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Versions: 00 01 02 03                                                   
   INTERNET-DRAFT                            P. Culley
   draft-culley-iwarp-mpa-02.txt               Hewlett-Packard Company
                                             U. Elzur
                                               Broadcom Corporation
                                             R. Recio
                                               IBM Corpration
                                             S. Bailey
                                               Sandburst Corporation
                                             J. Carrier
                                               Adaptec

                                             Expires: August 2003


             Marker PDU Aligned Framing for TCP Specification

1  Status of this Memo

   This document is an Internet-Draft and is subject to all provisions
   of Section 10 of RFC2026.

   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



2  Abstract

   A framing protocol is defined for TCP that is fully compliant with
   applicable TCP RFCs and fully interoperable with existing TCP
   implementations. The framing mechanism is designed to work as an
   "adaptation layer" between TCP and the Direct Data Placement [DDP]
   protocol, preserving the reliable, in-order delivery of TCP, while
   adding the preservation of higher-level protocol record boundaries
   that DDP requires.








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   Table of Contents

   1     Status of this Memo..........................................1
   2     Abstract.....................................................1
   3     Introduction.................................................4
   3.1   Motivation...................................................4
   3.2   Protocol Overview............................................5
   4     Glossary.....................................................7
   5     LLP and DDP requirements.....................................8
   5.1   TCP implementation Requirements to support MPA...............8
   5.1.1 TCP Transmit side............................................8
   5.1.2 TCP Receive side.............................................8
   5.2   MPA's interactions with DDP..................................9
   6     FPDU Formats................................................11
   6.1   Marker Format...............................................12
   7     Data Transfer Semantics.....................................13
   7.1   MPA Markers.................................................13
   7.2   CRC Calculation.............................................14
   7.3   MPA on TCP Sender Segmentation..............................17
   7.3.1 Effects of MPA on TCP Segmentation..........................17
   7.3.2 FPDU Size Considerations....................................18
   7.4   MPA Receiver FPDU Identification............................19
   7.4.1 Re-segmenting Middle boxes and non MPA-aware TCP senders....20
   8     Connection Semantics........................................22
   8.1   Connection setup............................................22
   8.2   Normal Connection Teardown..................................23
   9     Error Semantics.............................................24
   10    Security Considerations.....................................25
   10.1  Protocol-specific Security Considerations...................25
   10.2  Using IPsec With MPA........................................25
   11    IANA Considerations.........................................26
   12    References..................................................27
   12.1  Normative References........................................27
   12.2  Informative References......................................27
   13    Appendix....................................................29
   13.1  Receiver implementation.....................................29
   13.1.1  Transport & Network Layer Reassembly Buffers..............29
   14    Author's Addresses..........................................31
   15    Acknowledgments.............................................32
   16    Full Copyright Statement....................................35













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   Table of Figures

   Figure 1 ULP MPA TCP Layering.......................................6
   Figure 2 FPDU Format...............................................11
   Figure 3 Marker Format.............................................12
   Figure 4 Example FPDU Format with Marker...........................14
   Figure 5 Annotated Hex Dump of an FPDU.............................16
   Figure 6 Annotated Hex Dump of an FPDU with Marker.................16
   Figure 7: Example Startup negotiation..............................23



   Revision history

   [02] Enhanced descriptions of how MPA is used over an unmodified TCP.

   [02] Removed "No Packing" text.

   [02] Made MPA an adaptation layer for DDP, instead of a generalized
       framing solution.

   [02] Added clarifications of the MPA/TCP interaction for optimized
       implementations and that any such optimizations are to be used
       only when requested by MPA.

       Note: a discussion of reasons for these changes can be found in
       [ELZUR-MPA].


























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3  Introduction

   This section discusses the reason for creating MPA on TCP and a
   general overview of the protocol.  Later sections show the MPA
   headers (see section 6 on page 11), and detailed protocol
   requirements and characteristics (see section 7 on page 13), as well
   as Connection Semantics (section 8 on page 20), Error Semantics
   (section 9 on page 24), and Security Considerations (section 10 on
   page 25).

3.1  Motivation

   The Direct Data Placement protocol [DDP], when used with TCP [RFC793]
   requires a mechanism to detect record boundaries.  The DDP records
   are referred to as Upper Layer Protocol Data Units by this document.
   The ability to locate the Upper Layer Protocol Data Unit (ULPDU)
   boundary is useful to a hardware network adapter that uses DDP to
   directly place the data in the application buffer based on the
   control information carried in the ULPDU header.  This may be done
   without requiring that the packets arrive in order.  Potential
   benefits of this capability are the avoidance of the memory copy
   overhead and a smaller memory requirement for handling out of order
   or dropped packets.

   Many approaches have been proposed for a generalized framing
   mechanism.  Some are probabilistic in nature and others are
   deterministic.  A probabilistic approach is characterized by a
   detectable value embedded in the octet stream.  It is probabilistic
   because under some conditions the receiver may incorrectly interpret
   application data as the detectable value.  Under these conditions,
   the protocol may fail with unacceptable frequency.  A deterministic
   approach is characterized by embedded controls at known locations in
   the octet stream.  Because the receiver can guarantee it will only
   examine the data stream at locations that are known to contain the
   embedded control, the protocol can never misinterpret application
   data as being embedded control data.  For unambiguous handling of an
   out of order packet, the deterministic approach is preferred.

   The MPA protocol provides a framing mechanism for DDP running over
   TCP using the deterministic approach.  It allows the location of the
   ULPDU to be determined in the TCP stream even if the TCP segments
   arrive out of order.











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3.2  Protocol Overview

   MPA is described as an extra layer above TCP and below DDP.  The end-
   to-end data flow is:

   1.  The DDP's ULP negotiates the use of DDP and MPA at both ends of a
       connection.

   2.  DDP determines the Maximum ULPDU (MULPDU) size by querying MPA
       for this value.  MPA derives this information from TCP, when it
       is available, or chooses a reasonable value.  This information is
       already supported on many TCP implementations, including all
       modern flavors of BSD networking, through the TCP_MAXSEG socket
       option.

   3.  DDP creates ULPDUs of MULPDU size or smaller, and hands them to
       MPA at the sender.

   4.  MPA creates a Framed Protocol Data Unit (FPDU) by pre-pending a
       header, inserting markers, and appending a CRC after the ULPDU
       and PAD (if any).  MPA delivers the FPDU to TCP.

   5.  The TCP sender puts the FPDUs into the TCP stream.  If the TCP
       Sender is MPA-aware, it segments the TCP stream in such a way
       that a TCP Segment boundary is also the boundary of an FPDU.  TCP
       then passes each segment to the IP layer for transmission.

   6.  The TCP receiver may be MPA-aware or may not be MPA-aware. If it
       is MPA-aware, it may separate passing the TCP payload to MPA from
       passing the TCP payload ordering information to MPA. In either
       case, RFC compliant TCP wire behavior is observed at both the
       sender and receiver.

   7.  The MPA receiver locates and assembles complete FPDUs within the
       stream, verifies their integrity, and removes MPA markers,
       ULPDU_Length, PAD and CRC.

   8.  MPA then provides the complete ULPDUs to DDP.  MPA may also
       separate passing MPA payload to DDP from passing the MPA payload
       ordering information.

   The layering of PDUs with MPA is shown in Figure 1, below.

   MPA-aware TCP is a TCP layer which potentially contains some
   additional semantics as defined in this document.  MPA is implemented
   as a data stream ULP for TCP and is therefore RFC compliant.  MPA-
   aware TCP is RFC compliant.






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               +------------------+
               |     ULP client   |
               +------------------+  <- Consumer messages
               |        DDP       |
               +------------------+  <- ULPDUs
               |        MPA       |
               +------------------+  <- FPDUs (containing ULPDUs)
               |        TCP*      |
               +------------------+  <- TCP Segments (containing FPDUs)
               |      IP etc.     |
               +------------------+
                                      * TCP or MPA-aware TCP.

                       Figure 1 ULP MPA TCP Layering

   An MPA-aware TCP sender is able to segment the data stream such that
   TCP segments begin with FPDUs (FPDU Alignment).  This has significant
   advantages for receivers.  When segments arrive with aligned FPDUs
   the receiver usually need not buffer any portion of the segment,
   allowing DDP to place it in its destination memory immediately, thus
   avoiding copies from intermediate buffers (DDP's reason for
   existence).

   MPA with an MPA-aware TCP receiver allows a DDP on MPA implementation
   to recover ULPDUs that may be received out of order.  This enables a
   DDP on MPA implementation to save a significant amount of
   intermediate storage by placing the ULPDUs in the right locations in
   the application buffers when they arrive, rather than waiting until
   full ordering can be restored.

   MPA implementations that support recovery of out of order ULPDUs MUST
   support a mechanism to indicate the ordering of ULPDUs as the sender
   transmitted them and indicate when missing intermediate segments
   arrive.  These mechanisms allow DDP to reestablish record ordering
   and report Delivery of complete messages (groups of records).

   MPA also addresses enhanced data integrity.  Many users of TCP have
   noted that the TCP checksum is not as strong as could be desired
   [CRCTCP].  Studies have shown that the TCP checksum indicates
   segments in error at a much higher rate than the underlying link
   characteristics would indicate.  With these higher error rates, the
   chance that an error will escape detection, when using only the TCP
   checksum for data integrity, becomes a concern.  A stronger integrity
   check can reduce the chance of data errors being missed.

   MPA includes a CRC check to increase the ULPDU data integrity to the
   level provided by other modern protocols, such as SCTP [RFC2960].






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4  Glossary

   Delivery - (Delivered, Delivers) - For MPA, Delivery is defined as
       the process of informing DDP that a particular PDU is ordered for
       use.  This is specifically different from "passing the PDU to
       DDP", which may generally occur in any order, while the order of
       "Delivery" is strictly defined.

   EMSS - Effective Maximum Segment Size.  EMSS is the smaller of the
       TCP maximum segment size (MSS) as defined in RFC 793 [RFC793],
       and the current path Maximum Transfer Unit (MTU) [RFC1191].

   FPDU - Framing Protocol Data Unit.  The unit of data created by an
       MPA sender.

   FPDU Alignment - the property that a TCP segment begins with an FPDU.

   PDU - protocol data unit

   MPA - Marker-based ULP PDU Aligned Framing for TCP protocol.   This
       document defines the MPA protocol.

   MULPDU - Maximum ULPDU. The current maximum size of the record that
       is acceptable for DDP to pass to MPA for transmission.

   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 MPA on TCP devices installed in a host
       computer.

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

   ULP - Upper Layer Protocol. The protocol layer above the protocol
       layer currently being referenced. The ULP for MPA is DDP [DDP].

   ULPDU - Upper Layer Protocol Data Unit.  The data record defined by
      the layer above MPA (DDP).  ULPDU corresponds to DDP's "DDP
      Segment".











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5  LLP and DDP requirements

5.1  TCP implementation Requirements to support MPA

   The TCP implementation MUST inform MPA when the TCP connection is
   closed or has begun closing the connection (e.g. received a FIN).

5.1.1  TCP Transmit side

   To provide optimum performance, an MPA-aware transmit side TCP
   implementation SHOULD be enabled to:

   *   With an EMSS large enough to contain the FPDU(s), segment the
       outgoing TCP stream such that the first octet of every TCP
       Segment begins with an FPDU.  Multiple FPDUs MAY be packed into a
       single TCP segment as long as they are entirely contained in the
       TCP segment.

   *   Report the current EMSS to the MPA transmit layer.

   An MPA-aware TCP transmit side implementation MUST continue to use
   the method of segmentation expected by non-MPA applications (and
   described in TCP RFCs) when MPA is not enabled on the connection.
   When MPA is enabled above an MPA-aware TCP, it SHOULD specifically
   enable the segmentation rules described above for the DDP segments
   (FPDUs) posted for transmission.

   If the transmit side TCP implementation is not able to segment the
   TCP stream as indicated above, MPA should make a best effort to
   achieve that result.  For example, using the TCP_NODELAY socket
   option to disable the Nagle algorithm will usually result in many of
   the segments starting with an FPDU.

   If the transmit side TCP implementation is not able to report the
   EMSS, MPA may assume that TCP will use 1460 octet segments in
   creating FPDUs.  If the implementation has reason to believe that the
   TCP segment size is actually smaller than 1460, it may instead use a
   536 octet FPDU.

5.1.2  TCP Receive side

   When an MPA receive implementation and the MPA-aware receive side TCP
   implementation supports handling out of order ULPDUs, the TCP receive
   implementation SHOULD be enabled to:

   *   Pass incoming TCP segments to MPA as soon as they have been
       received and validated, even if not received in order.  The TCP
       layer MUST have committed to keeping each segment before it can
       be passed to the MPA.  This means that the segment must have
       passed the TCP, IP, and lower layer data integrity validation
       (i.e., checksum), must be in the receive window, must not be a
       duplicate, must be part of the same epoch (if timestamps are used

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       to verify this) and any other checks required by TCP RFCs.  The
       segment MUST NOT be passed to MPA more than once unless
       explicitly requested (see Section 9).

       This is not to imply that the data must be completely ordered
       before use.  An implementation may accept out of order segments,
       SACK them [RFC2018], and pass them to DDP when the reception of
       the segments needed to fill in the gaps arrive.  Such an
       implementation can "commit" to the data early on, and will not
       overwrite it even if (or when) duplicate data arrives.  MPA
       expects to utilize this "commit" to allow the passing of ULPDUs
       to DDP when they arrive, independent of ordering.

   *   Provide a mechanism to indicate the ordering of TCP segments as
       the sender transmitted them.  One possible mechanism might be
       attaching the TCP sequence number to each segment.

   *   Provide a mechanism to indicate when a given TCP segment (and the
       prior TCP stream) is complete.  One possible mechanism might be
       to utilize the leading (left) edge of the TCP Receive Window.

       DDP on MPA MUST utilize these two mechanisms to establish the
       Delivery semantics that DDP's consumers agree to.  These
       semantics are described fully in [DDP]. These include
       requirements on DDP's consumer to respect ownership of buffers
       prior to the time that DDP delivers them to the consumer.

   An MPA-aware TCP receive side implementation MUST continue to buffer
   TCP segments until completely ordered and then deliver them as
   expected by non-MPA applications (and described in TCP RFCs) when MPA
   is not enabled on the connection.  When MPA is enabled above an MPA-
   aware TCP, TCP SHOULD enable the in and out of order passing of data,
   and the separate ordering information as described above.

   When an MPA receive implementation is coupled with a TCP receive
   implementation that does not support the preceding mechanisms, TCP
   passes and Delivers incoming stream data to MPA in order.

5.2  MPA's interactions with DDP

   DDP requires MPA to maintain DDP record boundaries from the sender to
   the receiver.  When using MPA on TCP to send data, DDP provides
   records (ULPDUs) to MPA.  MPA will use the reliable transmission
   abilities of TCP to transmit the data, and will insert appropriate
   additional information into the TCP stream to allow the MPA receiver
   to locate the record boundary information.

   As such, MPA accepts complete records (ULPDUs) from DDP at the sender
   and returns them to DDP at the receiver.

   MPA combined with an MPA-aware TCP can only ensure FPDU Alignment
   with the TCP Header if the FPDU is less than or equal to TCP's EMSS.

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   Since FPDU alignment is generally desired by the receiver, DDP must
   cooperate with MPA to ensure FPDUs' lengths do not exceed the EMSS
   under normal conditions.  This is done with the MULPDU mechanism.

   MPA provides information to DDP on the current maximum size of the
   record that is acceptable to send (MULPDU).  DDP SHOULD limit each
   record size to MULPDU.  The range of MULPDU values MUST be between
   128 octets and 64768 octets, inclusive.

   The sending DDP MUST NOT post a ULPDU larger than 64768 octets to
   MPA. DDP MAY post a ULPDU of any size between one and 64768 octets,
   however MPA is NOT REQUIRED to support a ULPDU length that is greater
   than the current MULPDU.

   While the maximum theoretical length supported by the MPA header
   ULPDU_Length field is 65535, TCP over IP requires the IP datagram
   maximum length to be 65535 octets. To enable MPA to support FPDU
   Alignment, the maximum size of the FPDU must fit within an IP
   datagram. Thus the ULPDU limit of 64768 octets was derived by taking
   the maximum IP datagram length, subtracting from it the maximum total
   length of the sum of the IPv4 header, TCP header, IPv4 options, TCP
   options, and the worst case MPA overhead, and then rounding the
   result down to a 128 octet boundary.

   On receive, MPA MUST pass each ULPDU with its length to DDP when it
   has been validated.

   If an MPA implementation supports passing out of order ULPDUs to DDP,
   the MPA implementation SHOULD:

   *   Pass each ULPDU with its length to DDP as soon as it has been
       fully received and validated.

   *   Provide a mechanism to indicate the ordering of ULPDUs as the
       sender transmitted them.  One possible mechanism might be
       providing the TCP sequence number for each ULPDU.

   *   Provide a mechanism to indicate when a given ULPDU (and prior
       ULPDUs) are complete.  One possible mechanism might be to allow
       DDP to see the current outgoing TCP Ack sequence number.

   *   Provide an indication to DDP that the TCP has closed or has begun
       to close the connection (e.g. received a FIN).










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6  FPDU Formats

   MPA senders create FPDUs out of ULPDUs.  The format of an FPDU shown
   below MUST be used for all MPA FPDUs.  For purposes of clarity,
   markers are not 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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          ULPDU_Length         |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
      |                                                               |
      ~                                                               ~
      ~                            ULPDU                              ~
      |                                                               |
      |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                               |          PAD (0-3 octets)     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             CRC                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                           Figure 2 FPDU Format

   ULPDU_Length: 16 bits (unsigned integer).  This is the number of
   octets of the contained ULPDU.  It does not include the length of the
   FPDU header itself, the pad, the CRC, or of any markers that fall
   within the ULPDU. The 16-bit ULPDU Length field is large enough to
   support the largest IP datagrams for IPv4 or IPv6.

   PAD: The PAD field trails the ULPDU and contains between zero and
   three octets of data.  The pad data MUST be set to zero by the sender
   and ignored by the receiver (except for CRC checking).  The length of
   the pad is set so as to make the size of the FPDU an integral
   multiple of four.

   CRC: 32 bits, this CRC is used to verify the entire contents of the
   FPDU, using CRC32C See section 7.2 CRC Calculation on page 14.

   The FPDU adds a minimum of 6 octets to the length of the ULPDU.  In
   addition, the total length of the FPDU will include the length of any
   markers and from 0 to 3 pad octets added to round-up the ULPDU size.













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6.1  Marker Format

   The format of a marker MUST be as specified in Figure 3:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           RESERVED            |            FPDUPTR            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                          Figure 3 Marker Format

   RESERVED: The Reserved field MUST be set to zero on transmit and
   ignored on receive (except for CRC calculation).

   FPDUPTR: The FPDU Pointer is a relative pointer, 16-bits long,
   interpreted as an unsigned integer, that indicates the number of
   octets in the TCP stream from the beginning of the FPDU to the first
   octet of the entire marker.



































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7  Data Transfer Semantics

   This section discusses some characteristics and behavior of the MPA
   protocol as well as implications of that protocol.

7.1  MPA Markers

   MPA senders MUST insert a marker into the data stream at a 512 octet
   periodic interval in the TCP Sequence Number Space. The marker
   contains a 16 bit unsigned integer referred to as the FPDUPTR (FPDU
   Pointer).

   If the FPDUPTR's value is non-zero, the FPDU Pointer is a 16 bit
   relative back-pointer. FPDUPTR MUST contain the number of octets in
   the TCP stream from the beginning of the current FPDU to the first
   octet of the marker, unless the marker falls between FPDUs. Thus the
   location of the first octet of the previous FPDU header can be
   determined by subtracting the value of the given marker from the
   current octet-stream sequence number (i.e. TCP sequence number) of
   the first octet of the marker. Note that this computation must take
   into account that the TCP sequence number could have wrapped between
   the marker and the header.

   An FPDUPTR value of 0x0000 is a special case - it is used when the
   marker falls exactly between FPDUs.  In this case, the marker MUST be
   placed in the following FPDU and viewed as being part of that FPDU
   (e.g. for CRC calculation). Thus an FPDUPTR value of 0x0000 means
   that immediately following the marker is an FPDU header.

   Since all FPDUs are integral multiples of 4 octets, the bottom two
   bits of the FPDUPTR as calculated by the sender are zero.  MPA
   reserves these bits so they MUST be treated as zero for computation
   at the receiver.

   The MPA markers MUST be inserted immediately following MPA connection
   establishment, and at every 512th octet of the TCP octet stream
   thereafter.  As a result, the first marker has an FPDUPTR value of
   0x0000.  If the first marker begins at octet sequence number
   SeqStart, then markers are inserted such that the first octet of the
   marker is at octet sequence number SeqNum if the remainder of (SeqNum
   - SeqStart) mod 512 is zero.  Note that SeqNum can wrap.

   For example, if the TCP sequence number were used to calculate the
   insertion point of the marker, the starting TCP sequence number is
   unlikely to be zero, and 512 octet multiples are unlikely to fall on
   a modulo 512 of zero. If the MPA connection is started at TCP
   sequence number 11, then the 1st marker will begin at 11, and
   subsequent markers will begin at 523, 1035, etc.

   If an FPDU is large enough to contain multiple markers, they MUST all
   point to the same point in the TCP stream: the first octet of the
   FPDU.

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   If a marker interval contains multiple FPDUs (the FPDUs are small),
   the marker MUST point to the start of the FPDU containing the marker
   unless the marker falls between FPDUs, in which case the marker MUST
   be zero.

   The following example shows an FPDU containing a marker.

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       ULPDU Length (0x0010)   |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
      |                                                               |
      +                                                               +
      |                         ULPDU (octets 0-9)                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            (0x0000)           |        FPDU ptr (0x000C)      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        ULPDU (octets 10-15)                   |
      |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                               |          PAD (2 octets:0,0)   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              CRC                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                 Figure 4 Example FPDU Format with Marker

   MPA Receivers MUST preserve ULPDU boundaries when passing data to
   DDP. MPA Receivers MUST pass the ULPDU data and the ULPDU Length to
   DDP and not the markers, headers, and CRC.

7.2  CRC Calculation

   When sending an FPDU, the sender MUST include a valid CRC field.  The
   CRC field in the MPA FPDU MUST be computed using the CRC32C
   polynomial in the manner described in the iSCSI Protocol [iSCSI]
   document for Header and Data Digests.

















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   The fields which MUST be included in the CRC calculation when sending
   an FPDU are as follows:

   1)  If the first octet of the FPDU is the "ULPDU Length" field, the
       CRC-32c is calculated from the first octet of the "ULPDU Length"
       header, through all the ULPDU and markers (if present), to the
       last octet of the PAD (if present), inclusive. If there is a
       marker immediately following the PAD, the marker is included in
       the CRC calculation for this FPDU.

   2)  If the first octet of the FPDU is a marker, (i.e. the marker fell
       between FPDUs, and thus is required to be included in the second
       FPDU), the CRC-32c is calculated from the first octet of the
       marker, through the "ULPDU Length" header, through all the ULPDU
       and markers (if present), to the last octet of the PAD (if
       present), inclusive.

   3)  After calculating the CRC-32c, the resultant value is placed into
       the CRC field at the end of the FPDU.

   When an FPDU is received, the receiver MUST first perform the
   following:

   1)  Calculate the CRC of the incoming FPDU in the same fashion as
       defined above.

   2)  Verify that the calculated CRC-32c value is the same as the
       received CRC-32c value found in the FPDU CRC field.  If not, the
       receiver MUST treat the FPDU as an invalid FPDU.

   The procedure for handling invalid FPDUs is covered in the Error
   Section (see section 9 on page 24)

   The following is an annotated hex dump of an example FPDU sent as the
   first FPDU on the stream.  As such, it starts with a marker. The FPDU
   contains 24 octets of the contained ULPDU, which are all zeros. The
   CRC32c has been correctly calculated and can be used as a reference.
   See the [DDP] and [RDMA] specification for definitions of the DDP
   Control field, Queue, MSN, MO, and Send Data.














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       Octet Contents  Annotation
       Count

       0000    00 00   Marker: Reserved
       0002    00 00           FPDUPTR
       0004    00 2a   Length
       0006    40 03   DDP Control Field, Send with Last flag set
       0008    00 00   Reserved (STag position with no STag)
       000a    00 00
       000c    00 00   Queue = 0
       000e    00 00
       0010    00 00   MSN = 1
       0012    00 01
       0014    00 00   MO = 0
       0016    00 00
       0018    00 00
                       Send Data (24 octets of zeros)
       002e    00 00
       0030    4C 86   CRC32c
       0032    B3 84
                  Figure 5 Annotated Hex Dump of an FPDU

   The following is an example sent as the second FPDU of the stream
   where the first FPDU (which is not shown here) had a length of 492
   octets and was also a Send to Queue 0 with Last Flag set.  This
   example contains a marker.

       Octet Contents  Annotation
       Count

       01ec    00 2a   Length
       01ee    40 03   DDP Control Field: Send with Last Flag set
       01f0    00 00   Reserved (STag position with no STag)
       01f2    00 00
       01f4    00 00   Queue = 0
       01f6    00 00
       01f8    00 00   MSN = 2
       01fa    00 02
       01fc    00 00   MO = 0
       01fe    00 00
       0200    00 00   Marker: Reserved
       0202    00 14           FPDUPTR
       0204    00 00
                       Send Data (24 octets of zeros)
       021a    00 00
       021c    A1 9C   CRC32c
       021e    D1 03
            Figure 6 Annotated Hex Dump of an FPDU with Marker





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7.3  MPA on TCP Sender Segmentation

   The various TCP RFCs allow considerable choice in segmenting a TCP
   stream.  In order to optimize FPDU recovery at the MPA receiver, MPA
   specifies additional segmentation rules.

   MPA MUST encapsulate the ULPDU such that there is exactly one ULPDU
   contained in one FPDU.

   An MPA-aware TCP sender SHOULD, when enabled for MPA, on TCP
   implementations that support this, and with an EMSS large enough to
   contain at least one FPDU, segment the outbound TCP stream such that
   each TCP segment begins with an FPDU, and fully contains all included
   FPDUs.

        Implementation note: To achieve the previous segmentation rule,
        TCP's Nagle [RFC0896] algorithm SHOULD be disabled.

   There are exceptions to the above rule.  Once an ULPDU is provided to
   MPA, the MPA on TCP sender MUST transmit it or fail the connection;
   it cannot be repudiated.  As a result, during changes in MTU and
   EMSS, or when TCP's Receive Window size (RWIN) becomes too small, it
   may be necessary to send FPDUs that do not conform to the
   segmentation rule above.

   A possible, but less desirable, alternative is to use IP
   fragmentation on accepted FPDUs to deal with MTU reductions or
   extremely small EMSS.

   The sender MUST still format the FPDU according to FPDU format as
   shown in Figure 2.

   On a retransmission, TCP does not necessarily preserve original TCP
   segmentation boundaries. This can lead to the loss of FPDU alignment
   and containment within a TCP segment during TCP retransmissions. An
   MPA-aware TCP sender SHOULD try to preserve original TCP segmentation
   boundaries on a retransmission.

7.3.1  Effects of MPA on TCP Segmentation

   Applications expected to see strong advantages from Direct Data
   Placement include transaction-based applications and throughput
   applications. Request/response protocols typically send one FPDU per
   TCP segment and then wait for a response. Therefore, the application
   is expected to set TCP parameters such that it can trade off latency
   and wire efficiency. This is accomplished by setting the TCP_NODELAY
   socket option.

   When latency is not critical, and the application provides data in
   chunks larger than EMSS at one time,  the TCP implementation may
   "pack" any available stream data into TCP segments so that the
   segments are filled to the EMSS.  If the amount of data available is

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   not enough to fill the TCP segment when it is prepared for
   transmission, TCP can send the segment partly filled, or use the
   Nagle algorithm to wait for the ULP to post more data (discussed
   below).

   DDP/MPA senders will fill TCP segments to the EMSS with a single FPDU
   when a DDP message is large enough.  Since the DDP message may not
   exactly fit into TCP segments, a "message tail" often occurs that
   results in an FPDU that is smaller than a single TCP segment.  If a
   "message tail", small DDP messages, or the start of a larger DDP
   message are available, MPA MAY "pack" the resulting FPDUs into TCP
   segments.  When this is done, the TCP segments can be more fully
   utilized, but, due to the size constraints of FPDUs, segments may not
   be filled to the EMSS.

        Note that MPA receivers must do more processing of a TCP segment
        that contains multiple FPDUs, this may affect the performance of
        some receiver implementations.

   TCP implementations often utilize the "Nagle" [RFC0896] algorithm to
   ensure that segments are filled to the EMSS whenever the round trip
   latency is large enough that the source stream can fully fill
   segments before Acks arrive.  The algorithm does this by delaying the
   transmission of TCP segments until a ULP can fill a segment, or until
   an ACK arrives from the far side.  The algorithm thus allows for
   smaller segments when latencies are shorter to keep the ULP's end to
   end latency to reasonable levels.

   The Nagle algorithm is not mandatory to use [RFC1122].

   It is up to the ULP to decide if Nagle is useful with DDP/MPA.  Note
   that many of the applications expected to take advantage of MPA/DDP
   prefer to avoid the extra delays caused by Nagle. In such scenarios
   it is anticipated there will be minimal opportunity for packing at
   the transmitter and receivers may choose to optimize their
   performance for this anticipated behavior.

7.3.2  FPDU Size Considerations

   MPA defines the Maximum Upper Layer Protocol Data Unit (MULPDU) as
   the size of the largest ULPDU fitting in an FPDU.  For an empty TCP
   Segment, MULPDU is EMSS minus the FPDU overhead (6 octets) minus
   space for markers and pad octets.

     The maximum ULPDU Length for a single ULPDU MUST be computed as:

        MULPDU = EMSS - (6 + 4 * Ceiling(EMSS / 512) + EMSS mod 4)

   The formula above accounts for the worst-case number of markers.

   As a further optimization of the wire efficiency an MPA
   implementation MAY dynamically adjust the MULPDU (see section 7.3.1.

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   for latency and wire efficiency trade-offs). When one or more FPDUs
   are already packed into a TCP Segment, MULPDU MAY be reduced
   accordingly.

   DDP SHOULD provide ULPDUs that are as large as possible, but less
   than or equal to MULPDU.

   If the TCP implementation needs to adjust EMSS to support MTU
   changes, the MULPDU value is changed accordingly.

   In certain rare situations, the EMSS may shrink to very small sizes.
   If this occurs, the MPA on TCP sender MUST NOT shrink the MULPDU
   below 128 octets and is not required to follow the segmentation rules
   in Section 7.3 MPA on TCP Sender Segmentation on page 17.

   If one or more FPDUs are already packed into a TCP segment, such that
   the remaining room is less than 128 octets, MPA MUST NOT provide a
   MULPDU smaller than 128.  In this case, MPA would typically provide a
   MULPDU for the next full sized segment, but may still pack the next
   FPDU into the small remaining room, provide that the next FPDU is
   small enough to fit.

   The value 128 is chosen as to allow DDP designers room for the DDP
   Header and some user data.

7.4  MPA Receiver FPDU Identification

   An MPA receiver MUST first verify the FPDU before passing the ULPDU
   to DDP.  To do this, the receiver MUST:

   *   locate the start of the FPDU unambiguously,

   *   verify its CRC.

   If the above conditions are true, the MPA receiver passes the ULPDU
   to DDP.

   To detect the start of the FPDU unambiguously one of the following
   MUST be used:

   1:  In an ordered TCP stream, the ULPDU Length field in the current
       FPDU when FPDU has a valid CRC, can be used to identify the
       beginning of the next FPDU.

   2:  A Marker can always be used to locate the beginning of an FPDU
       (in FPDUs with valid CRCs).  Since the location of the marker is
       known in the octet stream (sequence number space), the marker can
       always be found.

   3:  Having found an FPDU by means of a Marker, following contiguous
       FPDUs can be found by using the ULPDU Lengths (from FPDUs with
       valid CRCs) to establish the next FPDU boundary.

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   The ULPDU Length field (see section 6) MUST be used to determine if
   the entire FPDU is present before forwarding the ULPDU to DDP.

   CRC calculation is discussed in section 7.2 on page 14 above.

7.4.1  Re-segmenting Middle boxes and non MPA-aware TCP senders

   Since MPA on MPA-aware TCP senders start FPDUs on TCP segment
   boundaries, a receiving DDP on MPA on TCP implementation may be able
   to optimize the reception of data in various ways.

   However, MPA receivers MUST NOT depend on FPDU Alignment on TCP
   segment boundaries.

   Some MPA senders may be unable to conform to the sender requirements
   because their implementation of TCP is not designed with MPA in mind.
   Even if the sender is MPA-aware, the network may contain "middle
   boxes" which modify the TCP stream by changing the segmentation.
   This is generally interoperable with TCP and its users and MPA must
   be no exception.

   The presence of markers in MPA allows an MPA receiver to recover the
   FPDUs despite these obstacles, although it may be necessary to
   utilize additional buffering at the receiver to do so.

   Some of the cases that a receiver may have to contend with are listed
   below as a reminder to the implementer:

   *   A single Aligned and complete FPDU, either in order, or out of
       order:  This can be passed to DDP as soon as validated, and
       Delivered when ordering is established.

   *   Multiple FPDUs in a TCP segment, aligned and fully contained,
       either in order, or out of order:  These can be passed to DDP as
       soon as validated, and Delivered when ordering is established.

   *   Incomplete FPDU: The receiver should buffer until the remainder
       of the FPDU arrives.  If the remainder of the FPDU is already
       available, this can be passed to DDP as soon as validated, and
       Delivered when ordering is established.

   *   Unaligned FPDU start: The partial FPDU must be combined with its
       preceding portion(s).  If the preceding parts are already
       available, and the whole FPDU is present, this can be passed to
       DDP as soon as validated, and Delivered when ordering is
       established.  If the whole FPDU is not available, the receiver
       should buffer until the remainder of the FPDU arrives.

   *   Combinations of Unaligned or incomplete FPDUs (and potentially
       other complete FPDUs) in the same TCP segment:  If any FPDU is
       present in its entirety, or can be completed with portions


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       already available, it can be passed to DDP as soon as validated,
       and Delivered when ordering is established.



















































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8  Connection Semantics

8.1  Connection setup

   DDP on MPA requires that DDP's consumer MUST activate DDP, MPA, and
   any TCP enhancements for MPA, on a TCP half connection at the same
   location in the octet stream at both the sender and the receiver.
   This is required in order for the marker scheme to correctly locate
   the markers.

   DDP, MPA, and any TCP enhancements for MPA, MAY be started separately
   in each direction, or enabled in both directions at once.

   This can be accomplished several ways, and is left up to DDP's ULP:

   *   DDP's ULP MAY require DDP on MPA startup immediately after TCP
       connection setup.  This has the advantage that no additional
       negotiation is needed (at least for MPA).  In this case the
       marker MUST be the first four octets sent (this marker has the
       special value 0x0000, meaning it belongs to the FPDU that
       follows).

       This may be accomplished by using a well-known port, or a service
       locator protocol to locate an appropriate port on which DDP on
       MPA is expected to operate.

   *   DDP's ULP MAY negotiate the start of DDP on MPA sometime after a
       normal TCP startup, using TCP streaming data exchanges on the
       same connection.  The exchange establishes that DDP on MPA (as
       well as other ULPs) will be used, and exactly locates the point
       in the octet stream where MPA is to begin operation.  Again, the
       marker is the first four octets sent when operation begins (this
       marker has the special value 0x0000, meaning it belongs to the
       FPDU that follows).  Note that such a negotiation protocol is
       outside the scope of this specification.  A simplified example of
       such a protocol is shown below.

















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     +-------------------------+
     |ULP streaming mode       |
     | <Hello> request to      |
     | transition to DDP/MPA   |           +--------------------------+
     | mode                    | --------> |ULP gets request;         |
     +-------------------------+           |sets its receiver to      |
                                           |DDP/MPA mode; sends       |
                                           |streaming mode DDP/MPA    |
     +-------------------------+           |<Hello Acknowledgement>   |
     |ULP receives DDP/MPA     | <-------- |                          |
     |<Hello Acknowledgement>; |           +--------------------------+
     |Sets transmitter and     |
     |receiver to DDP/MPA mode;|
     |                         |
     |The First DDP/MPA message|           +--------------------------+
     |Is then sent.            | --------> |When the DDP/MPA mode     |
     +-------------------------+           |message arrives, the ULP  |
                                           |sets its Transmit side to |
                                           |DDP/MPA mode and begins   |
                                           |full operation.           |
                                           +--------------------------+
                   Figure 7: Example Startup negotiation


8.2  Normal Connection Teardown

   Each half connection of MPA terminates when DDP closes the
   corresponding TCP half connection.

   A mechanism SHOULD be provided by MPA to DDP for DDP to be made aware
   that a graceful close of the LLP connection has been received by the
   LLP (e.g. FIN is received).





















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9  Error Semantics

   The following errors MUST be detected by MPA and the codes SHOULD be
   provided to DDP:

       Code Error

       1   TCP connection closed, terminated or lost.  This includes
           lost by timeout, too many retries, RST received or FIN
           received.

       2   Received MPA CRC does not match the calculated value for the
           FPDU.

       3   In the event that the CRC is valid, received MPA marker and
           'ULPDU Length' fields do not agree on the start of a FPDU.
           If the FPDU start determined from previous ULPDU Length
           fields does not match with the MPA marker position, MPA
           SHOULD deliver an error to DDP.  It may not be possible to
           make this check as a segment arrives, but the check SHOULD
           be made when a gap creating an out of order sequence is
           closed and any time a marker points to an already identified
           FPDU.  It is OPTIONAL for a receiver to check each marker,
           if multiple markers are present in an FPDU, or if the
           segment is received in order.

   When conditions 2 or 3 above are detected, an MPA-aware TCP
   implementation MAY choose to silently drop the TCP segment rather
   than reporting the error to DDP.  In this case, the sending TCP will
   retry the segment, usually correcting the error, unless the problem
   was at the source.  In that case, the source will usually exceed the
   number of retries and terminate the connection.

   Once MPA delivers an error of any type, it MUST NOT pass or deliver
   any additional FPDUs on that half connection.

   MPA MUST NOT close the TCP connection following a reported error.
   Closing the connection is the responsibility of DDP's ULP.

        Note that since MPA will not deliver any FPDUs on a half
        connection following an error detected on the receive side of
        that connection, DDP's ULP is expected to tear down the
        connection.  This may not occur until after one or more last
        messages are transmitted on the opposite half connection.  This
        allows a diagnostic error message to be sent.








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10 Security Considerations

   This section discusses the security considerations for MPA.

10.1 Protocol-specific Security Considerations

   The vulnerabilities of MPA to third-party attacks are no greater than
   any other protocol running over TCP.  A third party, by sending
   packets into the network that are delivered to an MPA receiver, could
   launch a variety of attacks that take advantage of how MPA operates.
   For example, a third party could send random packets that are valid
   for TCP, but contain no FPDU headers.  An MPA receiver reports an
   error to DDP when any packet arrives that cannot be validated as an
   FPDU when properly located on an FPDU boundary.  This would have a
   severe impact on performance.  Communication security mechanisms such
   as IPsec [RFC2401] may be used to prevent such attacks.  Independent
   of how MPA operates, a third party could use ICMP messages to reduce
   the path MTU to such a small size that performance would likewise be
   severely impacted.  Range checking on path MTU sizes in ICMP packets
   may be used to prevent such attacks.

10.2 Using IPsec With MPA

   IPsec can be used to protect against the packet injection attacks
   outlined above.  Because IPsec is designed to secure individual IP
   packets, MPA can run above IPsec without change.  IPsec packets are
   processed (e.g., integrity checked and decrypted) in the order they
   are received, and an MPA receiver will process the decrypted FPDUs
   contained in these packets in the same manner as FPDUs contained in
   unsecured IP packets.























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11 IANA Considerations

   If a well-known port is chosen as the mechanism to identify a DDP on
   MPA on TCP, the well-known port must be registered with IANA.
   Because the use of the port is DDP specific, registration of the port
   with IANA is left to DDP.















































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12 References

12.1 Normative References

   [iSCSI] Satran, J., "iSCSI", draft-ietf-ips-iscsi-20.txt (work in
       progress), January 2003.

   [RFC1191] Mogul, J., and Deering, S., "Path MTU Discovery", RFC 1191,
       November 1990.

   [RFC2018] Mathis, M., Mahdavi, J., Floyd, S., Romanow, A., "TCP
       Selective Acknowledgment Options", RFC 2018, October 1996.

   [RFC2026] Bradner, S., "The Internet Standards Process -- Revision
       3", BCP 9, RFC 2026, October 1996.

   [RFC793] Postel, J., "Transmission Control Protocol - DARPA Internet
       Program Protocol Specification", RFC 793, September 1981.

12.2 Informative References

   [CRCTCP] Stone J., Partridge, C., "When the CRC and TCP checksum
       disagree", ACM Sigcomm, Sept. 2000.

   [DDP] H. Shah et al., "Direct Data Placement over Reliable
       Transports", draft-shah-iwarp-ddp-00.txt (Work in progress),
       October 2002

   [RFC2401]  Atkinson, R., Kent, S., "Security Architecture for the
       Internet Protocol", RFC 2401, November 1998.

   [RFC0896] J. Nagle, "Congestion Control in IP/TCP Internetworks", RFC
       896, January 1984.

   [NagleDAck] Minshall G., Mogul, J., Saito, Y., Verghese, B.,
       "Application performance pitfalls and TCP's Nagle algorithm",
       Workshop on Internet Server Performance, May 1999.

   [RDMA] R. Recio et al., "RDMA Protocol Specification",
       draft-recio-iwarp-rdmap-00.txt, October 2002

   [RFC2960] R. Stewart et al., "Stream Control Transmission Protocol",
       RFC 2960, October 2000.

   [RFC792] Postel, J., "Internet Control Message Protocol". September
       1981

   [RFC1122] Braden, R.T., "Requirements for Internet hosts -
       communication layers". October 1989.




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   [ELZUR-MPA] Elzur, U., "Analysis of MPA over TCP Operations" draft-
       elzur-iwarp-mpa-tcp-analysis-00.txt, February 2003.



















































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13 Appendix

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

13.1 Receiver implementation

13.1.1 Transport & Network Layer Reassembly Buffers

   The use of reassembly buffers (either TCP reassembly buffers or IP
   fragmentation reassembly buffers) is implementation dependent. When
   MPA is enabled, reassembly buffers are needed if FPDU Alignment is
   lost or if IP fragmentation occurs. This is because the incoming out
   of order segment may not contain enough information for MPA to
   process all of the FPDU. For cases where a re-segmenting middle box
   is present, or where the TCP sender is not MPA-aware, the presence of
   markers significantly reduces the amount of buffering needed.

   Recovery from IP Fragmentation must be transparent to the MPA
   Consumers.

13.1.1.1 Network Layer Reassembly Buffers

   Most IP implementations set the IP Don't Fragment bit. Thus upon a
   path MTU change, intermediate devices drop the IP datagram if it is
   too large and reply with an ICMP message which tells the source TCP
   that the path MTU has changed. This causes TCP to emit segments
   conformant with the new path MTU size. Thus IP fragments under most
   conditions should never occur at the receiver. But it is possible.

   There are several options for implementation of network layer
   reassembly buffers:

   1.  drop any IP fragments, and reply with an ICMP message according
       to [RFC792] (fragmentation needed and DF set) to tell the Remote
       Peer to resize its TCP segment

   2.  support an IP reassembly buffer, but have it of limited size
       (possibly the same size as the local link's MTU). The end Node
       would normally never advertise a path MTU larger than the local
       link MTU. It is recommended that a dropped IP fragment cause an
       ICMP message to be generated according to RFC792.

   3.  multiple IP reassembly buffers, of effectively unlimited size.

   4.  support an IP reassembly buffer for the largest IP datagram (64
       KB).

   5.  support for a large IP reassembly buffer which could span
       multiple IP datagrams.



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   An implementation should support at least 2 or 3 above, to avoid
   dropping packets that have traversed the entire fabric.

   There is no end-to-end ACK for IP reassembly buffers, so there is no
   flow control on the buffer. The only end-to-end ACK is a TCP ACK,
   which can only occur when a complete IP datagram is delivered to TCP.
   Because of this, under worst case, pathological scenarios, the
   largest IP reassembly buffer is the TCP receive window (to buffer
   multiple IP datagrams that have all been fragmented).

   Note that if the Remote Peer does not implement re-segmentation of
   the data stream upon receiving the ICMP reply updating the path MTU,
   it is possible to halt forward progress because the opposite peer
   would continue to retransmit using a transport segment size that is
   too large. This deadlock scenario is no different than if the fabric
   MTU (not last hop MTU) was reduced after connection setup, and the
   remote Node's behavior is not compliant with [RFC1122].

13.1.1.2 TCP Reassembly buffers

   A TCP reassembly buffer is also needed. TCP reassembly buffers are
   needed if FPDU Alignment is lost when using TCP with MPA or when the
   MPA FPDU spans multiple TCP segments.

   Since lost FPDU Alignment often means that FPDUs are incomplete, an
   MPA on TCP implementation must have a reassembly buffer large enough
   to recover an FPDU that is less than or equal to the MTU of the
   locally attached link (this should be the largest possible advertised
   TCP path MTU). If the MTU is smaller than 140 octets, the buffer MUST
   be at least 140 octets long to support the minimum FPDU size.  The
   140 octets allows for the minimum MULPDU of 128, 2 octets of pad, 2
   of ULPDU_Length, 4 of CRC, and space for a possible marker. As usual,
   additional buffering may provide better performance.

   Note that if the TCP segment were not stored, it is possible to
   deadlock the MPA algorithm. If the path MTU is reduced, FPDU
   Alignment requires the source TCP to re-segment the data stream to
   the new path MTU. The source MPA will detect this condition and
   reduce the MPA segment size, but any FPDUs already posted to the
   source TCP will be re-segmented and lose FPDU Alignment. If the
   destination does not support a TCP reassembly buffer, these segments
   can never be successfully transmitted and the protocol deadlocks.

   When a complete FPDU is received, processing continues normally.









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14 Author's Addresses

   Stephen Bailey
       Sandburst Corporation
       600 Federal Street
       Andover, MA  01810 USA
       Phone: +1 978 689 1614
       Email: steph@sandburst.com

   Paul R. Culley
       Hewlett-Packard Company
       20555 SH 249
       Houston, Tx. USA 77070-2698
       Phone:  281-514-5543
       Email:  paul.culley@hp.com

   Uri Elzur
       Broadcom
       16215 Alton Parkway
       CA, 92618
       Phone: 949.585.6432
       Email:  uri@broadcom.com

   Renato J Recio
       IBM
       Internal Zip 9043
       11400 Burnett Road
       Austin,  Texas  78759
       Phone:  512-838-3685
       Email:  recio@us.ibm.com

   John Carrier
       Adaptec Inc.
       691 South Milpitas Blvd.
       Milpitas, CA 95035
       Phone:  360-378-8526
       Email:  John_Carrier@adaptec.com
















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15 Acknowledgments

   Dwight Barron
       Hewlett-Packard Company
       20555 SH 249
       Houston, Tx. USA 77070-2698
       Phone: 281-514-2769
       Email: dwight.barron@hp.com

   Jeff Chase
       Department of Computer Science
       Duke University
       Durham, NC 27708-0129 USA
       Phone: +1 919 660 6559
       Email: chase@cs.duke.edu

   Ted Compton
       EMC Corporation
       Research Triangle Park, NC 27709, USA
       Phone: 919-248-6075
       Email: compton_ted@emc.com

   Dave Garcia
       Hewlett-Packard Company
       19333 Vallco Parkway
       Cupertino, Ca. USA 95014
       Phone: 408.285.6116
       Email: dave.garcia@hp.com

   Hari Ghadia
       Adaptec, Inc.
       691 S. Milpitas Blvd.,
       Milpitas, CA 95035  USA
       Phone: +1 (408) 957-5608
       Email: hari_ghadia@adaptec.com

   Howard C. Herbert
       Intel Corporation
       MS CH7-404
       5000 West Chandler Blvd.
       Chandler, Arizona 85226
       Phone: 480-554-3116
       Email: howard.c.herbert@intel.com










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   Jeff Hilland
       Hewlett-Packard Company
       20555 SH 249
       Houston, Tx. USA 77070-2698
       Phone: 281-514-9489
       Email: jeff.hilland@hp.com

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

   Mike Krause
       Hewlett-Packard Corporation, 43LN
       19410 Homestead Road
       Cupertino, CA 95014 USA
       Phone: +1 (408) 447-3191
       Email: krause@cup.hp.com

   Dave Minturn
       Intel Corporation
       MS JF1-210
       5200 North East Elam Young Parkway
       Hillsboro, Oregon  97124
       Phone: 503-712-4106
       Email: dave.b.minturn@intel.com

   Jim Pinkerton
       Microsoft, Inc.
       One Microsoft Way
       Redmond, WA, USA 98052
       Email: jpink@microsoft.com

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

   Allyn Romanow
       Cisco Systems
       170 W Tasman Drive
       San Jose, CA 95134 USA
       Phone: +1 408 525 8836
       Email: allyn@cisco.com




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   Tom Talpey
       Network Appliance
       375 Totten Pond Road
       Waltham, MA 02451 USA
       Phone: +1 (781) 768-5329
       EMail: thomas.talpey@netapp.com

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

   Jim Wendt
       Hewlett Packard Corporation
       8000 Foothills Boulevard MS 5668
       Roseville, CA 95747-5668 USA
       Phone: +1 916 785 5198
       Email: jim_wendt@hp.com

   Jim Williams
       Emulex Corporation
       580 Main Street
       Bolton, MA 01740 USA
       Phone: +1 978 779 7224
       Email: jim.williams@emulex.com

























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16 Full Copyright Statement

   This document and the information contained herein is provided on an
   "AS IS" basis and ADAPTEC INC., AGILENT TECHNOLOGIES INC., BROADCOM
   CORPORATION, CISCO SYSTEMS INC., DUKE UNIVERSITY, EMC CORPORATION,
   EMULEX CORPORATION, HEWLETT-PACKARD COMPANY, INTERNATIONAL BUSINESS
   MACHINES CORPORATION, INTEL CORPORATION, MICROSOFT CORPORATION,
   NETWORK APPLIANCE INC., SANDBURST CORPORATION, THE INTERNET SOCIETY,
   AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES,
   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT
   THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY
   IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
   PURPOSE.

   Copyright (c) 2002 ADAPTEC INC., BROADCOM CORPORATION, CISCO SYSTEMS
   INC., EMC CORPORATION, HEWLETT-PACKARD COMPANY, INTERNATIONAL
   BUSINESS MACHINES CORPORATION, INTEL CORPORATION, MICROSOFT
   CORPORATION, NETWORK APPLIANCE INC., All Rights Reserved



































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