------| | y | iSCSI layer decides not to | L | | | e | enable Datamover for this | a | | | r | connection | y | | | | | e | | | | Deallocate_Connection_Resources| r | | | |------------------------------->| | | | | All Datamover-specific | | | | | resources deallocated | | | | | | | | Login | | | | | Phase | | | continues | | Regular Login negotiation continues | | |<---------------------------------------->| | | . | | . | | . Figure 6 iSCSI does not enable the Datamover ^Chadalapaka et al. Expires January, 2005 [Page 54] ^Internet-Draft DA 16 July 2004 | | | | ^ | | Full Feature Phase Control & | | | | | Data Transfer Using DM | D | | iSCSI | | | a | | Full Feature | i | | t | | Phase | S | | a | | (DM Enabled) | C | | m | | | S | Successful iSCSI Logout | o | | | I | | v | v | | Connection_Terminate | e | | L |------------------------------->| r | | a | Connection is terminated | | | y | Datamover-specific resources | L | Transport | e | deallocated, both connection | a | Connection | r | level & task level | y | is terminated | | | e | | | | r | | | | | | | | | Figure 7 A normal iSCSI connection termination | | | | ^ | | Full Feature Phase Control & | D | | iSCSI | | Data Transfer Using DM | a | | Full Feature | i | | t | | Phase | S | | a | | (DM Enabled) | C | | m | v | S | | o |<--Transport | I | Datamover-specific resources | v | Connection | | deallocated, both connection | e | Terminated (e.g. | L | level & task level | r | unexpected | a | | | FIN/RESET) | y | | L | | e | Connection_Terminate_Notify | a | | r |<-------------------------------| y | | | | e | | | | r | | | | | Figure 8 An abnormal iSCSI connection termination ^Chadalapaka et al. Expires January, 2005 [Page 55] ^Internet-Draft DA 16 July 2004 <-----Initiator-----> <-------Target-------> | | | | DM Msg holding | | | | SCSI | | | | SCSI Cmd PDU & | | | |SCSI Cmd | | Snd_Ctrl | |Unsol Imm Data | |Ctrl_Notify | |Cmd ---->| |---------->| |--------------->| |----------->| |-----> | | | | | | | | | | | | DM Msg holding | | | | | | Snd_Ctrl | |SCSI Dataout PDU| |Ctrl_Notify | | | |---------->| |--------------->| |----------->| | | | . | | . | | . | |Unsol | | . | D | . | D | . | |Data | | . | a | DM Msg holding | a | . | |Trans | i | Snd_Ctrl | t |SCSI Dataout PDU| t |Ctrl_Notify | i | | S |---------->| a |--------------->| a |----------->| S | | C | | m | | m | | C |Buf | S | | o | | o | | S |Avail | I | | v | | v | Get_Data | I |(R2T) | | | e |----------------| e |<-----------| |<----- | L | | r ||Solicited Data | r | . | L | . | a | | || Transfer | | . | a | . | y | | L |--------------->| L | . | y |Buf | e | | a | . | a | . | e |Avail | r | | y | . | y | Get_Data | r |(R2T) | | | e |----------------| e |<-----------| |<----- | | | r ||Solicited Data | r | | | | | | || Transfer | | | | | | | |--------------->| |Data_Cmp_Nfy| |Data | | | | | |----------->| |Trans | | | | | | | |Compl | | | | DM Msg holding | | | | ^Chadalapaka et al. Expires January, 2005 [Page 56] ^Internet-Draft DA 16 July 2004 SCSI | | | |SCSI Resp PDU & | | | |SCSI Resp | |Ctrl_Notify| | Sense Data | | Snd_Ctrl | |Resp <----| |<----------| |<---------------| |<-----------| |<----- | | | | | | | | Figure 9 A SCSI Write data transfer ^Chadalapaka et al. Expires January, 2005 [Page 57] ^Internet-Draft DA 16 July 2004 <-----Initiator-----> <-------Target-------> | | | | | | | | SCSI | | | | DM Msg holding | | | |SCSI Cmd | | Snd_Ctrl | | SCSI Cmd PDU | |Ctrl_Notify | |Cmd ---->| |---------->| |--------------->| |----------->| |-----> | | | | | | | | | | | D | SCSI Read | D | | |Buf | | | a | Data Transfer | a | Put_Data | |Avail | i | | t |<---------------| t |<-----------| i |<----- | S | | a | . | a | . | S | . | C | | m | . | m | . | C | . | S | | o | . | o | . | S | . | I | | v | SCSI Read | v | . | I |Buf | | | e | Data Transfer | e | Put_Data | |Avail | L | | r |<---------------| r |<-----------| L |<----- | a | | | | | | a | | y | | L | | L | | y | | e | | a | | a |Data_Cmp_Nfy| e |Data | r | | y | | y |----------->| r |Trans | | | e | | e | | |Compl | | | r | DM Msg holding | r | | | SCSI | | | |SCSI Resp PDU & | | | |SCSI Resp | |Ctrl_Notify| | Sense Data | | Snd_Ctrl | |Resp <----| |<----------| |<---------------| |<-----------| |<----- | | | | | | | | Figure 10 A SCSI Read data transfer ^Chadalapaka et al. Expires January, 2005 [Page 58] ^Internet-Draft DA 16 July 2004 <-----Initiator-----> <-------Target-------> | | | | | | | | SCSI | | | | DM Msg holding | | | |SCSI Cmd | | Snd_Ctrl | | SCSI Cmd PDU | |Ctrl_Notify | |Cmd ---->| |---------->| |--------------->| |----------->| |-----> | | | | | | | | | | | D | SCSI Read | D | Put_Data | |Buf | | | a | Data Transfer | a |Data_in.A=1 | |Avail | i | | t |<---------------| t |<-----------| i |<----- | S | | a | . | a | . | S | . | C | | m | . | m |Data_ACK_Nfy| C | . | S | | o | | o |----------->| S | . | I | | v | | v | . | I | | | | e | | e | . | | | L | | r | | r | | L | | a | | | | | | a | | y | | L | | L | | y | | e | | a | | a | | e |Data | r | | y | | y | | r |Trans | | | e | | e | | |Compl | | | r | DM Msg holding | r | | | SCSI | | | |SCSI Resp PDU & | | | |SCSI Resp | |Ctrl_Notify| | Sense Data | | Snd_Ctrl | |Resp <----| |<----------| |<---------------| |<-----------| |<----- | | | | | | | | Figure 11 A SCSI Read data acknowledgement ^Chadalapaka et al. Expires January, 2005 [Page 59] ^Internet-Draft DA 16 July 2004 <-----Initiator-----> <-------Target-------> | | | | | | | | SCSI | | | | DM Msg holding | | | |SCSI Cmd | | Snd_Ctrl | | SCSI Cmd PDU | |Ctrl_Notify | |Cmd ---->| |---------->| |--------------->| |----------->| |-----> | | | | | | | | | | | D | SCSI Read | D | | |Buf | | | a | Data Transfer | a | Put_Data | |Avail | i | | t |<---------------| t |<-----------| i |<----- | S | | a | . | a | . | S | . Abort| C | | m | DM Msg holding | m | . | C |Abort Task | S | Snd_Ctrl | o | Abort TMF Req | o |Ctrl_Notify | S |Task ---->| I |---------->| v |--------------->| v |----------->| I |----> | | | e | . | e | . | | Abort| L | | r | DM Msg holding| r | | L | . Done | a |Ctrl_Notify| | Abort TMF Res| | Snd_Ctrl | a |Aborted <----| y |<----------| L |<---------------| L |<-----------| y |<----- | e | | a | | a | | e | | r | | y | | y | | r | | | | e | | e | | | | | | r | | r | | | | | | | | | | | | |Dal_Tsk_Res| | | |Dal_Tsk_Res | | | |---------->| | | |<-----------| | | | | | | | | | Figure 12 Task resource cleanup on abort ^Chadalapaka et al. Expires January, 2005 [Page 60] ^Internet-Draft DA 16 July 2004 18 Full Copyright Statement Copyright (C) The Internet Society (2004). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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