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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 RFC 3821

IPS Working Group               M. Rajagopal, R. Bhagwat, R. A. Helland,
INTERNET-DRAFT                                           LightSand Comm.
<draft-ietf-ips-fcovertcpip-04.txt>           E. Rodriguez, Lucent Tech.
(Expires January, 2002)                              C. Carlson, QLogic
Category: standards-track                              D. Fraser, Compaq
                                                      D. Peterson, Cisco
                                                   L. Lamers, SAN Valley
                                     V. Chau, G. Hecht, Gadzoox Networks
                          S. Wilson, B. Snively, R. Weber, Brocade Comm.
                                   M. O'Donnell, A. Rijhsinghani, McDATA
                                            S. Rupanagunta, Aarohi Comm.
                                            V. Rangan, Rhapsody Networks
                                             J. Nelson, K. Hirata, Vixel
                                               M. Merhar, Pirus Networks
                                                     N. Wanamaker, Akara


                    Fibre Channel Over TCP/IP (FCIP)

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC 2026 [1].

   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/ietf/lid-abstracts.txt

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

Abstract

   Fibre Channel Over TCP/IP (FCIP) describes mechanisms that allow the
   interconnection of islands of Fibre Channel storage area networks
   over IP-based networks to form a unified storage area network in a
   single Fibre Channel fabric. FCIP relies on IP-based network
   services to provide the connectivity between the storage area
   network islands over local area networks, metropolitan area
   networks, or wide area networks.


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Conventions used in this document

   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 [2].

Table Of Contents

   1. Purpose, Motivation and Objectives . . . . . . . . . . . . . . . 3
   2. Relationship to Fibre Channel Standards  . . . . . . . . . . . . 4
   2.1 Relevant Fibre Channel Standards  . . . . . . . . . . . . . . . 4
   2.2 This Specification and Fibre Channel Standards  . . . . . . . . 5
   3. Terminology  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
   4. Open Issues  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
   5. Protocol Summary . . . . . . . . . . . . . . . . . . . . . . . . 7
   6. The FCIP Model . . . . . . . . . . . . . . . . . . . . . . . . . 9
   6.1 FCIP Protocol Model . . . . . . . . . . . . . . . . . . . . . . 9
   6.2 FCIP Link  . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   6.3 FC Entity  . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   6.4 FCIP Entity  . . . . . . . . . . . . . . . . . . . . . . . . . 12
   6.5 FCIP Link Endpoint (FCIP_LEP)  . . . . . . . . . . . . . . . . 13
   6.6 FCIP Data Engine (FCIP_DE) . . . . . . . . . . . . . . . . . . 14
   6.6.1 FCIP Encapsulation of FC Frames  . . . . . . . . . . . . . . 16
   6.6.2 FCIP Data Engine Error Detection and Recover . . . . . . . . 17
   6.6.2.1 TCP Assistance With Error Detection and Recovery . . . . . 17
   6.6.2.2 Errors in FCIP Headers and Discarding FCIP Frames  . . . . 17
   6.6.2.3 IP Network Transit Time Validation . . . . . . . . . . . . 18
   6.6.2.4 Synchronization Failures . . . . . . . . . . . . . . . . . 19
   7. Establishing and Maintaining a Synchronized Time Value  . . . . 20
   8. TCP Connection Management . . . . . . . . . . . . . . . . . . . 21
   8.1 TCP Connection Establishment . . . . . . . . . . . . . . . . . 21
   8.1.1 Creating a New TCP Connection  . . . . . . . . . . . . . . . 21
   8.1.2 Processing TCP Connect Requests  . . . . . . . . . . . . . . 21
   8.2 TCP Connection Parameters  . . . . . . . . . . . . . . . . . . 22
   8.2.1 TCP Selective Acknowledgement Option . . . . . . . . . . . . 22
   8.2.2 TCP Window Scale Option  . . . . . . . . . . . . . . . . . . 23
   8.2.3 IP DSCP Option . . . . . . . . . . . . . . . . . . . . . . . 23
   8.2.4 Protection against sequence number wrap  . . . . . . . . . . 23
   8.2.5 TCP No Delay Option  . . . . . . . . . . . . . . . . . . . . 23
   8.2.6 TCP Acknowledgement Timeout  . . . . . . . . . . . . . . . . 23
   8.3 TCP Connection Considerations  . . . . . . . . . . . . . . . . 23
   8.4 Flow Control Mapping between TCP and FC  . . . . . . . . . . . 24
   9. Security  . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
   9.1 Considerations . . . . . . . . . . . . . . . . . . . . . . . . 25
   9.2 IP Network Security Requirements . . . . . . . . . . . . . . . 25
   9.3 Integrated Security  . . . . . . . . . . . . . . . . . . . . . 26
   9.4 External Security Gateway  . . . . . . . . . . . . . . . . . . 26
   9.5 Security Information Exchanged Between FC and FCIP Entities  . 27


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   10. Performance  . . . . . . . . . . . . . . . . . . . . . . . . . 27
   10.1 Performance Considerations  . . . . . . . . . . . . . . . . . 27
   10.2 IP Quality of Service (QoS) Support . . . . . . . . . . . . . 28
   10.3 QoS Information Exchanged Between FC and FCIP Entities  . . . 28
   11. Dynamic Discovery of Participating FCIP Entities . . . . . . . 29
   11.1 Requirements  . . . . . . . . . . . . . . . . . . . . . . . . 29
   11.2 Discovery Information Exchanged Between FC and FCIP Entities  29
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
   13. Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . 31
   14. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 31
   15. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 31
   16. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 33

   Annex
   A  Example of synchronization recovery algorithm . . . . . . . . . 34
   B  Relationship between FCIP and IP over FC (IPFC) . . . . . . . . 39
   C  FC Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 39
   D  FCIP Requirements on an FC Entity . . . . . . . . . . . . . . . 41

1. Purpose, Motivation and Objectives

   Fibre Channel (FC) is a gigabit speed networking technology
   primarily used to implement Storage Area Networks (SANs). See
   section 2 for information about how Fibre Channel is standardized
   and the relationship of this specification to Fibre Channel standards.

   This specification describes mechanisms that allow the
   interconnection of islands of Fibre Channel SANs over IP Networks to
   form a unified SAN in a single Fibre Channel fabric. The motivation
   behind defining these interconnection mechanisms is a desire to
   connect physically remote FC sites allowing remote disk access, tape
   backup, and live mirroring.

   Fibre Channel standards have chosen nominal distances between switch
   elements that are less than the distances available in an IP
   Network. Since Fibre Channel and IP Networking technologies are
   compatible, it is logical to turn to IP Networking for extending the
   allowable distances between Fibre Channel switch elements.

   The fundamental assumption made in this specification is that the
   Fibre Channel traffic is carried over the IP Network in such a
   manner that the Fibre Channel Fabric and all Fibre Channel devices
   on the Fabric are unaware of the presence of the IP Network. This
   means that the FC datagrams MUST be delivered in such time as to
   comply with existing Fibre Channel specifications. The FC traffic
   MAY span LANs, MANs and WANs, so long as this fundamental assumption
   is adhered to.



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   The objectives of this document are to:

   1)  specify the encapsulation and mapping of Fibre Channel (FC)
       frames employing FC Frame Encapsulation [24].

   2)  apply the mechanism described in 1) to an FC Fabric using an IP
       network as an interconnect for two or more islands in an FC
       Fabric.

   3)  address any FC concerns arising from tunneling FC traffic over
       an IP-based network, including security, data integrity (loss),
       congestion, and performance. This will be accomplished by
       utilizing the existing IETF-specified suite of protocols.

   4)  be compatible with the referenced FC standards. While new work
       may be undertaken in T11 [8] to optimize and enhance FC Fabrics,
       this specification requires conformance only to the referenced
       FC standards.

   5)  be compatible with all applicable IETF standards so that the IP
       Network used to extend an FC Fabric can be used concurrently for
       other reasonable purposes.

2. Relationship to Fibre Channel Standards

2.1 Relevant Fibre Channel Standards

   FC is standardized under American National Standard for Information
   Systems of the National Committee for Information Technology
   Standards (ANSI-NCITS) in its T11 technical committee. T11 has
   specified a number of documents describing FC protocols, operations,
   and services. T11 documents of interest to readers of this
   specification include:

    - FC-BB   - Fibre Channel Backbone [3]
    - FC-BB-2 - Fibre Channel Backbone -2 [4]
    - FC-SW-2 - Fibre Channel Switch Fabric -2 [5]
    - FC-FS   - Fibre Channel Framing and Signaling [6]
    - FC-GS-3 - Fibre Channel Generic Services -3 (FC-GS-3) [7]

   FC-BB and FC-BB-2 describe the relationship between an FC Fabric and
   interconnect technologies not defined in by Fibre Channel standards
   (e.g., ATM and SONET).  FC-BB-2 is the natural Fibre Channel home
   for describing relationships to TCP/IP and FCIP.

   FC-SW-2 describes the switch components of an FC Fabric and FC-FS
   describes the FC Frame format and basic control features of Fibre
   Channel.


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   FC-GS-3 describes a collection of services that may be provided by
   the switches in an FC Fabric (e.g., name (directory) server and key
   distribution server).

   Additional information regarding T11 activities is available on the
   committee's web site [8].

2.2 This Specification and Fibre Channel Standards

   When considering the challenge of transporting FC Frames over an IP
   Network, it is logical to divide the standardization effort between
   TCP/IP requirements and Fibre Channel requirements to realize the
   highest quality of review for both topics. This specification covers
   the TCP/IP requirements for transporting FC Frames and the Fibre
   Channel documents described in section 2.1 cover the Fibre Channel
   requirements.

   This specification addresses only the requirements necessary to
   properly utilize an IP Network as a conduit for FC Frames. The
   result is a specification for an FCIP Entity (see section 6.4).

   A product that tunnels an FC Fabric through an IP Network must
   combine the FCIP Entity with an FC Entity (see section 6.3) using an
   implementation specific interface. The requirements placed on an FC
   Entity by this specification to achieve proper delivery of FC Frames
   are summarized in annex D. More information about FC Entities can be
   found in the Fibre Channel standards and an example of an FC Entity
   can be found in FC-BB-2 [4].

   No attempt is being made to define a specific API between an FCIP
   Entity and an FC Entity at this time because doing so risks
   compromising the performance and efficacy of the resulting products.
   Current experience in this area is simply insufficient to guide
   definition of the interface appropriately.

   The objectives and motivations of this specification are not
   impacted by the decision not to standardize a specific API between
   FCIP Entities and FC Entities because fully functional and compliant
   products can be built provided they contain both an FCIP Entity and
   an FC Entity. The only products that cannot be built are those that
   contain only one or the other and there is no urgent need for such
   products at this time.







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3. Terminology

   Terms needed to clarify the concepts presented in FCIP are defined
   here.

   FC End Node - A FC device that uses the connection services provided
   by the FC Fabric.

   FC Entity - The Fibre Channel specific element that combines with an
   FCIP Entity to form an interface between an FC Fabric and an IP
   Network (see section 6.3).

   FC Fabric - An entity that interconnects various Nx_Ports (see [6])
   attached to it, and is capable of routing FC Frames using only the
   destination ID information in a FC Frame header (see annex C).

   FC Frame - The basic unit of Fibre Channel data transfer (see annex
   C).

   FC Receiver Portal - The access point through which an FC Frame
   enters an FCIP Data Engine from the FC Entity.

   FC Transmitter Portal - The access point through which a
   reconstituted FC Frame leaves an FCIP Data Engine to the FC Entity.

   FCIP Data Engine (FCIP_DE) - The component of an FCIP Entity that
   handles FC Frame encapsulation, de-encapsulation, and transmission
   FCIP Frames through a single TCP connection (see section 6.6).

   FCIP Entity - The principal FCIP interface point to the IP Network
   (see section 6.4).

   FCIP Frame - An FC Frame plus the FC Frame Encapsulation [24] header
   and encoded EOF that contains the FC Frame (see section 6.6.1).

   FCIP Link - One or more TCP connections that connect one FCIP_LEP to
   another (see section 6.2).

   FCIP Link Endpoint (FCIP_LEP) - The component of an FCIP Entity that
   handles FC Frame encapsulation, de-encapsulation, and transmission
   through a single FCIP Link (see section 6.5).

   Encapsulated Frame Receiver Portal - The TCP access point through
   which an FCIP Frame is received from the IP Network by an FCIP Data
   Engine.





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   Encapsulated Frame Transmitter Portal - The TCP access point through
   which an FCIP Frame is transmitted to the IP Network by an FCIP Data
   Engine.

4. Open Issues

   This draft is a work in progress and this section identifies areas
   where the work is known to be incomplete and discusses the current
   status of these efforts. This section will be removed before this
   draft is considered for standardization.

    - FCIP Entity Discovery - The basic principles of FCIP Entity
      discovery are agreed and represented in section 5. Work on the
      details of dynamic FCIP Entity discovery are incomplete (see
      section 11). Work on FCIP Entity Discovery may change the way an
      FCIP Entity is identified from the currently specified IP
      Address usage.

    - Security - In general, FCIP will follow or subset the security
      mechanisms agreed for iSCSI. The basic principles of FCIP
      security requirements are agreed and described in section 5.
      Section 9 contains the latest information on the details of FCIP
      security. It must be noted that the association between IP
      Addresses and FCIP Entities is open to changes based on yet to
      be finalized decisions about security. The point at which a TCP
      connection is authorized to carry data is still being debated.

    - Timeout Coordination with Fibre Channel - In this revision, most
      timeout issues are treated as the responsibility of the FC
      Entity. Section 8.2.6 contains a discussion of the TCP
      Acknowledge Timeout that needs to be reviewed to determine if it
      is still needed.

5. Protocol Summary

   The FCIP protocol is summarized as follows:

   1)  The primary function of an FCIP Entity is forwarding FC Frames,
       employing FC Frame Encapsulation described in [24].

   2)  Viewed from the IP Network perspective, FCIP Entities are peers
       and communicate using TCP/IP. Each FCIP Entity is a TCP endpoint
       in the IP-based network.

   3)  Viewed from the FC Fabric perspective, pairs of FCIP Entities,
       in combination with their associated FC Entities, serve as an FC
       Frame transmission component of the FC Fabric. The FC End Nodes
       are unaware of the existence of the FCIP Link.


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   4)  FC Primitive Signals, Primitive Sequences, and Class 1 FC Frames
       are not transmitted across an FCIP Link because they cannot be
       encoded using FC Frame Encapsulation [24].

   5)  The path (route) taken by an encapsulated FC Frame follows the
       normal routing procedures of the IP Network.

   6)  At any instant in time, an FCIP Entity SHALL NOT have more than
       one IP Address.

   7)  An FCIP Entity may contain multiple FCIP Link Endpoints, but
       each FCIP Link Endpoint (FCIP_LEP) communicates with exactly one
       other FCIP_LEP.

   8)  When multiple FCIP_LEPs with multiple FCIP_DEs are in use,
       selection of which FCIP_DE to use for encapsulating and
       transmitting a given FC Frame is outside the scope of this
       document. FCIP Entities do not actively participate in FC Frame
       routing.

   9)  The FCIP Control & Services function MAY use TCP/IP quality of
       service features (see section 10.2) to support Fibre Channel
       capabilities.

   10) Each FCIP Entity is statically or dynamically configured with a
       list of IP addresses and port numbers corresponding to
       participating FCIP Entities. If dynamic discovery of
       participating FCIP Entities is supported, the function SHALL be
       performed using the Service Location Protocol (SLPv2) [22]. It
       is outside the scope of this specification to describe any
       static configuration method for participating FCIP Entity
       discovery. Refer to section 11 for a detailed description of
       dynamic discovery of participating FCIP Entities using SLPv2.

   11) FCIP Entities do not actively participate in the discovery of FC
       source and destination identifiers. Discovery of FC addresses
       (accessible via the FCIP Entity) is provided by techniques and
       protocols within the FC architecture as described in FC-FS [6],
       FC-SW-2 [5], and FC-GS-3 [7].










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   12) To support IP Network security, FCIP Entities MUST:
       a)  implement cryptographically protected authentication and
           cryptographic data integrity keyed to the authentication
           process, or
       b)  be capable of operating with external IP security mechanisms
           that provide cryptographically protected authentication and
           cryptographic data integrity keyed to the authentication
           process.
       FCIP entities MAY implement data privacy security features.
       Security features and requirements are detailed in section 9.

   13) On a given TCP connection, FCIP relies on TCP/IP to deliver a
       byte stream in the same order that it was sent.

   14) FCIP relies on both TCP and FC error recovery mechanisms to
       detect and recover from data loss and corruption within the IP
       Network.

6. The FCIP Model

6.1 FCIP Protocol Model

   The relationship between FCIP and other protocols is illustrated in
   figure 1.

       +------------------------+ FCIP Link +------------------------+
       |          FCIP          |===========|          FCIP          |
       +--------+------+--------+           +--------+------+--------+
       |  FC-2  |      |  TCP   |           |  TCP   |      |  FC-2  |
       +--------+      +--------+           +--------+      +--------+
       |  FC-1  |      |   IP   |           |   IP   |      |  FC-1  |
       +--------+      +--------+           +--------+      +--------+
       |  FC-0  |      |  LINK  |           |  LINK  |      |  FC-0  |
       +--------+      +--------+           +--------+      +--------+
            |          |   PHY  |           |   PHY  |           |
            |          +--------+           +--------+           |
            |               |                    |               |
            |               |     IP Network     |               |
            V               +--------------------+               V
         to Fibre                                             to Fibre
         Channel                                              Channel
       Environment                                          Environment

       Fig. 1  FCIP Protocol Stack Model

   Note that the objective of the FCIP Protocol is creation and
   maintenance of one or more FCIP Links.



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6.2 FCIP Link

   The FCIP Link is the basic unit of service provided by the FCIP
   Protocol to a FC Fabric. As shown in figure 2, an FCIP Link connects
   two portions of an FC Fabric using an IP Network as a transport to
   form a single FC Fabric.

       /\/\/\/\/\/\         /\/\/\/\/\/\         /\/\/\/\/\/\
       \    FC    /   FCIP  \    IP    /   Link  \    FC    /
       /  Fabric  \=========/  Network \=========/  Fabric  \
       \/\/\/\/\/\/         \/\/\/\/\/\/         \/\/\/\/\/\/

       Fig. 2  FCIP Link Model

   At the points where the ends of the FCIP Link meet portions of the
   FC Fabric, an FCIP Entity (see section 6.4) combines with an FC
   Entity as described in section 6.3 to serve as the interface between
   FC and IP.

   An FCIP Link SHALL contain at least one TCP connection and MAY
   contain more than one TCP connection. The endpoints of a single TCP
   connection are FCIP Data Engines (see section 6.6). The endpoints of
   a single FCIP Link are FCIP Link Endpoints (see section 6.5).

6.3 FC Entity

   A product that tunnels an FC Fabric through an IP Network must
   combine an FC Entity with an FCIP Entity (see section 6.4) to form a
   complete interface between the FC Fabric and IP Network as shown in
   figure 3.

       +----------+         /\/\/\/\/\/\         +----------+
       |   FCIP   |   FCIP  \    IP    /   Link  |   FCIP   |
       |  Entity  |=========/  Network \=========|  Entity  |
       +----------+         \/\/\/\/\/\/         +----------+
       |    FC    |                              |    FC    |
       |  Entity  |                              |  Entity  |
       +----------+                              +----------+
            |                                         |
       /\/\/\/\/\/\                              /\/\/\/\/\/\
       \    FC    /                              \    FC    /
       /  Fabric  \                              /  Fabric  \
       \/\/\/\/\/\/                              \/\/\/\/\/\/

       Fig. 3  FC Entity and FCIP Entity Model





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   In general, the combination of an FCIP Link and FC and FCIP Entities
   is intended to replace a Fibre Channel defined connection between
   Fibre Channel components. For example, this combination can be used
   to replace a hard-wire connection between two Fibre Channel
   switches. There are limitations on the generally intended usage of
   the combination shown in figure 3. For example, the combination
   cannot be used to replace cable connections in a Fibre Channel
   Arbitrated Loop because loop primitive signals cannot be
   encapsulated for transmission over TCP.

   The interface between the FC and FCIP Entities is implementation
   specific. The minimum requirements placed on an FC Entity by this
   specification are listed in annex D. More information about FC
   Entities can be found in the Fibre Channel standards and an example
   of an FC Entity can be found in FC-BB-2 [4].



































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6.4 FCIP Entity

   The model for an FCIP Entity is shown in figure 4.

       .......................................................
       : FCIP Entity                                         :
       :                                                     :
       :  +-----------+                                      :
       :  | FCIP      |                                      :
       :  | Control & |------------------------------------+ :
       :  | Services  |                                    | :
       :  | Module    |                                    | :
       :  +-----------+                                    | :
       :        |            +--------------------+        | :
       :        |   +-------+--------------------+|----+   | :
       :        |   |+-----+--------------------+|----+|   | :
       :        |   ||+----| FCIP Link Endpoint |----+||   | :
       :        |   |||    +--------------------+    |||   | :
       :.............................................|||.....:
                |   |||                              |||   |
                |   |||                              |||   o<--+
                |   |||                unique TCP    |||   |   |
                |   |||                connections-->|||   |   |
                |   |||                              |||   |   |
             +----------+                         /\/\/\/\/\/\ |
             |    FC    |                         \    IP    / |
             |  Entity  |                         /  Network \ |
             +----------+                         \/\/\/\/\/\/ |
                  |                                            |
             /\/\/\/\/\/\                   +------------------+
             \    FC    /                   +->IP Address &
             /  Fabric  \                   +->Well Known Port
             \/\/\/\/\/\/

       Fig. 4  FCIP Entity Model

   The FCIP Entity is the connection interface point for the IP Network
   and is the owner of the IP Address and Well Known Port used to form
   TCP connections. An FC Fabric to IP Network interface product SHALL
   contain one FCIP Entity for each IP Address assigned to the product.

   An FCIP Entity contains an FCIP Control & Services Module to provide
   the FC Entity with an interface to key IP Network features. The
   interfaces to the IP Network features is implementation specific,
   however, to maintain interoperability, the TCP/IP mechanisms used
   are specified in this document as follows:

    - TCP Connections - see section 8


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    - Security - see section 9
    - Performance - see section 10
    - Discovery - see section 11

   The FCIP Link Endpoints in an FCIP Entity provide the FC Frame
   encapsulation and transmission features of FCIP.

6.5 FCIP Link Endpoint (FCIP_LEP)

   Each time a TCP connection is formed to an IP Address for which no
   TCP connection already exists, the FCIP Entity SHALL create a new
   FCIP Link Endpoint containing one FCIP Data Engine.

   An FCIP_LEP is a transparent data translation point between an FC
   Entity and an IP Network. A pair of FCIP_LEPs communicating over one
   or more TCP connections create an FCIP Link to join two islands of a
   FC Fabric, producing a single FC Fabric.

   The IP Network over which the two FCIP_LEPs communicate is not aware
   of the FC payloads that it is carrying. Likewise, the FC End Nodes
   connected to the FC Fabric are unaware of the TCP/IP based transport
   employed in the structure of the FC Fabric.

   As shown in figure 5, the FCIP Link Endpoint contains one FCIP Data
   Engine for each TCP connection in the FCIP Link.

        ................................................
        : FCIP Link Endpoint                           :
        :                   +------------------+       :
        :          +-------+------------------+|----+  :
        :          |+-----+------------------+|----+|  :
        :          ||+----| FCIP Data Engine |----+||  :
        :          |||    +------------------+    |||  :
        :..............................................:
                   |||                            |||
              +----------+                    /\/\/\/\/\/\
              |    FC    |                    \    IP    /
              |  Entity  |                    /  Network \
              +----------+                    \/\/\/\/\/\/
                    |
              /\/\/\/\/\/\
              \    FC    /
              /  Fabric  \
              \/\/\/\/\/\/

       Fig. 5  FCIP Link Endpoint Model




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   An FCIP_LEP uses normal TCP based flow control mechanisms for
   managing its internal resources and matching them with the
   advertised TCP Receiver Window Size (see section 8.4). An FCIP_LEP
   MAY communicate with its FC Entity counterpart to coordinate flow
   control.

6.6 FCIP Data Engine (FCIP_DE)

   The model for one of the multiple FCIP_DEs that may be present in an
   FCIP_LEP is shown in figure 6.

              +--------------------------------+
              |                                |
              |-+    +------------------+    +-|
         C    |p|    |  Encapsulation   |    |p|    N
       F h -->|1|--->|     Engine       |--->|2|--> e
       i a    |-+    +------------------+    +-|    t
       b n    |                                |  I w
       r n    |-+    +------------------+    +-|  P o
       e e    |p|    | De-Encapsulation |    |p|    r
         l <--|4|<---|     Engine       |<---|3|<-- k
              |-+    +------------------+    +-|
              |                                |
              +--------------------------------+

       Fig. 6  FCIP Data Engine Model

   Data enters and leaves the FCIP_DE through four portals (p1 - p4).
   The portals do not process or examine the data that passes through
   them. They are only the named access points where the FCIP_DE
   interfaces with external world. The names of the portals are as
   follows:

   p1) FC Receiver Portal - The interface through which an FC Frame
       enters an FCIP_DE from the FC Entity.

   p2) Encapsulated Frame Transmitter Portal - The TCP interface
       through which an FCIP Frame is transmitted to the IP Network by
       an FCIP_DE.

   p3) Encapsulated Frame Receiver Portal - The TCP interface through
       which an FCIP Frame is received from the IP Network by an FCIP_DE.

   p4) FC Transmitter Portal - The interface through which a
       reconstituted FC Frame exits an FCIP_DE to the FC Entity.





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   The work of the FCIP_DE is done by the Encapsulation and De-
   Encapsulation Engines. The Engines have two functions:

   1)  Encapsulating and de-encapsulating FC Frames using the
       encapsulation format described in FC Frame Encapsulation [24]
       and in section 6.6.1 of this document, and

   2)  Detecting some data transmission errors and performing minimal
       error recovery as described in section 6.6.2.

   Data flows through the FCIP_DE as follows:

   1)  An FC Frame arrives at the FC Receiver Portal and is passed to
       the Encapsulation Engine. The FC Frame is assumed to have been
       processed by the FC Entity according to the applicable FC rules
       and is not validated by the FCIP_DE.

   2)  In the Encapsulation Engine, the encapsulation format described
       in FC Frame Encapsulation [24] and in section 6.6.1 of this
       document SHALL be applied to prepare the FC Frame for
       transmission over the IP Network. If the FC Entity has notified
       the FCIP_DE that a properly synchronized time value is available
       as described in section 7, that value SHALL be placed in the FC
       Frame Encapsulation header time stamp fields. Otherwise, the FC
       Frame Encapsulation headers time stamp fields SHALL be set to
       zero.

   3)  The entire encapsulated FC Frame (a.k.a. the FCIP Frame) SHALL
       be passed to the Encapsulated Frame Transmitter Portal where it
       SHALL be inserted in the TCP byte stream.

   4)  Transmission of the FCIP Frame over the IP Network follows all
       the TCP rules of operation. This includes but is not limited to
       the in-order delivery of bytes in the stream, as specified by
       TCP [9].

   5)  The FCIP Frame arrives at the partner FCIP Entity where it
       enters the FCIP_DE through the Encapsulated Frame Receiver
       Portal and is passed to the De-Encapsulation Engine for
       processing.

   6)  The De-Encapsulation Engine SHALL validate the incoming TCP byte
       stream as described in section 6.6.2 and SHALL de-encapsulate
       the FC Frame according to the encapsulation format described in
       FC Frame Encapsulation [24] and in section 6.6.1 of this document.

   7)  In the absence of errors, the de-encapsulated FC Frame SHALL be
       passed to the FC Transmitter Portal for delivery to the FC Entity.


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   Every FC Frame that arrives at the FC Receiver Portal SHALL be
   transmitted on the IP Network as described in steps 1 through 4
   above. In the absence of errors, data bytes arriving at the
   Encapsulated Frame Receiver Portal SHALL be de-encapsulated and
   forwarded to the FC Transmitter Portal as described in steps 5
   through 7.

6.6.1 FCIP Encapsulation of FC Frames

   The FCIP encapsulation of FC Frames employs FC Frame Encapsulation
   [24].

   The features from FC Frame Encapsulation that are unique to
   individual protocols SHALL be applied as follows for the FCIP
   encapsulation of FC Frames.

   The Protocol# field SHALL contain 1 in accordance with the IANA
   Considerations annex of FC Frame Encapsulation [24].

   The Protocol Specific field SHALL have the format shown in figure 7.
   Note: the word numbers in figure 7 are relative to the complete FC
   Frame Encapsulation header, not to the Protocol Specific field.

    W|------------------------------Bit------------------------------|
    o|                                                               |
    r|3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1                    |
    d|1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0|
     +---------------------------------------------------------------+
    1|               replication of encapsulation word 0             |
     +-------------------------------+-------------------------------+
    2|            reserved           |           -reserved           |
     +-------------------------------+-------------------------------+

       Fig. 7  FCIP Usage of FC Frame Encapsulation Protocol Specific
           field

   Word 1 of the Protocol Specific field SHALL contain an exact copy of
   word 0 in FC Frame Encapsulation [24].

   Word 2 of the Protocol Specific field is reserved for future
   enhancements to the FCIP protocol.

   The reserved field (bits 31-16 in word 2): SHALL contain 0.

   The -reserved field (bits 15-0 in word 2): SHALL contain 65535 (or
   0xFFFF).



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   The CRCV (CRC Valid) Flag SHALL be set to 0.

   The CRC field SHALL be set to 0.

6.6.2 FCIP Data Engine Error Detection and Recover

6.6.2.1 TCP Assistance With Error Detection and Recovery

   TCP [9] REQUIRES in order delivery, generation of TCP checksums, and
   checking of TCP checksums. Thus, the byte stream passed from TCP to
   the FCIP_LEP will be in order and free of errors detectable by the
   TCP checksum. If TCP did not perform these functions, the FCIP_LEP
   would have to.

6.6.2.2 Errors in FCIP Headers and Discarding FCIP Frames

   Bytes delivered through the Encapsulated Frame Receiver Portal that
   are not correctly delimited as defined by the FC Frame Encapsulation
   [24] SHALL NOT be forwarded on to the FC Entity.

   Synchronization of the FCIP_DE to the FCIP Frames in the data stream
   entering the Encapsulated Frame Receiver Portal is maintained using
   the FC Frame Encapsulation header's frame length field to determine
   where in the data stream the next FC Encapsulation header is
   located. Synchronization SHALL be verified on each FCIP Frame. The
   validity and positioning of the following FCIP Frame information
   SHOULD be used to verify synchronization:

   a)  Protocol # field and its ones complement;
   b)  Version field and its ones complement;
   c)  Replication of encapsulation word 0 in word 1;
   d)  Reserved field and its ones complement;
   e)  Flags field and its ones complement;
   f)  Length field and its ones complement;
   g)  Time stamp [integer] and time stamp [fraction] fields;
   h)  CRC field is equal to zero;
   i)  SOF fields and ones complement fields;
   j)  Format and values of FC header;
   k)  CRC of FC Frame;
   l)  EOF fields and ones complement fields; and/or
   m)  FC Frame Encapsulation header information in the next FCIP Frame.

   Errors in FCIP Frame headers SHOULD be considered carefully, since
   some may be synchronization errors. Errors in FCIP Frames detected
   by the FCIP_DE that affect synchronization with the Encapsulated
   Frame Receiver Portal byte stream SHALL be handled as defined by
   section 6.6.2.4.



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   An error in an FCIP Frame that effects the synchronization may
   require the FCIP Entity to notify the FC Entity that the previously
   delivered FC Frame was invalid.

   Whenever an FCIP_DE discards bytes delivered through the
   Encapsulated Frame Receiver Portal, it SHALL cause the FCIP Entity
   to notify the FC Entity of the condition and provide a suitable
   description of the reason bytes were discarded.

   The burden for recovering from discarded data falls on the FC Entity
   and other components of the FC Fabric and is outside the scope of
   this specification.

6.6.2.3 IP Network Transit Time Validation

   Fibre Channel routing and error recovery protocols require FC Frames
   to exit a receiving FCIP Entity within in a fixed interval from the
   time they entered a sending FCIP Entity, including IP Network
   transit time. If an FC Frame does not transit the IP Network in the
   fixed time interval required by Fibre Channel, then it MUST NOT exit
   the FCIP Entity.

   To implement this Fibre Channel requirement, the encapsulating
   FCIP_DE places a time stamp in each FCIP Frame header transmitted
   (see section 6.6).

   The de-encapsulating FCIP_DE is REQUIRED to enforce this Fibre
   Channel requirement based on three time values:
   a)  The SNTP time stamp in the FCIP Frame header (see section 6.6);
   b)  The DLY_LIM relative time provided by the FC Entity when a
       connection is created (see section 8.1); and
   c)  A synchronized SNTP time value for the FC Fabric maintained by
       the FC Entity (see section 7).

   The FCIP_DE SHALL NOT perform transit time validation on the
   received FCIP Frames when either of the following conditions exist:
   a)  the FC Frame Encapsulation [24] header does not contain a valid
       time stamp, or
   b)  the FC Entity has notified the FCIP_DE that the synchronized
       time value is not synchronized well enough for use as described
       in section 7.

   Otherwise, the FCIP_DE SHALL use the valid time stamp information in
   the FCIP Frame header to determine if received FCIP Frames have been
   delayed by more than DLY_LIM in the IP Network by comparing the SNTP
   time stamp in the FCIP Frame header adjusted by DLY_LIM to the
   current FC Fabric synchronized SNTP time.



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   If an FCIP Frame has been delayed by more than DLY_LIM in the IP
   Network, the FCIP_DE SHALL discard the FCIP Frame as described in
   section 6.6.2.2. The discarding of delayed FCIP Frames SHALL
   continue until a FCIP Frame is processed whose life in the IP
   Network is smaller than DLY_LIM.

   DLY_LIM is a time interval provided to the FCIP Entity by the FC
   Entity when the FCIP_DE is created (see section 8.1). DLY_LIM is a
   relative time, a time value that can be added to or subtracted from
   an SNTP v4 time to get a new SNTP v4 time that is later (for
   addition) or sooner (for subtraction) than the original SNTP v4 time.

   The burden for recovering from discarded FCIP Frames falls on the FC
   Entity and other components of the FC Fabric and is outside the
   scope of this specification.

6.6.2.4 Synchronization Failures

   If an FCIP_DE determines that it cannot find the next FCIP Frame
   header in the byte stream entering through the Encapsulated Frame
   Receiver Portal, the FCIP_DE SHALL either:

   a)  close the TCP connection [9] [10];
   b)  recover synchronization by searching the bytes delivered by the
       Encapsulated Frame Receiver Portal for a valid FCIP Frame header
       having the correct properties, and discarding bytes delivered by
       the Encapsulated Frame Receiver Portal until a valid FCIP Frame
       header is found; or
   c)  attempt to recover synchronization as described in b) and if
       synchronization cannot be recovered close the TCP connection as
       described in a).

   If the FCIP_DE attempts to recover synchronization, the
   resynchronization algorithm used SHALL meet the following
   requirements:

   a)  discard or identify with an EOFa (see annex section C.1) those
       FC Frames and fragments of FC Frames identified before
       synchronization has again been completely verified. The number
       of FC Frames not forwarded may vary based on the algorithm used;

   b)  return to sending valid FC Frames only after synchronization has
       been verified; and

   c)  close the TCP/IP connection if the algorithm ends without
       verifying successful synchronization. The probability of failing
       to synchronize successfully and the time necessary to determine


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       whether or not synchronization was successful may vary with the
       algorithm used.

   An example algorithm meeting these requirements can be found in
   annex A.

   The burden for recovering from the discarding of FCIP Frames during
   the optional resynchronization process described in this section
   falls on the FC Entity and other components of the FC Fabric and is
   outside the scope of this specification.

7. Establishing and Maintaining a Synchronized Time Value

   The FC Entity SHALL use Fibre Channel services and suitable internal
   clocks to establish and maintain a synchronized time value in Simple
   Network Time Protocol (SNTP) Version 4 format [13] for use by the
   FCIP_DE in:
   a)  building outgoing FC Frame Encapsulation headers, and
   b)  checking IP Network transit times in incoming FC Frame
       Encapsulation headers.
   The synchronized time value SHALL be maintained to an accuracy of at
   least 0.01% of the smallest DLY_LIM (see section 6.6.2.3) value
   passed to an FCIP_DE for the purpose of evaluating IP Network
   transit time.

   Note that since the FC Fabric is expected to have a single
   synchronized time value throughout, only one synchronized time value
   is needed for all FCIP_DEs regardless of their connection
   characteristics.

   If the FC Entity has not yet established a synchronized time value
   or if events in the FC Fabric cast suspicion on the accuracy of a
   previously established and maintained synchronized time value, the
   FC Entity SHAL notify the FCIP_DEs not to use the synchronized time
   value. Conversely, the FC Entity SHALL notify the FCIP_DEs when a
   previously unreliable value has been corrected to a properly
   synchronized time value. Since zero is an invalid time stamp value
   in the FC Frame Encapsulation, it may be simplest to use a value of
   zero to indicate the absence of a synchronized time value.











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8. TCP Connection Management

8.1 TCP Connection Establishment

8.1.1 Creating a New TCP Connection

   The FC Entity SHALL request creation of a new TCP Connection by
   transmitting at least the following information to the FCIP Entity:

    - IP Address
    - DLY_LIM (see section 6.6.2.3) for the FCIP_Link
    - TCP Connection Parameters (see section 8.2)
    - Security Parameters (see section 9)
    - Quality of Service Parameters (see section 10)

   In response to a request from the FC Entity the FCIP Entity shall
   generate a TCP connect request [9] to the FCIP Well-Known Port at
   the specified IP Address. If the TCP connect request is rejected,
   the FCIP Entity SHALL so inform the FC Entity.

   If the TCP connect request is accepted, and the IP Address is one to
   which no other TCP connections exist, the FCIP Entity SHALL:

   1)  Create a new FCIP_LEP for the new FCIP Link,

   2)  Create a new FCIP_DE within the newly created FCIP_LEP to
       service the new TCP connection, and

   3)  Inform the FC Entity of the new FCIP_LEP and FCIP_DE.

   If the TCP connect request is accepted, and the IP Address is one
   for which a TCP connection already exists, the FCIP Entity SHALL:

   1)  Create a new FCIP_DE within the existing FCIP_LEP to service the
       new TCP connection, and

   2)  Inform the FC Entity of the FCIP_LEP and new FCIP_DE.

8.1.2 Processing TCP Connect Requests

   The FCIP Entity SHALL listen for new TCP connection requests [9] on
   the FCIP Well-Known Port. An FCIP Entity MAY also accept and
   establish TCP connections to a TCP port number other than the FCIP
   Well-Known Port, as configured by the network administrator.

   Upon receipt of a TCP connect request, the FCIP Entity SHALL
   determine if a TCP connection already exists for the IP Address
   making the TCP connect request. The FCIP Entity SHALL notify the FC


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   Entity of the TCP connect request, transmitting at least the
   following information:

    - IP Address
    - DLY_LIM (see section 6.6.2.3) for the FCIP_Link (zero for a new
      FCIP_LEP)
    - Information about the FCIP_LEP, new or existing
    - Information about the FCIP_DE for the new TCP connection
    - TCP Connection Parameters (see section 8.2)
    - Security Parameters (see section 9)
    - Quality of Service Parameters (see section 10)

   In response to the information provided by the FCIP Entity, the FC
   Entity MUST either accept or reject the TCP connect request. If the
   FC Entity rejects the TCP connect request, the FCIP Entity SHALL
   terminate the TCP connect request [9]. If the FC Entity accepts the
   TCP connect request, the FCIP Entity SHALL:

   1)  Accept the TCP connect request,

   2)  Finalize creation of the new FCIP_DE for the new TCP connection,
       and

   3)  If the new TCP connection is to an IP Address for which no other
       TCP connection exists, finalize the creation of the FCIP_LEP.

8.2 TCP Connection Parameters

   In order to provide efficient management of FCIP_LEP resources as
   well as FCIP Link resources, coordination of certain TCP connection
   parameters between the FC Entity and FCIP Entity is RECOMMENDED.

8.2.1 TCP Selective Acknowledgement Option

   The Selective Acknowledgement option RFC 2883 [23] allows the
   receiver to acknowledge multiple lost packets in a single ACK,
   enabling faster recovery. If authorized by the FC Entity, an FCIP
   Entity MAY negotiate use of TCP SACK and use it for faster recovery
   from lost packets and holes in TCP sequence number space.











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8.2.2 TCP Window Scale Option

   This option allows TCP window sizes larger than 16-bit limits to be
   advertised by the receiver. It is necessary to allow data in long
   fat networks to fill the available pipe. This also implies buffering
   on the TCP sender that matches the (bandwidth*delay) product of the
   TCP connection. An FCIP_LEP SHALL use locally available mechanisms
   to set a window size that matches the available local buffer
   resources and the desired throughput.

8.2.3 IP DSCP Option

   The RECOMMENDED IP DSCP field setting is 101110 corresponding to the
   EF service.

   <Need better wording to fit current Diffserv specifications.>

8.2.4 Protection against sequence number wrap

   It is RECOMMENDED that FCIP Entities implement protection against
   sequence number wrap. It is quite possible that within a single
   connection, TCP sequence numbers wrap within a timeout window.

8.2.5 TCP No Delay Option

   FCIP Entities SHALL disable the Nagle TCP No Delay option. This
   option is designed for usage in a telnet environment.

8.2.6 TCP Acknowledgement Timeout

   TCP has a TCP acknowledgement timeout. This is a variable timeout.

   <Need to elaborate on TCP timeouts and define how Fibre Channel
   timeouts map to TCP timeouts.>

8.3 TCP Connection Considerations

   In idle mode, a TCP connection "keep alive" option of TCP is
   normally used to keep a connection alive. However, this timeout is
   fairly large and may prevent early detection of loss of
   connectivity. In order to facilitate faster detection of loss of
   connectivity, FC Entities SHOULD implement some form of Fibre
   Channel connection failure detection.







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8.4 Flow Control Mapping between TCP and FC

   The FCIP Entity and FC Entity are connected to the IP Network and FC
   Fabric, respectively, and they need to follow the flow control
   mechanisms of both TCP and FC, which work independent of each other.

   This section provides guidelines as to how the FCIP Entity can map
   TCP flow control to status notifications to the FC Entity.

   There are two scenarios when the flow control management becomes
   crucial:

   1)  When there is line speed mismatch between the FC and IP
       interfaces.

       Even though it is RECOMMENDED that both the FC and IP interfaces
       to the FC Entity and FCIP Entity, respectively, be of comparable
       speeds, it is possible to carry FC traffic over an IP Network
       that has a different line speed and bit error rate.

   2)  When the FC Fabric or IP Network encounters congestion.

       Even when both the FC Fabric or IP network are of comparable
       speeds, during the course of operation the FC Fabric or the IP
       Network could encounter congestion due to transient conditions.

   The FCIP Entity and FC Entity need to work cooperatively to use the
   available flow control mechanisms in the TCP and FC protocols to
   handle these situations. This specification does not specify any
   particular mechanism to handle the flow control but leaves this to
   implementation's choice.

   If the Encapsulated Frame Transmitter Portal is unable to transmit
   encapsulated FCIP Frames at the experienced data rate, the FCIP
   Entity MUST request that the FC Entity reduce the rate at which new
   FC Frames arrive at the FC Receiver Portal.

   If the FC Entity is unable to accept de-encapsulated FC Frames at
   the experienced rate through the FC Transmitter Portal, the FC
   Entity MAY request the FCIP Entity to reduce the rate at which new
   FC Frames are delivered. The FCIP_DE MAY use TCP windowing
   techniques to control the packet arrival rate from the IP Network.
   This MAY involve advertising zero-window on TCP connection(s)
   occasionally so that the TCP connection(s) are flow controlled while
   the FC Fabric is encountering congestion.





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9. Security

9.1 Considerations

   Using a wide-area, general purpose network such as an IP Network in
   a position normally occupied by physical cabling introduces some
   security problems not normally encountered in Fibre Channel Fabrics.
   FC transport media are typically protected physically from outside
   access; IP Networks typically invite outside access.

   The general effect is that the security of the entire FC Fabric is
   only as good as the security of the entire IP Network through which
   it tunnels. The following broad classes of attacks are possible:

   1)  Unauthorized Fibre Channel elements can gain access to resources
       through normal Fibre Channel processes.

   2)  Unauthorized agents can monitor and manipulate Fibre Channel
       traffic flowing over physical media used by the IP Network and
       under control of the agent.

   To a large extent, these security risks are typical of the risks
   facing any other application using an IP Network. They are mentioned
   here only because Fibre Channel storage networks are not normally
   suspicious of the media. Fibre Channel Fabric administrators will
   need to be aware of these additional security risks.

9.2 IP Network Security Requirements

   Security protocols and procedures used in other IP applications MAY
   be used for FCIP. FCIP Entities MUST ensure secure operation of FCIP
   Links by implementing one of the following two methods:

   1)  by using ESP [15] from the IPSec Security Protocol Suite with
       NULL encryption [16] for cryptographic data integrity and
       integrity of authentication. Authentication is performed using
       SRP [RFC2945]. This method is discussed in section 9.3; or

   2)  by appropriate configuration of an external entity that
       implements IP security using mechanisms such as IPSec and
       Virtual Private Networks. This method is discussed in section 9.4.

   The mechanism for configuring whether a particular deployment uses
   1) or 2) is outside the scope of this document.

   Note: Two overviews of the IPSec Security Protocol Suite are
   available in RFC 2401 [14] and RFC 2411 [17].



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9.3 Integrated Security

   When both FCIP Entity and IP Security implementations are integrated
   into a single device, IPSec ESP (in transport mode) MUST be
   implemented.

   Upon receiving a TCP connection request, the receiving FCIP Entity
   SHALL identify the FCIP Link per the IP address pair of the
   connection. It SHALL then verify that the FCIP Link has been
   previously authenticated. If not, the FCIP Entity SHALL authenticate
   a new peer using a separate TCP connection. This TCP connection is
   used for negotiation of SRP related parameters.

   <SRP message negotiation will be per iSCSI discussions>

   If authentication fails, the original TCP connection that initiated
   the authentication exchange is terminated and the FC Entity is not
   informed that a TCP connect request was received.

   If the authentication is successful, a new FCIP_LEP is created, with
   the authenticated FCIP Link as described in section 8.1.2.

   The FCIP Entity remembers the IP pair and the key material for
   authentication, so that any future TCP connections for that IP
   address pair bypasses this authentication step. The key material is
   then used as part of the ESP Security Parameters.

   <association of SRP key material with ESP header will be per iSCSI
   discussions>

9.4 External Security Gateway

   Figure 8 illustrates the use of an externally supplied security
   gateway for securing the FCIP Link.

   +--------+ Insecure +--------+ Secure  +--------+ Insecure +-------+
   | FCIP   | Network  | IPSec  | Network | IPSec  | Network  |FCIP   |
   | Entity |----------| Device |---------| Device |----------|Entity |
   +--------+          +--------+         +--------+          +-------+

       Fig. 8  External Security Gateway Model

   In this deployment, only certain parts of the FCIP Link are exposed
   to security threats and so only these specific parts of the FCIP
   Link need to be secured. The part of the network between the two
   security gateways is secured using devices implementing IPSec.




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   The IPSec Device or any other equivalent gateway is required to
   operate in tunnel mode, so that the IP addresses of the two FCIP
   Entities are visible through the security devices that are
   implemented.

9.5 Security Information Exchanged Between FC and FCIP Entities

   TBD

10. Performance

10.1 Performance Considerations

   Traditionally, the links between FC Fabric components have been
   characterized by low latency and high throughput. The purpose of
   FCIP is to replace some of these links with an IP Network, where low
   latency and high throughput are not as certain. It follows that FCIP
   Entities and their counterpart FC Entities probably will be
   interested in optimal use of the IP Network.

   Many options exist for ensuring low latency and high throughput in
   an IP Network. For example, a private IP Network might be
   constructed for the sole use of FCIP Entities. The options that are
   within the scope of this specification are discussed here.

   One option for increasing the probability that FCIP data streams
   will experience low latency and high throughput is the IP QoS
   techniques discussed in section 10.2. This option can have value
   when applied to a single TCP connection. Depending on the
   sophistication of the FC Entity, further value may be obtained by
   having multiple TCP connections with differing QoS characteristics.

   There are many reasons why an FC Entity might request creation of
   multiple TCP connections within an FCIP_LEP. These reasons include a
   desire to provide differentiated service for different TCP data
   connections between FCIP_LEPs or a preference to separately queue
   different streams of traffic not having a common in-order delivery
   requirement.

   At the time a new TCP connection is created, the FC Entity SHALL
   specify to the FCIP Entity the QoS characteristics (including but
   not limited to IP per-hop-behavior) to be used for the lifetime of
   that connection. This MAY be achieved by having:
   a)  only one set of QoS characteristics for all TCP connections;
   b)  a default set of QoS characteristics that the FCIP Entity
       applies in the absence of differing instructions from the FC
       Entity; or



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   c)  a sophisticated mechanism for exchanging QoS requirements
       information between the FC Entity and FCIP Entity each time a
       new TCP connection is created.

   Once established, the QoS characteristics of a TCP connection SHALL
   NOT be changed, since this specification provides no mechanism for
   the FC Entity to control such changes. The mechanism for providing
   different QoS characteristics in FCIP is the establishment of a
   different TCP connections and associated FCIP_DEs.

   When FCIP is used with a network with a large (bandwidth*delay)
   product, it is RECOMMENDED that FCIP_LEPs use the TCP mechanisms
   (window scaling and wrapped sequence protection) for Long Fat
   Networks (LFNs) as defined in RFC 1323 [11].

10.2 IP Quality of Service (QoS) Support

   Many methods of providing QoS have been devised or proposed. These
   include (but are not limited to) the following:

    - Multi-Protocol Label Switching (MPLS)
    - Differentiated Services Architecture (diffserv) -- RFC 2474
      [18], RFC 2475 [19], RFC 2597 [20], and RFC 2598 [21] -- and
      other forms of per-hop-behavior (PHB)
    - Integrated Services, RFC 1633 [12]
    - IEEE 802.1p

   The purpose of this specification is not to specify any particular
   form of IP QoS but rather to specify only those issues that must be
   addressed in order to maximize interoperability between FCIP
   equipment that has been manufactured by different vendors.

   It is RECOMMENDED that some form of preferential QoS be used for
   FCIP traffic to minimize latency and drop precedence. No particular
   form of QoS is recommended.

   If a PHB IP QoS is implemented, it is RECOMMENDED that it
   interoperate with diffserv (see RFC 2474 [18], RFC 2475 [19], RFC
   2597 [20], and RFC 2598 [21]).

   If diffserv/PHB QoS is NOT implemented, the DSCP field for all IP
   packets SHALL be set to '000000'.

10.3 QoS Information Exchanged Between FC and FCIP Entities

   At the time a new TCP connection is created, the FC Entity SHALL
   specify to the FCIP Entity the QoS characteristics to be used for
   the lifetime of that connection. The nature of the information


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   exchanged depends on the QoS method (see section 10.2) implemented
   by the FC Entity and FCIP Entity and on whether the FCIP Entity is
   designed to provide differing QoS characteristics for different TCP
   connections.

   The FCIP Entity SHALL instantiate the QoS characteristics specified
   by the FC Entity when it creates the TCP connection.

11. Dynamic Discovery of Participating FCIP Entities

11.1 Requirements

   If dynamic discovery of participating FCIP Entities is supported the
   function SHALL be performed using the Service Location Protocol
   (SLPv2) [22].

   Additional details TBD.

11.2 Discovery Information Exchanged Between FC and FCIP Entities

   TBD

12. References

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

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

   [3] Fibre Channel Backbone (FC-BB), T11 Project 1238-D, Rev 4.8,
       March 5, 2001 (www.t11.org).

   [4] Fibre Channel Backbone -2 (FC-BB-2), T11 Project 1466-D,
       (www.t11.org).

   [5] Fibre Channel Switch Fabric -2 (FC-SW-2), T11 Project 1305-D,
       Rev. 5.2, May 23, 2001 (www.t11.org).

   [6] Fibre Channel Framing and Signaling (FC-FS), T11 Project 1331-D,
       Rev 1.2, February 16, 2001 (www.t11.org).

   [7] Fibre Channel Generic Services -3, ANSI NCITS.348-200x, November
       28, 2000.

   [8] http://www.t11.org




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   [9] "Transmission Control Protocol", RFC 793, Sept. 1981.

   [10] Braden, R., "Requirements for Internet Hosts -- Communication
       Layers", RFC 1122, October 1989

   [11] Jacobson, V., Braden, R. and Borman, D., "TCP Extensions for
       High Performance", RFC 1323, May 1992.

   [12] R. Braden, et. al., ISI, "Integrated Services in the Internet
       Architecture: an Overview", RFC 1633, June 1994

   [13] Mills, D., "Simple Network Time Protocol (SNTP) Version 4 for
       IPv4, IPv6 and OSI", RFC 2030, October 1996.

   [14] Kent, S. and Atkinson, R., "Security Architecture for the
       Internet Protocol", RFC 2401, Nov. 1998.

   [15] Kent, S. and Atkinson, R., "IP Encapsulating Security Payload
       (ESP)", RFC 2406, Nov. 1998.

   [16] Glenn, R., Kent, S., "The NULL Encryption Algorithm and Its Use
       With IPsec", RFC 2410, Nov. 1998

   [17] Thayer, R., Glenn, R., and Doraswamy, N., "IP Security Document
       Roadmap", RFC 2411, Nov. 1998.

   [18] Nichols, K., Blake, S., Baker, F. and D. Black, "Definition of
       the Differentiated Services Field (DS Field) in the IPv4 and
       Ipv6 Headers", RFC 2474, December 1998.

   [19] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., Weiss,
       W., "An Architecture for Differentiated Services", RFC 2475,
       Dec. 1998.

   [20] Heinanen, J., Baker, F., Weiss, W., Wroclawski, J., "An Assured
       Forwarding PHB", RFC 2597, June 1999.

   [21] Jacobson, V., Nichols, K., Poduri, K., "An Expedited Forwarding
       PHB Group", RFC 2598, June 1999.

   [22] E.Guttman, C. Perkins, J. Veizades, M. Day. Service Location
       Protocol, version 2, RFC 2608, July, 1999.

   [23] Floyd, et al, "SACK Extension", RFC 2883, July 2000.

   [24] Weber, Rajagopal, Travostino, Chau, O'Donnell, Monia Merhar,
       "FC Frame Encapsulation", draft-ietf-ips-fcencapsulation-__.txt
       (RFC reference and date to be added during standards action).


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   The following reference concerns SLP, see [22]. It is not referenced
   in this revision of this draft but may be referenced in future
   revisions.

   [25] E.Guttman, C. Perkins, J. Kempf. Service Templates and Service:
       Schemes, RFC 2609, July 1999.

13. Bibliography

   The following references may prove informative to readers unfamiliar
   with Fibre Channel.

Kembel, R., "The Fibre Channel Consultant: A Comprehensive
Introduction", Northwest Learning Associates, 1998

14. Acknowledgments

   Funding for the RFC Editor function is currently provided by the
   Internet Society.

15. Authors' Addresses

   Murali Rajagopal                   Raj Bhagwat
   LightSand Communications, Inc.     LightSand Communications, Inc.
   24411 Ridge Route Dr.              24411 Ridge Route Dr.
   Suite 135                          Suite 135
   Laguna Hills, CA 92653             Laguna Hills, CA 92653
   USA                                USA
   Phone: +1 949 837 1733 x101        Phone: +1 949 837 1733 x104
   Email: muralir@lightsand.com       Email: rajb@lightsand.com

   R. Andy Helland                    Elizabeth G. Rodriguez
   LightSand Communications, Inc.     Lucent Technologies
   375 Los Coches Street              1202 Richardson Drive, Suite 104
   Milpitas, CA 95035                 Richardson, TX 75080
   USA                                USA
   Phone: +1 408 404 3119             Phone: +1 972 231 0672
   Fax: +1 408 941 2166               Fax: +1 972 644 5857
   Email: andyh@lightsand.com         Email: egrodriguez@lucent.com










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   Sriram Rupanagunta                 Neil Wanamaker
   Aarohi Communications              Akara
   3200 Montelena Drive               10624 Icarus Court
   San Jose, CA 95135                 Austin, TX 78726
   USA                                USA
   Phone: +1 408 966 8309             Phone: +1 512 257 7633
   Email: sriramr@aarohi-inc.com      Fax: +1 512 257 7877
                                      Email: nwanamaker@akara.com

   Steve Wilson                       Bob Snively
   Brocade Comm. Systems, Inc.        Brocade Comm. Systems, Inc.
   1745 Technology Drive              1745 Technology Drive
   San Jose, CA. 95110                San Jose, CA 95110
   USA                                USA
   Phone: +1 408 487 8128             Phone: +1 408 487 8135
   Fax: +1 408 487 8101               Email: rsnively@brocade.com
   email: swilson@brocade.com

   Ralph Weber
   ENDL Texas, representing Brocade
   Suite 102 PMB 178
   18484 Preston Road
   Dallas, TX 75252
   USA
   Phone: +1 214 912 1373
   Email: roweber@acm.org

   David Peterson                     Donald R. Fraser
   Cisco Systems - SRBU               Compaq Computer Corporation
   6450 Wedgwood Road                 301 Rockrimmon Blvd., Bldg. 5
   Maple Grove, MN 55311              Colorado Springs, CO 80919
   USA                                USA
   Phone: +1 763 398 1007             Phone: +1 719 548 3272
   Cell: +1 612 802 3299              Email: don.fraser@compaq.com
   Email: dap@cisco.com

   Vi Chau                            Gaby Hecht
   Gadzoox Networks, Inc.             Gadzoox Network, Inc.
   16241 Laguna Canyon Road           16241 Laguna Canyon Road
   Suite 100                          Suite 100
   Irvine, CA 92618                   Irvine, CA 92618
   USA                                USA
   Phone: +1 949 789 4639             Phone: +1 949 789 4642
   Fax: +1 949 453 1271               Fax: +1 949 453 1271
   Email: vchau@gadzoox.com           Email: ghecht@Gadzoox.com





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   Ken Hirata                         Jim Nelson
   Vixel Corporation                  Vixel Corporation
   15245 Alton Parkway, Suite 100     15245 Alton Parkway, Suite 100
   Irvine, CA 92618                   Irvine, CA 92618
   USA                                USA
   Phone: +1 949 788 6368             Phone: +1 949 450 6159
   Fax: +1 949 753 9500               Fax: +1 949 753 9500
   Email: ken.hirata@vixel.com        Email: Jim.Nelson@vixel.com

   Michael E. O'Donnell               Anil Rijhsinghani
   McDATA Corporation                 McDATA Corporation
   310 Interlocken Parkway            5 Brickyard lane
   Broomfield, Co. 80021              Westboro, MA 01581
   USA                                USA
   Phone: +1 303 460 4142             Phone: +1 508 870 6593
   Fax: +1 303 465 4996               Email:
   Email: modonnell@mcdata.com             anil.rijhsinghani@mcdata.com

   Milan J. Merhar                    Craig W. Carlson
   43 Nagog Park                      QLogic Corporation
   Pirus Networks                     6321 Bury Drive
   Acton, MA 01720                    Eden Prairie, MN 55346
   USA                                USA
   Phone: +1 978 206 9124             Phone: +1 952 932 4064
   Email: Milan@pirus.com             Email: craig.carlson@qlogic.com

   Venkat Rangan                      Larwrence J. Lamers
   Rhapsody Networks Inc.             SAN Valley
   3450 W. Warren Ave.                4611 Park Norton Place
   Fremont, CA 94538                  San Jose, CA 95136-2523
   USA                                USA
   Phone: +1 510 743 3018             Phone: +1 408 626 1285
   Fax: +1 510 687 0136               Email: ljlamers@ieee.org
   Email: venkat@rhapsodynetworks.com

16. Full Copyright Statement

   Copyright (C) The Internet Society (2001). All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph
   are included on all such copies and derivative works. However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of


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   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS 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.

ANNEX A - Example of synchronization recovery algorithm

   The contents of this annex are informative.

   Synchronization may be recovered as specified in section 6.6.2.4. An
   example of an algorithm for searching the bytes delivered to the
   Encapsulated Frame Receiver Portal for a valid FCIP Frame header is
   provided in this annex.

   This resynchronization uses the principle that a valid FCIP data
   stream must contain at least one valid header every 2176 bytes (the
   maximum length of an encapsulated FC Frame). Although other data
   patterns containing apparently valid headers may be contained in the
   stream, the FC CRC or FCIP Frame validity of the data patterns
   contained in the data stream will always be either interrupted by or
   resynchronized with the valid FCIP Frame headers.

   Consider the case shown in figure 9. A series of short FCIP Frames,
   perhaps from a trace, are embedded in larger FCIP Frames, say as a
   result of a trace file being transferred from one disk to another.
   The headers for the short FCIP Frames are denoted SFH and the long
   FCIP Frame headers are marked as LFH.

       +-+--+-+----+-+----+-+----+-+-+-+---+-+---
       |L|  |S|    |S|    |S|    |S| |L|   |S|
       |F|  |F|    |F|    |F|    |F| |F|   |F|...
       |H|  |H|    |H|    |H|    |H| |H|   |H|
       +-+--+-+----+-+----+-+----+-+-+-+---+-+---
       |                             |
       |<---------2176 bytes-------->|

       Fig. 9  Example of resynchronization data stream



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   A resynchronization attempt that starts just to the right of an LFH
   will find several SFH FCIP Frames before discovering that they do
   not represent the transmitted stream of FCIP Frames. Within 2176
   bytes plus or minus, however, the resynchronization attempt will
   encounter an SFH whose length does not match up with the next SFH
   because the LFH will fall in the middle of the short FCIP Frame
   pushing the next header farther out in the byte stream.

   Note that the resynchronization algorithm cannot forward any
   prospective FC Frames to the FC Transmitter Portal because until
   synchronization is completely established there is no certainty that
   anything that looked like an FCIP Frame really was one. For example,
   an SFH might fortuitously contain a length that points exactly to
   the beginning of an LFH. The LFH would identify the correct
   beginning of a transmitted FCIP Frame, but that in no way guarantees
   that the SFH was also a correct FCIP Frame header.

   There exist some data streams that cannot be resynchronized by this
   algorithm. If such a data stream is encountered, the algorithm
   causes the TCP connection to be closed.

   The resynchronization assumes that security and authentication
   procedures outside the FCIP Entity are protecting the valid data
   stream from being replaced by an intruding data stream containing
   valid FCIP data.

   The following steps are one example of how an FCIP_DE might
   resynchronize with the data stream entering the Encapsulated Frame
   Receiver Portal.

   1)  Search for candidate and strong headers:

       The data stream entering the Encapsulated Frame Receiver Portal
       is searched for 12 bytes in a row containing the required values
       for:
       a)  Protocol field,
       b)  Version field,
       c)  ones complement of the Protocol field,
       d)  ones complement of the Version field,
       e)  replication of encapsulation word 0 in word 1, and
       f)  Reserved field and its ones complement.

       If such a 12-byte grouping is found, the FCIP_DE assumes that it
       has identified bytes 0-2 of a candidate FCIP encapsulation header.

       All bytes up to and including the candidate header byte are
       discarded.



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       If no candidate header has been found after searching a
       specified number of bytes greater than some multiple of 2176
       (the maximum length of an FCIP Frame), resynchronization has
       failed and the TCP/IP connection is closed.

       Word 3 of the candidate header contains the Frame Length and
       Flags fields and their ones complements. If the fields are
       consistent with their ones complements, the candidate header is
       considered a strong candidate header. The Frame Length field is
       used to determine where in byte stream the next strong candidate
       header should be and processing continues at step 2).

   2)  Use multiple strong candidate headers to locate a verified
       candidate header:

       The Frame Length in one strong candidate header is used to skip
       incoming bytes until the expected location of the next strong
       candidate header is reached. Then the tests described in step 1)
       are applied to see if another strong candidate header has
       successfully been located.

       All bytes skipped and all bytes in all strong candidate headers
       processed are discarded.

       Strong candidate headers continue to be verified in this way for
       at least 4352 bytes (twice the maximum length of an FCIP Frame).
       If at anytime a verification test fails, processing restarts at
       step 1 and a retry counter is incremented. If the retry counter
       exceeds 3 retries, resynchronization has failed and the TCP
       connection is closed.

       After strong candidate headers haves been verified for at least
       4352 bytes, the next header identified is a verified candidate
       header and processing continues at step 3).

       Note: If a strong candidate header was part of the data content
       of an FCIP Frame, the FCIP Frame defined by that or a subsequent
       strong candidate header will eventually cross an actual header
       in the byte stream. As a result it will either identify the
       actual header as a strong candidate header or it will lose
       synchronization again because of the extra 28 bytes in the
       length, returning to step 1 as described above.

   3)  Use multiple strong candidate headers to locate a verified
       candidate header:

       Incoming bytes are skipped and discarded until the next verified
       candidate header is reached. Each verified candidate header is


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       tested against the full collection of tests listed in section
       6.6.2.2 as would normally be the case.

       Verified candidate headers continue to be located and tested in
       this way for a minimum of 4352 bytes (twice the maximum length
       of an FCIP Frame). If all verified candidate headers encountered
       are valid, the last verified candidate header is a valid header.
       At this point the FCIP_DE stops discarding bytes and begins
       normal FCIP de-encapsulation begins, including for the first
       time since synchronization was lost, delivery of FC frames
       through the FC Transmitter Portal according to normal FCIP rules.

       If any verified candidate headers are invalid but meet all the
       requirements of a strong candidate header, increment the retry
       counter and return to step 2). If any verified candidate headers
       are invalid and fail to meet the tests for a strong candidate
       header, increment the retry counter and return to step 1. If the
       retry counter exceeds 4 retries, resynchronization has failed
       and the TCP/IP connection is closed.

   A flowchart for this algorithm can be found in figure 10.





























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                         Synchronization is lost
                                  |
                     _____________v_______________
                    |                             |
                    | Search for candidate header |
       +----------->|                             |
       |            |   Found           Not Found |
       |            | (Strong candidate)          |
       |            |_____________________________|
       |                    |              |
       |                    |              + --------->Close TCP/IP
       |             _______v_____________________     Connection
       |            |                             |
       |            |   Enough strong candidate   |
       |      +---->|     headers identified?     |
       |      |     |                             |
       |      |     |     No               Yes    |
       |      |     |        (Verified candidate) |
       |      |     |_____________________________|
       |___________________|                |
       ^      |                             |
       |      |                             |
       |      |      _______________________v_____
       |      |     |                             |
       |      |     | Enough verified candidate   |
       |      |     |   headers validated?        |
       |      |     |                             |
       |      |     |     No               Yes    |
       |      |     |            (Resynchronized) |
       |      |     |_____________________________|
       |      |            |                |
       |      |      ______v__________      |      Resume
       |      |     |                 |     + ---> Normal
       |      |     | Synchronization |            De-encapsulation
       |      |     |      Lost?      |
       |      |     |                 |
       |      |     | No          Yes |
       |      |     |_________________|
       |      |        |           |
       |      |________|           |
       |___________________________|

       Fig. 10  Flow diagram of simple synchronization example







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ANNEX B - Relationship between FCIP and IP over FC (IPFC)

   The contents of this annex are informative.

   IPFC (RFC 2625) describes the encapsulation of IP packets in FC
   Frames. It is intended to facilitate IP communication over an FC
   network.

   FCIP describes the encapsulation of FC Frames in TCP segments which
   in turn are encapsulated inside IP packets for transporting over an
   IP network. It gives no consideration to the type of FC Frame that
   is being encapsulated. Therefore, the FC Frame may actually contain
   an IP packet as described in the IP over FC specification (RFC
   2625). In such a case, the data packet would have:

    - Data Link Header
    - IP Header
    - TCP Header
    - FCIP Header
    - FC Header
    - IP Header

   Note:   The two IP headers would not be identical to each other. One
   would have information pertaining to the final destination while the
   other would have information pertaining to the FCIP Entity.

   The two documents focus on different objectives. As mentioned above,
   implementation of FCIP will lead to IP encapsulation within IP.
   While perhaps inefficient, this should not lead to issues with IP
   communication. One caveat: if a Fibre Channel device is
   encapsulating IP packets in an FC Frame (e.g. an IPFC device), and
   that device is communicating with a device running IP over a non-FC
   medium, a second IPFC device may need to act as a gateway between
   the two networks. This scenario is not specifically addressed by FCIP.

   There is nothing in either of the specifications to prevent a single
   device from implementing both FCIP and IP-over-FC (IPFC), but this
   is implementation specific, and is beyond the scope of this document.



ANNEX C - FC Frame Format

   The contents of this annex are informative.

   All FC Frames have a standard format (see FC-FS [6]) much like LAN's
   802.x protocols. However, the exact size of each FC Frame varies
   depending on the size of the variable fields. The size of the


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   variable field ranges from 0 to 2112-bytes as shown in the FC Frame
   Format in figure 11 resulting in the minimum size FC Frame of 36
   bytes and the maximum size FC Frame of 2176 bytes. Valid FC Frame
   lengths are always a multiple of four bytes.

       +------+--------+-----------+----//-------+------+------+
       | SOF  |Frame   |Optional   |  Frame      | CRC  |  EOF |
       | (4B) |Header  |Header     | Payload     | (4B) | (4B) |
       |      |(24B)   |<----------------------->|      |      |
       |      |        | Data Field = (0-2112B)  |      |      |
       +------+--------+-----------+----//-------+------+------+

       Fig. 11  FC Frame Format

C.1 SOF and EOF Delimiters

   On an FC link, Start-of-Frame (SOF) and End-Of-Frame (EOF) are
   called Ordered Sets and are sent as special words constructed from
   the 8B/10B comma character (K28.5) followed by three additional 8B/
   10B data characters making them uniquely identifiable in the data
   stream.

   On an FC link the SOF delimiter serves to identify the beginning of
   an FC Frame and prepares the receiver for FC Frame reception. The
   SOF contains information about the FC Frame's Class of Service,
   position within a sequence, and in some cases, connection status.

   The EOF delimiter identifies the end of the FC Frame and the final
   FC Frame of a sequence. In addition, it serves to force the running
   disparity to negative. The EOF is used to end the connection in
   connection-oriented classes of service.

   A special EOF delimiter called EOFa (End Of Frame - Abort) is used
   to terminate a partial FC Frame resulting from a malfunction in a
   link facility during transmission. Since an FCIP Entity functions
   like a transmission link with respect to the rest of the FC Fabric,
   FCIP_DEs may use EOFa in their error recovery procedures.

   It is therefore important to preserve the information conveyed by
   the delimiters across the IP-based network, so that the receiving
   FCIP Entity can correctly reconstruct the FC Frame in its original
   SOF and EOF format before forwarding it to its ultimate FC
   destination on the FC link.

   When an FC Frame is encapsulated and sent over a byte-oriented
   interface, the SOF and EOF delimiters are represented as sequences
   of four consecutive bytes, which carry the equivalent Class of
   Service and FC Frame termination information as the FC ordered sets.


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   The representation of SOF and EOF in an encapsulation FC Frame is
   described in FC Frame Encapsulation [24].

C.2 Frame Header

   The FC Frame Header is transparent to the FCIP Entity. The FC Frame
   Header is 24 bytes long and has several fields that are associated
   with the identification and control of the payload. Current FC
   Standards allow up to 3 Optional Header fields [6]:

    - Network_Header (16-bytes)
    - Association_Header (32-bytes)
    - Device_Header (up to 64-bytes).

C.3 Frame Payload

   The FC Frame Payload is transparent to the FCIP Entity. An FC
   application level payload is called an Information Unit at the FC-4
   Level. This is mapped into the FC Frame Payload of the FC Frame. A
   large Information Unit is segmented using a structure consisting of
   FC Sequences. Typically, a Sequence consists of more than one FC
   Frame. FCIP does not maintain any state information regarding the
   relationship of FC Frames within a FC Sequence.

C.4 CRC

   The FC CRC is 4 bytes long and uses the same 32-bit polynomial used
   in FDDI and is specified in ANSI X3.139 Fiber Distributed Data
   Interface. This CRC value is calculated over the entire FC header
   and the FC payload; it does not include the SOF and EOF delimiters.

   Note: When FC Frames are encapsulated into FCIP Frames, the FC Frame
   CRC is untouched by the FCIP Entity.


ANNEX D - FCIP Requirements on an FC Entity

   The contents of this annex are informative for FCIP but might be
   considered normative on FC-BB-2.

   The capabilities that FCIP requires of an FC Entity include:

   1)  The FC Entity must deliver FC Frames to the correct FCIP Data
       Engine (in the correct FCIP Link Endpoint) and forward FC Frames
       from FCIP Data Engine(s) to the FC Fabric.

   2)  The only delivery ordering guarantee provided by FCIP is
       correctly ordered delivery of FC Frames between a pair of FCIP


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       Data Engines. FCIP expects the FC Entity to implement all other
       FC Frame delivery ordering requirements.

   3)  The FC Entity must support the FCIP Entity in the processing of
       incoming connect requests by deciding to accept a connect request.

   4)  The FC Entity may generate connect and terminate requests.

   5)  The FC Entity may instruct the FCIP Entity regarding TCP
       connection parameter settings and the DLY_LIM (see section
       6.6.2.3) to be applied to an FCIP Link.

   6)  The FC Entity must provide the FCIP_DE with a synchronized time
       value for use in building outgoing FCIP Encapsulated Frame
       headers and in checking incoming time stamp values. The FC
       Entity must notify the FCIP_DE when that value is not
       synchronized well enough to be used for these purposes.

   7)  The FC Entity may recover from connection failures.

   8)  The FC Entity must recover from events that the FCIP Entity
       cannot handle, such as:
       a)  loss of synchronization with FCIP Frame headers from the
           Encapsulated Frame Receiver Portal requiring resetting the
           TCP connection;
       b)  recovering from FCIP Frames that are discarded as a result
           of synchronization problems (see section 6.6.2.2 and section
           6.6.2.4) or delays in transiting the IP network (see section
           6.6.2.3);
       c)  additional examples, TBD

   9)  The FC Entity must work cooperatively with the FCIP Entity to
       manage flow control problems in either the IP Network or FC
       Fabric.

   10) The FC Entity may test for failed TCP connections.

   11) TBD support for dynamic discovery

   12) TBD support for security

   13) Communicate QoS needs when a TCP connection is created as
       described in section 11.2.

   14) TBD support for monitoring

   Note that the Fibre Channel standards MUST be consulted for a
   complete understanding of the requirements placed on an FC Entity.






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