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Versions: (draft-ko-iwarp-iser) 00 01 02 03 04 05 06 RFC 5046

INTERNET DRAFT                             Mike Ko
draft-ietf-ips-iser-03.txt                   IBM Corporation
                                           Mallikarjun Chadalapaka
                                             Hewlett-Packard Company
                                           Uri Elzur
                                             Broadcom Corporation
                                           Hemal Shah
                                             Intel Corporation
                                           Patricia Thaler
                                             Agilent Technologies, Inc.
                                           John Hufferd

                                           Expires: October, 2005


    iSCSI Extensions for RDMA Specification

Status of this Memo

   By submitting this Internet-Draft, I certify that any applicable
   patent or other IPR claims of which I am aware have been disclosed,
   or will be disclosed, and any of which I become aware will be
   disclosed, in accordance with RFC 3668.

   Internet-Drafts are working documents of the Internet Engineering
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Abstract

   iSCSI Extensions for RDMA provides the RDMA data transfer capability
   to iSCSI by layering iSCSI on top of the Remote Direct Memory Access
   Protocol (RDMAP).  The iWARP protocol suite provides RDMA Read and
   Write services, which enable data to be transferred directly into
   SCSI I/O Buffers without intermediate data copies.  This document



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   describes the extensions to the iSCSI protocol to support RDMA
   services as defined by the iWARP protocol suite.















































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   Table of Contents

   1    Definitions and Acronyms....................................7
   1.1  Definitions.................................................7
   1.2  Acronyms...................................................12
   2    Introduction...............................................15
   2.1  Motivation.................................................15
   2.2  Architectural Goals........................................16
   2.3  Protocol Overview..........................................17
   2.4  RDMA services and iSER.....................................18
   2.4.1  STag......................................................18
   2.4.2  Send......................................................19
   2.4.3  RDMA Write................................................19
   2.4.4  RDMA Read.................................................19
   2.5  SCSI Read Overview.........................................20
   2.6  SCSI Write Overview........................................20
   2.7  iSCSI/iSER Layering........................................20
   3    Upper Layer Interface Requirements.........................22
   3.1  Operational Primitives offered by iSER.....................22
   3.1.1  Send_Control..............................................22
   3.1.2  Put_Data..................................................23
   3.1.3  Get_Data..................................................23
   3.1.4  Allocate_Connection_Resources.............................23
   3.1.5  Deallocate_Connection_Resources...........................24
   3.1.6  Enable_Datamover..........................................24
   3.1.7  Connection_Terminate......................................25
   3.1.8  Notice_Key_Values.........................................25
   3.1.9  Deallocate_Task_Resources.................................25
   3.2  Operational Primitives used by iSER........................26
   3.2.1  Control_Notify............................................26
   3.2.2  Data_Completion_Notify....................................26
   3.2.3  Data_ACK_Notify...........................................26
   3.2.4  Connection_Terminate_Notify...............................27
   3.3  iSCSI Protocol Usage Requirements..........................27
   4    Lower Layer Interface Requirements.........................29
   4.1  Interactions with the iWARP Layer..........................29
   4.2  Interactions with the Transport Layer......................30
   5    Connection Setup and Termination...........................31
   5.1  iSCSI/iSER Connection Setup................................31
   5.1.1  Initiator Behavior........................................32
   5.1.2  Target Behavior...........................................34
   5.1.3  iSER Hello Exchange.......................................36
   5.2  iSCSI/iSER Connection Termination..........................37
   5.2.1  Normal Connection Termination at the Initiator............37
   5.2.2  Normal Connection Termination at the Target...............37
   5.2.3  Termination without Logout Request/Response PDUs..........38
   6    Login/Text Operational Keys................................40


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   6.1  HeaderDigest and DataDigest................................40
   6.2  MaxRecvDataSegmentLength...................................40
   6.3  RDMAExtensions.............................................40
   6.4  TargetRecvDataSegmentLength................................41
   6.5  InitiatorRecvDataSegmentLength.............................42
   6.6  OFMarker and IFMarker......................................42
   6.7  MaxOutstandingUnexpectedPDUs...............................43
   7    iSCSI PDU Considerations...................................44
   7.1  iSCSI Data-Type PDU........................................44
   7.2  iSCSI Control-Type PDU.....................................45
   7.3  iSCSI PDUs.................................................45
   7.3.1  SCSI Command..............................................45
   7.3.2  SCSI Response.............................................47
   7.3.3  Task Management Function Request/Response.................48
   7.3.4  SCSI Data-out.............................................50
   7.3.5  SCSI Data-in..............................................50
   7.3.6  Ready To Transfer (R2T)...................................53
   7.3.7  Asynchronous Message......................................55
   7.3.8  Text Request & Text Response..............................55
   7.3.9  Login Request & Login Response............................55
   7.3.10  Logout Request & Logout Response........................56
   7.3.11  SNACK Request...........................................56
   7.3.12  Reject..................................................56
   7.3.13  NOP-Out & NOP-In........................................56
   8    Flow Control and STag Management...........................58
   8.1  Flow Control for RDMA Send Message Types...................58
   8.2  Flow Control for RDMA Read Resources.......................58
   8.3  Flow Control for Control-Type PDUs from the Initiator......59
   8.4  Flow Control for Control-Type PDUs from the Target.........61
   8.5  STag Management............................................61
   8.5.1  Allocation of STags.......................................61
   8.5.2  Invalidation of STags.....................................62
   9    iSER Control and Data Transfer.............................64
   9.1  iSER Header Format.........................................64
   9.2  iSER Header Format for iSCSI Control-Type PDU..............64
   9.3  iSER Header Format for iSER Hello Message..................66
   9.4  iSER Header Format for iSER HelloReply Message.............67
   9.5  SCSI Data Transfer Operations..............................68
   9.5.1  SCSI Write Operation......................................68
   9.5.2  SCSI Read Operation.......................................69
   9.5.3  Bidirectional Operation...................................69
   10   iSER Error Handling and Recovery...........................70
   10.1   Error Handling............................................70
   10.1.1  Errors in the Transport Layer...........................70
   10.1.2  Errors in the iWARP protocol suite......................71
   10.1.3  Errors in the iSER Layer................................71
   10.1.4  Errors in the iSCSI Layer...............................73


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   10.2   Error Recovery............................................75
   10.2.1  SNACK Handling and PDU Recovery.........................75
   10.2.2  Connection Recovery.....................................76
   11   Security Considerations....................................77
   12   References.................................................78
   12.1   Normative References......................................78
   12.2   Informative References....................................78
   13   Appendix...................................................79
   13.1   iWARP Message Format for iSER.............................79
   13.1.1  iWARP Message Format for iSER Hello Message.............79
   13.1.2  iWARP Message Format for iSER HelloReply Message........80
   13.1.3  iWARP Message Format for SCSI Read Command PDU..........81
   13.1.4  iWARP Message Format for SCSI Read Data.................82
   13.1.5  iWARP Message Format for SCSI Write Command PDU.........83
   13.1.6  iWARP Message Format for RDMA Read Request..............84
   13.1.7  iWARP Message Format for Solicited SCSI Write Data......85
   13.1.8  iWARP Message Format for SCSI Response PDU..............86
   14   Author's Address...........................................87
   15   Acknowledgments............................................88
   16   Full Copyright Statement...................................89





























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   Table of Figures

   Figure 1 Example of iSCSI/iSER Layering in Full Feature Mode....21
   Figure 2 iSER Header Format.....................................64
   Figure 3 iSER Header Format for iSCSI Control-Type PDU..........65
   Figure 4 iSER Header Format for iSER Hello Message..............66
   Figure 5 iSER Header Format for iSER HelloReply Message.........67
   Figure 6 SendSE Message containing an iSER Hello Message........79
   Figure 7 SendSE Message containing an iSER HelloReply Message...80
   Figure 8 SendSE Message containing a SCSI Read Command PDU......81
   Figure 9 RDMA Write Message containing SCSI Read Data...........82
   Figure 10 SendSE Message containing a SCSI Write Command PDU....83
   Figure 11 RDMA Read Request Message.............................84
   Figure 12 RDMA Read Response Message containing SCSI Write Data.85
   Figure 13 SendInvSE Message containing SCSI Response PDU........86


































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1  Definitions and Acronyms

   Some of the following definitions are taken from [RDMAP].  In those
   definitions, the term ULP refers to the iSER Layer.

1.1  Definitions

   Advertisement (Advertised, Advertise, Advertisements, Advertises) -
       The act of informing a Remote Peer that a local node's buffer is
       available to it.  A Node makes a buffer available for incoming
       RDMA Read Request Message or incoming RDMA Write Message access
       by informing its RDMA/DDP peer of the Tagged Buffer identifiers
       (STag, TO, and buffer length).  This Advertisement of Tagged
       Buffer information is not defined by RDMA/DDP and is left to the
       ULP.  A typical method would be for the Local Peer to embed the
       Tagged Buffer's STag, TO, and buffer length in a Send Message
       destined for the Remote Peer.

   Completion (Completed, Complete, Completes) - Completion is defined
       as the process by the iWARP layer to inform the ULP, in this
       case the iSER Layer, that a particular RDMA Operation has
       performed all functions specified for the RDMA Operation.

   Connection - A connection is a logical circuit between the initiator
       and the target, e.g., a TCP connection.  Communication between
       the initiator and the target occurs over one or more
       connections.  The connections carry control messages, SCSI
       commands, parameters, and data within iSCSI Protocol Data Units
       (iSCSI PDUs).

   Connection Handle - An information element that identifies the
       particular iSCSI connection and is unique for a given iSCSI-iSER
       pair.  Every invocation of an Operational Primitive is qualified
       with the Connection Handle.

   Data Sink - The peer receiving a data payload.  Note that the Data
       Sink can be required to both send and receive RDMAP Messages to
       transfer a data payload.

   Data Source - The peer sending a data payload.  Note that the Data
       Source can be required to both send and receive RDMAP Messages
       to transfer a data payload.

   Datamover Interface (DI) - The interface between the iSCSI Layer and
       the Datamover Layer as described in [DA].




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   Datamover Layer - A layer that is directly below the iSCSI Layer and
       above the underlying transport layers.  This layer exposes and
       uses a set of transport independent Operational Primitives for
       the communication between the iSCSI Layer and itself.  The
       Datamover layer, operating in conjunction with the transport
       layers, moves the control and data information on the iSCSI
       connection.  In this specification, the iSER Layer is the
       Datamover layer.

   Datamover Protocol - A Datamover protocol is the wire-protocol that
       is defined to realize the Datamover layer functionality.  In
       this specification, the iSER protocol is the Datamover protocol.

   Event - An indication provided by the RDMAP Layer to the ULP to
       indicate a Completion or other condition requiring immediate
       attention.

   Inbound RDMA Read Queue Depth (IRD) - The maximum number of incoming
       outstanding RDMA Read Requests that the RNIC can handle on a
       particular RDMAP Stream at the Data Source.

   Invalidate STag - A mechanism used to prevent the Remote Peer from
       reusing a previous explicitly Advertised STag, until the Local
       Peer makes it available through a subsequent explicit
       Advertisement.

   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.

   iSCSI - The iSCSI protocol as defined in [RFC3720] is a mapping of
       the SCSI remote procedure model of SAM-2 over TCP.

   iSCSI control-type PDU - Any iSCSI PDU that is not an iSCSI data-
       type PDU and also not a SCSI Data-out PDU carrying solicited
       data 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.

   iSCSI data-type PDU - 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.  An iSCSI 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 - SCSI Data-In PDU and R2T PDU.


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   iSCSI Layer - A layer in the protocol stack implementation within an
       end node that implements the iSCSI protocol and interfaces with
       the iSER Layer via the Datamover Interface.

   iSCSI PDU (iSCSI Protocol Data Unit) - The iSCSI Layer at the
       initiator and the iSCSI Layer at the target divide their
       communications into messages.  The term "iSCSI protocol data
       unit" (iSCSI PDU) is used for these messages.

   iSCSI/iSER Connection - An iSER-assisted iSCSI connection.

   iSCSI/iSER Session - An iSER-assisted iSCSI session.

   iSCSI-iSER Pair - The iSCSI Layer and the underlying iSER Layer.

   iSER - iSCSI Extensions for RDMA, the protocol defined in this
       document.

   iSER-assisted - A term generally used to describe the operation of
       iSCSI when the iSER functionality is also enabled below the
       iSCSI Layer for the specific iSCSI/iSER connection in question.

   iSER-IRD - This variable represents the maximum number of incoming
       outstanding RDMA Read Requests that the iSER Layer at the
       initiator declares on a particular RDMAP Stream.

   iSER-ORD - This variable represents the maximum number of
       outstanding RDMA Read Requests that the iSER Layer can initiate
       on a particular RDMAP Stream.  This variable is maintained only
       by the iSER Layer at the target.

   iSER Layer - The layer that implements the iSCSI Extensions for RDMA
       (iSER) protocol.

   iWARP - A suite of wire protocols comprising of [RDMAP], [DDP], and
       [MPA] when layered above [TCP].  [RDMAP] and [DDP] may be
       layered above SCTP or other transport protocols.

   Local Mapping -                 - A task state record maintained by the iSER Layer
       that associates the Initiator Task Tag to the Local STag(s).
       The specifics of the record structure are implementation
       dependent.

   Local Peer - The RDMAP implementation on the local end of the
       connection.  Used to refer to the local entity when describing
       protocol exchanges or other interactions between two Nodes.



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   Node - A computing device attached to one or more links of a
       network.  A Node in this context does not refer to a specific
       application or protocol instantiation running on the computer.
       A Node may consist of one or more RNICs installed in a host
       computer.

   Operational Primitive - An Operational Primitive 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 and a Datamover layer 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.  A full discussion of the Operational
       Primitive types and request-response semantics available to
       iSCSI and iSER can be found in [DA].

   Outbound RDMA Read Queue Depth (ORD) - The maximum number of
       outstanding RDMA Read Requests that the RNIC can initiate on a
       particular RDMAP Stream at the Data Sink.

   RDMA-enabled Network Interface Controller (RNIC) - A network I/O
       adapter or embedded controller with iWARP functionality.

   RDMA Operation - A sequence of RDMAP Messages, including control
       Messages, to transfer data from a Data Source to a Data Sink.
       The following RDMA Operations are defined - RDMA Write
       Operation, RDMA Read Operation, Send Operation, Send with
       Invalidate Operation, Send with Solicited Event Operation, Send
       with Solicited Event and Invalidate Operation, and Terminate
       Operation.

   RDMA Protocol (RDMAP) - A wire protocol that supports RDMA
       Operations to transfer ULP data between a Local Peer and the
       Remote Peer as described in [RDMAP].

   RDMA Read Operation - An RDMA Operation used by the Data Sink to
       transfer the contents of a Data Source buffer from the Remote
       Peer to a Data Sink buffer at the Local Peer.  An RDMA Read
       operation consists of a single RDMA Read Request Message and a
       single RDMA Read Response Message.

   RDMA Read Request - An RDMAP Message used by the Data Sink to
       request the Data Source to transfer the contents of a buffer.
       The RDMA Read Request Message describes both the Data Source and
       the Data Sink buffers.


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   RDMA Read Response - An RDMAP Message used by the Data Source to
       transfer the contents of a buffer to the Data Sink, in response
       to an RDMA Read Request.  The RDMA Read Response Message only
       describes the Data Sink buffer.

   RDMA Write Operation - An RDMA Operation used by the Data Source to
       transfer the contents of a Data Source buffer from the Local
       Peer to a Data Sink buffer at the Remote Peer.  The RDMA Write
       Message only describes the Data Sink buffer.

   RDMAP Message - The sequence of RDMAP packets which represent a
       single RDMA operation or a part of RDMA Read Operation.

   RDMAP Stream - A single bidirectional association between the peer
       RDMAP layers on two Nodes over a single transport-level stream.
       For iSER, the association is created when the iSCSI connection
       transitions to iSER-assisted mode following a successful iSCSI
       Login Phase during which iSER support is negotiated.

   Remote Direct Memory Access (RDMA) - A method of accessing memory on
       a remote system in which the local system specifies the remote
       location of the data to be transferred.  Employing an RNIC in the
       remote system allows the access to take place without
       interrupting the processing of the CPU(s) on the system.

   Remote Mapping -                  - A task state record maintained by the iSER Layer
       that associates the Initiator Task Tag to the Advertised STag(s).
       The specifics of the record structure are implementation
       dependent.

   Remote Peer - The RDMAP implementation on the opposite end of the
       connection.  Used to refer to the remote entity when describing
       protocol exchanges or other interactions between two Nodes.

   SCSI Layer - This layer builds/receives SCSI CDBs (Command
       Descriptor Blocks) and sends/receives them with the remaining
       command execute [SAM2] parameters to/from the iSCSI Layer.

   Send - An RDMA Operation that transfers the contents of a ULP Buffer
       from the Local Peer to a Buffer at the Remote Peer.

   Send Message Type - A Send Message, Send with Invalidate Message,
       Send with Solicited Event Message, or Send with Solicited Event
       and Invalidate Message.

   SendInvSE Message - A Send with Solicited Event and Invalidate
       Message.


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   SendSE Message - A Send with Solicited Event Message

   Sequence Number (SN) - DataSN for a SCSI Data-in PDU and R2TSN for
       an R2T PDU.  The semantics for both types of sequence numbers
       are as defined in [RFC3720].

   Session, iSCSI Session - The group of Connections that link an
       initiator SCSI port with a target SCSI port form an iSCSI
       session (equivalent to a SCSI I-T nexus).  Connections can be
       added to and removed from a session even while the I-T nexus is
       intact.  Across all connections within a session, an initiator
       sees one and the same target.

   Solicited Event (SE) - A facility by which an RDMA Operation sender
       may cause an Event to be generated at the recipient, if the
       recipient is configured to generate such an Event, when a Send
       with Solicited Event or Send with Solicited Event and Invalidate
       Message is received.

   Steering Tag (STag) - An identifier of a Tagged Buffer on a Node as
       defined in [RDMAP] and [DDP].

   Tagged Buffer - A buffer that is explicitly Advertised to a Remote
       Peer through exchange of an STag, Tagged Offset, and length.

   Tagged Offset (TO) - The offset within a Tagged Buffer.

   Traditional iSCSI - Refers to the iSCSI protocol as defined in
       [RFC3720] (i.e. without the iSER enhancements).

   Untagged Buffer - A buffer that is not explicitly Advertised to the
       Remote Peer.

1.2  Acronyms

   Acronym        Definition

   --------------------------------------------------------------

   AHS            Additional Header Segment

   BHS            Basic Header Segment

   CO             Connection Only

   CRC            Cyclic Redundancy Check



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   DDP            Direct Data Placement Protocol

   DI             Datamover Interface

   IANA           Internet Assigned Numbers Authority

   IETF           Internet Engineering Task Force

   I/O            Input - Output

   IO             Initialize Only

   IP             Internet Protocol

   IPsec          Internet Protocol Security

   iSER           iSCSI Extensions for RDMA

   ITT            Initiator Task Tag

   LO             Leading Only

   MPA            Marker PDU Aligned Framing for TCP

   NOP            No Operation

   NSG            Next Stage (during the iSCSI Login Phase)

   OS             Operating System

   PDU            Protocol Data Unit

   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

   RNIC           RDMA-enabled Network Interface Controller

   SAM2           SCSI Architecture Model - 2

   SCSI           Small Computer Systems Interface


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   SNACK          Selective Negative Acknowledgment - also

                  Sequence Number Acknowledgement for data

   STag           Steering Tag

   SW             Session Wide

   TCP            Transmission Control Protocol

   TMF            Task Management Function

   TO             Tagged Offset

   ULP            Upper Level Protocol


































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2  Introduction

2.1  Motivation

   The iSCSI protocol ([RFC3720]) is a mapping of the SCSI remote
   procedure invocation model (see [SAM2]) over the TCP protocol.  SCSI
   commands are carried by iSCSI requests and SCSI responses and status
   are carried by iSCSI responses.  Other iSCSI protocol exchanges and
   SCSI Data are also transported in iSCSI PDUs.

   Out-of-order TCP segments in the Traditional iSCSI model have to be
   stored and reassembled before the iSCSI protocol layer within an end
   node can place the data in the iSCSI buffers.  This reassembly is
   required because not every TCP segment is likely to contain an iSCSI
   header to enable its placement and TCP itself does not have a built-
   in mechanism for signaling ULP message boundaries to aid placement
   of out-of-order segments.  This TCP reassembly at high network
   speeds is quite counter-productive for the following reasons: wasted
   memory bandwidth in data copying, need for reassembly memory, wasted
   CPU cycles in data copying, and the general store-and-forward
   latency from an application perspective.  TCP reassembly was
   recognized as a serious issue in [RFC3720], and the notion of a
   "sync and steering layer" was introduced that is optional to
   implement and use.  One specific sync and steering mechanism, called
   "markers", was defined in [RFC3720] which provides an application-
   level way of framing iSCSI PDUs within the TCP data stream even when
   the TCP segments are not yet reassembled to be in-order.

   With these defined techniques in [RFC3720], a Network Interface
   Controller customized for iSCSI (SNIC) could offload the TCP/IP
   processing and support direct data placement.

   Supporting direct data placement is the main function of the iWARP
   protocol suite.  A NIC enhanced with the RDMAP/DDP functions (RNIC)
   can be used by any application that has been extended to support
   RDMA.

   With the availability of RNICs within a host system, which does not
   have SNICs, it is appropriate for iSCSI to be able to exploit the
   direct data placement function of the RNIC like other applications.

   iSCSI Extensions for RDMA (iSER) is designed precisely to take
   advantage of generic RDMA technologies - iSER's goal is to permit
   iSCSI to employ direct data placement and RDMA capabilities using a
   generic RNIC.  In summary, iSCSI/iSER protocol stack is designed to
   enable scaling to high speeds by relying on a generic data placement



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   process and RDMA technologies and products, which enable direct data
   placement of both in-order and out-of-order data.

   This document describes iSER as a protocol extension to iSCSI, both
   for convenience of description and also because it is true in a very
   strict protocol sense.  However, it is to be noted that iSER is in
   reality extending the connectivity of the iSCSI protocol defined in
   [RFC3720], and the name iSER reflects this reality.

   When the iSCSI protocol as defined in [RFC3720] (i.e. without the
   iSER enhancements) is intended in the rest of the document, the term
   "Traditional iSCSI" is used to make the intention clear.

2.2  Architectural Goals

   This section summarizes the architectural goals that guided the
   design of iSER.

   1. Provide iWARP-based data transfer model for iSCSI that enables
     direct in order or out of order data placement of SCSI data into
     pre-allocated SCSI buffers while maintaining in order data
     delivery.

   2. Not require any major changes to SCSI Architecture Model (SAM/SAM-
     2/SAM-3) and SCSI command set standards.

   3. Utilize existing iSCSI infrastructure (sometimes referred to as
     "iSCSI ecosystem") including but not limited to MIB,
     bootstrapping, negotiation, naming & discovery, and security.

   4. Not require iSCSI full feature phase interoperability between an
     end node operating in Traditional iSCSI mode, and an end node
     operating in iSER-assisted mode.

   5. Allow initiator and target implementations that utilize generic
     RNICs and implement iSCSI and iSER in software (not require iSCSI
     or iSER specific assists in the iWARP protocol suite or RNIC).

   6. Require full and only generic iWARP functionality at both the
     initiator and the target.

   7. Require a session to operate in the Traditional iSCSI data
     transfer mode if iSER is not supported by either the initiator or
     the target.

   8. Implement a light weight Datamover protocol for iSCSI with minimal
     state maintenance.


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2.3  Protocol Overview

   Consistent with the architectural goals stated in section 2.2, the
   iSER protocol does not require changes in the iSCSI ecosystem or any
   related SCSI specifications.  iSER protocol defines the mapping of
   iSCSI PDUs to RDMAP Messages in such a way that it is entirely
   feasible to realize iSCSI/iSER implementations that are based on
   generic RNICS.  The iSER protocol layer requires minimal state
   maintenance to assist an iSCSI full feature phase connection,
   besides being oblivious to the notion of an iSCSI session.  The
   crucial protocol aspects of iSER may be summarized thus:

   1. iSER-assisted mode is negotiated during the iSCSI login for each
      session, and an entire iSCSI session can only operate in one mode
      (i.e. a connection in a session cannot operate in iSER-assisted
      mode if a different connection of the same session is already in
      full feature mode in the Traditional iSCSI mode).

   2. Once in iSER-assisted mode, all iSCSI interactions on that
      connection use RDMAP Messages.

   3. A Send Message Type is used for carrying an iSCSI control-type
      PDU preceded by an iSER header.  See section 7.2 for more details
      on iSCSI control-type PDUs.

   4. RDMA Write, RDMA Read Request, and RDMA Read Response Messages
      are used for carrying control and all data information associated
      with the iSCSI data-type PDUs.  See section 7.1 for more details
      on iSCSI data-type PDUs.

   5. Target drives all data transfer (with the exception of iSCSI
      unsolicited data) for SCSI writes and SCSI reads, by issuing RDMA
      Read Requests and RDMA Writes respectively.

   6. The iWARP protocol suite guarantees data integrity.  (For TCP,
      iWARP uses a CRC-enhanced framing layer on TCP).  For this
      reason, iSCSI header and data digests are negotiated to "None"
      for iSCSI/iSER sessions.

   7. The iSCSI error recovery hierarchy defined in [RFC3720] is fully
      supported by iSER.

   8. iSER requires no changes to iSCSI authentication, security, and
      text mode negotiation mechanisms.

   Note that Traditional iSCSI implementations may have to be adapted
   to employ iSER.  It is expected that the adaptation when required is


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   likely to be centered around the upper layer interface requirements
   of iSER (section 3).

2.4  RDMA services and iSER

   iSER is designed to work with software and/or hardware protocol
   stacks providing the protocol services defined in [RDMAP].  The
   following subsections describe the key protocol elements of RDMAP
   that iSER relies on.

2.4.1  STag

   An STag is the RNIC-unique identifier of an I/O Buffer that the iSER
   Layer Advertises to the remote iSCSI/iSER node in order to complete
   a SCSI I/O.

   In iSER, Advertisement is the act of informing the target by the
   initiator that an I/O Buffer is available at the initiator for RDMA
   Read or RDMA Write access by the target.  The initiator Advertises
   the I/O Buffer by including the STag in the header of an iSER
   Message containing the SCSI Command PDU to the target.  The base
   Tagged Offset is not explicitly specified, but the target must
   always assume it as zero.  The buffer length is as specified in the
   SCSI Command PDU.

   The iSER Layer at the initiator Advertises the STag for the I/O
   Buffer of each SCSI I/O to the iSER Layer at the target in the iSER
   header of the SendSE Message containing the SCSI Command PDU, unless
   the I/O can be completely satisfied by unsolicited data alone.

   The iSER Layer at the target provides the STag for the I/O Buffer
   that is the Data Sink of an RDMA Read Operation (section 2.4.4) to
   the RDMAP layer on the initiator node - i.e. this is completely
   transparent to the iSER Layer at the initiator.

   The iSER protocol is defined so that the Advertised STag is
   automatically invalidated upon a normal completion of the associated
   task.  This automatic invalidation is realized via the SendInvSE
   Message carrying the SCSI Response PDU.  There are two exceptions to
   this automatic invalidation - bidirectional commands, and abnormal
   completion of a command.  The iSER Layer at the initiator is
   required to explicitly invalidate the STag in these cases, in
   addition to sanity checking the automatic invalidation even when
   that does happen.





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2.4.2  Send

   Send is the RDMA Operation that is not addressed to an Advertised
   buffer by the sending side, and thus uses Untagged buffers on the
   receiving side.

   The iSER Layer at the initiator uses the Send Operation to transmit
   any iSCSI control-type PDU to the target.  As an example, the
   initiator uses Send Operations to transfer iSER Messages containing
   SCSI Command PDUs to the iSER Layer at the target.

   An iSER layer at the target uses the Send Operation to transmit any
   iSCSI control-type PDU to the initiator.  As an example, the target
   uses Send Operations to transfer iSER Messages containing SCSI
   Response PDUs to the iSER Layer at the initiator.

2.4.3  RDMA Write

   RDMA Write is the RDMA Operation that is used to place data into an
   Advertised buffer on the receiving side.  The sending side addresses
   the Message using an STag and a Tagged Offset that are valid on the
   Data Sink.

   The iSER Layer at the target uses the RDMA Write Operation to
   transfer the contents of a local I/O Buffer to an Advertised I/O
   Buffer at the initiator.  The iSER Layer at the target uses the RDMA
   Write to transfer whole or part of the data required to complete a
   SCSI Read command.

   The iSER Layer at the initiator does not employ RDMA Writes.

2.4.4  RDMA Read

   RDMA Read is the RDMA Operation that is used to retrieve data from
   an Advertised buffer on a remote node.  The sending side of the RDMA
   Read Request addresses the Message using an STag and a Tagged Offset
   that are valid on the Data Source in addition to providing a valid
   local STag and Tagged Offset that identify the Data Sink.

   The iSER Layer at the target uses the RDMA Read Operation to
   transfer the contents of an Advertised I/O Buffer at the initiator
   to a local I/O Buffer at the target.  The iSER Layer at the target
   uses the RDMA Read to fetch whole or part of the data required to
   complete a SCSI Write.

   The iSER Layer at the initiator does not employ RDMA Reads.



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2.5  SCSI Read Overview

   The iSER Layer at the initiator receives the SCSI Command PDU from
   the iSCSI Layer.  The iSER Layer at the initiator generates an STag
   for the I/O Buffer of the SCSI Read and Advertises the buffer by
   including the STag as part of the iSER header for the PDU.  The iSER
   Message is transferred to the target using a SendSE Message.

   The iSER Layer at the target uses one or more RDMA Writes to
   transfer the data required to complete the SCSI Read.

   The iSER Layer at the target uses a SendInvSE Message to transfer
   the SCSI Response PDU back to the iSER Layer at the initiator.  The
   iSER Layer at the initiator notifies the iSCSI Layer of the
   availability of the SCSI Response PDU.

2.6  SCSI Write Overview

   The iSER Layer at the initiator receives the SCSI Command PDU from
   the iSCSI Layer.  If solicited data transfer is involved, the iSER
   Layer at the initiator generates an STag for the I/O Buffer of the
   SCSI Write and Advertises the buffer by including the STag as part
   of the iSER header for the PDU.  The iSER Message is transferred to
   the target using a SendSE Message.

   The iSER Layer at the initiator may optionally send one or more non-
   immediate unsolicited data PDUs to the target using Send Message
   Types.

   If solicited data transfer is involved, the iSER Layer at the target
   uses one or more RDMA Reads to transfer the data required to
   complete the SCSI Write.

   The iSER Layer at the target uses a SendInvSE Message to transfer
   the SCSI Response PDU back to the iSER Layer at the initiator.  The
   iSER Layer at the initiator notifies the iSCSI Layer of the
   availability of the SCSI Response PDU.

2.7   iSCSI/iSER Layering

   iSCSI Extensions for RDMA (iSER) is layered between the iSCSI layer
   and the RDMAP layer.  Figure 1 shows an example of the relationship
   between SCSI, iSCSI, iSER, RDMAP, and the rest of the iWARP stack
   when the transport layer is TCP.





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                 +-------------------------------------+
                 |              SCSI                   |
                 +-------------------------------------+
                 |              iSCSI                  |
      DI ------> +-------------------------------------+
                 |              iSER                   |
                 +-------------------------------------+
                 |              RDMAP                  |
                 +-------------------------------------+
                 |               DDP                   |
                 +-------------------------------------+
                 |               MPA                   |
                 +-------------------------------------+
                 |               TCP                   |
                 +-------------------------------------+
       Figure 1 Example of iSCSI/iSER Layering in Full Feature Mode

































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3  Upper Layer Interface Requirements

   This section discusses the upper layer interface requirements in the
   form of an abstract model of the required interactions between the
   iSCSI Layer and the iSER Layer.  The abstract model used here is
   derived from the architectural model described in [DA].

   The interface requirements are specified by Operational Primitives.
   An Operational Primitive is an abstract functional interface
   procedure between the iSCSI Layer and the iSER Layer that requests
   one layer to perform a specific action on behalf of the other layer
   or notifies the other layer of some event.  Whenever an Operational
   Primitive in invoked, the Connection_Handle qualifier is used to
   identify a particular iSCSI connection.  For some Operational
   Primitives, a Data_Descriptor is used to identify the iSCSI/SCSI
   data buffer associated with the requested or completed operation.

   The abstract model and the Operational Primitives defined in this
   section facilitate the description of the iSER protocol.  In the
   rest of the iSER specification, the compliance statements related to
   the use of these Operational Primitives are only for the purpose of
   the required interactions between the iSCSI Layer and the iSER
   Layer.  Note that the compliance statements related to the
   Operational Primitives in the rest of this specification only
   mandate functional equivalence on implementations, but do not put
   any requirements on the implementation specifics of the interface
   between the iSCSI Layer and the iSER Layer.

   Each Operational Primitive is invoked with a set of qualifiers which
   specify the information context for performing the specific action
   being requested of the Operational Primitive.  While the qualifiers
   are required, the method of realizing the qualifiers (e.g., by
   passing synchronously with invocation, or by retrieving from task
   context, or by retrieving from shared memory, etc.) is
   implementation dependent.

3.1  Operational Primitives offered by iSER

   The iSER protocol layer MUST support the following Operational
   Primitives to be used by the iSCSI protocol layer.

3.1.1  Send_Control

       Input qualifiers:  Connection_Handle, BHS and AHS (if any) of
       the iSCSI PDU, iSCSI PDU specific qualifiers

       Return results:  Not specified


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   This is used by the iSCSI Layers at the initiator and the target to
   request the outbound transfer of an iSCSI control-type PDU (see
   section 7.2).  For details on iSCSI PDU specific qualifiers, see
   section 7.3.  The iSCSI Layer can only invoke the Send_Control
   Operational Primitive when the connection is in iSER-assisted mode.

3.1.2  Put_Data

       Input qualifiers:  Connection_Handle, content of a SCSI Data-in
       PDU header, Data_Descriptor, Notify_Enable

       Return results:  Not specified

   This is used by the iSCSI Layer at the target to request the
   outbound transfer of data for a SCSI Data-in PDU from the buffer
   identified by the Data_Descriptor qualifier.  The iSCSI Layer can
   only invoke the Put_Data Operational Primitive when the connection
   is in iSER-assisted mode.

   The Notify_Enable qualifier is used to indicate to the iSER Layer
   whether or not it should generate an eventual local completion
   notification to the iSCSI Layer.  See section 3.2.2 on
   Data_Completion_Notify for details.

3.1.3  Get_Data

       Input qualifiers:  Connection_Handle, content of an R2T PDU,
       Data_Descriptor, Notify_Enable

       Return results:  Not specified

   This used by the iSCSI Layer at the target to request the inbound
   transfer of solicited data requested by an R2T PDU into the buffer
   identified by the Data_Descriptor qualifier.  The iSCSI Layer can
   only invoke the Get_Data Operational Primitive when the connection
   is in iSER-assisted mode.

   The Notify_Enable qualifier is used to indicate to the iSER Layer
   whether or not it should generate the eventual local completion
   notification to the iSCSI Layer.  See section 3.2.2 on
   Data_Completion_Notify for details.

3.1.4  Allocate_Connection_Resources

       Input qualifiers:  Connection_Handle, Resource_Descriptor
       (optional)



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       Return results:  Status

   This is used by the iSCSI Layers at the initiator and the target to
   request the allocation of all connection resources necessary to
   support iWARP for an operational iSCSI/iSER connection.  The iSCSI
   Layer may optionally specify the implementation-specific resource
   requirements for the iSCSI connection using the Resource_Descriptor
   qualifier.

   A return result of Status=success means the invocation succeeded,
   and a return result of Status=failure means that the invocation
   failed.  If the invocation is for a Connection_Handle for which an
   earlier invocation succeeded, the request will be ignored by the
   iSER Layer and the result of Status=success will be returned.  Only
   one Allocate_Connection_Resources Operational Primitive invocation
   can be outstanding for a given Connection_Handle at any time.

3.1.5  Deallocate_Connection_Resources

       Input qualifiers:  Connection_Handle

       Return results:  Not specified

   This is used by the iSCSI Layers at the initiator and the target to
   request the deallocation of all connection resources that were
   allocated earlier as a result of a successful invocation of the
   Allocate_Connection_Resources Operational Primitive.

3.1.6  Enable_Datamover

       Input qualifiers:  Connection_Handle,
       Transport_Connection_Descriptor, Final Login_Response_PDU
       (optional)

       Return results:  Not specified

   This is used by the iSCSI Layers at the initiator and the target to
   request that a specified iSCSI connection be transitioned to iSER-
   assisted mode.  The Transport_Connection_Descriptor qualifier is
   used to identify the specific connection associated with the
   Connection_Handle.  The iSCSI layer can only invoke the
   Enable_Datamover Operational Primitive when 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 PDU that concludes
   the iSCSI Login phase and which must be sent as a byte stream as


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   expected by the iSCSI Layer at the initiator.  When this qualifier
   is used, the iSER Layer at the target MUST transmit this final Login
   Response PDU before transitioning to iSER-assisted mode.

3.1.7  Connection_Terminate

       Input qualifiers:  Connection_Handle

       Return results:  Not specified

   This is used by the iSCSI Layers at the initiator and the target to
   request that a specified iSCSI/iSER connection be terminated and all
   associated connection and task resources be freed.  When this
   Operational Primitive invocation returns to the iSCSI layer, the
   iSCSI layer may assume full ownership of all iSCSI-level resources,
   e.g. I/O Buffers, associated with the connection.

3.1.8  Notice_Key_Values

       Input qualifiers:  Connection_Handle, number of keys, list of
       Key-Value pairs

       Return results:  Not specified

   This is used by the iSCSI Layers at the initiator and the target to
   request the iSER Layer to take note of the specified Key-Value pairs
   which were negotiated by the iSCSI peers for the connection.

3.1.9  Deallocate_Task_Resources

       Input qualifiers:  Connection_Handle, ITT

       Return results:  Not specified

   This is used by the iSCSI Layers at the initiator and the target to
   request the deallocation of all iWARP-specific resources allocated
   by the iSER Layer for the task identified by the ITT qualifier.
   This Operational Primitive is only used for tasks that did not
   conclude with a SCSI Response PDU, and is not used when a SCSI
   Response PDU normally concludes a task.  iWARP-specific task
   resources are deallocated by the iSER Layer when a SCSI Response PDU
   normally concludes a task, even if the SCSI Status was not success.







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3.2  Operational Primitives used by iSER

   The iSER layer MUST use the following Operational Primitives offered
   by the iSCSI protocol layer when the connection is in iSER-assisted
   mode.

3.2.1  Control_Notify

       Input qualifiers:  Connection_Handle, an iSCSI control-type PDU

       Return results:  Not specified

   This is used by the iSER Layers at the initiator and the target to
   notify the iSCSI Layer of the availability of an inbound iSCSI
   control-type PDU.  A PDU is described as "available" to the iSCSI
   Layer when the iSER Layer notifies the iSCSI Layer of the reception
   of that inbound PDU, along with an implementation-specific
   indication as to where the received PDU is.

3.2.2  Data_Completion_Notify

       Input qualifiers:  Connection_Handle, ITT, SN

       Return results:  Not specified

   This is used by the iSER Layer to notify the iSCSI Layer of the
   completion of outbound data transfer that was requested by the iSCSI
   Layer only if the invocation of the Put_Data Operational Primitive
   (see section 3.1.2) was qualified with Notify_Enable set.  SN refers
   to the DataSN associated with the SCSI Data-In PDU.

   This is used by the iSER Layer to notify the iSCSI Layer of the
   completion of inbound data transfer that was requested by the iSCSI
   Layer only if the invocation of the Get_Data Operational Primitive
   (see section 3.1.3) was qualified with Notify_Enable set.  SN refers
   to the R2TSN associated with the R2T PDU.

3.2.3  Data_ACK_Notify

       Input qualifier:  Connection_Handle, ITT, DataSN

       Return results:  Not specified

   This is used by the iSER Layer at the target to notify the iSCSI
   Layer of the arrival of the data acknowledgement (as defined in
   [RFC3720]) requested earlier by the iSCSI Layer for the outbound
   data transfer via an invocation of the Put_Data Operational


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   Primitive where the A-bit in the SCSI Data-in PDU is set to 1.  See
   section 7.3.5.  DataSN refers to the expected 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].

3.2.4  Connection_Terminate_Notify

       Input qualifiers:  Connection_Handle

       Return results:  Not specified

   This is used by the iSER Layers at the initiator and the target to
   notify the iSCSI Layer of the unsolicited termination or failure of
   an iSCSI/iSER connection.  The iSER Layer MUST deallocate the
   connection and task resources associated with the terminated
   connection before the invocation of this Operational Primitive.
   Note that the Connection_Terminate_Notify Operational Primitive is
   not invoked when the termination of the connection was earlier
   requested by the local iSCSI Layer.

3.3  iSCSI Protocol Usage Requirements

   An iSER-assisted iSCSI protocol layer should satisfy the following
   protocol usage requirements from the iSER protocol:

   1.  The iSCSI Layers at both the initiator and the target MUST
       negotiate the RDMAExtensions key (see section 6.3) to "Yes" on
       the leading connection.  If the invocation of the
       Allocate_Connection_Resources Operational Primitive to the iSER
       layer fails after this key is negotiated to "Yes", the iSCSI
       layer MUST fail the iSCSI Login process or terminate the
       connection as appropriate.  See section 10.1.3.1 for details.

   2.  The iSCSI Layer at the initiator MUST set ExpDataSN = 0 in Task
       Management Function Requests for Task Allegiance Reassignment
       for read/bidirectional commands, so as to cause the target to
       send all unacknowledged read data.

   3.  The iSCSI Layer at the target MUST always return the SCSI status
       in a separate SCSI Response PDU for read commands, i.e., there
       MUST NOT be a "phase collapse" in concluding a SCSI Read
       Command.

   4.  The iSCSI Layers at both the initiator and the target MUST
       successfully negotiate the InitiatorRecvDataSegmentLength key



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       (see section 6.5) for each iSER-assisted connection, and follow
       its defined semantics.

   5.  The iSCSI Layer at both the initiator and the target MUST
       successfully negotiate the TargetRecvDataSegmentLength key (see
       section 6.4) for each iSER-assisted connection, and follow its
       defined semantics.

   6.  The iSCSI Layer at the initiator SHOULD NOT issue proactive
       (based on time-outs) SNACKs for PDUs that it presumes are lost.







































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4  Lower Layer Interface Requirements

4.1  Interactions with the iWARP Layer

   The iSER protocol layer is layered on top of the iWARP protocol
   stack (see Figure 1) and the following are the key features that are
   assumed to be supported by iWARP:

   *  The RDMAP layer supports all basic RDMAP operations, including
      RDMA Write Operation, RDMA Read Operation, Send Operation, Send
      with Invalidate Operation, Send with Solicited Event Operation,
      Send with Solicited Event & Invalidate Operation, and Terminate
      Operation.

   *  The RDMAP/DDP layers provide reliable, in-order message delivery
      and direct data placement.

   *  The RDMAP layer encapsulates a single iSER Message into a single
      RDMAP message on the Data Source side.  The RDMAP layer
      decapsulates the iSER Message before delivering it to the iSER
      Layer on the Data Sink side.

   *  When the iSER Layer provides the STag to be remotely invalidated
      to the RDMAP layer for a SendInvSE Message, the RDMAP layer uses
      this STag as the STag to be invalidated in the SendInvSE Message.

   *  The RDMAP layer uses the STag and Tagged Offset provided by the
      iSER Layer for the RDMA Write and RDMA Read Request Messages.

   *  When the RDMAP layer delivers the content of an RDMA Send Message
      Type to the iSER Layer, the RDMAP layer provides the length of
      the RDMA Send message.  This ensures that the iSER Layer does not
      have to carry a length field in the iSER header.

   *  When the RDMAP layer delivers the SendSE or SendInvSE Message to
      the iSER Layer, it notifies the iSER Layer with the mechanism
      provided on that interface.

   *  When the RDMAP layer delivers a SendInvSE Message to the iSER
      Layer, it passes the value of the STag that was invalidated.

   *  The RDMAP layer propagates all status and error indications to
      the iSER Layer.

   *  The iWARP implementation supports the enabling of the iWARP mode
      after Connection establishment.



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   *  Whenever the iSER Layer terminates the RDMAP Stream, the RDMAP
      layer terminates the associated Connection.

4.2  Interactions with the Transport Layer

   The iSER Layer does not interface with the transport layer (e.g.,
   TCP) directly.  During Connection setup, the iSCSI Layer is
   responsible for setting up the Connection.  If the login is
   successful, the iSCSI Layer invokes the Enable_Datamover Operational
   Primitive to request the iSER Layer to transition to the iSER-
   assisted mode for that iSCSI connection.  See section 5.1 on
   iSCSI/iSER Connection Setup.  After transitioning to iSER-assisted
   mode, the iWARP layer is responsible for maintaining the Connection
   and reports to the iSER Layer of any Connection failures.



































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5  Connection Setup and Termination

5.1  iSCSI/iSER Connection Setup

   During connection setup, the iSCSI Layer at the initiator is
   responsible for establishing a connection with the target.  After
   the connection is established, the iSCSI Layers at the initiator and
   the target enter the Login Phase using the same rules as outlined in
   [RFC3720].  Transition to iSER-assisted mode occurs when the
   connection transitions into the iSCSI full feature phase following a
   successful login negotiation between the initiator and the target in
   which iSER-assisted mode is negotiated and the connection resources
   necessary to support iWARP have been allocated at both the initiator
   and the target.

   iSER-assisted mode MUST be enabled only if it is negotiated on the
   leading connection during the LoginOperationalNegotiation Stage of
   the iSCSI Login Phase.  iSER-assisted mode is negotiated using the
   RDMAExtensions=<boolean-value> key.  Both the initiator and the
   target MUST exchange the RDMAExtensions key with the value set to
   "Yes" to enable iSER-assisted mode.  If both the initiator and the
   target fail to negotiate the RDMAExtensions key set to "Yes", then
   the connection MUST continue with the login semantics as defined in
   [RFC3720].

   iSER-assisted mode is defined for a Normal session only and the
   RDMAExtensions key MUST NOT be negotiated for a Discovery session.

   An iSER enabled node is not required to initiate the RDMAExtensions
   key exchange if its preference is for the Traditional iSCSI mode.
   The RDMAExtensions key, if offered, MUST be sent in the first
   available Login Response or Login Request PDU in the
   LoginOperationalNegotiation stage.  This is due to the fact that the
   value of some login parameters might depend on whether iSER-assisted
   mode is enabled or not.

   iSER-assisted mode is a session-wide attribute.  If both the
   initiator and the target negotiated RDMAExtensions="Yes" on the
   leading connection of a session, then all subsequent connections of
   the same session MUST enable iSER-assisted mode without having to
   exchange RDMAExtensions key during the iSCSI Login Phase.
   Conversely, if both the initiator and the target failed to negotiate
   RDMAExtensions to "Yes" on the leading connection of a session, then
   the RDMAExtensions key MUST NOT be negotiated further on any
   additional subsequent connection of the session.




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   When the RDMAExtensions key is negotiated to "Yes", the HeaderDigest
   and the DataDigest keys MUST be negotiated to "None" on all
   iSCSI/iSER connections participating in that iSCSI session.  This is
   because, for an iSCSI/iSER connection, the iWARP protocol suite
   provides a CRC32c-based error detection for all iWARP Messages.
   Furthermore, all SCSI Read data are sent using RDMA Write Messages
   instead of the SCSI Data-in PDUs, and all solicited SCSI write data
   are sent using RDMA Read Response Messages instead of the SCSI Data-
   out PDUs.  HeaderDigest and DataDigest which apply to iSCSI PDUs
   would not be appropriate for RDMA Read and RDMA Write operations
   used with iSER.

5.1.1  Initiator Behavior

   If the outcome of the iSCSI negotiation is to enable iSER-assisted
   mode, then on the initiator side, prior to sending the Login Request
   with the T (Transit) bit set to 1 and the NSG (Next Stage) field set
   to FullFeaturePhase, the iSCSI Layer MUST request the iSER Layer to
   allocate the connection resources necessary to support iWARP by
   invoking the Allocate_Connection_Resources Operational Primitive.
   The connection resources required are defined by implementation and
   are outside the scope of this specification.  The iSCSI Layer may
   invoke the Notice_Key_Values Operational Primitive before invoking
   the Allocate_Connection_Resources Operational Primitive to request
   the iSER Layer to take note of the negotiated values of the iSCSI
   keys for the Connection.  The specific keys to be passed in as input
   qualifiers are implementation dependent.  These may include, but not
   limited to, MaxOutstandingR2T, ErrorRecoveryLevel, etc.

   Among the connection resources allocated at the initiator is the
   Inbound RDMA Read Queue Depth (IRD).  As described in section 9.5.1,
   R2Ts are transformed by the target into RDMA Read operations.  IRD
   limits the maximum number of simultaneously incoming outstanding
   RDMA Read Requests per an RDMAP Stream from the target to the
   initiator.  The required value of IRD is outside the scope of the
   iSER specification.  The iSER Layer at the initiator MUST set IRD to
   1 or higher if R2Ts are to be used in the connection.  However, the
   iSER Layer at the initiator MAY set IRD to 0 based on implementation
   configuration which indicates that no R2Ts will be used on that
   connection.  Initially, the iSER-IRD value at the initiator SHOULD
   be set to the IRD value at the initiator and MUST NOT be more than
   the IRD value.

   On the other hand, the Outbound RDMA Read Queue Depth (ORD) MAY be
   set to 0 since the iSER Layer at the initiator does not issue RDMA
   Read Requests to the target.



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   If the iSCSI Layer invokes the Allocate_Connection_Resources
   Operational Primitive after the connection resources necessary to
   support iWARP are known through iSCSI negotiation, then only the
   connection resources required are allocated.  However, failure to
   allocate the requested connection resources locally results in a
   login failure and its handling is described in section 10.1.3.1.

   If the iSCSI Layer invokes the Allocate_Connection_Resources
   Operational Primitive before the iSCSI Login Phase, it avoids the
   potential login failure due to failure to allocate the requested
   connection resources.  However, since the connection resources
   necessary to support iWARP are not yet known, the connection
   resources to be allocated must equal or exceed whatever is required
   as determined in the later iSCSI negotiation.  As a result,
   resources are allocated but unused if the connection resources
   required are less than the allocated ones unless the iSCSI Layer
   frees up the unused resources.  In the event that the iSCSI login
   fails, or if the connection is to remain in Traditional iSCSI mode,
   the connection resources to support iWARP MUST be deallocated as
   described in section 10.1.4.6.

   If the iSER Layer at the initiator is successful in allocating the
   connection resources necessary to support iWARP, the following
   events MUST occur in the specified sequence:

   1.  The iSER Layer MUST return a success status to the iSCSI Layer
       in response to the Allocate_Connection_Resources Operational
       Primitive.

   2.  After the target returns the Login Response with the T bit set
       to 1 and the NSG field set to FullFeaturePhase, and a status
       class of 0 (Success), the iSCSI Layer MUST request the iSER
       Layer to transition to iSER-assisted mode by invoking the
       Enable_Datamover Operational Primitive with the following
       qualifiers.  (See section 10.1.4.6 for the case when the status
       class is not Success.):

       a.  Connection_Handle that identifies the iSCSI connection.

       b.  Transport_Connection_Descriptor which identifies the
           specific transport connection associated with the
           Connection_Handle.

   3.  The iSER Layer MUST enable iWARP and transition the connection
       to iSER-assisted mode.




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   4.  The iSER Layer MUST send the iSER Hello Message as the first
       RDMAP message.  See Section 5.1.3 on iSER Hello Exchange.

   If an iSCSI implementation wants to ensure that the resources
   necessary to support iWARP are allocated and therefore invokes the
   Allocate_Connection_Resources Operational Primitive prior to
   initiating the iSCSI negotiation, then it is responsible for
   managing the resource deallocation if the iSCSI login fails or if
   the negotiated values of the iSCSI keys are different than the
   allocated value.

5.1.2  Target Behavior

   If the outcome of the iSCSI negotiation is to enable iSER-assisted
   mode, then on the target side, prior to sending the Login Response
   with the T (Transit) bit set to 1 and the NSG (Next Stage) field set
   to FullFeaturePhase, the iSCSI Layer MUST request the iSER Layer to
   allocate the resources necessary to support iWARP by invoking the
   Allocate_Connection_Resources Operational Primitive.  The connection
   resources required are defined by implementation and are outside the
   scope of this specification.  Optionally, the iSCSI Layer may invoke
   the Notice_Key_Values Operational Primitive before invoking the
   Allocate_Connection_Resources Operational Primitive to request the
   iSER Layer to take note of the negotiated values of the iSCSI keys
   for the Connection.  The specific keys to be passed in as input
   qualifiers are implementation dependent.  These may include, but not
   limited to, MaxOutstandingR2T, ErrorRecoveryLevel, etc.

   Among the connection resources allocated at the target is the
   Outbound RDMA Read Queue Depth (ORD).  As described in section
   9.5.1, R2Ts are transformed by the target into RDMA Read operations.
   The ORD limits the maximum number of simultaneously outstanding RDMA
   Read Requests per RDMAP Stream from the target to the initiator.
   Initially, the iSER-ORD value at the target SHOULD be set to the ORD
   value at the target.

   On the other hand, the IRD at the target MAY be set to 0 since the
   iSER Layer at the target does not expect RDMA Read Requests to be
   issued by the initiator.

   If the iSCSI Layer invokes the Allocate_Connection_Resources
   Operational Primitive after the connection resources necessary to
   support iWARP are known through iSCSI negotiation, then only the
   connection resources required are allocated.  However, failure to
   allocate the requested connection resources locally results in a
   login failure and its handling is described in section 10.1.3.1.



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   If the iSCSI Layer invokes the Allocate_Connection_Resources
   Operational Primitive before the iSCSI Login Phase, it avoids the
   potential login failure due to failure to allocate the requested
   connection resources.  However, since the connection resources
   necessary to support iWARP are not yet known, the connection
   resources to be allocated must equal or exceed whatever is required
   as determined in the later iSCSI negotiation.  As a result,
   resources are allocated but unused if the connection resources
   required are less than the allocated ones unless the iSCSI Layer
   frees up the unused resources.  In the event that the iSCSI login
   fails, or if the connection is to remain in Traditional iSCSI mode,
   the connection resources to support iWARP MUST be deallocated as
   described in section 10.1.4.6.

   If the iSER Layer at the target is successful in allocating the
   connection resources necessary to support iWARP, the following
   events MUST occur in the specified sequence:

   1.  The iSER Layer MUST return a success status to the iSCSI Layer
       in response to the Allocate_Connection_Resources Operational
       Primitive.

   2.  The iSCSI Layer MUST request the iSER Layer to transition to
       iSER-assisted mode by invoking the Enable_Datamover Operational
       Primitive with the following qualifiers:

       a.  Connection_Handle that identifies the iSCSI connection.

       b.  Transport_Connection_Descriptor which identifies the
           specific transport connection associated with the
           Connection_Handle.

       c.  The final transport layer (e.g. TCP) message containing the
           Login Response with the T bit set to 1 and the NSG field set
           to FullFeaturePhase

   3.  The iSER Layer MUST send the final SCSI Login Response PDU in
       byte stream mode to conclude the iSCSI Login Phase.

   4.  After sending the final SCSI Login Response PDU in byte stream
       mode, the iSER Layer MUST enable iWARP and transition the
       connection to iSER-assisted mode.

   5.  After receiving the iSER Hello Message from the initiator, the
       iSER Layer MUST respond with the iSER HelloReply Message to be
       sent as the first RDMAP Message.  See section 5.1.3 on iSER
       Hello Exchange for more details.


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   Note: In the above sequence, the operations as described in the
   bullets 3 and 4 must be performed atomically.  Failure to do this
   may result in race conditions.

5.1.3  iSER Hello Exchange

   After the connection transitions into the iSER-assisted mode, the
   first RDMAP Message sent by the iSER Layer at the initiator to the
   target MUST be the iSER Hello Message.  The iSER Hello Message is
   used by the iSER Layer at the initiator to declare iSER parameters
   to the target.  See section 9.3 on iSER Header Format for iSER Hello
   Message.

   In response to the iSER Hello Message, the iSER Layer at the target
   MUST return the iSER HelloReply Message as the first RDMAP Message
   sent by the target.  The iSER HelloReply Message is used by the iSER
   Layer at the target to declare iSER parameters to the initiator.
   See section 9.4 on iSER Header Format for iSER HelloReply Message.

   In the iSER Hello Message, the iSER Layer at the initiator declares
   the iSER-IRD value to the target.

   Upon receiving the iSER Hello Message, the iSER Layer at the target
   MUST set the iSER-ORD value to the minimum of the iSER-ORD value at
   the target and the iSER-IRD value declared by the initiator.  The
   iSER Layer at the target MAY adjust (lower) its ORD value to match
   the iSER-ORD value if the iSER-ORD value is smaller than the ORD
   value at the target in order to free up the unused resources.

   In the iSER HelloReply Message, the iSER Layer at the target
   declares the iSER-ORD value to the initiator.

   Upon receiving the iSER HelloReply Message, the iSER Layer at the
   initiator MAY adjust (lower) its IRD value to match the iSER-ORD
   value in order to free up the unused resources, if the iSER-ORD
   value declared by the target is smaller than the iSER-IRD value
   declared by the initiator.

   It is an iSER level negotiation failure if the iSER parameters
   declared in the iSER Hello Message by the initiator is unacceptable
   to the target.  See section 10.1.3.2 on the handling of the error
   situation.







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5.2  iSCSI/iSER Connection Termination

5.2.1  Normal Connection Termination at the Initiator

   The iSCSI Layer at the initiator terminates an iSCSI/iSER connection
   normally by invoking the Send_Control Operational Primitive
   qualified with the Logout Request PDU.  The iSER Layer at the
   initiator MUST use a SendSE Message to send the Logout Request PDU
   to the target.  After the iSER Layer at the initiator receives the
   SendSE Message containing the Logout Response PDU from the target,
   it MUST notify the iSCSI Layer by invoking the Control_Notify
   Operational Primitive qualified with the Logout Response PDU.

   After the iSCSI logout process is complete, the iSCSI layer at the
   target is responsible for closing the iSCSI/iSER connection as
   described in Section 5.2.2.  After the RDMAP layer at the initiator
   reports that the Connection has been closed, the iSER Layer at the
   initiator MUST deallocate all connection and task resources (if any)
   associated with the connection, invalidate the Local Mapping(s) (if
   any) that associate the ITT(s) used on that connection to the local
   STag(s) before notifying the iSCSI Layer by invoking the
   Connection_Terminate_Notify Operational Primitive.

5.2.2  Normal Connection Termination at the Target

   Upon receiving the SendSE Message containing the Logout Request PDU,
   the iSER Layer at the target MUST notify the iSCSI Layer at the
   target by invoking the Control_Notify Operational Primitive
   qualified with the Logout Request PDU.  The iSCSI Layer completes
   the logout process by invoking the Send_Control Operational
   Primitive qualified with the Logout Response PDU.  The iSER Layer at
   the target MUST use a SendSE Message to send the Logout Response PDU
   to the initiator.  After the iSCSI logout process is complete, the
   iSCSI Layer at the target MUST request the iSER Layer at the target
   to terminate the RDMAP Stream by invoking the Connection_Terminate
   Operational Primitive.

   As part of the termination process, the RDMAP layer MUST close the
   Connection.  When the RDMAP layer notifies the iSER Layer after the
   RDMAP stream and the associated Connection are terminated, the iSER
   Layer MUST deallocate all connection and task resources (if any)
   associated with the connection, and invalidate the Local and Remote
   Mapping(s) (if any) that associate the ITT(s) used on that
   connection to the local STag(s) and the Advertised STag(s)
   respectively.




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5.2.3  Termination without Logout Request/Response PDUs

5.2.3.1  Connection Termination Initiated by the iSCSI Layer

   The Connection_Terminate Operational Primitive MAY be invoked by the
   iSCSI Layer to request the iSER Layer to terminate the RDMAP Stream
   without having previously exchanged the Logout Request and Logout
   Response PDUs between the two iSCSI/iSER nodes.  As part of the
   termination process, the RDMAP layer will close the Connection.
   When the RDMAP layer notifies the iSER Layer after the RDMAP stream
   and the associated Connection are terminated, the iSER Layer MUST
   perform the following actions.

   If the Connection_Terminate Operational Primitive is invoked by the
   iSCSI Layer at the target, then the iSER Layer at the target MUST
   deallocate all connection and task resources (if any) associated
   with the connection, and invalidate the Local and Remote Mappings
   (if any) that associate the ITT(s) used on the connection to the
   local STag(s) and the Advertised STag(s) respectively.

   If the Connection_Terminate Operational Primitive is invoked by the
   iSCSI Layer at the initiator, then the iSER Layer at the initiator
   MUST deallocate all connection and task resources (if any)
   associated with the connection, and invalidate the Local Mapping(s)
   (if any) that associate the ITT(s) used on the connection to the
   local STag(s).

5.2.3.2  Connection Termination Notification to the iSCSI Layer

   If the iSCSI/iSER connection is terminated without the invocation of
   Connection_Terminate from the iSCSI Layer, the iSER Layer MUST
   notify the iSCSI Layer that the iSCSI/iSER connection has been
   terminated by invoking the Connection_Terminate_Notify Operational
   Primitive.

   Prior to invoking Connection_Terminate_Notify, the iSER Layer at the
   target MUST deallocate all connection and task resources (if any)
   associated with the connection, and invalidate the Local and Remote
   Mappings (if any) that associate the ITT(s) used on the connection
   to the local STag(s) and the Advertised STag(s) respectively.

   Prior to invoking Connection_Terminate_Notify, the iSER Layer at the
   initiator MUST deallocate all connection and task resources (if any)
   associated with the connection, and invalidate the Local Mappings
   (if any) that associate the ITT(s) used on the connection to the
   local STag(s).



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   If the remote iSCSI/iSER node initiated the closing of the
   Connection (e.g., by sending a TCP FIN or TCP RST), the iSER Layer
   MUST notify the iSCSI Layer after the RDMAP layer reports that the
   Connection is closed by invoking the Connection_Terminate_Notify
   Operational Primitive.

   Another example of a Connection termination without a preceding
   logout is when the iSCSI Layer at the initiator does an implicit
   logout (connection reinstatement).








































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6  Login/Text Operational Keys

   Certain iSCSI login/text operational keys have restricted usage in
   iSER, and additional keys are used to support the iSER protocol
   functionality.  All other keys defined in [RFC3720] and not
   discussed in this section may be used on iSCSI/iSER connections with
   the same semantics.

6.1  HeaderDigest and DataDigest

   Irrelevant when: RDMAExtensions=Yes

   Negotiations resulting in RDMAExtensions=Yes for a session implies
   HeaderDigest=None and DataDigest=None for all connections in that
   session and overrides both the default and an explicit setting.

6.2  MaxRecvDataSegmentLength

   For an iSCSI connection belonging to a session in which
   RDMAExtensions=Yes was negotiated on the leading connection of the
   session, MaxRecvDataSegmentLength need not be declared in the Login
   Phase.  Instead InitiatorRecvDataSegmentLength (as described in
   section 6.5) and TargetRecvDataSegmentLength (as described in
   section 6.4) keys are negotiated.  The values of the local and
   remote MaxRecvDataSegmentLength are derived from the
   InitiatorRecvDataSegmentLength and TargetRecvDataSegmentLength keys
   even if the MaxRecvDataSegmentLength was declared during the login
   phase.

   In the full feature phase, the initiator MUST consider the value of
   its local MaxRecvDataSegmentLength (that it would have declared to
   the target) as having the value of InitiatorRecvDataSegmentLength,
   and the value of the remote MaxRecvDataSegmentLength (that would
   have been declared by the target) as having the value of
   TargetRecvDataSegmentLength.  Similarly, the target MUST consider
   the value of its local MaxRecvDataSegmentLength (that it would have
   declared to the initiator) as having the value of
   TargetRecvDataSegmentLength, and the value of the remote
   MaxRecvDataSegmentLength (that would have been declared by the
   initiator) as having the value of InitiatorRecvDataSegmentLength.

   The MaxRecvDataSegmentLength key is applicable only for iSCSI
   control-type PDUs.

6.3  RDMAExtensions

   Use: LO (leading only)


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   Senders: Initiator and Target

   Scope: SW (session-wide)

   RDMAExtensions=<boolean-value>

   Irrelevant when: SessionType=Discovery

   Default is No

   Result function is AND

   This key is used by the initiator and the target to negotiate the
   support for iSER-assisted mode.  To enable the use of iSER-assisted
   mode, both the initiator and the target MUST exchange
   RDMAExtensions=Yes.  iSER-assisted mode MUST NOT be used if either
   the initiator or the target offers RDMAExtensions=No.

   An iSER-enabled node is not required to initiate the RDMAExtensions
   key exchange if it prefers to operate in the Traditional iSCSI mode.
   However, if the RDMAExtensions key is to be negotiated, an initiator
   MUST offer the key in the first Login Request PDU in the
   LoginOperationalNegotiation stage of the leading connection, and a
   target MUST offer the key in the first Login Response PDU with which
   it is allowed to do so (i.e., the first Login Response PDU issued
   after the first Login Request PDU with the C bit set to 0) in the
   LoginOperationalNegotiation stage of the leading connection.  In
   response to the offered key=value pair of RDMAExtensions=yes, an
   initiator MUST respond in the next Login Request PDU with which it
   is allowed to do so, and a target MUST respond in the next Login
   Response PDU with which it is allowed to do so.

   Negotiating the RDMAExtensions key first enables a node to negotiate
   the optimal value for other keys.  Certain iSCSI keys such as
   MaxBurstLength, MaxOutstandingR2T, ErrorRecoveryLevel, InitialR2T,
   ImmediateData, etc., may be negotiated differently depending on
   whether connection is in Traditional iSCSI mode or iSER-assisted
   mode.

6.4  TargetRecvDataSegmentLength

   Use: IO (Initialize only)

   Senders: Initiator and Target

   Scope: CO (connection-only)



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   Irrelevant when: RDMAExtensions=No

   TargetRecvDataSegmentLength=<numerical-value-512-to-(2**24-1)>

   Default is 8192 bytes

   Result function is minimum

   This key is relevant only for the iSCSI connection of an iSCSI
   session if RDMAExtensions=Yes was negotiated on the leading
   connection of the session.  It is used by the initiator and the
   target to negotiate the maximum size of the data segment that an
   initiator may send to the target in an iSCSI control-type PDU.  For
   SCSI Command PDUs and SCSI Data-out PDUs containing non-immediate
   unsolicited data to be sent by the initiator, the initiator MUST
   send all non-Final PDUs with a data segment size of exactly
   TargetRecvDataSegmentLength whenever the PDUs constitute a data
   sequence whose size is larger than TargetRecvDataSegmentLength.

6.5  InitiatorRecvDataSegmentLength

   Use: IO (Initialize only)

   Senders: Initiator and Target

   Scope: CO (connection-only)

   Irrelevant when: RDMAExtensions=No

   InitiatorRecvDataSegmentLength=<numerical-value-512-to-(2**24-1)>

   Default is 8192 bytes

   Result function is minimum

   This key is relevant only for the iSCSI connection of an iSCSI
   session if RDMAExtensions=Yes was negotiated on the leading
   connection of the session.  It is used by the initiator and the
   target to negotiate the maximum size of the data segment that a
   target may send to the initiator in an iSCSI control-type PDU.

6.6  OFMarker and IFMarker

   Irrelevant when: RDMAExtensions=Yes





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   Negotiations resulting in RDMAExtensions=Yes for a session implies
   OFMarker=No and IFMarker=No for all connections in that session and
   overrides both the default and an explicit setting.

6.7  MaxOutstandingUnexpectedPDUs

   Use: LO (leading only), Declarative

   Senders: Initiator and Target

   Scope: SW (session-wide)

   Irrelevant when: RDMAExtensions=No

   MaxOutstandingUnexpectedPDUs=<numerical-value-from-2-to-(2**32-1) |
   None>

   Default is None

   This key is used by the initiator and the target to declare the
   maximum number of outstanding "unexpected" control-type PDUs that it
   can receive.  It is intended to allow the receiving side to
   determine the amount of buffer resources needed beyond the normal
   flow control mechanism available in iSCSI.  An initiator or target
   should select a value such that it would not impose an unnecessary
   constraint on the iSCSI layer under normal circumstances.  See
   sections 8.3 and 8.4 for the usage of this key.






















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7  iSCSI PDU Considerations

   When a connection is in the iSER-assisted mode, two types of message
   transfers are allowed between the iSCSI Layer at the initiator and
   the iSCSI Layer at the target.  These are known as the iSCSI data-
   type PDUs and the iSCSI control-type PDUs and these terms are
   described in the following sections.

7.1  iSCSI Data-Type PDU

   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 in the full feature phase of an
   iSCSI/iSER connection.  An iSCSI data-type PDU, when requested for
   transmission by the iSCSI Layer in the sending node, results in the
   data being transferred without the participation of the iSCSI Layers
   at the sending and the receiving nodes.  This is due to the fact
   that the PDU itself is not delivered as-is to the iSCSI Layer in the
   receiving node.  Instead, the data transfer operations are
   transformed into the appropriate RDMA operations which are handled
   by the RNIC.  The set of iSCSI data-type PDUs consists of SCSI Data-
   in PDUs and R2T PDUs.

   If the invocation of the Operational Primitive by the iSCSI Layer to
   request the iSER Layer to process an iSCSI data-type PDU is
   qualified with Notify_Enable set, then upon completing the RDMA
   operation, the iSER Layer at the target MUST notify the iSCSI Layer
   at the target by invoking the Data_Completion_Notify Operational
   Primitive qualified with ITT and SN.  There is no data completion
   notification at the initiator since the RDMA operations are
   completely handled by the RNIC at the initiator and the iSER Layer
   at the initiator is not involved with the data transfer associated
   with iSCSI data-type PDUs.

   If the invocation of the Operational Primitive by the iSCSI Layer to
   request the iSER Layer to process an iSCSI data-type PDU is
   qualified with Notify_Enable cleared, then upon completing the RDMA
   operation, the iSER Layer at the target MUST NOT notify the iSCSI
   Layer at the target and MUST NOT invoke the Data_Completion_Notify
   Operational Primitive.

   If an operation associated with an iSCSI data-type PDU fails for any
   reason, the contents of the Data Sink buffers associated with the
   operation are considered indeterminate.





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7.2  iSCSI Control-Type PDU

   Any iSCSI PDU that is not an iSCSI data-type PDU and also not a SCSI
   Data-out PDU carrying solicited data is defined as an iSCSI control-
   type PDU.  The iSCSI Layer invokes the Send_Control Operational
   Primitive to request the iSER Layer to process an iSCSI control-type
   PDU.  iSCSI control-type PDUs are transferred using RDMAP Send
   Message Types.  Specifically, it is to be noted that SCSI Data-Out
   PDUs carrying unsolicited data are defined as iSCSI control-type
   PDUs.  See section 7.3.4 on the treatment of SCSI Data-out PDUs.

   When the iSER Layer receives an iSCSI control-type PDU, it MUST
   notify the iSCSI Layer by invoking the Control_Notify Operational
   Primitive qualified with the iSCSI control-type PDU.

7.3  iSCSI PDUs

   This section describes the handling of each of the iSCSI PDU types
   by the iSER Layer.  The iSCSI Layer requests the iSER Layer to
   process the iSCSI PDU by invoking the appropriate Operational
   Primitive.  A Connection_Handle MUST qualify each of these
   invocations.  In addition, BHS and the optional AHS of the iSCSI PDU
   as defined in [RFC3720] MUST qualify each of the invocations.  The
   qualifying Connection_Handle, the BHS and the AHS are not explicitly
   listed in the subsequent sections.

7.3.1  SCSI Command

       Type:  control-type PDU

       PDU-specific qualifiers (for SCSI Write or bidirectional
       command):  ImmediateDataSize, UnsolicitedDataSize,
       DataDescriptorOut

       PDU-specific qualifiers (for SCSI Read or bidirectional
       command):  DataDescriptorIn

   The iSER Layer at the initiator MUST send the SCSI command in a
   SendSE Message to the target.

   For a SCSI Write or bidirectional command, the iSCSI Layer at the
   initiator MUST invoke the Send_Control Operational Primitive as
   follows:

   *  If there is immediate data to be transferred for the SCSI write
      or bidirectional command, the qualifier ImmediateDataSize MUST be
      used to define the number of bytes of immediate unsolicited data


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      to be sent with the write or bidirectional command, and the
      qualifier DataDescriptorOut MUST be used to define the
      initiator's I/O Buffer containing the SCSI Write data.

   *  If there is unsolicited data to be transferred for the SCSI Write
      or bidirectional command, the qualifier UnsolicitedDataSize MUST
      be used to define the number of bytes of immediate and non-
      immediate unsolicited data for the command.  The iSCSI Layer will
      issue one or more SCSI Data-out PDUs for the non-immediate
      unsolicited data.  See Section 7.3.4 on SCSI Data-out.

   *  If there is solicited data to be transferred for the SCSI Write
      or bidirectional command, as indicated by the Expected Data
      Transfer Length in the SCSI Command PDU exceeding the value of
      UnsolicitedDataSize, the iSER Layer at the initiator MUST do the
      following:

       a.  It MUST allocate a Write STag for the I/O Buffer defined by
           the qualifier DataDescriptorOut.  DataDescriptorOut
           describes the I/O buffer starting with the immediate
           unsolicited data (if any), followed by the non-immediate
           unsolicited data (if any) and solicited data.  This means
           that the BufferOffset for the SCSI Data-out for this command
           is equal to the TO.  This implies zero TO for this STag
           points to the beginning of this I/O Buffer.

       b.  It MUST establish a Local Mapping that associates the
           Initiator Task Tag (ITT) to the Write STag.

       c.  It MUST Advertise the Write STag to the target by sending it
           as the Write STag in the iSER header of the iSER Message
           (the payload of the RDMAP SendSE Message) containing the
           SCSI Write or bidirectional command PDU.  See section 9.2 on
           iSER Header Format for iSCSI Control-Type PDU.

   For a SCSI Read or bidirectional command, the iSCSI Layer at the
   initiator MUST invoke the Send_Control Operational Primitive
   qualified with DataDescriptorIn which defines the initiator's I/O
   Buffer for receiving the SCSI Read data.  The iSER Layer at the
   initiator MUST do the following:

       a.  It MUST allocate a Read STag for the I/O Buffer.

       b.  It MUST establish a Local Mapping that associates the
           Initiator Task Tag (ITT) to the Read STag.




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       c.  It MUST Advertise the Read STag to the target by sending it
           as the Read STag in the iSER header of the iSER Message (the
           payload of the RDMAP SendSE Message) containing the SCSI
           Read or bidirectional command PDU.  See section 9.2 on iSER
           Header Format for iSCSI Control-Type PDU.

   If the amount of unsolicited data to be transferred in a SCSI
   Command exceeds TargetRecvDataSegmentLength, then the iSCSI Layer at
   the initiator MUST segment the data into multiple iSCSI control-type
   PDUs, with the data segment length in all PDUs generated except the
   last one having exactly the size TargetRecvDataSegmentLength.  The
   data segment length of the last iSCSI control-type PDU carrying the
   unsolicited data can be up to TargetRecvDataSegmentLength.

   When the iSER Layer at the target receives the SCSI Command, it MUST
   establish a Remote Mapping that associates the ITT to the Advertised
   Write STag and the Read STag if present in the iSER header.  The
   Write STag is used by the iSER Layer at the target in handling the
   data transfer associated with the R2T PDU(s) as described in section
   7.3.6.  The Read STag is used in handling the SCSI Data-in PDU(s)
   from the iSCSI Layer at the target as described in section 7.3.5.

7.3.2  SCSI Response

       Type:  control-type PDU

       PDU-specific qualifiers:  DataDescriptorStatus

   The iSCSI Layer at the target MUST invoke the Send_Control
   Operational Primitive qualified with DataDescriptorStatus which
   defines the buffer containing the sense and response information.
   The iSCSI Layer at the target MUST always return the SCSI status for
   a SCSI command in a separate SCSI Response PDU.  "Phase collapse"
   for transferring SCSI status in a SCSI Data-in PDU MUST NOT be used.
   The iSER Layer at the target sends the SCSI Response PDU according
   to the following rules:

   *  If no STags were Advertised by the initiator in the iSER Message
      containing the SCSI command PDU, then the iSER Layer at the
      target MUST send a SendSE Message containing the SCSI Response
      PDU.

   *  If the initiator Advertised a Read STag in the iSER Message
      containing the SCSI Command PDU, then the iSER Layer at the
      target MUST send a SendInvSE Message containing the SCSI Response
      PDU.  The RDMAP header of the SendInvSE Message MUST carry the
      Read STag to be invalidated at the initiator.


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   *  If the initiator Advertised only the Write STag in the iSER
      Message containing the SCSI command PDU, then the iSER Layer at
      the target MUST send a SendInvSE Message containing the SCSI
      Response PDU.  The RDMAP header of the SendInvSE Message MUST
      carry the Write STag to be invalidated at the initiator.

   When the iSCSI Layer at the target invokes the Send_Control
   Operational Primitive to send the SCSI Response PDU, the iSER Layer
   at the target MUST invalidate the Remote Mapping that associates the
   ITT to the Advertised STag(s) before transferring the SCSI Response
   PDU to the initiator.

   Upon receiving the SendInvSE Message containing the SCSI Response
   PDU from the target, the RDMAP layer at the initiator will
   invalidate the STag specified in the RDMAP header.  The iSER
   Layer at the initiator MUST ensure that the correct STag is
   invalidated.  If both the Read and the Write STags were Advertised
   earlier by the initiator, then the iSER Layer at the initiator MUST
   explicitly invalidate the Write STag upon receiving the SendInvSE
   Message because the RDMAP header of the SendInvSE Message can only
   carry one STag (in this case the Read STag) to be invalidated.

   The iSER Layer at the initiator MUST ensure the invalidation of the
   STag(s) used in a command before notifying the iSCSI Layer at the
   initiator by invoking the Control_Notify Operational Primitive
   qualified with the SCSI Response.  This precludes the possibility of
   using the STag(s) after the completion of the command thereby
   causing data corruption.

   When the iSER Layer at the initiator receives the SendSE or the
   SendInvSE Message containing the SCSI Response PDU, it SHOULD
   invalidate the Local Mapping that associates the ITT to the local
   STag(s).  The iSER Layer MUST ensure that all local STag(s)
   associated with the ITT are invalidated before notifying the iSCSI
   Layer of the SCSI Response PDU by invoking the Control_Notify
   Operational Primitive qualified with the SCSI Response.

7.3.3  Task Management Function Request/Response

       Type:  control-type PDU

       PDU-specific qualifiers (for TMF Request):  DataDescriptorOut,
       DataDescriptorIn

   The iSER Layer MUST use a SendSE Message to send the Task Management
   Function Request/Response PDU.



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   For the Task Management Function Request with the TASK REASSIGN
   function, the iSER Layer at the initiator MUST do the following:

   *  It MUST use the ITT as specified in the Referenced Task Tag from
      the Task Management Function Request PDU to locate the existing
      STag(s), if any, in the Local Mapping(s) that associates the ITT
      to the local STag(s).

   *  It MUST invalidate the existing STag(s), if any, and the Local
      Mapping(s) that associates the ITT to the local STag(s).

   *  It MUST allocate a Read STag for the I/O Buffer as defined by the
      qualifier DataDescriptorIn if the Send_Control Operational
      Primitive invocation is qualified with DataDescriptorIn.

   *  It MUST allocate a Write STag for the I/O Buffer as defined by
      the qualifier DataDescriptorOut if the Send_Control Operational
      Primitive invocation is qualified with DataDescriptorOut.

   *  If STags are allocated, it MUST establish new Local Mapping(s)
      that associate the ITT to the allocated STag(s).

   *  It MUST Advertise the STags, if allocated, to the target in the
      iSER header of the SendSE Message carrying the iSCSI PDU, as
      described in section 9.2.

   For the Task Management Function Request with the TASK REASSIGN
   function for a SCSI Read or bidirectional command, the iSCSI Layer
   at the initiator MUST set ExpDataSN to 0 since the data transfer and
   acknowledgements happen transparently to the iSCSI Layer at the
   initiator.  This provides the flexibility to the iSCSI Layer at the
   target to request transmission of only the unacknowledged data as
   specified in [RFC3720].

   When the iSER Layer at the target receives the Task Management
   Function Request with the TASK REASSIGN function, it MUST do the
   following:

   *  It MUST use the ITT as specified in the Referenced Task Tag from
      the Task Management Function Request PDU to locate the mappings
      that associate the ITT to the Advertised STag(s) and the local
      STag(s), if any.

   *  It MUST invalidate the local STaq(s), if any, associated with the
      ITT.




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   *  It MUST replace the Advertised STag(s) in the Remote Mapping that
      associates the ITT to the Advertised STag(s) with the Write STag
      and the Read STag if present in the iSER header.  The Write STag
      is used in the handling of the R2T PDU(s) from the iSCSI Layer at
      the target as described in section 7.3.6.  The Read STag is used
      in the handling of the SCSI Data-in PDU(s) from the iSCSI Layer
      at the target as described in section 7.3.5.

7.3.4  SCSI Data-out

       Type:  control-type PDU

       PDU-specific qualifiers:  DataDescriptorOut

   The iSCSI Layer at the initiator MUST invoke the Send_Control
   Operational Primitive qualified with DataDescriptorOut which defines
   the initiator's I/O Buffer containing unsolicited SCSI Write data.

   If the amount of unsolicited data to be transferred as SCSI Data-out
   exceeds TargetRecvDataSegmentLength, then the iSCSI Layer at the
   initiator MUST segment the data into multiple iSCSI control-type
   PDUs, with the DataSegmentLength having the value of
   TargetRecvDataSegmentLength in all PDUs generated except the last
   one.  The DataSegmentLength of the last iSCSI control-type PDU
   carrying the unsolicited data can be up to
   TargetRecvDataSegmentLength.  The iSCSI Layer at the target MUST
   perform the reassembly function for the unsolicited data.

   For unsolicited data, if the F bit is set to 0 in a SCSI Data-out
   PDU, the iSER Layer at the initiator MUST use a Send Message to send
   the SCSI Data-out PDU.  If the F bit set to 1, the iSER Layer at the
   initiator MUST use a SendSE Message to send the SCSI Data-out PDU.

   Note that for solicited data, the SCSI Data-out PDUs are not used
   since R2T PDUs are not delivered to the iSCSI layer at the
   initiator; instead R2T PDUs are transformed by the iSER layer at the
   target into RDMA Read operations.  (See section 7.3.6.)

7.3.5  SCSI Data-in

       Type:  data-type PDU

       PDU-specific qualifiers:  DataDescriptorIn

   When the iSCSI Layer at the target is ready to return the SCSI Read
   data to the initiator, it MUST invoke the Put_Data Operational
   Primitive qualified with DataDescriptorIn which defines the SCSI


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   Data-in buffer.  See section 7.1 on the general requirement on the
   handling of iSCSI data-type PDUs.  SCSI Data-in PDU(s) are used in
   SCSI Read data transfer as described in section 9.5.2.

   The iSER Layer at the target MUST do the following for each
   invocation of the Put_Data Operational Primitive:

   1.  It MUST use the ITT in the SCSI Data-in PDU to locate the remote
       Read STag in the Remote Mapping that associates the ITT to
       Advertised STag(s).  The Remote Mapping was established earlier
       by the iSER Layer at the target when the SCSI Read Command was
       received from the initiator.

   2.  It MUST generate and send an RDMA Write Message containing the
       read data to the initiator.

       a.  It MUST use the remote Read STag as the Data Sink STag of
           the RDMA Write Message.

       b.  It MUST use the Buffer Offset from the SCSI Data-in PDU as
           the Data Sink Tagged Offset of the RDMA Write Message.

       c.  It MUST use DataSegmentLength from the SCSI Data-in PDU to
           determine the amount of data to be sent in the RDMA Write
           Message.

   3.  It MUST associate DataSN and ITT from the SCSI Data-in PDU with
       the RDMA Write operation.  If the Put_Data Operational Primitive
       invocation was qualified with Notify_Enable set, then when the
       iSER Layer at the target receives a completion from the RDMAP
       layer for the RDMA Write Message, the iSER Layer at the target
       MUST notify the iSCSI Layer by invoking the
       Data_Completion_Notify Operational Primitive qualified with
       DataSN and ITT.  Conversely, if the Put_Data Operational
       Primitive invocation was qualified with Notify_Enable cleared,
       then the iSER Layer at the target MUST NOT notify the iSCSI
       Layer on completion and MUST NOT invoke the
       Data_Completion_Notify Operational Primitive.

   When the A-bit is set to 1 in the SCSI Data-in PDU, the iSER Layer
   at the target MUST notify the iSCSI Layer at the target when the
   data transfer is complete at the initiator.  To perform this
   additional function, the iSER Layer at the target can take advantage
   of the operational ErrorRecoveryLevel if previously disclosed by the
   iSCSI Layer via an earlier invocation of the Notice_Key_Values
   Operational Primitive.  There are two approaches that can be taken:



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   1.  If the iSER Layer at the target knows that the operational
       ErrorRecoveryLevel is 2, or if the iSER Layer at the target does
       not know the operational ErrorRecoveryLevel, then the iSER Layer
       at the target MUST issue a zero-length RDMA Read Message
       following the RDMA Write Message.  When the iSER Layer at the
       target receives a completion for the RDMA Read Message from the
       RDMAP layer, implying that the RNIC at the initiator has
       completed processing the RDMA Write Message due to the
       completion ordering semantics of RDMAP, the iSER Layer at the
       target MUST notify the iSCSI Layer at the target by invoking the
       Data_Ack_Notify Operational Primitive qualified with ITT and
       DataSN (see section 3.2.3).

   2.  If the iSER Layer at the target knows that the operational
       ErrorRecoveryLevel is 1, then the iSER Layer at the target MUST
       do one of the following:

       a.  It MUST notify the iSCSI Layer at the target by invoking the
           Data_Ack_Notify Operational Primitive qualified with ITT and
           DataSN (see section 3.2.3) when it receives the local
           completion from the RDMAP layer for the RDMA Write Message.
           This is allowed since digest errors do not occur in iSER
           (see section 10.1.4.2) and a CRC error will cause the
           connection to be terminated and the task to be terminated
           anyway.  The local RDMA Write completion from the RDMAP
           layer guarantees that the RDMAP layer will not access the
           I/O Buffer again to transfer the data associated with that
           RDMA Write operation.

       b.  Alternatively, it MUST use the same procedure for handling
           the data transfer completion at the initiator as for
           ErrorRecoveryLevel 2.

   It should be noted that the iSCSI Layer at the target cannot set the
   A-bit to 1 if the ErrorRecoveryLevel=0.

   SCSI status MUST always be returned in a separate SCSI Response PDU.
   The S bit in the SCSI Data-in PDU MUST always be set to 0.  There
   MUST NOT be a "phase collapse" in the SCSI Data-in PDU.

   Since the RDMA Write Message only transfers the data portion of the
   SCSI Data-in PDU but not the control information in the header, such
   as ExpCmdSN, if timely updates of such information is crucial, the
   iSCSI Layer at the initiator MAY issue NOP-out PDUs to request the
   iSCSI Layer at the target to respond with the information using NOP-
   in PDUs.



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7.3.6  Ready To Transfer (R2T)

       Type:  data-type PDU

       PDU-specific qualifiers:  DataDescriptorOut

   In order to send an R2T PDU, the iSCSI Layer at the target MUST
   invoke the Get_Data Operational Primitive qualified with
   DataDescriptorOut which defines the I/O Buffer for receiving the
   SCSI Write data from the initiator.  See section 7.1 on the general
   requirements on the handling of iSCSI data-type PDUs.

   The iSER Layer at the target MUST do the following for each
   invocation of the Get_Data Operational Primitive:

   1.  It MUST ensure a valid local STag for the I/O Buffer and a valid
       Local Mapping that associates the Initiator Task Tag (ITT) to
       the local STag.  This may involve allocating a valid local STag
       and establishing a Local Mapping.

   2.  It MUST use the ITT in the R2T to locate the remote Write STag
       in the Remote Mapping that associates the ITT to Advertised
       STag(s).  The Remote Mapping was established earlier by the iSER
       Layer at the target when the iSER Message containing the
       Advertised Write STag and the SCSI Command PDU for a SCSI Write
       or bidirectional command was received from the initiator.

   3.  If the iSER-ORD value at the target is set to 0, the iSER Layer
       at the target MUST terminate the connection and free up the
       resources associated with the connection (as described in 5.2.3)
       if it received the R2T PDU from the iSCSI Layer at the target.
       Upon termination of the connection, the iSER Layer at the target
       MUST notify the iSCSI Layer at the target by invoking the
       Connection_Terminate_Notify Operational Primitive.

   4.  If the iSER-ORD value at the target is set to greater than 0,
       the iSER Layer at the target MUST transform the R2T PDU into an
       RDMA Read Request Message.  While transforming the R2T PDU, the
       iSER Layer at the target MUST ensure that the number of
       outstanding RDMA Read Request Messages does not exceed iSER-ORD
       value.  To transform the R2T PDU, the iSER Layer at the target:

       a.  MUST derive the local STag and local Tagged Offset from the
           DataDescriptorOut that qualified the Get_Data invocation.

       b.  MUST use the local STag as the Data Sink STag of the RDMA
           Read Request Message.


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       c.  MUST use the local Tagged Offset as the Data Sink Tagged
           Offset of the RDMA Read Request Message.

       d.  MUST use the Desired Data Transfer Length from the R2T PDU
           as the RDMA Read Message Size of the RDMA Read Request
           Message.

       e.  MUST use the remote Write STag as the Data Source STag of
           the RDMA Read Request Message.

       f.  MUST use the Buffer Offset from the R2T PDU as the Data
           Source Tagged Offset of the RDMA Read Request Message.

   5.  It MUST associate R2TSN and ITT from the R2T PDU with the RDMA
       Read operation.  If the Get_Data Operational Primitive
       invocation was qualified with Notify_Enable set, then when the
       iSER Layer at the target receives a completion from the RDMAP
       layer for the RDMA Read operation, the iSER Layer at the target
       MUST notify the iSCSI Layer by invoking the
       Data_Completion_Notify Operational Primitive qualified with
       R2TSN and ITT.  Conversely, if the Get_Data Operational
       Primitive invocation was qualified with Notify_Enable cleared,
       then the iSER Layer at the target MUST NOT notify the iSCSI
       Layer on completion and MUST NOT invoke the
       Data_Completion_Notify Operational Primitive.

   When the RDMAP layer at the initiator receives a valid RDMA Read
   Request Message, it will return an RDMA Read Response Message
   containing the solicited write data to the target.  When the RDMAP
   layer at target receives the RDMA Read Response Message from the
   initiator, it will place the solicited data in the I/O Buffer
   referenced by the Data Sink STag in the RDMA Read Response Message.

   Since the RDMA Read Request Message from the target does not
   transfer the control information in the R2T PDU such as ExpCmdSN, if
   timely updates of such information is crucial, the iSCSI Layer at
   the initiator MAY issue NOP-out PDUs to request the iSCSI Layer at
   the target to respond with the information using NOP-in PDUs.

   Similarly, since the RDMA Read Response Message from the initiator
   only transfers the data but not the control information normally
   found in the SCSI Data-out PDU, such as ExpStatSN, if timely updates
   of such information is crucial, the iSCSI Layer at the target MAY
   issue NOP-in PDUs to request the iSCSI Layer at the initiator to
   respond with the information using NOP-out PDUs.




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7.3.7  Asynchronous Message

       Type:  control-type PDU

       PDU-specific qualifiers:  DataDescriptorSense

   The iSCSI Layer MUST invoke the Send_Control Operational Primitive
   qualified with DataDescriptorSense which defines the buffer
   containing the sense and iSCSI Event information.  The iSER Layer
   MUST use a SendSE Message to send the Asynchronous Message PDU.

7.3.8  Text Request & Text Response

       Type:  control-type PDU

       PDU-specific qualifiers:  DataDescriptorTextOut (for Text
       Request), DataDescriptorIn (for Text Response)

   The iSCSI Layer MUST invoke the Send_Control Operational Primitive
   qualified with DataDescriptorTextOut (or DataDescriptorIn) which
   defines the Text Request (or Text Response) buffer.  The iSER Layer
   MUST use SendSE Messages to send the Text Request and Text Response
   PDUs.

7.3.9  Login Request & Login Response

       Type:  control-type PDU

       PDU-specific qualifiers:  DataDescriptorLoginReqeuest (for Login
       Request), DataDescriptorLoginResponse (for Login Response)

   The Login Request PDUs and the Login Response PDUs are exchanged
   when the connection between the initiator and the target is still in
   the byte stream mode.  During the login negotiation, the iSCSI Layer
   interacts with the transport layer directly and the iSER Layer is
   not involved.  See section 5.1 on iSCSI/iSER Connection Setup.

   If the iSCSI Layer attempts to send a Login Request (or a Login
   Response) PDU during the full feature phase, it MUST invoke the
   Send_Control Operational Primitive qualified with
   DataDescriptorLoginRequest (or DataDescriptorLoginResponse) which
   defines the Login Request (or Login Response) buffer.  The iSER
   Layer MUST handle it as an iSCSI control-type PDU as described in
   section 7.2, and use SendSE Messages to send the Login Request and
   Login Response PDUs.




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7.3.10 Logout Request & Logout Response

       Type:  control-type PDU

       PDU-specific qualifiers:  None

   The iSER Layer MUST use a SendSE Message to send the Logout Request
   or Logout Response PDU.  Section 5.2.1 and 5.2.2 describe the
   handling of the Logout Request and the Logout Response at the
   initiator and the target and the interactions between the initiator
   and the target to terminate a connection.

7.3.11 SNACK Request

       Type:  control-type PDU

       PDU-specific qualifiers:  None

   Since HeaderDigest and DataDigest must be negotiated to "None",
   there are no digest errors when the connection is in iSER-assisted
   mode.  Also since RDMAP delivers all messages in the order they were
   sent, there are no sequence errors when the connection is in iSER-
   assisted mode.  Therefore the iSCSI Layer SHOULD NOT send SNACK
   Request PDUs.  In particular, the Proactive (Time out) SNACK SHOULD
   NOT be issued.  If the iSCSI Layer invokes the Send_Control
   Operational Primitive to request the iSER Layer to send a SNACK
   Request, the iSER Layer MUST handle it as an iSCSI control-type PDU
   as described in section 7.2, and use a SendSE Message to send the
   SNACK Request PDU.  Upon receiving the iSER Message containing the
   SNACK PDU, the iSER Layer notifies the iSCSI Layer using the
   Control_Notify Operational Primitive.

7.3.12 Reject

       Type:  control-type PDU

       PDU-specific qualifiers:  DataDescriptorReject

   The iSCSI Layer MUST invoke the Send_Control Operational Primitive
   qualified with DataDescriptorReject which defines the Rejct buffer.
   The iSER Layer MUST use a SendSE Message to send the Reject PDU.

7.3.13 NOP-Out & NOP-In

       Type:  control-type PDU




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       PDU-specific qualifiers:  DataDescriptorNOPOut (for NOP-Out),
       DataDescriptorNOPIn (for NOP-In)

   The iSCSI Layer MUST invoke the Send_Control Operational Primitive
   qualified with DataDescriptorNOPOut (or DataDescriptorNOPIn) which
   defines the Ping (or Return Ping) data buffer.  The iSER Layer MUST
   use SendSE Messages to send the NOP-Out (or NOP-In) PDU.










































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8  Flow Control and STag Management

8.1  Flow Control for RDMA Send Message Types

   RDMAP Send Message Types are used by the iSER Layer to transfer
   iSCSI control-type PDUs.  Each RDMAP Send Message Type consumes an
   Untagged Buffer at the Data Sink.  However, neither the RDMAP layer
   nor the iSER Layer provides an explicit flow control mechanism for
   the RDMAP Send Message Types.  Therefore, the iSER Layer SHOULD
   provision enough Untagged buffers for handling incoming RDMAP Send
   Message Types to prevent a buffer underrun condition at the RDMAP
   layer.  If a buffer underrun happens, it may result in the
   termination of the connection.  An implementation may choose to
   satisfy this requirement by using a common buffer pool shared across
   multiple connections, with usage limits on a per connection basis
   and usage limits on the buffer pool itself.  In such an
   implementation, exceeding the buffer usage limit for a connection or
   the buffer pool itself may trigger interventions from the iSER Layer
   to replenish the buffer pool and/or to isolate the connection
   causing the problem.

8.2  Flow Control for RDMA Read Resources

   The total number of RDMA Read operations that can be active
   simultaneously on an iSCSI/iSER connection depends on the amount of
   resources allocated as declared in the iSER Hello exchange described
   in section 5.1.3.  Exceeding the number of RDMA Read operations
   allowed on a connection will result in the connection being
   terminated by the RDMAP layer.  The iSER Layer at the target
   maintains the iSER-ORD to keep track of the maximum number of RDMA
   Read Requests that can be issued by the iSER Layer on a particular
   RDMAP Stream.

   During connection setup (see section 5.1), iSER-IRD is known at the
   initiator and iSER-ORD is known at the target after the iSER Layers
   at the initiator and the target have respectively allocated the
   connection resources necessary to support iWARP, as directed by the
   Allocate_Connection_Resources Operational Primitive from the iSCSI
   Layer before the end of the iSCSI Login Phase.  In the full feature
   phase, the first message sent by the initiator is the iSER Hello
   Message (see section 9.3) which contains the value of iSER-IRD.  In
   response to the iSER Hello Message, the target sends the iSER
   HelloReply Message (see section 9.4) which contains the value of
   iSER-ORD.  The iSER Layer at both the initiator and the target MAY
   adjust (lower) the resources associated with iSER-IRD and iSER-ORD
   respectively to match the iSER-ORD value declared in the HelloReply
   Message.  The iSER Layer at the target MUST flow control the RDMA


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   Read Request Messages to not exceed the iSER-ORD value at the
   target.

8.3  Flow Control for Control-Type PDUs from the Initiator

   The control-type PDUs that can be sent by an initiator to a target
   can be grouped into the following categories:

   1.  Regulated:  Control-type PDUs in this category are regulated by
       the iSCSI CmdSN window mechanism and the immediate flag is not
       set.

   2.  Unregulated but Expected:  Control-type PDUs in this category
       are not regulated by the iSCSI CmdSN window mechanism but are
       expected by the target.

   3.  Unregulated and Unexpected:  Control-type PDUs in this category
       are not regulated by the iSCSI CmdSN window mechanism and are
       "unexpected" by the target.

   For the control-type PDUs that can be sent by the initiator in the
   Regulated category, the queuing capacity required of the iSCSI layer
   at the target is described in section 3.2.2.1 of [RFC3720].  For
   each of these control-type PDUs sent by the initiator, the initiator
   MUST provision for the buffer resources required for the
   corresponding control-type PDU to be returned from the target.  The
   following is a list of the PDUs that can be sent by the initiator
   and the PDUs that are sent by the target in response:

       a.  When an initiator sends a SCSI Command PDU, it expects a
           SCSI Response PDU from the target.  Alternatively, the
           target can respond with the Reject PDU before the task is
           active.

       b.  When the initiator sends a Task Management Function Request
           PDU, it expects a Task Management Function Response PDU from
           the target.

       c.  When the initiator sends a Text Request PDU, it expects a
           Text Response PDU from the target.

       d.  When the initiator sends a Login Request PDU, it expects a
           Login Response PDU from the target.

       e.  When the initiator sends a Logout Request PDU, it expects a
           Logout Response PDU from the target.



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       f.  When the initiator sends a NOP-out PDU as a ping request
           with ITT != 0xffffffff and TTT = 0xffffffff, it expects a
           NOP-in PDU from the target with the same ITT and TTT as in
           the ping request.

   For the control-type PDUs in the Unregulated but Expected category,
   the amount of buffering resources required at the target can be
   predetermined.  The following is a list of the PDUs in this
   category:

       a.  SCSI Data-out PDUs are used by the initiator to send
           unsolicited data.  The amount of buffer resources required
           by the target can be determined using FirstBurstLength.
           Note that SCSI Data-out PDUs are not used for solicited
           data since the R2T PDU which is used for solicitation is
           transformed into RDMA Read operations by the iSER layer at
           the target.  See section 7.3.4.

       b.  A NOP-out PDU with ITT = 0xffffffff and TTT != 0xffffffff is
           sent as a ping response by the initiator to the NOP-in PDU
           sent as a ping request by the target.

   The number of PDUs in the Unregulated and Unexpected category which
   can be sent by an initiator is controlled by
   MaxOutstandingUnexpectedPDUs declared by the target.  (See section
   6.7.)  After a PDU in this category is sent by the initiator, it is
   outstanding until it is retired.  At any time, the number of
   outstanding PDUs MUST not exceed MaxOutstandingUnexpectedPDUs.  The
   following is a list of the PDUs in this category and the conditions
   for retiring the outstanding PDU:

       a.  For the PDUs listed in the Regulated category but with the
           immediate flag set, a PDU is outstanding until the target
           responds with the corresponding response PDU.

       b.  SNACK PDUs are not needed in iSER.  (See section 7.3.11.)  A
           SNACK PDU which is sent by the initiator anyway is
           outstanding until the target responds with a SCSI Response
           PDU for the referenced command.

       c.  For a NOP-out PDU with ITT = TTT = 0xffffffff and CmdSN = x,
           the PDU is outstanding until the initiator sends a non-
           immediate control-type PDU on the same connection with CmdSN
           = y (where y is at least x) and the target responds with a
           control-type PDU on any connection where ExpCmdSN is at
           least y+1.  (Implementation note:  To avoid complexity, a
           NOP-out PDU with ITT != 0xffffffff can be used instead.)


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8.4  Flow Control for Control-Type PDUs from the Target

   Control-type PDUs that can be sent by a target and are expected by
   the initiator are listed in the Regulated category.  (See section
   8.3.)

   For the control-type PDUs that can be sent by a target and are
   unexpected by the initiator, the number is controlled by
   MaxOutstandingUnexpectedPDUs declared by the initiator.  (See
   section 6.7.)  After a PDU in this category is sent by a target, it
   is outstanding until it is retired.  At any time, the number of
   outstanding PDUs MUST not exceed MaxOutstandingUnexpectedPDUs.  The
   following is a list of the PDUs in this category and the conditions
   for retiring the outstanding PDU:

       a.  For an Asynchronous Message PDU with StatSN = x, the PDU is
           outstanding until the initiator sends a control-type PDU
           with ExpStatSN set to at least x+1.

       b.  For a Reject PDU with StatSN = x which is sent after a task
           is active, the PDU is outstanding until the initiator sends
           a control-type PDU with ExpStatSN set to at least x+1.

       c.  For a NOP-in PDU with ITT = TTT = 0xffffffff and StatSN = x,
           the PDU is outstanding until the initiator responds with a
           control-type PDU on the same connection where ExpStatSN is
           at least x+1.  (Implementation note: To avoid complexity, a
           NOP-in PDU with TTT != 0xffffffff can be used instead.)

       d.  For a NOP-in PDU sent as a ping request with ITT =
           0xffffffff and TTT != 0xffffffff, the PDU is outstanding
           until the initiator sends a NOP-out PDU with the same ITT
           and TTT as in the ping request.

8.5  STag Management

   An STag, as defined in [RDMAP], is an identifier of a Tagged Buffer
   used in an RDMA operation.  The allocation and the subsequent
   invalidation of the STags are specified in this document if the
   STags are exposed on the wire by being Advertised in the iSER header
   or declared in the RDMAP header of an iWARP Message.

8.5.1  Allocation of STags

   When the iSCSI Layer at the initiator invokes the Send_Control
   Operational Primitive to request the iSER Layer at the initiator to
   process a SCSI Command, zero, one, or two STags may be allocated by


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   the iSER Layer.  See section 7.3.1 for details.  The number of STags
   allocated depends on whether the command is unidirectional or
   bidirectional and whether solicited write data transfer is involved
   or not.

   When the iSCSI Layer at the initiator invokes the Send_Control
   Operational Primitive to request the iSER Layer at the initiator to
   process a Task Management Function Request with the TASK REASSIGN
   function, besides allocating zero, one, or two STags, the iSER Layer
   MUST invalidate the existing STags, if any, associated with the ITT.
   See section 7.3.3 for details.

   The iSER Layer at the target allocates a local Data Sink STag when
   the iSCSI Layer at the target invokes the Get_Data Operational
   Primitive to request the iSER Layer to process an R2T PDU.  See
   section 7.3.6 for details.

8.5.2  Invalidation of STags

   The invalidation of the STags at the initiator at the completion of
   a unidirectional or bidirectional command when the associated SCSI
   Response PDU is sent by the target is described in section 7.3.2.

   When a unidirectional or bidirectional command concludes without the
   associated SCSI Response PDU being sent by the target, the iSCSI
   Layer at the initiator MUST request the iSER Layer at the initiator
   to invalidate the STags by invoking the Deallocate_Task_Resources
   Operational Primitive qualified with ITT.  In response, the iSER
   Layer at the initiator MUST locate the STag(s) (if any) in the Local
   Mapping that associates the ITT to the local STag(s).  The iSER
   Layer at the initiator MUST invalidate the STag(s) (if any) and the
   Local Mapping.

   For an RDMA Read operation used to realize a SCSI Write data
   transfer, the iSER Layer at the target SHOULD invalidate the Data
   Sink STag at the conclusion of the RDMA Read operation referencing
   the Data Sink STag (to permit the immediate reuse of buffer
   resources).

   For an RDMA Write operation used to realize a SCSI Read data
   transfer, the Data Source STag at the target is not declared to the
   initiator and is not exposed on the wire.  Invalidation of the STag
   is thus not specified.

   When a unidirectional or bidirectional command concludes without the
   associated SCSI Response PDU being sent by the target, the iSCSI
   Layer at the target MUST request the iSER Layer at the target to


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   invalidate the STags by invoking the Deallocate_Task_Resources
   Operational Primitive qualified with ITT.  In response, the iSER
   Layer at the target MUST locate the local STag(s) (if any) in the
   Local Mapping that associates the ITT to the local STag(s).  The
   iSER Layer at the target MUST invalidate the local STag(s) (if any)
   and the mapping.











































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9  iSER Control and Data Transfer

   For iSCSI data-type PDUs (see section 7.1), the iSER Layer uses RDMA
   Read and RDMA Write operations to transfer the solicited data.  For
   iSCSI control-type PDUs (see section 7.2), the iSER Layer uses RDMAP
   Send Message Types.

9.1 iSER Header Format

   An iSER header MUST be present in every RDMAP Send Message Type.
   The iSER header is located in the first 12 bytes of the message
   payload of the RDMAP Send Message Type, as shown in Figure 2.

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Opcode|                  Opcode Specific Fields               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Opcode Specific Fields                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Opcode Specific Fields                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                        Figure 2 iSER Header Format

   Opcode - Operation Code: 4 bits

        The Opcode field identifies the type of iSER Messages:

           0001b = iSCSI control-type PDU

           0010b = iSER Hello Message

           0011b = iSER HelloReply Message

           All other opcodes are reserved.

9.2  iSER Header Format for iSCSI Control-Type PDU

   The iSER Layer uses RDMAP Send Message Types to transfer iSCSI
   control-type PDUs (see section 7.2).  The message payload of each of
   the RDMAP Send Message Types used for transferring an iSER Message
   contains an iSER Header followed by an iSCSI control-type PDU.

   The iSER header in an RDMAP Send Message Type carrying an iSCSI
   control-type PDU MUST have the format as described in Figure 3.




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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       |W|R|                                                   |
      | 0001b |S|S|                  Reserved                         |
      |       |V|V|                                                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Write STag (or N/A)                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Read STag (or N/A)                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          Figure 3 iSER Header Format for iSCSI Control-Type PDU

   WSV - Write STag Valid flag: 1 bit

        This flag indicates the validity of the Write STag field of the
        iSER Header.  If set to one, the Write STag field in this iSER
        Header is valid.  If set to zero, the Write STag field in this
        iSER Header MUST be ignored at the receiver.  The Write STag
        Valid flag is set to one when there is solicited data to be
        transferred for a SCSI Write or bidirectional command, or when
        there are non-immediate unsolicited and solicited data to be
        transferred for the referenced task specified in a Task
        Management Function Request with the TASK REASSIGN function.

   RSV - Read STag Valid flag: 1 bit

        This flag indicates the validity of the Read STag field of the
        iSER Header.  If set to one, the Read STag field in this iSER
        Header is valid.  If set to zero, the Read STag field in this
        iSER Header MUST be ignored at the receiver.  The Read STag
        Valid flag is set to one for a SCSI Read or bidirectional
        command, or a Task Management Function Request with the TASK
        REASSIGN function.

   Write STag - Write Steering Tag: 32 bits

        This field contains the Write STag when the Write STag Valid
        flag is set to one.  For a SCSI Write or bidirectional command,
        the Write STag is used to Advertise the initiator's I/O Buffer
        containing the solicited data.  For a Task Management Function
        Request with the TASK REASSIGN function, the Write STag is used
        to Advertise the initiator's I/O Buffer containing the non-
        immediate unsolicited data and solicited data.  This Write STag
        is used as the Data Source STag in the resultant RDMA Read
        operation(s).  When the Write STag Valid flag is set to zero,
        this field MUST be set to zero.


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   Read STag - Read Steering Tag: 32 bits

        This field contains the Read STag when the Read STag Valid flag
        is set to one.  The Read STag is used to Advertise the
        initiator's Read I/O Buffer of a SCSI Read or bidirectional
        command, or a Task Management Function Request with the TASK
        REASSIGN function.  This Read STag is used as the Data Sink
        STag in the resultant RDMA Write operation(s).  When the Read
        STag Valid flag is zero, this field MUST be set to zero.

   Reserved:

        Reserved fields MUST be set to zero on transmit and MUST be
        ignored on receive.

9.3  iSER Header Format for iSER Hello Message

   An iSER Hello Message MUST only contain the iSER header which MUST
   have the format as described in Figure 4.  iSER Hello Message is the
   first RDMAP Message sent on the RDMAP Stream from the iSER Layer at
   the initiator to the iSER Layer at the target.

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       |       |       |       |                               |
      | 0010b | Rsvd  | MaxVer| MinVer|           iSER-IRD            |
      |       |       |       |       |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Reserved                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Reserved                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            Figure 4 iSER Header Format for iSER Hello Message

   MaxVer - Maximum Version: 4 bits

        This field specifies the maximum version of the iSER protocol
        supported.  It MUST be set to 1 to indicate the version of the
        specification described in this document.

   MinVer - Minimum Version: 4 bits

        This field specifies the minimum version of the iSER protocol
        supported.  It MUST be set to 1 to indicate the version of the
        specification described in this document.



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   iSER-IRD: 16 bits

        This field contains the value of the iSER-IRD at the initiator.

   Reserved (Rsvd):

        Reserved fields MUST be set to zero on transmit, and MUST be
        ignored on receive.

9.4  iSER Header Format for iSER HelloReply Message

   An iSER HelloReply Message MUST only contain the iSER header which
   MUST have the format as described in Figure 5.  The iSER HelloReply
   Message is the first RDMAP Message sent on the RDMAP Stream from the
   iSER Layer at the target to the iSER Layer at the initiator.

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       |     |R|       |       |                               |
      | 0011b |Rsvd |E| MaxVer| CurVer|           iSER-ORD            |
      |       |     |J|       |       |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Reserved                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Reserved                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          Figure 5 iSER Header Format for iSER HelloReply Message

   REJ - Reject flag: 1 bit

        This flag indicates whether the target is rejecting this
        connection.  If set to one, the target is rejecting the
        connection.

   MaxVer - Maximum Version: 4 bits

        This field specifies the maximum version of the iSER protocol
        supported.  It MUST be set to 1 to indicate the version of the
        specification described in this document.

   CurVer - Current Version: 4 bits

        This field specifies the current version of the iSER protocol
        supported.  It MUST be set to 1 to indicate the version of the
        specification described in this document.



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   iSER-ORD: 16 bits

        This field contains the value of the iSER-ORD at the target.

   Reserved (Rsvd):

        Reserved fields MUST be set to zero on transmit, and MUST be
        ignored on receive.

9.5 SCSI Data Transfer Operations

   The iSER Layer at the initiator and the iSER Layer at the target
   handle each SCSI Write, SCSI Read, and bidirectional operation as
   described below.

9.5.1  SCSI Write Operation

   The iSCSI Layer at the initiator MUST invoke the Send_Control
   Operational Primitive to request the iSER Layer at the initiator to
   send the SCSI Write Command.  The iSER Layer at the initiator MUST
   request the RDMAP layer to transmit a SendSE Message with the
   message payload consisting of the iSER header followed by the SCSI
   Command PDU and immediate data (if any).  If there is solicited
   data, the iSER Layer MUST Advertise the Write STag in the iSER
   header of the SendSE Message, as described in section 9.2.  Upon
   receiving the SendSE Message, the iSER Layer at the target MUST
   notify the iSCSI Layer at the target by invoking the Control_Notify
   Operational Primitive qualified with the SCSI Command PDU.  See
   section 7.3.1 for details on the handling of the SCSI Write Command.

   For the non-immediate unsolicited data, the iSCSI Layer at the
   initiator MUST invoke a Send_Control Operational Primitive qualified
   with the SCSI Data-out PDU.  Upon receiving each Send or SendSE
   Message containing the non-immediate unsolicited data, the iSER
   Layer at the target MUST notify the iSCSI Layer at the target by
   invoking the Control_Notify Operational Primitive qualified with the
   SCSI Data-out PDU.  See section 7.3.4 for details on the handling of
   the SCSI Data-out PDU.

   For the solicited data, when the iSCSI Layer at the target has an
   I/O Buffer available, it MUST invoke the Get_Data Operational
   Primitive qualified with the R2T PDU.  See section 7.3.6 for details
   on the handling of the R2T PDU.

   When the data transfer associated with this SCSI Write operation is
   complete, the iSCSI Layer at the target MUST invoke the Send_Control
   Operational Primitive when it is ready to send the SCSI Response


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   PDU.  Upon receiving a SendSE or SendInvSE Message containing the
   SCSI Response PDU, the iSER Layer at the initiator MUST notify the
   iSCSI Layer at the initiator by invoking the Control_Notify
   Operational Primitive qualified with the SCSI Response PDU.  See
   section 7.3.2 for details on the handling of the SCSI Response PDU.

9.5.2  SCSI Read Operation

   The iSCSI Layer at the initiator MUST invoke the Send_Control
   Operational Primitive to request the iSER Layer at the initiator to
   send the SCSI Read Command.  The iSER Layer at the initiator MUST
   request the RDMAP layer to transmit a SendSE Message with the
   message payload consisting of the iSER header followed by the SCSI
   Command PDU.  The iSER Layer at the initiator MUST Advertise the
   Read STag in the iSER header of the SendSE Message, as described in
   section 9.2.  Upon receiving the SendSE Message, the iSER Layer at
   the target MUST notify the iSCSI Layer at the target by invoking the
   Control_Notify Operational Primitive qualified with the SCSI Command
   PDU.  See section 7.3.1 for details on the handling of the SCSI Read
   Command.

   When the requested SCSI data is available in the I/O Buffer, the
   iSCSI Layer at the target MUST invoke the Put_Data Operational
   Primitive qualified with the SCSI Data-in PDU.  See section 7.3.5
   for details on the handling of the SCSI Data-in PDU.

   When the data transfer associated with this SCSI Read operation is
   complete, the iSCSI Layer at the target MUST invoke the Send_Control
   Operational Primitive when it is ready to send the SCSI Response
   PDU.  Upon receiving the SendInvSE Message containing the SCSI
   Response PDU, the iSER Layer at the initiator MUST notify the iSCSI
   Layer at the initiator by invoking the Control_Notify Operational
   Primitive qualified with the SCSI Response PDU.  See section 7.3.2
   for details on the handling of the SCSI Response PDU.

9.5.3  Bidirectional Operation

   The initiator and the target handle the SCSI Write and the SCSI Read
   portions of this bidirectional operation the same as described in
   Section 9.5.1 and Section 9.5.2 respectively.









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10 iSER Error Handling and Recovery

   [RDMAP] and the protocols below it provide the iSER Layer with
   reliable in-order delivery.  Therefore, the error management needs
   of an iSER-assisted connection are somewhat different than those of
   a Traditional iSCSI connection.

10.1 Error Handling

   iSER error handling is described in the following sections,
   classified loosely based on the sources of errors:

   1. Those originating at the transport layer (e.g., TCP).

   2. Those originating at the RDMAP layer.

   3. Those originating at the iSER Layer.

   4. Those originating at the iSCSI Layer.

10.1.1 Errors in the Transport Layer

   If the transport layer is TCP, then TCP packets with errors are
   silently dropped by the TCP layer and result in retransmission at
   the TCP layer.  This has no impact on the iSER Layer.  However,
   connection loss (e.g., link failure) and unexpected termination
   (e.g., TCP graceful or abnormal close without the iSCSI Logout
   exchanges) at the transport layer will cause the iSCSI/iSER
   connection to be terminated as well.

10.1.1.1 Failure in the Transport Layer Before iWARP is Enabled

   If the Connection is lost or terminated before the iSCSI Layer
   invokes the Allocate_Connection_Resources Operational Primitive, the
   login process is terminated and no further action is required.

   If the Connection is lost or terminated after the iSCSI Layer has
   invoked the Allocate_Connection_Resources Operational Primitive,
   then the iSCSI Layer MUST request the iSER Layer to deallocate all
   connection resources by invoking the Deallocate_Connection_Resources
   Operational Primitive.

10.1.1.2 Failure in the Transport Layer After iWARP is Enabled

   If the Connection is lost or terminated after the iSCSI Layer has
   invoked the Enable_Datamover Operational Primitive, the iSER Layer
   MUST notify the iSCSI Layer of the connection loss by invoking the


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   Connection_Terminate_Notify Operational Primitive.  Prior to
   invoking the Connection_Terminate_Notify Operational Primitive, the
   iSER layer MUST perform the actions described in Section 5.2.3.2.

10.1.2 Errors in the iWARP protocol suite

   The RDMAP layer does not have error recovery operations built in.
   If errors are detected at the RDMAP layer, the RDMAP layer will
   terminate the RDMAP Stream and the associated Connection.

10.1.2.1 Errors Detected in the Local RDMAP Layer

   If an error is encountered at the local RDMAP layer, the RDMAP layer
   MAY send a Terminate Message to the Remote Peer to report the error
   if possible.  (See [RDMAP] for the list of errors where a Terminate
   Message is sent.)  The RDMAP layer is responsible for terminating
   the Connection.  After the RDMAP layer notifies the iSER Layer that
   the Connection is terminated, the iSER Layer MUST notify the iSCSI
   Layer by invoking the Connection_Terminate_Notify Operational
   Primitive.  Prior to invoking the Connection_Terminate_Notify
   Operational Primitive, the iSER layer MUST perform the actions
   described in Section 5.2.3.2.

10.1.2.2 Errors Detected in the RDMAP Layer at the Remote Peer

   If an error is encountered at the RDMAP layer at the Remote Peer,
   the RDMAP layer at the Remote Peer may send a Terminate Message to
   report the error if possible.  If it is unable to send the Terminate
   Message, the Connection is terminated.  This is treated the same as
   a failure in the transport layer after iWARP is enabled as described
   in section 10.1.1.2.

   If an error is encountered at the RDMAP layer at the Remote Peer and
   it is able to send a Terminate Message, the RDMAP layer at the
   Remote Peer is responsible for terminating the connection.  After
   the local RDMAP layer notifies the iSER Layer that the Connection is
   terminated, the iSER Layer MUST notify the iSCSI Layer by invoking
   the Connection_Terminate_Notify Operational Primitive.  Prior to
   invoking the Connection_Terminate_Notify Operational Primitive, the
   iSER layer MUST perform the actions described in Section 5.2.3.2.

10.1.3 Errors in the iSER Layer

   The error handling due to errors at the iSER Layer is described in
   the following sections.




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10.1.3.1 Insufficient Connection Resources to Support iWARP at
         Connection Setup

   After the iSCSI Layer at the initiator invokes the
   Allocate_Connection_Resources Operational Primitive during the iSCSI
   login negotiation phase, if the iSER Layer at the initiator fails to
   allocate the connection resources necessary to support iWARP, it
   MUST return a status of failure to the iSCSI Layer at the initiator.
   The iSCSI Layer at the initiator MUST terminate the Connection as
   described in Section 5.2.3.1.

   After the iSCSI Layer at the target invokes the
   Allocate_Connection_Resources Operational Primitive during the iSCSI
   login negotiation phase, if the iSER Layer at the target fails to
   allocate the connection resources necessary to support iWARP, it
   MUST return a status of failure to the iSCSI Layer at the target.
   The iSCSI Layer at the target MUST send a Login Response with a
   status class of 3 (Target Error), and a status code of "0302" (Out
   of Resources).  The iSCSI Layers at the initiator and the target
   MUST terminate the Connection as described in Section 5.2.3.1.

10.1.3.2 iSER Negotiation Failures

   If the iWARP or iSER related parameters declared by the initiator in
   the iSER Hello Message is unacceptable to the iSER Layer at the
   target, the iSER Layer at the target MUST set the Reject (REJ) flag,
   as described in section 9.4, in the iSER HelloReply Message.  The
   following are the cases when the iSER Layer MUST set the REJ flag to
   1 in the HelloReply Message:

   *  The initiator-declared iSER-IRD value is greater than 0 and the
      target-declared iSER-ORD value is 0.

   *  The initiator-supported and the target-supported iSER protocol
      versions do not overlap.

   After requesting the RDMAP layer to send the iSER HelloReply
   Message, the handling of the error situation is the same as that for
   iSER format errors as described in section 10.1.3.3.

10.1.3.3 iSER Format Errors

   The following types of errors in an iSER header are considered
   format errors:

   *  Illegal contents of any iSER header field



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   *  Inconsistent field contents in an iSER header

   *  Length error for an iSER Hello or HelloReply Message (see section
      9.3 and 9.4)

   When a format error is detected, the following events MUST occur in
   the specified sequence:

   1.  The iSER Layer MUST request the RDMAP layer to terminate the
       RDMAP Stream.  The RDMAP layer MUST terminate the associated
       Connection.

   2.  The iSER Layer MUST notify the iSCSI Layer of the connection
       termination by invoking the Connection_Terminate_Notify
       Operational Primitive.  Prior to invoking the
       Connection_Terminate_Notify Operational Primitive, the iSER
       layer MUST perform the actions described in Section 5.2.3.2.

10.1.3.4 iSER Protocol Errors

   The first iSER Message sent by the iSER Layer at the initiator after
   transitioning into iSER-assisted mode MUST be the iSER Hello Message
   (see section 9.3).  Likewise, the first iSER Message sent by the
   iSER Layer at the target after transitioning into iSER-assisted mode
   MUST be the iSER HelloReply Message (see section 9.4).  Failure to
   send the iSER Hello or HelloReply Message, as indicated by the wrong
   Opcode in the iSER header, is a protocol error.  The handling of
   this error situation is the same as that for iSER format errors as
   described in section 10.1.3.3.

   If the sending side of an iSER-enabled connection acts in a manner
   not permitted by the negotiated or declared login/text operational
   key values as described in section 6, this is a protocol error and
   the receiving side MAY handle this the same as for iSER format
   errors as described in section 10.1.3.3.

10.1.4 Errors in the iSCSI Layer

   The error handling due to errors at the iSCSI Layer is described in
   the following sections.  For error recovery, see section 10.2.

10.1.4.1 iSCSI Format Errors

   When an iSCSI format error is detected, the iSCSI Layer MUST request
   the iSER Layer to terminate the RDMAP Stream by invoking the
   Connection_Terminate Operational Primitive.  For more details on the
   connection termination, see Section 5.2.3.1.


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10.1.4.2 iSCSI Digest Errors

   In the iSER-assisted mode, the iSCSI Layer will not see any digest
   error because both the HeaderDigest and the DataDigest keys are
   negotiated to "None".

10.1.4.3 iSCSI Sequence Errors

   For Traditional iSCSI, sequence errors are caused by dropped PDUs
   due to header or data digest errors.  Since digests are not used in
   iSER-assisted mode and the RDMAP layer will deliver all messages in
   the order they were sent, sequence errors will not occur in iSER-
   assisted mode.

10.1.4.4 iSCSI Protocol Error

   When the iSCSI Layer handles certain protocol errors by dropping the
   connection, the error handling is the same as that for iSCSI format
   errors as described in section 10.1.4.1.

   When the iSCSI Layer uses the iSCSI Reject PDU and response codes to
   handle certain other protocol errors, no special handling at the
   iSER Layer is required.

10.1.4.5 SCSI Timeouts and Session Errors

   This is handled at the iSCSI Layer and no special handling at the
   iSER Layer is required.

10.1.4.6 iSCSI Negotiation Failures

   For negotiation failures that happen during the Login Phase at the
   initiator after the iSCSI Layer has invoked the
   Allocate_Connection_Resources Operational Primitive and before the
   Enable_Datamover Operational Primitive has been invoked, the iSCSI
   Layer MUST request the iSER Layer to deallocate all connection
   resources by invoking the Deallocate_Connection_Resources
   Operational Primitive.  The iSCSI Layer at the initiator MUST
   terminate the Connection.

   For negotiation failures during the Login Phase at the target, the
   iSCSI Layer can use a Login Response with a status class other than
   0 (success) to terminate the Login Phase.  If the iSCSI Layer has
   invoked the Allocate_Connection_Resources Operational Primitive and
   before the Enable_Datamover Operational Primitive has been invoked,
   the iSCSI Layer at the target MUST request the iSER Layer at the
   target to deallocate all connection resources by invoking the


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   Deallocate_Connection_Resources Operational Primitive.  The iSCSI
   Layer at both the initiator and the target MUST terminate the
   Connection.

   During the iSCSI Login Phase, if the iSCSI Layer at the initiator
   receives a Login Response from the target with a status class other
   than 0 (Success) after the iSCSI Layer at the initiator has invoked
   the Allocate_Connection_Resources Operational Primitive, the iSCSI
   Layer MUST request the iSER Layer to deallocate all connection
   resources by invoking the Deallocate_Connection_Resources
   Operational Primitive.  The iSCSI Layer MUST terminate the
   Connection in this case.

   For negotiation failures during the full feature phase, the error
   handling is left to the iSCSI Layer and no special handling at the
   iSER Layer is required.

10.2 Error Recovery

   Error recovery requirements of iSCSI/iSER are the same as that of
   Traditional iSCSI.  All three ErrorRecoveryLevels as defined in
   [RFC3720] are supported in iSCSI/iSER.

   *  For ErrorRecoveryLevel 0, session recovery is handled by iSCSI
      and no special handling by the iSER Layer is required.

   *  For ErrorRecoveryLevel 1, see section 10.2.1 on SNACK Handling
      and PDU Recovery.

   *  For ErrorRecoveryLevel 2, see section 10.2.2 on Connection
      Recovery.

   The iSCSI Layer may invoke the Notice_Key_Values Operational
   Primitive during connection setup to request the iSER Layer to take
   note of the value of the operational ErrorRecoveryLevel, as
   described in sections 5.1.1 and 5.1.2.

10.2.1 SNACK Handling and PDU Recovery

   As described in sections 10.1.4.2 and 10.1.4.3, digest and sequence
   errors will not occur in the iSER-assisted mode.  If the RDMAP layer
   detects an error, it will close the iSCSI/iSER connection, as
   described in section 10.1.2.  Therefore, PDU recovery is not useful
   in the iSER-assisted mode.





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   The iSCSI Layer at the initiator SHOULD disable timeout-driven
   proactive SNACKs.  If the iSCSI Layer at the target receives a
   SNACK, it MUST respond to it as required by [RFC3720].

   The iSCSI Layer at the initiator SHOULD disable iSCSI timeout-driven
   PDU retransmissions.

10.2.2 Connection Recovery

   The iSCSI Layer at the initiator MAY reassign connection allegiance
   for non-immediate commands which are still in progress and are
   associated with the failed connection by using a Task Management
   Function Request with the TASK REASSIGN function.  See section 7.3.3
   for more details.

   When the iSCSI Layer at the initiator does a task reassignment for a
   SCSI Write command, it MUST qualify the Send_Control Operational
   Primitive invocation with DataDescriptorOut which defines the I/O
   Buffer for both the non-immediate unsolicited data and the solicited
   data.  This allows the iSCSI Layer at the target to use recovery
   R2Ts to request for data originally sent as unsolicited and
   solicited from the initiator.

   When the iSCSI Layer at the target accepts a reassignment request
   for a SCSI Read command, it MUST request the iSER Layer to process
   SCSI Data-in for all unacknowledged data by invoking the Put_Data
   Operational Primitive.  See section 7.3.5 on the handling of SCSI
   Data-in.

   When the iSCSI Layer at the target accepts a reassignment request
   for a SCSI Write command, it MUST request the iSER Layer to process
   a recovery R2T for any non-immediate unsolicited data and any
   solicited data sequences that have not been received by invoking the
   Get_Data Operational Primitive.  See section 7.3.6 on the handling
   of Ready To Transfer (R2T).

   The iSCSI Layer at the target MUST NOT issue recovery R2Ts on an
   iSCSI/iSER connection for a task for which the connection allegiance
   was never reassigned.  The iSER Layer at the target MAY reject such
   a recovery R2T received via the Get_Data Operational Primitive
   invocation from the iSCSI Layer at the target, with an appropriate
   error code.

   The iSER Layer at the target will process the requests invoked by
   the Put_Data and Get_Data Operational Primitives for a reassigned
   task in the same way as for the original commands.



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11 Security Considerations

   Since iSER is layered on top of the iWARP layer and provides the
   RDMA extensions to the iSCSI protocol, the security considerations
   of iSER are the same as that of the underlying RDMAP layer as
   described in [RDMAP].

   All the security protocol mechanisms described in [RFC3720] MAY be
   deployed for an iSCSI/iSER connection.  If the IPsec mechanism is
   used, then it MUST be established before the connection transitions
   from the Traditional iSCSI mode to the iSER-assisted mode.






































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12 References

12.1 Normative References

   [RFC3720] J. Satran et al., "iSCSI", RFC 3720, April 2004

   [RDMAP] R. Recio et al., "An RDMA Protocol Specification", IETF
       Internet-draft draft-ietf-rddp-rdmap-03.txt (work in progress),
       February 2005

   [DDP] H. Shah et al., "Direct Data Placement over Reliable
       Transports", IETF Internet-draft draft-ietf-rddp-ddp-04.txt
       (work in progress), February 2005

   [MPA] P. Culley et al., "Marker PDU Aligned Framing for TCP
       Specification", IETF Internet-draft draft-ietf-rddp-mpa-02.txt
       (work in progress), February 2005

   [TCP] Postel, J., "Transmission Control Protocol", STD 7, RFC 793,
       September 1981

12.2 Informative References

   [SAM2] T10/1157D, SCSI Architecture Model - 2 (SAM-2)

   [DA] M. Chadalapaka et al., "Datamover Architecture for iSCSI", IETF
       Internet-draft, draft-ietf-ips-da-02.txt (work in progress),
       April 2005

   [VERBS] J. Hilland et al., "RDMA Protocol Verbs Specification",
       RDMAC Consortium Draft Specification draft-hilland-iwarp-verbs-
       v1.0-RDMAC, April 2003

   [IPSEC] S. Kent et al., "Security Architecture for the Internet
       Protocol", RFC 2401, November 1998














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13 Appendix

13.1 iWARP Message Format for iSER

   This section is for information only and is NOT part of the
   standard.  It simply depicts the iWARP Message format for the
   various iSER Messages when the transport layer is TCP.

13.1.1 iWARP Message Format for iSER Hello Message

   The following figure depicts an iSER Hello Message encapsulated in
   an iWARP SendSE Message.

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         MPA Header            |  DDP Control  | RDMA Control  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Reserved                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       (Send) Queue Number                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                 (Send) Message Sequence Number                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      (Send) Message Offset                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | 0010b | Zeros | 0001b | 0001b |           iSER-IRD            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           All Zeros                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           All Zeros                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           MPA CRC                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Figure 6 SendSE Message containing an iSER Hello Message














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13.1.2 iWARP Message Format for iSER HelloReply Message

   The following figure depicts an iSER HelloReply Message encapsulated
   in an iWARP SendSE Message.  The Reject (REJ) flag is set to 0.

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         MPA Header            |  DDP Control  | RDMA Control  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Reserved                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       (Send) Queue Number                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                 (Send) Message Sequence Number                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      (Send) Message Offset                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | 0011b |Zeros|0| 0001b | 0001b |           iSER-ORD            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           All Zeros                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           All Zeros                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           MPA CRC                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Figure 7 SendSE Message containing an iSER HelloReply Message






















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13.1.3 iWARP Message Format for SCSI Read Command PDU

   The following figure depicts a SCSI Read Command PDU embedded in an
   iSER Message encapsulated in an iWARP SendSE Message.  For this
   particular example, in the iSER header, the Write STag Valid flag is
   set to zero, the Read STag Valid flag is set to one, the Write STag
   field is set to all zeros, and the Read STag field contains a valid
   Read STag.

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         MPA Header            |  DDP Control  | RDMA Control  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Reserved                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       (Send) Queue Number                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                 (Send) Message Sequence Number                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      (Send) Message Offset                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | 0001b |0|1|                  All zeros                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         All Zeros                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         Read STag                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       SCSI Read Command PDU                   |
    //                                                             //
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           MPA CRC                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Figure 8 SendSE Message containing a SCSI Read Command PDU














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13.1.4 iWARP Message Format for SCSI Read Data

   The following figure depicts an iWARP RDMA Write Message carrying
   SCSI Read data in the payload:

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         MPA Header            |   DDP Control | RDMA Control  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       Data Sink STag                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                   Data Sink Tagged Offset                     |
    +                                                               +
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      SCSI Read data                           |
    //                                                             //
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           MPA CRC                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           Figure 9 RDMA Write Message containing SCSI Read Data


























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13.1.5 iWARP Message Format for SCSI Write Command PDU

   The following figure depicts a SCSI Write Command PDU embedded in an
   iSER Message encapsulated in an iWARP SendSE Message.  For this
   particular example, in the iSER header, the Write STag Valid flag is
   set to one, the Read STag Valid flag is set to zero, the Write STag
   field contains a valid Write STag, and the Read STag field is set to
   all zeros since it is not used.

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         MPA Header            |  DDP Control  | RDMA Control  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Reserved                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       (Send) Queue Number                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                 (Send) Message Sequence Number                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      (Send) Message Offset                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | 0001b |1|0|                  All zeros                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Write STag                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         All Zeros                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       SCSI Write Command PDU                  |
    //                                                             //
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           MPA CRC                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Figure 10 SendSE Message containing a SCSI Write Command PDU














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13.1.6 iWARP Message Format for RDMA Read Request

   An iSCSI R2T is transformed into an iWARP RDMA Read Request Message.
   The following figure depicts an iWARP RDMA Read Request Message:

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         MPA Header            |  DDP Control  | RDMA Control  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      Reserved (Not Used)                      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |              DDP (RDMA Read Request) Queue Number             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |        DDP (RDMA Read Request) Message Sequence Number        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |             DDP (RDMA Read Request) Message Offset            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     Data Sink STag (SinkSTag)                 |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    +                  Data Sink Tagged Offset (SinkTO)             +
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                  RDMA Read Message Size (RDMARDSZ)            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     Data Source STag (SrcSTag)                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    +                 Data Source Tagged Offset (SrcTO)             +
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           MPA CRC                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
               Figure 11 RDMA Read Request Message














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13.1.7 iWARP Message Format for Solicited SCSI Write Data

   The following figure depicts an iWARP RDMA Read Response Message
   carrying the solicited SCSI Write data in the payload:

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         MPA Header            |  DDP Control  | RDMA Control  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       Data Sink STag                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                   Data Sink Tagged Offset                     |
    +                                                               +
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       SCSI Write Data                         |
    //                                                             //
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           MPA CRC                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      Figure 12 RDMA Read Response Message containing SCSI Write Data


























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13.1.8 iWARP Message Format for SCSI Response PDU

   The following figure depicts a SCSI Response PDU embedded in an iSER
   Message encapsulated in an iWARP SendInvSE Message:

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         MPA Header            |  DDP Control  | RDMA Control  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      Invalidate STag                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       (Send) Queue Number                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                 (Send) Message Sequence Number                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      (Send) Message Offset                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | 0001b |0|0|                  All Zeros                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           All Zeros                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           All Zeros                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       SCSI Response PDU                       |
    //                                                             //
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           MPA CRC                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         Figure 13 SendInvSE Message containing SCSI Response PDU


















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14 Author's Address

   Mallikarjun Chadalapaka
       Hewlett-Packard Company
       8000 Foothills Blvd.
       Roseville, CA 95747-5668, USA
       Phone: +1-916-785-5621
       Email: cbm@rose.hp.com

   Uri Elzur
       Broadcom Corporation
       16215 Alton Parkway
       Irvine, California 92619-7013, USA
       Phone: +1-949-926-6432
       Email: Uri@Broadcom.com

   John Hufferd
       Email: jlhufferd@comcast.net

   Mike Ko
       IBM Corp.
       650 Harry Rd.
       San Jose, CA 95120, USA
       Phone: +1-408-927-2085
       Email: mako@us.ibm.com

   Hemal Shah
       Intel Corporation
       MS AN1-PTL1
       1501 South Mopac Expressway, #400
       Austin, Texas 78746, USA
       Phone: +1-512-732-3963
       Email: hemal.shah@intel.com

   Patricia Thaler
       Agilent Technologies, Inc.
       1101 Creekside Ridge Drive, #100
       M/S-RG10
       Roseville, CA 95678, USA
       Phone: +1-916-788-5662
       email: pat_thaler@agilent.com








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15 Acknowledgments

   This protocol was developed by a design team that, in addition to
   the authors, included Dwight Barron (HP), John Carrier (formerly
   from Adaptec), Ted Compton (EMC), Paul R. Culley (HP), Jeff Hilland
   (HP), Mike Krause (HP), Jim Pinkerton (Microsoft), Renato J. Recio
   (IBM), Julian Satran (IBM), Tom Talpey (Network Appliance), and Jim
   Wendt (HP).









































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16 Full Copyright Statement

   Copyright (C) The Internet Society (2005).  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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