[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits] [IPR]

Versions: 00 01 02 03 04 05 06 07 08 09 10 11 RFC 7145

Storage Maintenance (StorM) Working Group                    Michael Ko
Internet Draft                                          Huawei Symantec
Intended status : Proposed Standard                 Alexander Nezhinsky
Expires : January 2012                                         Mellanox
Obsoletes: RFC 5046                                        July 1, 2011



                  iSCSI Extensions for RDMA Specification
                       draft-ietf-storm-iser-02.txt

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with
   the provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other documents
   at any time.  It is inappropriate to use Internet-Drafts as
   reference material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on January, 2012.

Abstract

   iSCSI Extensions for RDMA provides the RDMA data transfer capability
   to iSCSI by layering iSCSI on top of an RDMA-Capable Protocol.  An
   RDMA-Capable Protocol provides RDMA Read and Write services, which
   enable data to be transferred directly into SCSI I/O Buffers without
   intermediate data copies.  This document describes the extensions to
   the iSCSI protocol to support RDMA services as provided by an RDMA-
   Capable Protocol.

   This document obsoletes RFC5046







Ko                       Expires January 2012                 [Page 1]

Internet-Draft            iSER Specification                July 2011

   Table of Contents

   1    Definitions and Acronyms....................................6
   1.1  Definitions.................................................6
   1.2  Acronyms...................................................12
   1.3  Conventions................................................14
   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........................................21
   3    Upper Layer Interface Requirements.........................22
   3.1  Operational Primitives offered by iSER.....................22
   3.1.1  Send_Control..............................................23
   3.1.2  Put_Data..................................................23
   3.1.3  Get_Data..................................................23
   3.1.4  Allocate_Connection_Resources.............................24
   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...........................................27
   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 RCaP 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.......................................35
   5.2  iSCSI/iSER Connection Termination..........................36
   5.2.1  Normal Connection Termination at the Initiator............36
   5.2.2  Normal Connection Termination at the Target...............37
   5.2.3  Termination without Logout Request/Response PDUs..........37


Ko                       Expires January 2012                 [Page 2]

Internet-Draft            iSER Specification                July 2011

   6    Login/Text Operational Keys................................40
   6.1  HeaderDigest and DataDigest................................40
   6.2  MaxRecvDataSegmentLength...................................40
   6.3  RDMAExtensions.............................................41
   6.4  TargetRecvDataSegmentLength................................42
   6.5  InitiatorRecvDataSegmentLength.............................42
   6.6  OFMarker and IFMarker......................................43
   6.7  MaxOutstandingUnexpectedPDUs...............................43
   6.8  MaxAHSLength...............................................43
   6.9  WriteAddressForSolicitedDataOnly...........................44
   6.10   iSERHelloRequired.........................................44
   7    iSCSI PDU Considerations...................................46
   7.1  iSCSI Data-Type PDU........................................46
   7.2  iSCSI Control-Type PDU.....................................47
   7.3  iSCSI PDUs.................................................47
   7.3.1  SCSI Command..............................................47
   7.3.2  SCSI Response.............................................49
   7.3.3  Task Management Function Request/Response.................50
   7.3.4  SCSI Data-out.............................................52
   7.3.5  SCSI Data-in..............................................52
   7.3.6  Ready To Transfer (R2T)...................................55
   7.3.7  Asynchronous Message......................................57
   7.3.8  Text Request & Text Response..............................57
   7.3.9  Login Request & Login Response............................57
   7.3.10  Logout Request & Logout Response........................57
   7.3.11  SNACK Request...........................................58
   7.3.12  Reject..................................................58
   7.3.13  NOP-Out & NOP-In........................................58
   8    Flow Control and STag Management...........................59
   8.1  Flow Control for RDMA Send Message Types...................59
   8.1.1  Flow Control for Control-Type PDUs from the Initiator.....59
   8.1.2  Flow Control for Control-Type PDUs from the Target........62
   8.2  Flow Control for RDMA Read Resources.......................63
   8.3  STag Management............................................63
   8.3.1  Allocation of STags.......................................64
   8.3.2  Invalidation of STags.....................................64
   9    iSER Control and Data Transfer.............................66
   9.1  iSER Header Format.........................................66
   9.2  iSER Header Format for iSCSI Control-Type PDU..............66
   9.3  iSER Header Format for iSER Hello Message..................69
   9.4  iSER Header Format for iSER HelloReply Message.............70
   9.5  SCSI Data Transfer Operations..............................71
   9.5.1  SCSI Write Operation......................................71
   9.5.2  SCSI Read Operation.......................................72
   9.5.3  Bidirectional Operation...................................72
   10   iSER Error Handling and Recovery...........................73
   10.1   Error Handling............................................73


Ko                       Expires January 2012                 [Page 3]

Internet-Draft            iSER Specification                July 2011

   10.1.1  Errors in the Transport Layer...........................73
   10.1.2  Errors in the RCaP Layer................................74
   10.1.3  Errors in the iSER Layer................................74
   10.1.4  Errors in the iSCSI Layer...............................76
   10.2   Error Recovery............................................78
   10.2.1  PDU Recovery............................................78
   10.2.2  Connection Recovery.....................................79
   11   Security Considerations....................................80
   12   IANA Considerations........................................81
   13   References.................................................82
   13.1   Normative References......................................82
   13.2   Informative References....................................82
   14   Appendix A: Summary of Changes from RFC 5046...............84
   15   Appendix B: Message Format for iSER........................86
   15.1   iWARP Message Format for iSER Hello Message...............86
   15.2   iWARP Message Format for iSER HelloReply Message..........87
   15.3   iWARP Message Format for SCSI Read Command PDU............88
   15.4   iWARP Message Format for SCSI Read Data...................89
   15.5   iWARP Message Format for SCSI Write Command PDU...........90
   15.6   iWARP Message Format for RDMA Read Request................91
   15.7   iWARP Message Format for Solicited SCSI Write Data........92
   15.8   iWARP Message Format for SCSI Response PDU................93
   16   Appendix C: Architectural discussion of iSER over InfiniBand94
   16.1   Host side of iSCSI & iSER connections in Infiniband.......94
   16.2   Storage side of iSCSI & iSER mixed network environment....95
   16.3   Discovery processes for an InfiniBand Host................95
   16.4   IBTA Connection specifications............................96
   17   Acknowledgments............................................97





















Ko                       Expires January 2012                 [Page 4]

Internet-Draft            iSER Specification                July 2011

   Table of Figures

   Figure 1 Example of iSCSI/iSER Layering in Full Feature Phase....21
   Figure 2 iSER Header Format......................................66
   Figure 3 iSER Header Format for iSCSI Control-Type PDU...........67
   Figure 4 iSER Header Format for iSER Hello Message...............69
   Figure 5 iSER Header Format for iSER HelloReply Message..........70
   Figure 6 SendSE Message containing an iSER Hello Message.........86
   Figure 7 SendSE Message containing an iSER HelloReply Message....87
   Figure 8 SendSE Message containing a SCSI Read Command PDU.......88
   Figure 9 RDMA Write Message containing SCSI Read Data............89
   Figure 10 SendSE Message containing a SCSI Write Command PDU.....90
   Figure 11 RDMA Read Request Message..............................91
   Figure 12 RDMA Read Response Message containing SCSI Write Data..92
   Figure 13 SendInvSE Message containing SCSI Response PDU.........93
   Figure 14 iSCSI and iSER on IB...................................94
   Figure 15 Storage Controller with TCP, iWARP, and IB Connections.95
































Ko                       Expires January 2012                 [Page 5]

Internet-Draft            iSER Specification                July 2011

1  Definitions and Acronyms

1.1  Definitions

   Advertisement (Advertised, Advertise, Advertisements, Advertises) -
       The act of informing a remote iSER Layer 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 the remote iSER Layer of the Tagged
       Buffer identifiers (STag, TO, and buffer length).  Note that
       this Advertisement of Tagged Buffer information is the
       responsibility of the iSER Layer on either end and is not
       defined by the RDMA-Capable Protocol.  A typical method would be
       for the iSER Layer to embed the Tagged Buffer's STag, TO, and
       buffer length in a Send Message destined for the remote iSER
       Layer.

   Completion (Completed, Complete, Completes) - Completion is defined
       as the process by the RDMA-Capable Protocol layer to inform 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 RCaP 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 RCaP Messages to
       transfer a data payload.

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

   Datamover Layer - A layer that is directly below the iSCSI Layer and
       above the underlying transport layers.  This layer exposes and


Ko                       Expires January 2012                 [Page 6]

Internet-Draft            iSER Specification                July 2011

       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 RDMA-Capable Protocol layer to
       the iSER Layer 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 RDMA-Capable Controller
       can handle on a particular RCaP Stream at the Data Source.  For
       some RDMA-Capable Protocol layers, the term "IRD" may be known
       by a different name.  For example, for InfiniBand, the
       equivalent for IRD is the Responder Resources.

   Invalidate STag - A mechanism used to prevent the Remote Peer from
       reusing a previous explicitly Advertised STag, until the iSER
       Layer at the local node 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 Architecture 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



Ko                       Expires January 2012                 [Page 7]

Internet-Draft            iSER Specification                July 2011

       to the remote iSCSI Layer.  The following iSCSI PDUs constitute
       the set of iSCSI data-type PDUs - SCSI Data-In PDU and R2T PDU.

   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 RCaP Stream.

   iSER-ORD - This variable represents the maximum number of
       outstanding RDMA Read Requests that the iSER Layer can initiate
       on a particular RCaP 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.




Ko                       Expires January 2012                 [Page 8]

Internet-Draft            iSER Specification                July 2011

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

   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 RDMA-Capable Controllers
       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 RDMA-Capable Controller
       can initiate on a particular RCaP Stream at the Data Sink.  For
       some RDMA-Capable Protocol layer, the term "ORD" may be known by
       a different name.  For example, for InfiniBand, the equivalent
       for ORD is the Initiator Depth.

   Phase-Collapse - Refers to the optimization in iSCSI where the SCSI
       status is transferred along with the final SCSI Data-in PDU from
       a target.  See section 3.2 in [RFC3720].

   RCaP Message - One or more packets of the network layer comprising a
       single RDMA operation or a part of an RDMA Read Operation of the
       RDMA-Capable Protocol.  For iWARP, an RCaP Message is known as
       an RDMAP Message.

   RCaP Stream - A single bidirectional association between the peer
       RDMA-Capable Protocol layers on two Nodes over a single
       transport-level stream.   For iWARP, an RCaP Stream is known as
       an RDMAP Stream, and the association is created following a
       successful Login Phase during which iSER support is negotiated.





Ko                       Expires January 2012                 [Page 9]

Internet-Draft            iSER Specification                July 2011

   RDMA-Capable Protocol (RCaP) - The protocol or protocol suite that
       provides a reliable RDMA transport functionality, e.g., iWARP,
       InfiniBand, etc.

   RDMA-Capable Controller - A network I/O adapter or embedded
       controller with RDMA functionality.  For example, for iWARP,
       this could be an RNIC, and for InfiniBand, this could be a HCA
       (Host Channel Adapter) or TCA (Target Channel Adapter).

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

   RDMA Operation - A sequence of RCaP 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 RCaP 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.

   RDMA Read Response - An RCaP 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.

   Remote Direct Memory Access (RDMA) - A method of accessing memory on
       a remote system in which the local system specifies the remote


Ko                       Expires January 2012                [Page 10]

Internet-Draft            iSER Specification                July 2011

       location of the data to be transferred.  Employing an RDMA-
       Capable Controller 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 implementation of the RDMA-Capable Protocol 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 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.

   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.


Ko                       Expires January 2012                [Page 11]

Internet-Draft            iSER Specification                July 2011

   Steering Tag (STag) - An identifier of a Tagged Buffer on a Node
       (Local or Remote) as defined in [RDMAP] and [DDP].  For other
       RDMA-Capable Protocols, the Steering Tag may be known by
       different names but will be herein referred to as STags.  For
       example, for Infiniband, a Remote STag is known as an R-Key, and
       a Local STag is known as an L-Key, and both will be considered
       STags.

   Tagged Buffer - A buffer that is explicitly Advertised to the iSER
       Layer at the remote node through the 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
       iSER Layer at the remode node.

1.2  Acronyms

   Acronym        Definition

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

   AHS            Additional Header Segment

   BHS            Basic Header Segment

   CO             Connection Only

   CRC            Cyclic Redundancy Check

   DDP            Direct Data Placement Protocol

   DI             Datamover Interface

   HCA            Host Channel Adapter

   IANA           Internet Assigned Numbers Authority

   IB             Infiniband

   IETF           Internet Engineering Task Force

   I/O            Input - Output


Ko                       Expires January 2012                [Page 12]

Internet-Draft            iSER Specification                July 2011

   IO             Initialize Only

   IP             Internet Protocol

   IPoIB          IP over Infiniband

   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

   SNACK          Selective Negative Acknowledgment - also

                  Sequence Number Acknowledgement for data

   STag           Steering Tag

   SW             Session Wide


Ko                       Expires January 2012                [Page 13]

Internet-Draft            iSER Specification                July 2011

   TCA            Target Channel Adapter

   TCP            Transmission Control Protocol

   TMF            Task Management Function

   TTT            Target Transfer Tag

   TO             Tagged Offset

   ULP            Upper Level Protocol

1.3  Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119.
































Ko                       Expires January 2012                [Page 14]

Internet-Draft            iSER Specification                July 2011

2  Introduction

2.1  Motivation

   The iSCSI protocol ([RFC3720]) is a mapping of the SCSI Architecture
   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, but most iSCSI
   implementations do not support iSCSI "markers", making SNIC
   marker-based direct data placement unusable in practice.

   The generic term RDMA-Capable Protocol (RCaP) is used to refer to
   protocol stacks that provide the RDMA functionality, such as iWARP
   and InfiniBand.

   With the availability of RDMA-Capable Controllers 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 RDMA-
   Capable Controller 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 RDMA-Capable Controller.  In summary, iSCSI/iSER protocol


Ko                       Expires January 2012                [Page 15]

Internet-Draft            iSER Specification                July 2011

   stack is designed to enable scaling to high speeds by relying on a
   generic data placement 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 an RDMA 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 [SAM2]
     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. Require a session to operate in the Traditional iSCSI data
     transfer mode if iSER is not supported by either the initiator or
     the target (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 to utilize generic
     RDMA-Capable Controllers such as RNICs, or implement iSCSI and
     iSER in software (not require iSCSI or iSER specific assists in
     the RCaP implementation or RDMA-Capable Controller).

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

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


Ko                       Expires January 2012                [Page 16]

Internet-Draft            iSER Specification                July 2011

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 RCaP Messages in such a way that it is entirely
   feasible to realize iSCSI/iSER implementations that are based on
   generic RDMA-Capable Controllers.  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 phase in the Traditional iSCSI mode).

   2. Once in iSER-assisted mode, all iSCSI interactions on that
      connection use RCaP 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. RCaP is responsible for ensuring data integrity.  (For example,
      iWARP includes a CRC-enhanced framing layer called MPA on top of
      TCP; and for Infiniband, the CRCs are included in the Reliable
      Connection mode).  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.  (However, see section 7.3.11 on the handling
      of SNACK Request PDUs.)

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


Ko                       Expires January 2012                [Page 17]

Internet-Draft            iSER Specification                July 2011

   Note that Traditional iSCSI implementations may have to be adapted
   to employ iSER.  It is expected that the adaptation when required is
   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 RCaP documents
   such as [RDMAP], [IB], etc.  The following subsections describe the
   key protocol elements of RCaP services that iSER relies on.

2.4.1  STag

   An STag is the identifier of an I/O Buffer unique to an RDMA-Capable
   Controller 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 RCaP 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.



Ko                       Expires January 2012                [Page 18]

Internet-Draft            iSER Specification                July 2011

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 Command.

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



Ko                       Expires January 2012                [Page 19]

Internet-Draft            iSER Specification                July 2011

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.












Ko                       Expires January 2012                [Page 20]

Internet-Draft            iSER Specification                July 2011

2.7   iSCSI/iSER Layering

   iSCSI Extensions for RDMA (iSER) is layered between the iSCSI layer
   and the RCaP layer.  Note that the RCaP layer may be composed of one
   or more distinct protocol layers depending on the specifics of the
   RCaP.  Figure 1 shows an example of the relationship between SCSI,
   iSCSI, iSER, and the different RCaP layers.  For TCP, the RCaP is
   iWARP.  For Infiniband, the RCaP is the Reliable Connected Transport
   Service.  Note that the iSCSI layer as described here supports the
   RDMA Extensions as used in iSER.

                 +-------------------------------------+
                 |              SCSI                   |
                 +-------------------------------------+
                 |              iSCSI                  |
      DI ------> +-------------------------------------+
                 |              iSER                   |
                 +---------+--------------+------------+
                 |  RDMAP  |              |            |
                 +---------+  Infiniband  |            |
                 |   DDP   |   Reliable   |   Other    |
                 +---------+  Connected   |   RDMA-    |
                 |   MPA   |  Transport   |  Capable   |
                 +---------+   Service    |  Protocol  |
                 |   TCP   |              |            |
                 +---------+--------------+------------+
                 |         |  Infiniband  |   Other    |
                 |    IP   |   Network    |  Network   |
                 |         |    Layer     |   Layer    |
                 +---------+--------------+------------+


       Figure 1 Example of iSCSI/iSER Layering in Full Feature Phase
















Ko                       Expires January 2012                [Page 21]

Internet-Draft            iSER Specification                July 2011

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].  [DA] also
   provides a functional overview of the interactions between the iSCSI
   Layer and the datamover layer as intended by the Datamover
   Architecture.

   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.






Ko                       Expires January 2012                [Page 22]

Internet-Draft            iSER Specification                July 2011

3.1.1  Send_Control

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

       Return results:  Not specified

   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).  Qualifiers that only apply for a particular control-
   type PDU are known as PDU-specific qualifiers, e.g.,
   ImmediateDataSize for a SCSI Write command.  For details on 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 is 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.



Ko                       Expires January 2012                [Page 23]

Internet-Draft            iSER Specification                July 2011

   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)

       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 RCaP 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




Ko                       Expires January 2012                [Page 24]

Internet-Draft            iSER Specification                July 2011

   This is used by the iSCSI Layers at the initiator and the target to
   request that iSER-assisted mode be used for the connection.  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.

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 RCaP-specific resources allocated by
   the iSER Layer for the task identified by the ITT qualifier.  The
   iSER Layer may require a certain number of RCaP-specific resources
   associated with the ITT for each new iSCSI task.  In the normal
   course of execution, these task-level resources in the iSER Layer


Ko                       Expires January 2012                [Page 25]

Internet-Draft            iSER Specification                July 2011

   are assumed to be transparently allocated on each task initiation
   and deallocated on the conclusion of each task as appropriate.  In
   exception scenarios where the task does not conclude with a SCSI
   Response PDU, the iSER Layer needs to be notified of the individual
   task terminations to aid its task-level resource management.  This
   Operational Primitive is used for this purpose, and is not needed
   when a SCSI Response PDU normally concludes a task.  Note that RCaP-
   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.

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.


Ko                       Expires January 2012                [Page 26]

Internet-Draft            iSER Specification                July 2011

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
   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

   To operate in an iSER-assisted mode, 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
   RDMAExtensions key is not negotiated to "Yes", then iSER-assisted
   mode MUST NOT be used.  If the RDMAExtensons key is negotiated to
   "Yes" but the invocation of the Allocate_Connection_Resources
   Operational Primitive to the iSER layer fails, the iSCSI layer MUST
   fail the iSCSI Login process or terminate the connection as
   appropriate.  See section 10.1.3.1 for details.

   If the RDMAExtensions key is negotiated to "Yes", the iSCSI Layer
   MUST satisfy the following protocol usage requirements from the iSER
   protocol:



Ko                       Expires January 2012                [Page 27]

Internet-Draft            iSER Specification                July 2011

   1.  The iSCSI Layer at the initiator MUST set ExpDataSN to 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.

   2.  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.

   3.  The iSCSI Layers at both the initiator and the target MUST
       support the keys as defined in section 6 on Login/Text
       Operational Keys.  If used as specified, these keys MUST NOT be
       answered with NotUnderstood and the semantics as defined MUST be
       followed for each iSER-assisted connection.

   4.  The iSCSI Layer at the initiator MUST NOT issue SNACKs for PDUs.
































Ko                       Expires January 2012                [Page 28]

Internet-Draft            iSER Specification                July 2011

4  Lower Layer Interface Requirements

4.1  Interactions with the RCaP Layer

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

   *  The RCaP layer supports all basic RDMA 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 RCaP layer provides reliable, in-order message delivery and
      direct data placement.

   *  When the iSER Layer initiates an RDMA Read Operation following an
      RDMA Write Operation on one RCaP Stream, the RDMA Read Response
      Message processing on the remote node will be started only after
      the preceding RDMA Write Message payload is placed in the memory
      of the remote node.

   *  The RCaP layer encapsulates a single iSER Message into a single
      RCaP Message on the Data Source side.  The RCaP 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 RCaP layer for a SendInvSE Message, the RCaP layer uses
      this STag as the STag to be invalidated in the SendInvSE Message.

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

   *  When the RCaP layer delivers the content of an RDMA Send Message
      Type to the iSER Layer, the RCaP 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 RCaP 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 RCaP layer delivers a SendInvSE Message to the iSER
      Layer, it passes the value of the STag that was invalidated.



Ko                       Expires January 2012                [Page 29]

Internet-Draft            iSER Specification                July 2011

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

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

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

4.2  Interactions with the Transport Layer

   After the iSER connection is established, the RCaP layer and the
   underlying transport layer are responsible for maintaining the
   Connection and reporting to the iSER Layer any Connection failures.





























Ko                       Expires January 2012                [Page 30]

Internet-Draft            iSER Specification                July 2011

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].  The connection transitions into the iSCSI full feature
   phase in iSER-assisted mode 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 RCaP
   have been allocated at both the initiator and the target.  The same
   connection MUST be used for both the iSCSI Login phase and the
   subsequent iSER-assisted full feature phase.

   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].  If the RDMAExtensions key is not negotiated to Yes, then
   for some RCaP implementation (such as [IB]), the connection may need
   to be re-established in TCP capable mode.  (For InfiniBand this will
   require an [IPoIB] type connection.)

   iSER-assisted mode is defined for a Normal session only and the
   RDMAExtensions key MUST NOT be negotiated for a Discovery session.
   Discovery sessions are always conducted using the transport layer as
   described in [RFC3720].

   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.


Ko                       Expires January 2012                [Page 31]

Internet-Draft            iSER Specification                July 2011

   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.

   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, RCaP is responsible for
   providing error detection that is at least as good as a 32-bit CRC
   for all iSER 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 RCaP 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.

   To minimize the potential for a denial of service attack, the iSCSI
   Layer MUST NOT request the iSER Layer to allocate the connection
   resources necessary to support RCaP until the iSCSI layer is
   sufficiently far along in the iSCSI Login Phase that it is
   reasonably certain that the peer side is not an attacker.  In
   particular, if the Login Phase includes a SecurityNegotiation stage,
   the iSCSI Layer MUST defer the connection resource allocation (i.e.
   invoking the Allocate_Connection_Resources Operational Primitive) to
   the LoginOperationalNegotiation stage ([RFC3720]) so that the
   resource allocation occurs after the authentication phase is
   completed.




Ko                       Expires January 2012                [Page 32]

Internet-Draft            iSER Specification                July 2011

   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 RCaP 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.

   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 iSER Layer at the initiator is successful in allocating the
   connection resources necessary to support RCaP, 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 invoke 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 send the iSER Hello Message as the first
       iSER Message if iSERHelloRequired is negotiated to "Yes".  See
       Section 5.1.3 on iSER Hello Exchange.



Ko                       Expires January 2012                [Page 33]

Internet-Draft            iSER Specification                July 2011

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 RCaP 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.

   To minimize the potential for a denial of service attack, the iSCSI
   Layer MUST NOT request the iSER Layer to allocate the connection
   resources necessary to support RCaP until the iSCSI layer is
   sufficiently far along in the iSCSI Login Phase that it is
   reasonably certain that the peer side is not an attacker.  In
   particular, if the Login Phase includes a SecurityNegotiation stage,
   the iSCSI Layer MUST defer the connection resource allocation (i.e.
   invoking the Allocate_Connection_Resources Operational Primitive) to
   the LoginOperationalNegotiation stage ([RFC3720]) so that the
   resource allocation occurs after the authentication phase is
   completed.

   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 RCaP 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.

   Failure to allocate the requested connection resources locally
   results in a login failure and its handling is described in section
   10.1.3.1.





Ko                       Expires January 2012                [Page 34]

Internet-Draft            iSER Specification                July 2011

   If the iSER Layer at the target is successful in allocating the
   connection resources necessary to support RCaP, 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 invoke 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 Login Response PDU in the
       native transport mode to conclude the iSCSI Login Phase.  If the
       underlying transport is TCP, then the iSER Layer MUST send the
       final Login Response PDU in byte stream mode.

   4.  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 iSER Message if iSERHelloRequired is
       negotiated to "Yes".  See section 5.1.3 on iSER Hello Exchange
       for more details.

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

5.1.3  iSER Hello Exchange

   If iSERHelloRequired is negotiated to "Yes", the first iSER 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 iSER Message
   sent by the target.  The iSER HelloReply Message is used by the iSER


Ko                       Expires January 2012                [Page 35]

Internet-Draft            iSER Specification                July 2011

   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 are unacceptable
   to the target.  This includes the following:

   *  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.

   See section 10.1.3.2 on the handling of the error situation.

   If iSERHelloRequired is negotiated to "No", then the iSER layer at
   the initiator MUST NOT send the iSER Hello Message to the target,
   and if an iSER Hello Message or an iSER HelloReply Message is sent,
   then it is treated as an iSER protocol error.  See section 10.1.3.4
   for more details.

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


Ko                       Expires January 2012                [Page 36]

Internet-Draft            iSER Specification                July 2011

   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 RCaP 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 RCaP Stream by invoking the Connection_Terminate
   Operational Primitive.

   As part of the termination process, the RCaP layer MUST close the
   Connection.  When the RCaP layer notifies the iSER Layer after the
   RCaP 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.

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 RCaP Stream
   without having previously exchanged the Logout Request and Logout
   Response PDUs between the two iSCSI/iSER nodes.  As part of the


Ko                       Expires January 2012                [Page 37]

Internet-Draft            iSER Specification                July 2011

   termination process, the RCaP layer will close the Connection.  When
   the RCaP layer notifies the iSER Layer after the RCaP 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).

   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 RCaP layer reports that the
   Connection is closed by invoking the Connection_Terminate_Notify
   Operational Primitive.





Ko                       Expires January 2012                [Page 38]

Internet-Draft            iSER Specification                July 2011

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














































Ko                       Expires January 2012                [Page 39]

Internet-Draft            iSER Specification                July 2011

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, and MUST be ignored if it is declared.  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.

   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.

   Note that RFC 3720 requires that when a target receives a NOP-Out
   request with a valid Initiator Task Tag, it responds with a NOP-In
   with the same Initiator Task Tag that was provided in the NOP-Out
   request.  Furthermore, it returns the first MaxRecvDataSegmentLength
   bytes of the initiator provided Ping Data.  Since there is no
   MaxRecvDataSegmentLength common to the initiator and the target in



Ko                       Expires January 2012                [Page 40]

Internet-Draft            iSER Specification                July 2011

   iSER, the length of the data sent with the NOP-Out request MUST not
   exceed InitiatorMaxRecvDataSegmentLength.

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

6.3  RDMAExtensions

   Use: LO (leading only)

   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



Ko                       Expires January 2012                [Page 41]

Internet-Draft            iSER Specification                July 2011

   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)

   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 in the
   full feature phase.  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



Ko                       Expires January 2012                [Page 42]

Internet-Draft            iSER Specification                July 2011

   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 in the
   full feature phase.

6.6  OFMarker and IFMarker

   Irrelevant when: RDMAExtensions=Yes

   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) |
   0>

   Default is 4

   This key is used by the initiator and the target to declare the
   maximum number of outstanding "unexpected" iSCSI control-type PDUs
   that it can receive in the full feature phase.  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.  The value of 0 is defined to indicate that the
   declarer has no limit on the maximum number of outstanding
   "unexpected" iSCSI control-type PDUs that it can receive.  See
   sections 8.1.1 and 8.1.2 for the usage of this key.  Note that iSER
   Hello and HelloReply Messages are not iSCSI control-type PDUs and
   are not affected by this key.

6.8  MaxAHSLength

   Use: LO (leading only), Declarative


Ko                       Expires January 2012                [Page 43]

Internet-Draft            iSER Specification                July 2011

   Senders: Initiator and Target

   Scope: SW (session-wide)

   Irrelevant when: RDMAExtensions=No

   MaxAHSLength=<numerical-value-from-2-to-(2**32-1) | 0>

   Default is 256

   This key is used by the intiator and target to declare the maximum
   size of AHS in an iSCSI control-type PDU that it can receive in the
   full feature phase.  It is intended to allow the receiving side to
   determine the amount of resources needed for receive buffering.  An
   initiator or target should select a value such that it would not
   impose an unnecessary constraint on the iSCSI Layer under normal
   circumstances.  The value of 0 is defined to indicate that the
   declarer has no limit on the maximum size of AHS in iSCSI control-
   type PDUs that it can receive.

6.9  WriteAddressForSolicitedDataOnly

   Use: LO (leading only), Declarative

   Senders: Initiator

   Scope: SW (session-wide)

   RDMAExtensions=<boolean-value>

   Irrelevant when: RDMAExtensions=No

   Default is No

   This key is used by the intiator to declare to the target the origin
   of the Write Virtual Address used in the iSER header of an iSCSI
   control-type PDU.  When set to No, the Write Virtual Address points
   to an I/O buffer that contains all the write data, including both
   the unsolicited and solicited data.  When set to Yes, the Write
   Virtual Address points to an I/O buffer that only contains the
   solicited data.

6.10 iSERHelloRequired

   Use: LO (leading only), Declarative

   Senders: Initiator


Ko                       Expires January 2012                [Page 44]

Internet-Draft            iSER Specification                July 2011

   Scope: SW (session-wide)

   RDMAExtensions=<boolean-value>

   Irrelevant when: RDMAExtensions=No

   Default is No

   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 intiator to declare to
   the target if the iSER Hello Exchange is required.  When set to Yes,
   the iSER layers MUST perform the iSER Hello Exchange as described in
   5.1.3.  When set to No, the iSER layers MUST NOT perform the iSER
   Hello Exchange.


































Ko                       Expires January 2012                [Page 45]

Internet-Draft            iSER Specification                July 2011

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 RDMA-Capable Controller.  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 RDMA-Capable Controller 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.





Ko                       Expires January 2012                [Page 46]

Internet-Draft            iSER Specification                July 2011

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 Send Message
   Types of RCaP.  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


Ko                       Expires January 2012                [Page 47]

Internet-Draft            iSER Specification                July 2011

      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 SendSE Message of RCaP) 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.




Ko                       Expires January 2012                [Page 48]

Internet-Draft            iSER Specification                July 2011

       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 SendSE Message of RCaP) 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 header of the SendInvSE Message MUST carry the Read
      STag to be invalidated at the initiator.


Ko                       Expires January 2012                [Page 49]

Internet-Draft            iSER Specification                July 2011

   *  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 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 RCaP layer at the initiator will invalidate
   the STag specified in the 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 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 PDU.

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.



Ko                       Expires January 2012                [Page 50]

Internet-Draft            iSER Specification                July 2011

   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.




Ko                       Expires January 2012                [Page 51]

Internet-Draft            iSER Specification                July 2011

   *  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 is 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


Ko                       Expires January 2012                [Page 52]

Internet-Draft            iSER Specification                July 2011

   Primitive qualified with DataDescriptorIn which defines the SCSI
   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 RCaP
       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:


Ko                       Expires January 2012                [Page 53]

Internet-Draft            iSER Specification                July 2011

   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 Request Message
       following the RDMA Write Message.  When the iSER Layer at the
       target receives a completion for the RDMA Read Request Message
       from the RCaP layer, implying that the RDMA-Capable Controller
       at the initiator has completed processing the RDMA Write Message
       due to the completion ordering semantics of RCaP, 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 RCaP 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 RCaP layer
           guarantees that the RCaP 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.



Ko                       Expires January 2012                [Page 54]

Internet-Draft            iSER Specification                July 2011

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.


Ko                       Expires January 2012                [Page 55]

Internet-Draft            iSER Specification                July 2011

       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 RCaP
       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 RCaP 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 RCaP
   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.




Ko                       Expires January 2012                [Page 56]

Internet-Draft            iSER Specification                July 2011

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 (or Text Response
   PDUs).

7.3.9  Login Request & Login Response

   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 underlying
   transport is TCP, 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.

   The iSCSI Layer MUST not send a Login Request (or a Login Response)
   PDU during the full feature phase.  A Login Request (or a Login
   Response) PDU, if used, MUST be treated as an iSCSI protocol error.
   The iSER Layer MAY reject such a PDU from the iSCSI Layer with an
   appropriate error code.  If a Login Request PDU is received by the
   iSCSI Layer at the target, it MUST respond with a Reject PDU with a
   reason code of "protocol error".

7.3.10 Logout Request & Logout Response

       Type:  control-type PDU

       PDU-specific qualifiers:  None



Ko                       Expires January 2012                [Page 57]

Internet-Draft            iSER Specification                July 2011

   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

   Since HeaderDigest and DataDigest must be negotiated to "None",
   there are no digest errors when the connection is in iSER-assisted
   mode.  Also since RCaP 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 MUST NOT send SNACK
   Request PDUs.  A SNCAK Request PDU, if used, MUST be treated as an
   iSCSI protocol error.  The iSER Layer MAY reject such a PDU from the
   iSCSI Layer with an appropriate error code.  If a SNACK Request PDU
   is received by the iSCSI Layer at the target, it MUST respond with a
   Reject PDU with a reason code of "protocol error".

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 Reject 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

       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.









Ko                       Expires January 2012                [Page 58]

Internet-Draft            iSER Specification                July 2011

8  Flow Control and STag Management

8.1  Flow Control for RDMA Send Message Types

   Send Message Types in RCaP are used by the iSER Layer to transfer
   iSCSI control-type PDUs.  Each Send Message Type in RCaP consumes an
   Untagged Buffer at the Data Sink.  However, neither the RCaP layer
   nor the iSER Layer provides an explicit flow control mechanism for
   the Send Message Types.  Therefore, the iSER Layer SHOULD provision
   enough Untagged buffers for handling incoming Send Message Types to
   prevent buffer exhaustion at the RCaP layer.  If buffer exhaustion
   occurs, it may result in the termination of the connection.

   An implementation may choose to satisfy the buffer 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.

   iSER also provides the MaxOutstandingUnexpectedPDUs key to be 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.

   The buffer resources required at both the initiator and the target
   as a result of control-type PDUs sent by the initiator is described
   in section 8.1.1.  The buffer resources required at both the
   initiator and target as a result of control-type PDUs sent by the
   target is described in section 8.1.2.

8.1.1  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.



Ko                       Expires January 2012                [Page 59]

Internet-Draft            iSER Specification                July 2011

   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.

8.1.1.1  Control-Type PDUs from the Initiator in the Regulated Category

   Control-type PDUs that can be sent by the initiator in this category
   are regulated by the iSCSI CmdSN window mechanism and the immediate
   flag is not set.

   The queuing capacity required of the iSCSI layer at the target is
   described in section 3.2.2.1 of [RFC3720].  For each of the control-
   type PDUs that can be sent by the initiator in this category, the
   initiator MUST provision for the buffer resources required for the
   corresponding control-type PDU sent as a response 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.

       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 Logout Request PDU, it expects a
           Logout Response PDU from the target.

       e.  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.

   The response from the target for any of the PDUs enumerated here may
   alternatively be in the form of a Reject PDU sent instead before the
   task is active, as described in section 6.3 of [RFC3720].

8.1.1.2  Control-Type PDUs from the Initiator in the Unregulated but
         Expected Category

   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:


Ko                       Expires January 2012                [Page 60]

Internet-Draft            iSER Specification                July 2011

       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 TTT != 0xffffffff is sent as a ping
           response by the initiator to the NOP-In PDU sent as a ping
           request by the target.

8.1.1.3  Control-Type PDUs from the Initiator in the Unregulated and
         Unexpected Category

   PDUs in the Unregulated and Unexpected category are PDUs with the
   immediate flag set.  The number of PDUs in this category which can
   be sent by an initiator is controlled by the value of
   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 unexpected PDUs MUST not exceed the value of
   MaxOutstandingUnexpectedPDUs declared by the target.

   The target uses the value of MaxOutstandingUnexpectedPDUs that it
   declared to determine the amount of buffer resources required for
   control-type PDUs in this category that can be sent by an initiator.
   For the initiator, for each of the control-type PDUs that can be
   sent in this category, the initiator MUST provision for the buffer
   resources if required for the corresponding control-type PDU that
   can be sent as a response from the target.

   An outstanding PDU in this category is retired as follows.  If the
   CmdSN of the PDU sent by the initiator in this category is 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.

   When the number of outstanding unexpected control-type PDUs equals
   MaxOutstandingUnexpectedPDUs, the iSCSI Layer at the initiator MUST
   NOT generate any unexpected PDUs which otherwise it would have
   generated, even if it is intended for immediate delivery.






Ko                       Expires January 2012                [Page 61]

Internet-Draft            iSER Specification                July 2011

8.1.2  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
   8.1.1.1.)

   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 unexpected PDUs MUST not exceed the value of
   MaxOutstandingUnexpectedPDUs declared by the initiator.  The
   initiator uses the value of MaxOutstandingUnexpectedPDUs that it
   declared to determine the amount of buffer resources required for
   control-type PDUs in this category that can be sent by a target.
   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 = 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.  But if the NOP-In PDU is sent as a ping
           request with TTT != 0xffffffff, the PDU can also be retired
           when the initiator sends a NOP-Out PDU with the same ITT and
           TTT as in the ping request.  Note that when a target sends a
           NOP-In PDU as a ping request, it must provision a buffer for
           the NOP-Out PDU sent as a ping response from the initiator.

   When the number of outstanding unexpected control-type PDUs equals
   MaxOutstandingUnexpectedPDUs, the iSCSI Layer at the target MUST NOT
   generate any unexpected PDUs which otherwise it would have
   generated, even if its intent is to indicate an iSCSI error
   condition (e.g., Asynchronous Message, Reject).  Task timeouts as in
   the initiator waiting for a command completion or other connection
   and session level exceptions will ensure that correct operational
   behavior will result in these cases despite not generating the PDU.
   This rule overrides any other requirements elsewhere which require
   that a Reject PDU MUST be sent.


Ko                       Expires January 2012                [Page 62]

Internet-Draft            iSER Specification                July 2011

   (Implementation note:  SCSI task timeout and recovery can be a
   lengthy process and hence SHOULD be avoided by proper provisioning
   of resources.)

   (Implementation note:  To ensure that the initiator has a means to
   inform the target that outstanding PDUs have been retired, the
   target should reserve the last unexpected control-type PDU allowable
   by the value of MaxOutstandingUnexpectedPDUs declared by the
   initiator for sending a NOP-In ping request with TTT != 0xffffffff
   to allow the initiator to return the NOP-Out ping response with the
   current ExpStatSN.)

8.2  Flow Control for RDMA Read Resources

   If iSERHelloRequired is negotiated to "Yes", then 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 RCaP 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 RCaP 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 RCaP, 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, if iSERHelloRequired is ngtiated to "Yes", then 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 Read Request
   Messages to not exceed the iSER-ORD value at the target.

8.3  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



Ko                       Expires January 2012                [Page 63]

Internet-Draft            iSER Specification                July 2011

   STags are exposed on the wire by being Advertised in the iSER header
   or declared in the header of an RCaP Message.

8.3.1  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
   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.

8.3.2  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).



Ko                       Expires January 2012                [Page 64]

Internet-Draft            iSER Specification                July 2011

   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
   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.



































Ko                       Expires January 2012                [Page 65]

Internet-Draft            iSER Specification                July 2011

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 Send
   Message Types of RCaP.

9.1 iSER Header Format

   An iSER header MUST be present in every Send Message Type of RCaP.
   The iSER header is located in the first 12 bytes of the message
   payload of the Send Message Type of RCaP, 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 Send Message Types of RCaP to transfer iSCSI
   control-type PDUs (see section 7.2).  The message payload of each of
   the Send Message Types of RCaP used for transferring an iSER Message
   contains an iSER Header followed by an iSCSI control-type PDU.

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




Ko                       Expires January 2012                [Page 66]

Internet-Draft            iSER Specification                July 2011

       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                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Write Virtual Address High               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Write Virtual Address Low                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             Read STag                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Read Virtual Address High               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Read Virtual Address Low                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          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,


Ko                       Expires January 2012                [Page 67]

Internet-Draft            iSER Specification                July 2011

        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 and ignored on receive.

   Write Virtual Address High: 32 bits

        This field contains the high order bits of the Virtual Address
        for the SCSI Write command when the Write STag Valid flag is
        set to one.  When the Write STag Valid flag is set to zero,
        this field MUST be set to zero and ignored on receive.

   Write Virtual Address Low: 32 bits

        This field contains the low order bits of the Virtual Address
        for the SCSI Write command when the Write STag Valid flag is
        set to one.  When the Write STag Valid flag is set to zero,
        this field MUST be set to zero and ignored on receive.

   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 and
        ignored on receive.

   Read Virtual Address High: 32 bits

        This field contains the high order bits of the Virtual Address
        for the SCSI Read command when the Read STag Valid flag is set
        to one.  When the Read STag Valid flag is set to zero, this
        field MUST be set to zero and ignored on receive.

   Read Virtual Address Low: 32 bits

        This field contains the low order bits of the Virtual Address
        for the SCSI Read command when the Read STag Valid flag is set
        to one.  When the read STag Valid flag is set to zero, this
        field MUST be set to zero and ignored on receive.


Ko                       Expires January 2012                [Page 68]

Internet-Draft            iSER Specification                July 2011

   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.  If iSERHelloRequired is
   negotiated to "Yes", then iSER Hello Message is the first iSER
   Message sent on the RCaP 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 10 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 10 to indicate the version of the
        specification described in this document.

   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.



Ko                       Expires January 2012                [Page 69]

Internet-Draft            iSER Specification                July 2011

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.  If iSERHelloRequired
   is negotiated to "Yes", then the iSER HelloReply Message is the
   first iSER Message sent on the RCaP 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 10 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 10 to indicate the version of the
        specification described in this document.

   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.


Ko                       Expires January 2012                [Page 70]

Internet-Draft            iSER Specification                July 2011

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 RCaP 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
   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.






Ko                       Expires January 2012                [Page 71]

Internet-Draft            iSER Specification                July 2011

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 RCaP 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.















Ko                       Expires January 2012                [Page 72]

Internet-Draft            iSER Specification                July 2011

10 iSER Error Handling and Recovery

   RCaP provides 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 RCaP 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 detected 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 RCaP Mode 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 RCaP Mode 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
   Connection_Terminate_Notify Operational Primitive.  Prior to


Ko                       Expires January 2012                [Page 73]

Internet-Draft            iSER Specification                July 2011

   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 RCaP Layer

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

10.1.2.1 Errors Detected in the Local RCaP Layer

   If an error is encountered at the local RCaP layer, the RCaP layer
   MAY send a Terminate Message to the Remote Peer to report the error
   if possible.  (For iWARP, see [RDMAP] for the list of errors where a
   Terminate Message is sent.)  The RCaP layer is responsible for
   terminating the Connection.  After the RCaP 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 RCaP Layer at the Remote Peer

   If an error is encountered at the RCaP layer at the Remote Peer, the
   RCaP 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 RDMA is enabled as described
   in section 10.1.1.2.

   If an error is encountered at the RCaP layer at the Remote Peer and
   it is able to send a Terminate Message, the RCaP layer at the Remote
   Peer is responsible for terminating the connection.  After the local
   RCaP 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.





Ko                       Expires January 2012                [Page 74]

Internet-Draft            iSER Specification                July 2011

10.1.3.1 Insufficient Connection Resources to Support RCaP 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 RCaP, 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 RCaP, 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 iSERHelloRequired is negotiated to "Yes" and the RCaP 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 RCaP 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


Ko                       Expires January 2012                [Page 75]

Internet-Draft            iSER Specification                July 2011

   *  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 RCaP layer to terminate the RCaP
       Stream.  The RCaP 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

   If iSERHelloRequired is negotiated to "Yes", then the first iSER
   Message sent by the iSER Layer at the initiator MUST be the iSER
   Hello Message (see section 9.3).  In this case the first iSER
   Message sent by the iSER Layer at the target 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 RCaP Stream by invoking the
   Connection_Terminate Operational Primitive.  For more details on the
   connection termination, see Section 5.2.3.1.


Ko                       Expires January 2012                [Page 76]

Internet-Draft            iSER Specification                July 2011

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 RCaP 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


Ko                       Expires January 2012                [Page 77]

Internet-Draft            iSER Specification                July 2011

   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 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 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 RCaP 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.

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



Ko                       Expires January 2012                [Page 78]

Internet-Draft            iSER Specification                July 2011

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.










Ko                       Expires January 2012                [Page 79]

Internet-Draft            iSER Specification                July 2011

11 Security Considerations

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

   Since iSER-assisted iSCSI protocol is still functionally iSCSI from
   a security considerations perspective, all of the iSCSI security
   requirements as described in [RFC3720] and [RFC3723] apply.  If iSER
   is layered on top of a non-IP based RCaP layer, all the security
   protocol mechanisms applicable to that RCaP layer is also applicable
   to an iSCSI/iSER connection.  If iSER is layered on top of a non-IP
   protocol, the IPsec mechanism as specified in [RFC3720] MUST be
   implemented at any point where the iSER protocol enters the IP
   network (e.g., via gateways), and the non-IP protocol SHOULD
   implement (optional to use) a packet by packet security protocol
   equal in strength to the IPsec mechanism specified by [RFC3720].

   To minimize the potential for a denial of service attack, the iSCSI
   Layer MUST NOT request the iSER Layer to allocate the connection
   resources necessary to support RCaP until the iSCSI layer is
   sufficiently far along in the iSCSI Login Phase that it is
   reasonably certain that the peer side is not an attacker, as
   described in sections 5.1.1 and 5.1.2.
























Ko                       Expires January 2012                [Page 80]

Internet-Draft            iSER Specification                July 2011

12 IANA Considerations

   This document has no actions for IANA.














































Ko                       Expires January 2012                [Page 81]

Internet-Draft            iSER Specification                July 2011

13 References

13.1 Normative References

   [RFC5046] M. Ko et al., "iSCSI Externsions for Remote Direct Memory
       Access", RFC 5046, October 2007

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

   [RFC3723] B. Aboba et al., "Securing Block Storage Protocols over
       IP", RFC 3723, April 2004.

   [RDMAP] R. Recio et al., "An RDMA Protocol Specification", RFC 5040,
       October 2007

   [DDP] H. Shah et al., "Direct Data Placement over Reliable
       Transports", RFC 5041, October 2007

   [MPA] P. Culley et al., "Marker PDU Aligned Framing for TCP
       Specification", RFC 5044, October 2007

   [RDDPSEC] J. Pinkerton et al., "DDP/RDMAP Security", RFC 5042,
       October 2007

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

   [RFC2119] Bradner, S., "Key Words for use in RFCs to Indicate
       Requirement Levels", BCP 14, RFC 2119, March 1997

13.2 Informative References

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

   [DA] M. Chadalapaka et al., "Datamover Architecture for iSCSI", RFC
       5047, October 2007

   [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

   [IB] InfiniBand Architecture Specification Volume 1 Release 1.2,
       October 2004



Ko                       Expires January 2012                [Page 82]

Internet-Draft            iSER Specification                July 2011

   [IPoIB] H.K. Chu et al, "Transmission of IP over InfiniBand", RFC
       4391, March 2006















































Ko                       Expires January 2012                [Page 83]

Internet-Draft            iSER Specification                July 2011

14 Appendix A: Summary of Changes from RFC 5046

   1. Removed the requirement that a connection be opened in "normal"
     TCP mode and transitioned to zero-copy mode.  This allows the spec
     to conform to existing implementation for both Infiniband and
     iWARP.  Changes were made in sections 2, 3.1.6, 4.2, 5.1, 5.1.1,
     5.1.2, 5.1.3, 10.1.3.4, and 11.

   2. Added a clause in section 6.2 to clarify that
     MaxRecvDataSegmentLength must be ignored if it is declared in the
     Login Phase.

   3. Added a clause in section 6.2 to clarify that the initiator must
     not send more than InitiatorMaxRecvDataSegmentLength worth of data
     when a NOP-Out request is sent with a valid Initiator Task Tag.
     Since InitiatorMaxRecvDataSegmentLength can be smaller than
     TargetMaxRecvDataSegmentLength, returning the original data in the
     NOP-Out request in this situation can overflow the receive buffer
     unless the length of the data sent with the NOP-Out request is
     less than InitiatorMaxRecvDataSegmentLength.

   4. Changed the default of MaxOutstandingUnexpectedPDUs from 0
     (unlimited) to 4.

   5. Added MaxAHSLength key in section 6.8 to set a limit on the AHS
     Length.  This is useful when posting receive buffers in knowing
     what the maximum possible message length is in a PDU which
     contains AHS.

   6. Added WriteAddressForSolicitedDataOnly key in section 6.9 to
     indicate how the memory region will be used.  An initiator can
     treat the memory regions intended for unsolicited and solicited
     data differently, and can use different registration modes.  In
     contrast, RFC 5046 treats the memory occupied by the data as a
     contiguous (or virtually contiguous, by means of scatter-gather
     mechanisms) and homogenous region.  Adding a new key will allow
     different memory models to be accommodated.

   7. Added iSERHelloRequired key in section 6.10 to make it optional to
     use iSER Hello messages.  iSER Hello messages are required for
     certain RCaP implementations such as iWARP but can cause problems
     for others such as InfiniBand.  Changes were made in sections
     5.1.1, 5.1.2, 5.1.3, 8.2, 9.3, 9.4, 10.1.3.2 and 10.1.3.4.

   8. Added two 64-bit fields in iSER header in section 9.2 for the Read
     Virtual Address and the Write Virtual Address to conform to the
     Infiniband format.  This allows one implementation such as the


Ko                       Expires January 2012                [Page 84]

Internet-Draft            iSER Specification                July 2011

     OFED stack to be used in both the Infiniband and the iWARP
     environment.















































Ko                       Expires January 2012                [Page 85]

Internet-Draft            iSER Specification                July 2011

15 Appendix B: Message Format for iSER

   This section is for information only and is NOT part of the
   standard.

15.1 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

















Ko                       Expires January 2012                [Page 86]

Internet-Draft            iSER Specification                July 2011

15.2 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






















Ko                       Expires January 2012                [Page 87]

Internet-Draft            iSER Specification                July 2011

15.3 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














Ko                       Expires January 2012                [Page 88]

Internet-Draft            iSER Specification                July 2011

15.4 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


























Ko                       Expires January 2012                [Page 89]

Internet-Draft            iSER Specification                July 2011

15.5 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














Ko                       Expires January 2012                [Page 90]

Internet-Draft            iSER Specification                July 2011

15.6 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














Ko                       Expires January 2012                [Page 91]

Internet-Draft            iSER Specification                July 2011

15.7 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


























Ko                       Expires January 2012                [Page 92]

Internet-Draft            iSER Specification                July 2011

15.8 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


















Ko                       Expires January 2012                [Page 93]

Internet-Draft            iSER Specification                July 2011

16 Appendix C: Architectural discussion of iSER over InfiniBand

   This section explains how an InfiniBand network (with Gateways)
   would be structured.  It is informational only and is intended to
   provide insight on how iSER is used in an InfiniBand environment.

16.1 Host side of iSCSI & iSER connections in Infiniband

   Figure 14 defines the topologies in which iSCSI and iSER will be
   able to operate on an InfiniBand Network.

   +---------+ +---------+ +---------+ +---------+ +--- -----+
   |  Host   | |  Host   | |   Host  | |   Host  | |   Host  |
   |         | |         | |         | |         | |         |
   +---+-+---+ +---+-+---+ +---+-+---+ +---+-+---+ +---+-+---+
   |HCA| |HCA| |HCA| |HCA| |HCA| |HCA| |HCA| |HCA| |HCA| |HCA|
   +-v-+ +-v-+ +-v-+ +-v-+ +-v-+ +-v-+ +-v-+ +-v-+ +-v-+ +-v-+
     |----+------|-----+-----|-----+-----|-----+-----|-----+---> To IB
   IB|        IB |        IB |        IB |        IB |    SubNet2 SWTCH
   +-v-----------v-----------v-----------v-----------v---------+
   |                  InfiniBand Switch for Subnet1            |
   +---+-----+--------+-----+--------+-----+------------v------+
       | TCA |        | TCA |        | TCA |            |
       +-----+        +-----+        +-----+            | IB
      /  IB   \      /  IB   \      /       \     +--+--v--+--+
     |  iSER   |    |  iSER   |    |  IPoIB  |    |  | TCA |  |
     | Gateway |    | Gateway |    | Gateway |    |  +-----+  |
     |   to    |    |   to    |    |   to    |    | Storage   |
     |  iSCSI  |    |  iSER   |    |   IP    |    | Controller|
     |   TCP   |    |  iWARP  |    |Ethernet |    +-----+-----+
     +---v-----|    +---v-----|    +----v----+
         | EN           | EN            | EN
         +--------------+---------------+----> to IP based storage
           Ethernet links that carry iSCSI or iWARP

                      Figure 14 iSCSI and iSER on IB

   In Figure 14, the Host systems are connected via the InfiniBand Host
   Channel Adapters (HCAs) to the InfiniBand links.  With the use of IB
   switch(es), the InfiniBand links connect the HCA to InfiniBand
   Target Channel Adapters (TCAs) located in gateways or Storage
   Controllers.  An iSER-capable IB-IP Gateway converts the iSER
   Messages encapsulated in IB protocols to either standard iSCSI, or
   iSER Messages for iWARP.  An [IPoIB] Gateway converts the InfiniBand
   [IPoIB] protocol to IP protocol, and in the iSCSI case, permits
   iSCSI to be operated on an IB Network between the Hosts and the
   [IPoIB] Gateway.


Ko                       Expires January 2012                [Page 94]

Internet-Draft            iSER Specification                July 2011

16.2 Storage side of iSCSI & iSER mixed network environment

   Figure 15 shows a storage controller that has three different portal
   groups: one supporting only iSCSI (TPG-4), one supporting iSER/iWARP
   or iSCSI (TPG-2), and one supporting iSER/IB (TPG-1).


          |                |                |
          |                |                |
    +--+--v--+----------+--v--+----------+--v--+--+
    |  | IB  |          |iWARP|          | EN  |  |
    |  |     |          | TCP |          | NIC |  |
    |  |(TCA)|          | RNIC|          |     |  |
    |  +-----|          +-----+          +-----+  |
    |   TPG-1            TPG-2            TPG-4   |
    |  9.1.3.3          9.1.2.4          9.1.2.6  |
    |                                             |
    |                  Storage Controller         |
    |                                             |
    +---------------------------------------------+

     Figure 15 Storage Controller with TCP, iWARP, and IB Connections

   The normal iSCSI portal group advertising processes (via SLP, iSNS,
   or SendTargets) are available to a Storage Controller.

16.3 Discovery processes for an InfiniBand Host

   An InfiniBand Host system can gather portal group IP address from
   SLP, iSNS, or the SendTargets discovery processes by using TCP/IP
   via [IPoIB].  After obtaining one or more remote portal IP
   addresses, the Initiator uses the standard IP mechanisms to resolve
   the IP address to a local outgoing interface and the destination
   hardware address (Ethernet MAC or IB GID of the target or a gateway
   leading to the target).  If the resolved interface is an [IPoIB]
   network interface, then the target portal can be reached through an
   InfiniBand fabric.  In this case the Initiator can establish an
   iSCSI/TCP or iSCSI/iSER session with the Target over that InfiniBand
   interface, using the Hardware Address (InfiniBand GID) obtained
   through the standard Address Resolution (ARP) processes.

   If more than one IP address are obtained through the discovery
   process, the Initiator should select a Target IP address that is on
   the same IP subnet as the Initiator if one exists.  This will avoid
   a potential overhead of going through a gateway when a direct path
   exists.



Ko                       Expires January 2012                [Page 95]

Internet-Draft            iSER Specification                July 2011

   In addition a user can configure manual static IP route entries if a
   particular path to the target is preferred.

16.4 IBTA Connection specifications

   It is outside the scope of this document, but it is expected that
   the InfiniBand Trade Association (IBTA) has or will define:

   *  The iSER ServiceID

   *  A Means for permitting a Host to establish a connection with a
      peer InfiniBand end-node, and that peer indicating when that
      end-node supports iSER, so the Host would be able to fall back
      to iSCSI/TCP over [IPoIB].

   *  A Means for permitting the Host to establish connections with
      IB iSER connections on storage controllers or IB iSER connected
      Gateways in preference to [IPoIB] connected Gateways/Bridges or
      connections to Target Storage Controllers that also accept
      iSCSI via [IPoIB].

   *  A Means for combining the IB ServiceID for iSER and the IP port
      number such that the IB Host can use normal IB connection
      processes, yet ensure that the iSER target peer can actually
      connect to the required IP port number.
























Ko                       Expires January 2012                [Page 96]

Internet-Draft            iSER Specification                July 2011

17 Acknowledgments

   Credit goes to the authors of [RFC5046], M. Ko, M. Chadalapaka, J.
   Hufferd, U. Elzur, H. Shah, and P. Thaler for coming up with the
   first version of the iSER specification.


Author's Address

   Michael Ko
   Huawei Symantec
   20245 Stevens Creek Blvd.
   Cupertino, CA 95014, USA
   Phone: +1-408-510-7465
   Email: michael@huaweisymantec.com

   Alexander Nezhinsky
   Mellanox Technologies
   13 Zarchin St.
   Raanana 43662, Israel
   Phone: +972-74-712-9000
   Email: alexandern@mellanox.com, nezhinsky@gmail.com


Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with
   respect to this document.  Code Components extracted from this
   document must include Simplified BSD License text as described in
   Section 4.e of the Trust Legal Provisions and are provided without
   warranty as described in the Simplified BSD License.











Ko                       Expires January 2012                [Page 97]


Html markup produced by rfcmarkup 1.109, available from https://tools.ietf.org/tools/rfcmarkup/