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Versions: (draft-doria-forces-protocol) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 RFC 5810

Network Working Group                               A. Doria (co-editor)
Internet-Draft                                                      ETRI
Expires: April 25, 2005                                 October 25, 2004



                     ForCES Protocol Specification
                   draft-ietf-forces-protocol-01.txt


Status of this Memo


   This document is an Internet-Draft and is subject to all provisions
   of section 3 of RFC 3667.  By submitting this Internet-Draft, each
   author represents that any applicable patent or other IPR claims of
   which he or she is aware have been or will be disclosed, and any of
   which he or she become aware will be disclosed, in accordance with
   RFC 3668.


   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on April 25, 2005.


Copyright Notice


   Copyright (C) The Internet Society (2004).


Abstract


   This specification documents the Forwarding and Control Element
   Separation protocol.  This protocol is designed to be used between a
   Control Element and a Forwarding Element in a Routing Network
   Element.


Authors


   The participants in the ForCES Protocol Team, co-authors and




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   co-editors, of this draft, are:


   Ligang Dong (Zhejiang Gongshang University), Avri Doria (ETRI), Ram
   Gopal (Nokia), Robert Haas (IBM), Jamal Hadi Salim (Znyx), Hormuzd M
   Khosravi (Intel), and Weiming Wang (Zhejiang Gongshang University).


Table of Contents


   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1   Sections of this document  . . . . . . . . . . . . . . . .  4
   2.  Definitions  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     3.1   Protocol Framework . . . . . . . . . . . . . . . . . . . .  8
       3.1.1   The PL layer . . . . . . . . . . . . . . . . . . . . . 10
       3.1.2   The TML layer  . . . . . . . . . . . . . . . . . . . . 11
       3.1.3   The FEM/CEM Interface  . . . . . . . . . . . . . . . . 11
     3.2   ForCES Protocol Phases . . . . . . . . . . . . . . . . . . 12
       3.2.1   Pre-association  . . . . . . . . . . . . . . . . . . . 12
       3.2.2   Post-association . . . . . . . . . . . . . . . . . . . 13
     3.3   Protocol Mechanisms  . . . . . . . . . . . . . . . . . . . 14
       3.3.1   Of Transactions, Atomicity and 2 Phase Commits . . . . 14
       3.3.2   FE, CE, and FE protocol LFBs . . . . . . . . . . . . . 15
       3.3.3   Scaling by Concurrency . . . . . . . . . . . . . . . . 15
   4.  TML Requirements . . . . . . . . . . . . . . . . . . . . . . . 17
     4.1   TML Parameterization . . . . . . . . . . . . . . . . . . . 18
   5.  Common Header  . . . . . . . . . . . . . . . . . . . . . . . . 19
   6.  Protocol Messages  . . . . . . . . . . . . . . . . . . . . . . 22
     6.1   Core ForCES LFBs . . . . . . . . . . . . . . . . . . . . . 22
       6.1.1   FE Protocol LFB  . . . . . . . . . . . . . . . . . . . 23
       6.1.2   FE LFB . . . . . . . . . . . . . . . . . . . . . . . . 23
       6.1.3   CE LFB . . . . . . . . . . . . . . . . . . . . . . . . 24
     6.2   Association Messages . . . . . . . . . . . . . . . . . . . 25
       6.2.1   Association Setup Message  . . . . . . . . . . . . . . 25
       6.2.2   Association Setup Response Message . . . . . . . . . . 27
       6.2.3   Association Teardown Message . . . . . . . . . . . . . 29
     6.3   Configuration Messages . . . . . . . . . . . . . . . . . . 30
       6.3.1   Config Message . . . . . . . . . . . . . . . . . . . . 30
       6.3.2   Config Response Message  . . . . . . . . . . . . . . . 32
     6.4   Query and Query Response Messages  . . . . . . . . . . . . 34
       6.4.1   Query Message  . . . . . . . . . . . . . . . . . . . . 34
       6.4.2   Query Response Message . . . . . . . . . . . . . . . . 36
     6.5   Event Notification and Response Messages . . . . . . . . . 37
       6.5.1   Event Notification Message . . . . . . . . . . . . . . 38
       6.5.2   Event Notification Response Message  . . . . . . . . . 40
     6.6   Packet Redirect Message  . . . . . . . . . . . . . . . . . 41
     6.7   Heartbeat Message  . . . . . . . . . . . . . . . . . . . . 45
     6.8   Operation Summary  . . . . . . . . . . . . . . . . . . . . 45
   7.  Protocol Scenarios . . . . . . . . . . . . . . . . . . . . . . 47




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     7.1   Association Setup state  . . . . . . . . . . . . . . . . . 47
     7.2   Association Established state or Steady State  . . . . . . 48
   8.  High Availability Support  . . . . . . . . . . . . . . . . . . 51
     8.1   Responsibilities for HA  . . . . . . . . . . . . . . . . . 53
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 54
     9.1   No Security  . . . . . . . . . . . . . . . . . . . . . . . 54
       9.1.1   Endpoint Authentication  . . . . . . . . . . . . . . . 54
       9.1.2   Message authentication . . . . . . . . . . . . . . . . 55
     9.2   ForCES PL and TML security service . . . . . . . . . . . . 55
       9.2.1   Endpoint authentication service  . . . . . . . . . . . 55
       9.2.2   Message authentication service . . . . . . . . . . . . 55
       9.2.3   Confidentiality service  . . . . . . . . . . . . . . . 56
   10.   Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . 57
   11.   References . . . . . . . . . . . . . . . . . . . . . . . . . 58
   11.1  Normative References . . . . . . . . . . . . . . . . . . . . 58
   11.2  Informational References . . . . . . . . . . . . . . . . . . 58
       Author's Address . . . . . . . . . . . . . . . . . . . . . . . 58
   A.  Individual Authors/Editors Contact . . . . . . . . . . . . . . 59
   B.  IANA considerations  . . . . . . . . . . . . . . . . . . . . . 61
   C.  Implementation Notes . . . . . . . . . . . . . . . . . . . . . 62
     C.1   TML considerations . . . . . . . . . . . . . . . . . . . . 62
       C.1.1   PL Flag inference by TML . . . . . . . . . . . . . . . 62
       C.1.2   Message type inference to Mapping at the TML . . . . . 63
   D.  Changes between -00 and -01  . . . . . . . . . . . . . . . . . 64
       Intellectual Property and Copyright Statements . . . . . . . . 65



























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1.  Introduction


   This specification provides a draft definition of an IP-based
   protocol for Control Element control of an Forwarding Element.  The
   protocol is a TLV based protocol that include commands for transport
   of LFB information as well as TLVs for association, configuration,
   status, and events.


   This specification does not specify a transport mechanism for
   messages, but does include a discussion of the services that must be
   provided by the transport interface.


1.1  Sections of this document


   Section 2 provides a glossary of terminology used in the
   specification.


   Section 3 provides an overview of the protocol including a discussion
   on the protocol framework, descriptions of the protocol layer (PL)
   and a transport mapping layer (TML), as well as of the ForCES
   protocol mechanisms.


   While this document does not define the TML, Section 4 details the
   services that the TML must provide.


   The Forces protocol is defined to have a common header for all other
   message types.  The header is defined in Section 5, while the
   protocol messages are defined in Section 6.


   Section 7 describes several Protocol Scenarios and includes message
   exchange descriptions.


   Section 8 describes mechanism in the protocol to support high
   availability mechanisms including redundancy and fail over.  Section
   9 defines the security mechanisms provided by the PL and TML.

















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2.  Definitions


   This document follows the terminology defined by the ForCES
   Requirements in [RFC3654] and by the ForCES framework in [RFC3746].
   This document also uses the terminology defined by ForCES FE model in
   [FE-MODEL].  We copy the definitions of some of the terminology as
   indicated below:


   Addressable Entity (AE) - A physical device that is directly
   addressable given some interconnect technology.  For example, on IP
   networks, it is a device to which we can communicate using an IP
   address; and on a switch fabric, it is a device to which we can
   communicate using a switch fabric port number.


   Forwarding Element (FE) - A logical entity that implements the ForCES
   protocol.  FEs use the underlying hardware to provide per-packet
   processing and handling as directed/controlled by a CE via the ForCES
   protocol.


   Control Element (CE) - A logical entity that implements the ForCES
   protocol and uses it to instruct one or more FEs how to process
   packets.  CEs handle functionality such as the execution of control
   and signaling protocols.


   Pre-association Phase - The period of time during which a FE Manager
   (see below) and a CE Manager (see below) are determining which FE and
   CE should be part of the same network element.


   Post-association Phase - The period of time during which a FE does
   know which CE is to control it and vice versa, including the time
   during which the CE and FE are establishing communication with one
   another.


   FE Model  - A model that describes the logical processing functions
   of a FE.


   FE Manager (FEM) - A logical entity that operates in the
   pre-association phase and is responsible for determining to which
   CE(s) a FE should communicate.  This process is called CE discovery
   and may involve the FE manager learning the capabilities of available
   CEs.  A FE manager may use anything from a static configuration to a
   pre-association phase protocol (see below) to determine which CE(s)
   to use.  Being a logical entity, a FE manager might be physically
   combined with any of the other logical entities such as FEs.


   CE Manager (CEM) - A logical entity that operates in the
   pre-association phase and is responsible for determining to which
   FE(s) a CE should communicate.  This process is called FE discovery




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   and may involve the CE manager learning the capabilities of available
   FEs.  A CE manager may use anything from a static configuration to a
   pre-association phase protocol (see below) to determine which FE to
   use.  Being a logical entity, a CE manager might be physically
   combined with any of the other logical entities such as CEs.


   ForCES Network Element (NE) - An entity composed of one or more CEs
   and one or more FEs.  To entities outside a NE, the NE represents a
   single point of management.  Similarly, a NE usually hides its
   internal organization from external entities.


   High Touch Capability - This term will be used to apply to the
   capabilities found in some forwarders to take action on the contents
   or headers of a packet based on content other than what is found in
   the IP header.  Examples of these capabilities include NAT-PT,
   firewall, and L7 content recognition.


   Datapath -- A conceptual path taken by packets within the forwarding
   plane inside an FE.


   LFB (Logical Function Block) type -- A template representing a
   fine-grained, logically separable and well-defined packet processing
   operation in the datapath.  LFB types are the basic building blocks
   of the FE model.


   LFB (Logical Function Block) Instance -- As a packet flows through an
   FE along a datapath, it flows through one or multiple LFB instances,
   with each implementing an instance of a certain LFB type.  There may
   be multiple instances of the same LFB in an FE's datapath.  Note that
   we often refer to LFBs without distinguishing between LFB type and
   LFB instance when we believe the implied reference is obvious for the
   given context.


   LFB Metadata -- Metadata is used to communicate per-packet state from
   one LFB to another, but is not sent across the network.  The FE model
   defines how such metadata is identified, produced and consumed by the
   LFBs, but not how metadata is encoded within an implementation.


   LFB Attribute -- Operational parameters of the LFBs that must be
   visible to the CEs are conceptualized in the FE model as the LFB
   attributes.  The LFB attributes include, for example, flags, single
   parameter arguments, complex arguments, and tables that the CE can
   read or/and write via the ForCES protocol (see below).


   LFB Topology -- Representation of how the LFB instances are logically
   interconnected and placed along the datapath within one FE.
   Sometimes it is also called intra-FE topology, to be distinguished
   from inter-FE topology.




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   FE Topology -- A representation of how the multiple FEs within a
   single NE are interconnected.  Sometimes this is called inter-FE
   topology, to be distinguished from intra-FE topology (i.e., LFB
   topology).


   Inter-FE Topology -- See FE Topology.


   Intra-FE Topology -- See LFB Topology.


   Following terminologies are defined by this document:


   ForCES Protocol - While there may be multiple protocols used within
   the overall ForCES architecture, the term "ForCES protocol" refers
   only to the protocol used at the Fp reference point in the ForCES
   Framework in RFC3746 [RFC3746].  This protocol does not apply to
   CE-to-CE communication, FE-to-FE communication, or to communication
   between FE and CE managers.  Basically, the ForCES protocol works in
   a master-slave mode in which FEs are slaves and CEs are masters.
   This document defines the specifications for this ForCES protocol.


   ForCES Protocol Layer (ForCES PL) -- A layer in ForCES protocol
   architecture that defines the ForCES protocol messages, the protocol
   state transfer scheme, as well as the ForCES protocol architecture
   itself (including requirements of ForCES TML (see below)).
   Specifications of ForCES PL are defined by this document.


   ForCES Protocol Transport Mapping Layer (ForCES TML) -- A layer in
   ForCES protocol architecture that specifically addresses the protocol
   message transportation issues, such as how the protocol messages are
   mapped to different transport media (like TCP, IP, ATM, Ethernet,
   etc), and how to achieve and implement reliability, multicast,
   ordering, etc.  The ForCES TML is specifically addressed in a
   separate ForCES TML Specification document.



















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3.  Overview


   The reader is referred to the Framework document [RFC3746], and in
   particular sections 3 and 4, for an architectural overview and an
   explanation of how the ForCES protocol fits in.  There may be some
   content overlap between the framework document and this section in
   order to provide clarity.


3.1  Protocol Framework


   Figure 1 below is reproduced from the Framework document for clarity.
   It shows a NE with two CEs and two FEs.


                             ---------------------------------------
                             | ForCES Network Element              |
      --------------   Fc    | --------------      --------------  |
      | CE Manager |---------+-|     CE 1   |------|    CE 2    |  |
      --------------         | |            |  Fr  |            |  |
            |                | --------------      --------------  |
            | Fl             |         |  |    Fp       /          |
            |                |       Fp|  |----------| /           |
            |                |         |             |/            |
            |                |         |             |             |
            |                |         |     Fp     /|----|        |
            |                |         |  /--------/      |        |
      --------------     Ff  | --------------      --------------  |
      | FE Manager |---------+-|     FE 1   |  Fi  |     FE 2   |  |
      --------------         | |            |------|            |  |
                             | --------------      --------------  |
                             |   |  |  |  |          |  |  |  |    |
                             ----+--+--+--+----------+--+--+--+-----
                                 |  |  |  |          |  |  |  |
                                 |  |  |  |          |  |  |  |
                                   Fi/f                   Fi/f


          Fp: CE-FE interface
          Fi: FE-FE interface
          Fr: CE-CE interface
          Fc: Interface between the CE Manager and a CE
          Ff: Interface between the FE Manager and an FE
          Fl: Interface between the CE Manager and the FE Manager
          Fi/f: FE external interface


                 Figure 1: ForCES Architectural Diagram


   The ForCES protocol domain is found in the Fp Reference Point.  The
   Protocol Element configuration reference points, Fc and Ff also play
   a role in the booting up of the Forces Protocol.  The protocol




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   element configuration is out of scope of the ForCES protocol but is
   touched on in this document since it is an integral part of the
   protocol pre-association phase.


   Figure 2 below shows further breakdown of the Fp interface by example
   of a MPLS QoS enabled Network Element.


         -------------------------------------------------
         |       |       |       |       |       |       |
         |OSPF   |RIP    |BGP    |RSVP   |LDP    |. . .  |
         |       |       |       |       |       |       |
         -------------------------------------------------
         |               ForCES Interface                |
         -------------------------------------------------
                                 ^   ^
                                 |   |
                         ForCES  |   |data
                         control |   |packets
                         messages|   |(e.g., routing packets)
                                 |   |
                                 v   v
         -------------------------------------------------
         |               ForCES Interface                |
         -------------------------------------------------
         |       |       |       |       |       |       |
         |LPM Fwd|Meter  |Shaper |MPLS   |Classi-|. . .  |
         |       |       |       |       |fier   |       |
         -------------------------------------------------


               Figure 2: Examples of CE and FE functions


   The ForCES Interface shown in Figure 2 constitutes two pieces: the PL
   and TML layer.



















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   This is depicted in Figure 3 below.


         +------------------------------------------------
         |               CE PL layer                     |
         +------------------------------------------------
         |              CE TML layer                     |
         +------------------------------------------------
                                   ^
                                   |
                      ForCES       |   (i.e  Forces data + control
                      PL           |    packets )
                      messages     |
                      over         |
                      specific     |
                      TML          |
                      encaps       |
                      and          |
                      transport    |
                                   |
                                   v
         +------------------------------------------------
         |              FE TML layer                     |
         +------------------------------------------------
         |               FE PL layer                     |
         +------------------------------------------------


                       Figure 3: ForCES Interface


   The PL layer is in fact the ForCES protocol.  Its semantics and
   message layout are defined in this document.  The TML Layer is
   necessary to connect two ForCES PL layers as shown in Figure 3 above.
   The TML is out of scope for this document but is within scope of
   ForCES.  This document defines requirements the PL needs the TML to
   meet.


   Both the PL and the TML layers are standardized by the IETF.  While
   only one PL layer is defined, different TMLs are expected to be
   standardized.  To interoperate the TML layer at the CE and FE are
   expected to conform to the same definition.


   On transmit, the PL layer delivers its messages to the TML layer.
   The TML layer delivers the message to the destination TML layer(s).
   On receive, the TML delivers the message to its destination PL
   layer(s).


3.1.1  The PL layer


   The PL is common to all implementations of ForCES and is standardized




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   by the IETF as defined in this document.  The PL layer is responsible
   for associating an FE or CE to an NE.  It is also responsible for
   tearing down such associations.  An FE uses the PL layer to throw
   various subscribed-to events to the CE PL layer as well as respond to
   various status requests issued from the CE PL.  The CE configures
   both the FE and associated LFBs attributes using the PL layer.  In
   addition the CE may send various requests to the FE to activate or
   deactivate it, reconfigure its HA parametrization, subscribe to
   specific events etc.  More details in Section 6.


3.1.2  The TML layer


   The TML layer is essentially responsible for transport of the PL
   layer messages.  The TML is where the issues of how to achieve
   transport level reliability, congestion control, multicast, ordering,
   etc are handled.  It is expected more than one TML will be
   standardized.  The different TMLs each could implement things
   differently based on capabilities of underlying media and transport.
   However, since each TML is standardized, interoperability is
   guaranteed as long as both endpoints support the same TML.  All
   ForCES Protocol Layer implementations should be portable across all
   TMLs, because all TMLs have the same top edge semantics as defined in
   this document.


3.1.3  The FEM/CEM Interface


   The FEM and CEM components, although valuable in the setup and
   configurations of both the PL and TML layers, are out of scope of the
   ForCES protocol.  The best way to think of them are as
   configurations/parameterizations for the PL and TML before they
   become active (or even at runtime based on implementation).  In the
   simplest case, the FE or CE read a static configuration file which
   they use as the FEM/CEM interface.  RFC 3746 has a lot more detailed
   descriptions on how the FEM and CEM could be used.  We discuss the
   pre-association phase where the CEM and FEM play briefly in section
   Section 3.2.1.


   An example of typical things FEM/CEM would configure would be TML
   specific parameterizations such as:
   a.  how the TML connection should happen (example what IP addresses
       to use, transport modes etc);
   b.  the ID for the FE or CE would also be issued at this point.
   c.  Security parameterization such as keys etc.
   d.  Connection association parameters


   Example "send up to 3 association messages each 1 second apart" Vs "
   send up to 4 association messages with increasing exponential
   timeout".




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3.2  ForCES Protocol Phases


   ForCES, in relation to NEs, involves two phases: the Pre-Association
   phase where configuration/initialization/bootup of the TML and PL
   layer happens, and the association phase where the ForCES protocol
   operates.


3.2.1  Pre-association


   The ForCES interface is configured during the pre-association phase.
   In a simple setup, the configuration is static and is read from a
   saved config file.  All the parameters for the association phase are
   well known after the pre-association phase is complete.  A protocol
   such as DHCP may be used to retrieve the config parameters instead of
   reading them from a static config file.  Note, this will still be
   considered static pre-association.  Dynamic configuration may also
   happen using the Fc, Ff and Fl reference points.  Vendors may use
   their own proprietary service discovery protocol to pass the
   parameters.


   the following are  scenarios reproduced from the Framework Document
   to show a pre-association example.



      <----Ff ref pt--->              <--Fc ref pt------->
      FE Manager      FE                CE Manager    CE
       |              |                 |             |
       |              |                 |             |
    (security exchange)               (security exchange)
      1|<------------>| authentication 1|<----------->|authentication
       |              |                 |             |
     (FE ID, attributes)              (CE ID, attributes)
      2|<-------------| request        2|<------------|request
       |              |                 |             |
      3|------------->| response       3|------------>|response
      (corresponding CE ID)          (corresponding FE ID)
       |              |                 |             |
       |              |                 |             |


 Figure 4: Examples of a message exchange over the Ff and Fc reference
                                 points











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      <-----------Fl ref pt-------------->            |


      FE Manager      FE               CE Manager     CE
       |              |                 |             |
       |              |                 |             |
      (security exchange)               |             |
      1|<------------------------------>|             |
       |              |                 |             |
      (a list of CEs and their attributes)            |
      2|<-------------------------------|             |
       |              |                 |             |
      (a list of FEs and their attributes)            |
      3|------------------------------->|             |
       |              |                 |             |
       |              |                 |             |


    Figure 5: An example of a message exchange over the Fl reference
                                 point


   Before the transition to the association phase, the FEM will have
   established contact with the appropriate CEM component.
   Initialization of the ForCES interface will be completed, and
   authentication as well as capability discovery may be complete as
   well.  Both the FE and CE would have the necessary information for
   connecting to each other for configuration, accounting,
   identification and authentication purposes.  Both sides also would
   have all the necessary protocol parameters such as timers, etc.  The
   Fl reference point may continue to operate during the association
   phase and may be used to force a disassociation of an FE or CE.
   Because the pre-association phase is out of scope, these details are
   not discussed any further in this specification.  The reader is
   referred to the framework document [RFC3746] for more detailed
   discussion.


3.2.2  Post-association


   In this phase, the FE and CE components communicate with each other
   using the ForCES protocol (PL over TML) as defined in this document.
   There are three sub-phases:
   o  Association setup state
   o  Established State
   o  Association teardown state.


3.2.2.1  Association setup state


   The FE attempts to join the NE.  The FE may be rejected or accepted.
   Once granted access into the NE, capabilities exchange happens with
   the CE querying the FE.  Once the CE has the FE capability




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   information, the CE can offer an initial configure (possibly to
   restore state) and can query certain attributes within either an LFB
   or the FE itself.


   More details are provided in the protocol scenarios section.


   On successful completion of this state, the FE joins the NE and is
   moved to the Established State.


3.2.2.2  Association Established state


   In this state the FE is continuously updated or queried.  The FE may
   also send asynchronous event notifications to the CE or synchronous
   heartbeat notifications.  This continues until a termination is
   initiated by either the CE or the FE.


   Refer to section on protocol scenarios Section 7 for more details.


3.3  Protocol Mechanisms


   Various semantics are exposed to the protocol users via the PL header
   including: Transaction capabilities, atomicity of transactions, two
   phase commits, batching/parallelization, High Availability and
   failover as well as command windows.


3.3.1  Of Transactions, Atomicity and 2 Phase Commits


   A transaction is a sequence of operations that is guaranteed to be
   atomic in the presence of any failures by the CEs or FEs.  Operation
   in this sense implies the PL operation within the message body TLV.
   An example of a transaction could be a config PL msg with a sequence
   of operations: "route-add A B,C:route-del X" (each operation in its
   own TLV).


   If a transaction is split across more than one message, then all
   messages in the the transaction MUST arrive at the destination before
   they are executed on either the LFB or FE.  All operations are
   executed serially in the order specified by the transaction.  If any
   of the sequence of operations in a transaction fails then the
   transaction is declared as a failure.  This is an all-or-nothing
   approach and is needed to ensure consistency of a transaction across
   multiple FEs.


   A transaction may be atomic within an FE alone or across the NE.  In
   both cases the atomic requirement for a transaction MUST be met.  The
   PL message header exposes the ability to mark a start of transaction
   and end of transaction using flags.  These flags can be used to
   derive a classical transactional two phase commit[ACID paper ref




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   here].


3.3.2  FE, CE, and FE protocol LFBs


   Whereas the four key PL messages, Association Setup, Response, and
   Teardown, as well as Heartbeat, have a specific types assigned mostly
   for simplicity and monitoring reasons, all other PL messages follow
   the LFB structure as this provides more flexibility for future
   enhancements.  In addition, this shows how the ForCES protocol itself
   can be controlled by the very same type of structures (LFBs) it uses
   to control functions such as IP forwarding, filtering, etc.


   To achieve this, the following LFBs are used:
   o  FE Protocol LFB
   o  FE LFB
   o  CE LFB
   These LFBs are detailed in Section 6.1.  A short description is
   provided here:
   o  The FE Protocol LFB is a logical entity in each FE that is used to
      control the ForCES protocol.  The CE operates on this LFB to
      subscribe or unsubscribe to Heartbeat messages, define the
      Heartbeat interval, or to discover which ForCES protocol version
      is supported and which TMLs the FE supports.  The FE Protocol LFB
      also contains the various ForCES ID to be used: unicast IDs and
      table of the PL multicast IDs the FE must be listening to.  [TBD:
      do we need a CE Protocol LFB?]
   o  The FE LFB (referred to as "FE attributes" in the model draft)
      should not be confused with the FE Protocol Object.  The FE LFB is
      a logical entity in each FE and contains attributes relative to
      the FE itself, and not to the operation of the ForCES protocol
      between the CE and the FE.  Such attributes can be FEState (refer
      to model draft), vendor, etc.  The FE LFB contains in particular
      an table that maps a virtual LFB Instance ID to one or more
      Instance IDs of LFBs in the FE.
   o  The CE LFB is the counterpart of the FE LFB.  The CE LFB is a
      logical entity in each CE and contains attributes relative to the
      CE itself, and not to the operation of the ForCES protocol between
      the CE and the FE.  This LFB can be used to convey event
      notifications from a CE to FEs.  Some events may be sent by the CE
      without prior subscription by the FEs.


3.3.3  Scaling by Concurrency


   It is desirable that the PL layer not become the bottleneck when
   larger bandwidth pipes become available.  To pick a mythical example
   in today's terms, if a 100Gbps pipe is available and there is
   sufficient work then the PL layer should be able to take advantage of
   this and use all of the 100Gbps pipe.  Two mechanisms are provided to




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   achieve this.  The first one is batching and the second one is a
   command window.


   Batching is the ability to send multiple commands (such as config) in
   one PDU.  The size of the batch will be affected by, amongst other
   things, the path MTU.  The commands may be part of the same
   transaction or part of unrelated transactions that are independent of
   each other.


   Command windowing allows for pipelining of independent transactions
   which do not affect each other.  Each independent transaction could
   consist of one or more batches.


3.3.3.1  Batching


   There are several batching levels at different protocol hierarchies.
   o  multiple PL PDUs can be aggregated under one TML message
   o  multiple LFB classes and instances can be addressed within one PL
      PDU
   o  Multiple operations can be addressed to a single LFB class and
      instance


3.3.3.2  Command Pipelining


   TBD



























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4.  TML Requirements


   The requirements below are expected to be delivered by the TML.  This
   text does not define how such mechanisms are delivered.  As an
   example they could be defined to be delivered via hardware or
   inter-TML protocol level schemes.


   Each TML must describe how it contributes to achieving the listed
   ForCES requirements.  If for any reason a TML does not provide a
   service listed below a justification needs to be provided.
   1.  Reliability
       As defined by RFC 3654, section 6 #6.
   2.  Security
       TML provides security services to the ForCES PL.  TML layer
       should support the following security services and describe how
       they are achieved.
       *  Endpoint authentication of FE and CE.
       *  Message Authentication
       *  Confidentiality service
   3.  Congestion Control
       The congestion control scheme used needs to be defined.
       Additionally, the circumstances under which notification is sent
       to the PL to notify it of congestion must be defined.
   4.  Uni/multi/broadcast addressing/delivery if any
       If there is any mapping between PL and TML level
       Uni/Multi/Broadcast addressing it needs to be defined.
   5.  Timeliness


       Editorial Note:  Does the TML allow for obsoleting msgs? If yes,
                        it needs to define how.
   6.  HA decisions
       It is expected that availability of transport links is the TML's
       responsibility.  However, on config basis, the PL layer may wish
       to participate in link failover schemes and therefore the TML
       must support this capability.
       Please refer to the HA Section Section 8 for details.
   7.  Encapsulations used.
       Different types of TMLs will encapsulate the PL messages on
       different types of headers.  The TML needs to specify the
       encapsulation used.
   8.  Prioritization
       It is expected that the TML will be able to handle up to 8
       priority levels needed by the PL layer and will provide
       preferential treatment.
       TML needs to define how this is achieved.







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4.1  TML Parameterization


   It is expected that it should be possible to use a configuration
   reference point, such as the FEM or the CEM, to configure the TML.


   Some of the configured parameters may include:
   o  PL ID
   o  Connection Type and associated data.  For example if a TML uses
      IP/TCP/UDP then parameters such as TCP and UDP ports, IP addresses
      need to be configured.
   o  Number of transport connections
   o  Connection Capability, such as bandwidth, etc.
   o  Allowed/Supported Connection QoS policy (or Congestion Control
      Policy)






































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5.  Common Header


        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
                        0               1               2             3
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |version| rsvd  | Message Type  |             Length            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                          Source ID                            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                        Destination ID                         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                        Sequence Number                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                             Flags                             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                        Figure 6: Common Header


   The message is 32 bit aligned.


   Version (4 bit):
       Version number.  Current version is 1.
   rsvd (4 bit):
       Unused at this point.  A receiver should not interpret this
       field.
   Command (8 bits):
       Commands are defined in Section 6.
   Source ID  (32 bit):
   Dest ID (32 bit):
       *   Each of the source and Dest IDs are 32 bit IDs which
           recognize the termination points.  Ideas discussed so far are
           desire to recognize if ID belongs to FE or CE by inspection.
           Suggestions for achieving this involves partitioning of the
           ID allocation.  Another alternative maybe to use flags to
           indicate direction (this avoids partition).
       *   IDs will allow multi/broad/unicast
       *   Addressing
           a.  As ForCES may run between multiple CEs and FEs and over
               different protocols such as IPv4 and IPv6, or directly
               over Ethernet or other switching-fabric interconnects, it
               is necessary to create an addressing scheme for ForCES
               entities.  Mappings to the underlying TML-level
               addressing can then be defined as appropriate.
           b.  Fundamentally, unique IDs are assigned to CEs and FEs.  A
               split address space is used to distinguish FEs from CEs.
               Even though we can assume that in a large NE there are
               typically two or more orders of magnitude more FEs than




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               CEs, the address space is split uniformly for simplicity.
           c.  Special IDs are reserved for FE broadcast, CE broadcast,
               and NE broadcast.
           d.  Subgroups of FEs belonging, for instance, to the same
               VPN, may be assigned a multicast ID.  Likewise, subgroups
               of CEs that act, for instance, in a back-up mode may be
               assigned a multicast ID.  These FEs and CE multicast IDs
               are chosen in a distinct portion of the ID address space.
               Such a multicast ID may comprise FEs, CEs, or a mix of
               both.
           e.  As a result, the address space allows up to 2^30 (over a
               billion) CEs and the same amount of FEs.


       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
       0               1               2               3
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |TS |                           sub-ID                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                       Figure 7: ForCES ID Format


           f.  The ForCES ID is 32 bits.  The 2 most significant bits
               called Type Switch (TS) are used to split the ID space as
               follows:
               A.  TS    Corresponding ID range       Assignment
               B.  --    ----------------------       ----------
               C.  0b00   0x00000000 to 0x3FFFFFFF     FE IDs (2^30)
               D.  0b01   0x40000000 to 0x7FFFFFFF     CE IDs (2^30)
               E.  0b10   0x80000000 to 0xBFFFFFFF     reserved
               F.  0b11   0xC0000000 to 0xFFFFFFEF     multicast IDs
                   (2^30 - 16)
               G.  0b11   0xFFFFFFF0 to 0xFFFFFFFC     reserved
               H.  0b11   0xFFFFFFFD                   all CEs broadcast
               I.  0b11   0xFFFFFFFE                   all FEs broadcast
               J.  0b11   0xFFFFFFFF                   all FEs and CEs
                   (NE) broadcast
           g.  It is desirable to address multicast and/or broadcast
               messages to some LFB instances of a given class.  For
               instance, assume FEs FEa and FEb:
               -   FEa has LFBs LFBaX1 and LFBaX2 of class X
               -   similarly, FEb has two LFBs LFBbX1 and LFBbX2 of
                   class X.
               A broadcast message should be addressable to only LFBs
               LFBaX1 and LFBbX1 (this can be the case for instance if
               these two LFBs belong to the same VPN).  To achieve this,
               a VPN ID (3 octets OUI and 4 octets VPN Index) as defined
               in RFC 2685 should be used within the ForCES message body




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               as a TLV.


               As an alternative, a particular multicast ID MAY be
               associated to a given VPN ID through some configuration
               means.  Messages delivered to such a multicast ID MUST
               only be applied to LFBs belonging to that VPN ID.


   Sequence (32 bits)
       Unique to a PDU.  [Discussion: There may be impact on the effect
       of subsequence numbers].
   length (16 bits):
       length of header + the rest of the message in DWORDS (4 byte
       increments).
   Flags(32 bits):
       Identified so far:
       - ACK indicator(2 bit)
           The description for using the two bits is:
               'NoACK' (00)
               'SuccessACK'(01)
               'UnsuccessACK'(10)
               'ACKAll' (11)
       - Priority (3 bits)
           TBD
       - Throttle flag
       - Batch (2 bits)
       - Atomicity (1 or 2 bits)



   Editorial Note:  There are several open issues, listed below, in the
                    header which still need to be settled:


                    1.  Parallelization of PL Windowing/subsequence
                        Someone to look into ISCSI
                    2.  events and replies and relation to peer to peer
                        vs master slave
                    3.  We need to discuss whether some of the Flags
                        such as those for Atomicity, Batching are needed
                        in the common header or only belong to the
                        Config message.













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6.  Protocol Messages


   The general structure of most messages is as follows (in BNF format):



        PL level PDU :=   MAINHDR<LFBselect>+
        LFBselect    :=   LFBCLASSID LFBInstance <OPER>+
        OPER         :=   <OPERATION [<path-data>]*>+



   o  MAINHDR defines msg type, Target FE/CE ID etc.  The MAINHDR also
      defines the content.  As an example the content of a "config"
      message would be different from an "association" message.
   o  LFBCLASSID is a 32 bit unique identifier per LFB class defined at
      class creation time.
   o  LFBInstance is a 32 bit unique instance identifier of an LFB class
   o  OPERATION is one of {ADD,DEL,etc.} depending on the message type
   o  path-data identifies the exact element targeted.  It may have zero
      or more data values associated.


   In summary this approach has the following characteristic:
   o  there can be one or more LFB Class + InstanceId combo targeted in
      a message (batch)
   o  There can one or more operation on an addressed LFB
      classid+instanceid combo(batch)
   o  There can be one or more path targets per operation (batch)
   o  Paths may have zero or more data values associated (flexibility
      and operation specific)


   It should be noted that the above is optimized for the case of a a
   single classid+instance targeting.  To target multiple instances
   within the same class, multiple LFBselect are needed.


6.1  Core ForCES LFBs


   There are three LFBs that are used to control the operation of the
   ForCES protocol and to interact with FEs and CEs:
      FE protocol LFB
      FE LFB
      CE LFB


   Although these LFBs have the same form and interface as other LFBs,
   they are special in many respects: they have fixed well-known LFB
   Class and Instance IDs.  They are statically defined (no dynamic
   instantiation allowed) and their status cannot be changed by the
   protocol: any operation to change the state of such LFBs (for
   instance, in order to disable the LFB) must result in an error.
   Moreover, these LFBs must exist before the first ForCES message can




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   be sent or received.  All attributes in these LFBs must have
   pre-defined default values.  Finally, these LFBs do not have input or
   output ports and do not integrate into the intra-FE LFB topology.


6.1.1  FE Protocol LFB


   The FE Protocol LFB is a logical entity in each FE that is used to
   control the ForCES protocol.  The FE Protocol LFB Class ID is
   assigned the value 0x1.  The FE LFB Instance ID is assigned the value
   0x1.  There must always be one and only one instance of the FE
   Protocol LFB in an FE.  The values of the attributes in the FE
   Protocol LFB have pre-defined default values that are specified here.
   Unless explicit changes are made to these values using Config
   messages from the CE, these default values MUST be used for the
   operation of the protocol.


   The FE Protocol LFB consists of the following elements:
   o  FE Protocol events that can be subscribed/unsubscribed:
      *  FE heartbeat
      *  FE TML events (TBD)
   o  FE Protocol capabilities (read-only):
      *  Supported ForCES protocol version(s) by the FE
      *  Supported ForCES FE model(s) by the FE
      *  Some TML capability description(s)
   o  FE Protocol attributes (can be read and set):
      *  Current version of the ForCES protocol
      *  Current version of the FE model
      *  FE unicast ID
      *  FE multicast ID(s) (list)
      *  Association Expiry Timer
      *  Heartbeat Interval
      *  Primary CE
      *  FE failover and restart policy
      *  CE failover and restart policy
         Note:  Is there a difference between the CE and FE failover
                policies?
         TBD:   Define default values for each attribute where
                applicable.


6.1.2  FE LFB


   The FE LFB is a logical entity in each FE and contains attributes
   relative to the FE itself, and not to the operation of the ForCES
   protocol.  The FE LFB Class ID is assigned the value 0x2.  The FE LFB
   Instance ID is assigned the value 0x1.  There must always be one and
   only one instance of the FE LFB in an FE.


   The FE LFB consists of the following elements:




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      FE Events:
      *  FEAllEvents: subscribing to this corresponds to subscribing to
         all events below
      *  FEStatusChange: events that signal FE Status:
         +  Up
         +  Down
         +  Active
         +  Inactive
         +  Failover
      *  FE DoS alert
      *  FE capability change
      FE attributes:
      *  FEStatus: to set the FE mode as:
         +  Active
         +  Inactive
         +  Shutdown
         Note:  This replaces the State Maintenance messages
      *  FELFBInstancelist
      *  FENeighborList
      *  MIID table: a list of virtual LFB Instance IDs that map to a
         list of Instance IDs of LFBs in that FE
      *  FE Behavior Exp.  Timer
      *  HA Mode
      *  FE DoS protection policy
      *  FEPrivateData: Proprietary info such as name, vendor, model.
         Note:  The attributes below were previously under Query
                message.
      *  Inter-FE topology Intra-FE topology


6.1.3  CE LFB


   The CE LFB is a logical entity in each CE and contains attributes
   relative to the CE itself, and not to the operation of the ForCES
   protocol.


   The CE LFB consists of the following elements:
      CE Events:
      *  CEAllEvents: subscribing to this corresponds to subscribing to
         all events listed below.
         Note:  Do we want to allow an FE to explicitly subscribe to CE
                events?
      *  CEStatusChange: events that signal CE
         Up/Down/Active/Inactive/Failover.
         Note:  Such events do not necessarily need to be subscribed to,
                they can fire even without subscription and be sent to
                the FE






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      Note:  TBD: what else do we need in the CE LFB?


6.2  Association Messages


   The ForCES Association messages are used to establish and teardown
   associations between FEs and CEs.


6.2.1  Association Setup Message


   This message is sent by the FE to the CE to setup a ForCES
   association between them.  This message could also be used by CEs to
   join a ForCES NE, however CE-to-CE communication is not covered by
   this protocol.


   Message transfer direction:
      FE to CE
   Message Header:
      The Message Type in the header is set MessageType= 'Association
      Setup'.  The ACK flag in the header is ignored, because the setup
      message will always expect to get a response from the message
      receiver (CE) whether the setup is successful or not.  The Src ID
      (FE ID) may be set to O in the header which means that the FE
      would like the CE to assign a FE ID for the FE in the setup
      response message.
   Message body:
      The setup message body consists of LFBSelect & FE Name TLV, the
      format of which is as follows:

























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        main hdr (eg type =  Association setup)
             |
             |
             +--- T = LFBselect
             |        |
             |        +-- LFBCLASSID = FE object
             |        |
             |        |
             |        +-- LFBInstance = 0x1
             |
             +--- T = Operation = SHOW
                      |
                      +-- FE NAME



           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


          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |        Type = LFB select      |               Length          |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |                 LFB Class ID = FE Object                      |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |                        LFB Instance ID                        |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |        Type = operation Show  |               Length          |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |                       FE Name string                          |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |                                                               |
          ~                   FE Object LFB (including HBI, etc)          ~
          |                                                               |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                                Figure 9


   Type (16 bits):
      LFB Select
   Length (16 bits):
      Length of the TLV including the T and L fields, in bytes.
   FE Object LFB:
      This contains the FE parameters e.g.  HBI will be exchanged with
      the CE using this LFB.
   FE Name String:
      This is a string which contains the FE name (part of FE Object
      LFB).






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      Editorial Note:  In certain situations (such as use of multicast
                       IDs), it might not be possible to make use of the
                       procedure described above for the FE to
                       dynamically obtain an ID from the CE.  Such
                       situations need to be identified.


6.2.2  Association Setup Response Message


   This message is sent by the CE to the FE in response to the Setup
   message.  It indicates to the FE whether the setup is successful or
   not, i.e.  whether an association is established.


   Message transfer direction:
       CE to FE
   Message Header:
       The Message Type in the header is set MessageType= 'Setup
       Response'.  The ACK flag in the header is always ignored, because
       the setup response message will never expect to get any more
       response from the message receiver (FE).  The Dst ID in the
       header will be set to some FE ID value assigned by the CE if the
       FE had requested that in the setup message (by SrcID = 0).
   Message body:
       The setup response message body consists of LFBSelect & Result
       TLV, the format of which is as follows:




























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        main hdr (eg type =  Association setup response)
             |
             |
             +--- T = LFBselect
             |        |
             |        +-- LFBCLASSID = FE object
             |        |
             |        |
             |        +-- LFBInstance = 0x1
             |
             +--- T = FEResult
                      |
                      +-- resultvalue


            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


          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |        Type = LFB select      |               Length          |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |                 LFB Class ID = FE Object                      |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |                        LFB Instance ID                        |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |        Type = operation Show  |               Length          |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |                                                               |
          ~                   FE Object LFB (optional)                    ~
          |                                                               |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |       Type = Result           |               Length          |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |         Result                |              Reserved         |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                               Figure 10


   Type (16 bits):
       LFB Select
   Length (16 bits):
       Length of the TLV including the T and L fields, in bytes.
   FE Object LFB:
       The FE parameters e.g.  HBI may be exchanged using this LFB.
   Result (16 bits):
       This indicates whether the setup msg was successful or whether
       the FE request was rejected by the CE.






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6.2.3  Association Teardown Message


   This message can be sent by the FE or CE to any ForCES element to end
   its ForCES association with that element.


   Message transfer direction:
       CE to FE, or FE to CE (or CE to CE)
   Message Header:
       The Message Type in the header is set MessageType= "Asso.
       Teardown".  The ACK flag in the header is always ignored, because
       the teardown message will never expect to get any response from
       the message receiver.
   Message body:
       The association teardown message body consists of LFBSelect &
       FEReason TLV, the format of which is as follows:




        main hdr (eg type =  Association tear)
             |
             |
             +--- T = LFBselect
             |        |
             |        +-- LFBCLASSID = FE object
             |        |
             |        |
             |        +-- LFBInstance = 0x1
             |
             +--- T = FEReason
                      |
                      +-- "myreason"



           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


          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |        Type = LFB select      |               Length          |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |                 LFB Class ID = FE Object                      |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |                        LFB Instance ID                        |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |         Type = T.reason       |               Length          |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |                   Reason                                      |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+






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                               Figure 11


   Type (16 bits):
       LFB Select
   Length (16 bits):
       Length of the TLV including the T and L fields, in bytes.
   T.reason (32 bits):
       This indicates the reason why the association is being
       terminated.


6.3  Configuration Messages


   The ForCES Configuration messages are used by the CEs to configure
   the FEs in a ForCES NE and report the results back to the CE.


6.3.1  Config Message


   This message is sent by the CE to the FE to configure FE or LFB
   attributes.  This message is also used by the CE to
   subscribe/unsubscribe to FE and LFB events.


   Message transfer direction:
       CE to FE
   Message Header:
       The Message Type in the header is set MessageType= 'Config'.  The
       ACK flag in the header is can be used by the CE to turn off any
       response from the FE.  The default behavior is to turn on the ACK
       to get the config response from the FE.
   Message body:
       The Config message body consists of one or more TLVs, the format
       of a single (LFB) TLV is as follows:


        main hdr (eg type = config)
             |
             |
             +--- T = LFBselect
             |        |
             |        +-- LFBCLASSID = target LFB class
             |        |
             |        |
             |        +-- LFBInstance = target LFB instance
             |        |
             |        |
             |        +-- T = operation { ADD, DEL,  etc}
             |        |   |
             |        |   +--  // one or more path targets
             |        |        // under discussion
             |        |




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             |        +-- T = operation { ADD, DEL,  etc}
             |        |   |
             |        |   +--  // one or more path targets
             |        |        // under discussion
             |        |
             |        +-- T = operation { ADD, DEL,  etc}
             |        |   |
             |        |   +--  // one or more path targets
             |        |        // under discussion
             |        |



         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
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |        Type = LFB select      |               Length          |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                          LFB Class ID                         |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        LFB Instance ID                        |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |    Type = Operations (ADD)    |               Length          |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        ~                         Config data                           ~
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |    Type = Operations (DEL)    |               Length          |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        ~                         Config data                           ~
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                               Figure 12


   Type (16 bits):
       LFB Select.
   Length (16 bits):
       Length of the TLV including the T and L fields, in bytes.
   LFB Class ID (16 bits):
       This field uniquely recognizes the LFB class/type.
   LFB Instance ID (16 bits):
       This field uniquely identifies the LFB instance.
   Type (16 bits):
       The operations include, ADD, DEL, UPDATE/REPLACE, DEL ALL, EVENT
       SUBSCRIBE, EVENT UNSUBSCRIBE, PACKET SUBSCRIBE, PACKET
       UNSUBSCRIBE, CANCEL.




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   Length (16 bits):
       Length of the TLV including the T and L fields, in bytes.
   Config Data (variable length):
       This will carry LFB specific data (<path>, single or Array LFB
       specific entries).  The config data might itself be of the form
       of a TLV.
       *Note:  FE Activate/Deactivate, Shutdown FE commands for State
              Maintenance will be sent using Config messages.
       *Note:  For Event subscription, the events will be defines by the
              individual LFBs.


6.3.2  Config Response Message


   This message is sent by the FE to the CE in response to the Config
   message.  It indicates whether the Config was successful or not on
   the FE and also gives a detailed response regarding the configuration
   result of each attribute.


   Message transfer direction:
       FE to CE
   Message Header:
       The Message Type in the header is set MessageType= 'Config
       Response'.  The ACK flag in the header is always ignored, because
       the config response message will never expect to get any more
       response from the message receiver (CE).
   Message body:
       The Config response message body consists of one or more TLVs,
       the format of a single TLV is as follows:
























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          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


        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |        Type = LFB select      |               Length          |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                          LFB Class ID                         |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        LFB Instance ID                        |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |    Type = Operations (ADD)    |               Length          |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |     Operation Result          |           reserved            |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        ~                         Config Result                         ~
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |    Type = Operations (DEL)    |               Length          |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |     Operation Result          |           reserved            |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        ~                         Config Result                         ~
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                               Figure 13


   Type (16 bits):
       LFB Select.
   Length (16 bits):
       Length of the TLV including the T and L fields, in bytes.
   LFB Class ID (16 bits):
       This field uniquely recognizes the LFB class/type.
   LFB Instance ID (16 bits):
       This field uniquely identifies the LFB instance.
   Type (16 bits):
       The operations are same as those defined for Config messages.
   Length (16 bits):
       Length of the TLV including the T and L fields, in bytes.
   Operation Result (16 bits):
       This indicates the overall result of the config operation,
       whether it was successful or it failed.
   Config Result (variable length):
       This will carry LFB specific results (single or Array LFB
       specific result entries).  The config result might itself be of
       the form of a TLV.





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6.4  Query and Query Response Messages


   The ForCES query and query response messages are used for one ForCES
   element (CE or FE) to query other ForCES element(s) for various kinds
   of information.  Current version of ForCES protocol limits the use of
   the messages only for CE to query information of FE.


6.4.1  Query Message


   As usual, a query message is composed of a common header and a
   message body that consists of one or more TLV data format.  Detailed
   description of the message is as below.


   Message transfer direction:
       Current version limits the query message transfer direction only
       from CE to FE.
   Message Header:
       The Message Type in the header is set to MessageType= 'Query'.
       The ACK flag in the header SHOULD be set 'ACKAll', meaning a full
       response for a query message is always expected.  If the ACK flag
       is set other values, the meaning of the flag will then be
       ignored, and a full response will still be returned by message
       receiver.
   Message body:
       The query message body consists of (at least) one or more than
       one TLVs that describe entries to be queried.  The TLV is called
       LFBselect TLV and the data format is as below:



         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
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |        Type = LFBselect       |               Length          |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                          LFB Class ID                         |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        LFB Instance ID                        |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        Operation TLV                          |
        .                                                               .
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        ~                           ...                                 ~
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        Operation TLV                          |
        .                                                               .
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                               Figure 14




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       Editorial Note:
                        1.  Under discussion is whether there is a need
                            for explicit multiple LFB insatance
                            addressing here.  One way to realize it is
                            to define a specific Instance select TLV to
                            substitute above 'LFB Instance ID' field.
                            The TLV may have following format:


           INSselectTLV := Type Length Value
           Type := INSselect
           Value := InstanceID (RangeMark | Instance ID)+



                        2.  An applicable RangeMark is '0xffffffff', the
                            value of which is the same as Instance
                            broadcast ID.  Because there will be no
                            broadcast address applied in this place,
                            there will be no worry of ambiguity here.


   Operation TLV:
       The Operation TLV for the 'Query' message is formatted as:


        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |    Type = GET                 |               Length          |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        Path(or Attribute ID?)                 |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                            Query Data                         |
        .                                                               .
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                               Figure 16


   Path(or Attribute ID?):
       [Under discussion and TBD]


       Editorial Note:  There is a debate on whether we should use a
                        'Path' or simply an 'Attribute ID' or a 'Table
                        ID' here at the protocol layer.  A Path is used
                        for data indexing for a table, while an
                        'Attribute ID' or a 'Table ID' only specify
                        which attribute or table to use, leaving table
                        index to be included in followed data.







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   Query Data:
       [Under discussion and TBD]


   To better understand the above PDU format, we can show a tree
   structure for the format as below:


   main hdr (type = Query)
        |
        |
        +--- T = LFBselect
        |        |
        |        +-- LFBCLASSID = target LFB class
        |        |
        |        |
        |        +-- LFBInstance = target LFB instance
        |        |
        |        |
        |        +-- T = operation { GET }
        |        |   |
        |        |   +--  // one or more path targets
        |        |        // under discussion
        |        +-- T = operation { GET }
        |        |   |
        |        |   +--  // one or more path targets
        |        |


                               Figure 17



6.4.2  Query Response Message


   When receiving a query message, the receiver should process the
   message and come up with a query result.  The receiver sends the
   query result back to the message sender by use of the Query Response
   Message.  The query result can be the information being queried if
   the query operation is successful, or can also be error codes if the
   query operation fails, indicating the reasons for the failure.


   A query response message is also composed of a common header and a
   message body consists of one or more TLVs describing the query
   result.  Detailed description of the message is as below.


   Message transfer direction:
       Current version limits the query response message transfer
       direction only from FE to CE.







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   Message Header:
       The Message Type in the header is set to MessageType=
       'QueryResponse'.  The ACK flag in the header SHOULD be set
       'NoACK', meaning no further response for a query response message
       is expected.  If the ACK flag is set other values, the meaning of
       the flag will then be ignored.  The Sequence Number in the header
       SHOULD keep the same as that of the query message to be
       responded, so that the query message sender can keep track of the
       responses.
   Message body:
       The message body for a query response message consists of (at
       least) one or more than one TLVs that describe query results for
       individual queried entries.  The TLV is also called LFBselect
       TLV, and has exactly the same data format as query message,
       except the Operation TLV inside is different.  The order of the
       TLV here matches the TLVs in the corresponding Query message, and
       the TLV number should keep the same.  The Operation TLV here is a
       'GET-RESPONSE' TLV and the data is  'Query Response Data', as
       below:


        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |    Type = GET-RESPOSE         |               Length          |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        Path(or Attribute ID?)                 |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        Query Response Data                    |
        .                                                               .
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                               Figure 18


   Query Response Data:
       [Under discussion and TBD]


6.5  Event Notification and Response Messages


   The Event Notification Message is used for one ForCES element to
   asynchronously notify one or more other ForCES elements in the same
   ForCES NE on just happened events in it.  The Event Notification
   Response Message is used for the receiver of the Event Notification
   Message to acknowledge the reception of the event notification.


   Events in current ForCES protocol can be categorized into following
   types:
   o  Events happened in CE
   o  Events happened in FE


   Events can also be categorized into two classes according to whether




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   they need subscription or not.  An event in one ForCES element that
   needs to be subscribed will send notifications to other ForCES
   elements only when the other elements have subscribed to the element
   for the event notification.  How to subscribe/unsubscribe for an
   event is described in the Configure Message in Section 6.3.  An event
   that needs not to be subscribed will always send notifications to
   other ForCES elements when the event happens.  An event definition
   made by ForCES protocol, ForCES FE model, or by vendors will state if
   the event needs subscription or not.


   Editorial Note:  There is an argument that it is preferable to have
                    all events subscribable.


6.5.1  Event Notification Message


   As usual, an Event Notification Message is composed of a common
   header and a message body that consists of one or more TLV data
   format.  Detailed description of the message is as below.
   Message Transfer Direction:
      FE to CE, or CE to FE
   Message Header:
      The Message Type in the message header is set to
      MessageType = 'EventNotification'.  The ACK flag in the header can
      be set as: ACK flag ='NoACK'|'SuccessAck'|'UnsuccessACK'|'ACKAll'.
      Note that the 'Success' here only means the receiver of the
      message has successfully received the message.
   Message Body:
      The message body for an event notification message consists of (at
      least) one or more than one TLVs that describe the notified
      events.  The TLV is defined as follows:



         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
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |        Type = LFBselect       |               Length          |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                          LFB Class ID                         |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        LFB Instance ID                        |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        Operation TLV                          |
        .                                                               .
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        ~                           ...                                 ~
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        Operation TLV                          |
        .                                                               .
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




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                               Figure 19


   Operation TLV:
      This is a TLV that describes the event to be notified, as follows:


        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |    Type = REPORT              |               Length          |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        Path(or Event ID?)                     |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                            Event Data                         |
        .                                                               .
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                               Figure 20


   Path(or Event ID):
      [Under discussion and TBD]
   Event Data:
      [Under discussion and TBD]


   To better understand the above PDU format, we can show a tree
   structure for the format as below:


   main hdr (type = Event Notification)
        |
        |
        +--- T = LFBselect
        |        |
        |        +-- LFBCLASSID = target LFB class
        |        |
        |        |
        |        +-- LFBInstance = target LFB instance
        |        |
        |        |
        |        +-- T = operation { REPORT }
        |        |   |
        |        |   +--  // one or more path targets
        |        |        // under discussion
        |        +-- T = operation { REPORT }
        |        |   |
        |        |   +--  // one or more path targets
        |        |



                               Figure 21






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6.5.2  Event Notification Response Message


   After sending out an Event Notification Message, the sender may be
   interested in ensuring that the message has been received by
   receivers, especially when the sender thinks the event notification
   is vital for system management.  An Event Notification Response
   Message is used for this purpose.  The ACK flag in the Event
   Notification Message header are used to signal if such acknowledge is
   requested or not by the sender.


   Detailed description of the message is as below:
   Message Transfer Direction:
      From FE to CE or from CE to FE, just inverse to the direction of
      the Event Notification Message that it responses.
   Message Header:
      The Message Type in the header is set MessageType=
      'EventNotificationResponse'.  The ACK flag in the header SHOULD be
      set 'NoACK', meaning no further response for the message is
      expected.  If the ACK flag is set other values, the meaning of the
      flag will then be ignored.  The Sequence Number in the header
      SHOULD keep the same as that of the message to be responded, so
      that the event notificatin message sender can keep track of the
      responses.
   Message Body:
      The message body for an event notification response message
      consists of (at least) one or more than one TLVs that describe the
      notified events.  The TLV is also called LFBselect TLV, and has
      exactly the same data format as Event Notification Message, except
      the Operation TLV inside is different.  The order of the TLV here
      matches the TLVs in the corresponding Event Message, and the TLV
      number should keep the same.  The Operation TLV here is a
      'REPORT-RESPONSE' TLV and the data is 'Event Response Data', as
      below:



        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |    Type = REPORT-RESPONSE     |               Length          |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        Path(or Event ID?)                     |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |    Result     |   Reason      |         Code                  |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                               Figure 22







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   Path(or Event ID?):
      [Under discussion and TBD]
   Result:
      This describes the reception result of the event notification
      message as below:


        Result Value             Meaning
        'Success'       The event has been successfully received.
        'Unsuccess'     The event has not been successfully received.


   Reason, Code:
      This describes the reason and possible error code when the message
      is not successfully received.  Note that only the failure at the
      protocol layer rather than the transport layer can be handled
      here, that is, if even the header part of the message to be
      responded can not be correctly received, the response to the
      message will not be able to be generated by the receiver.


      Editorial Note:  There is a debate on whether the Event
                       Notification Response Message is necessary or
                       not.  The pro for it is some event notification
                       senders may be interested in knowing if receivers
                       have had success/unsuccess receptions of the
                       events or not.  An alternative to generate such
                       response is for the protocol to define a
                       universal ACK message so that it can act as
                       responses for any types of messages as well as
                       the event notification messages, when the message
                       senders are interested in knowing whether the
                       messages have been successfully received or not
                       (different from the responses for the message
                       processing results).


6.6  Packet Redirect Message


   Packet redirect message is used to transfer data packets between CE
   and FE.  Usually these data packets are IP packets, though they may
   sometimes associated with some metadata generated by other LFBs in
   the model, or they may occasionally be other protocol packets, which
   usually happen when CE and FE are jointly implementing some
   high-touch operations.  Packets redirected from FE to CE are the data
   packets that come from forwarding plane, and usually are the data
   packets that need high-touch operations in CE,or packets for which
   the IP destination address is the NE.  Packets redirected from CE to
   FE are the data packets that come from the CE and are decided by CE
   to put into forwarding plane in FE.


   Supplying such a redirect path between CE and FE actually leads to a




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   possibility of this path being DoS attacked.  Attackers may
   maliciously try to send huge spurious packets that will be redirected
   by FE to CE, making the redirect path been congested.  ForCES
   protocol and the TML layer will jointly supply approaches to prevent
   such DoS attack.  To define a specific 'Packet Redirect Message'
   makes TML and CE able to distinguish the redirect messages from other
   ForCES protocol messages.


   By properly configuring related LFBs in FE, a packet can also be
   mirrored to CE instead of purely redirected to CE, i.e., the packet
   is duplicated and one is redirected to CE and the other continues its
   way in the LFB topology.


   Editorial Note:  There are also discussions on how LFBs in FE model
                    that are related to packet redirect operations
                    should be defined.  Although it is out of the scope
                    of forces protocol, how to define the LFBs affect
                    the Packet Redirect Message described here.  Because
                    currently it is still in progress in FE model on how
                    to define such LFBs, we try to post some thoughts on
                    this here for discussion.  They will be removed
                    later along with the progress of the FE model work.


        Thought 1:  To define LFBs called 'RedirectSink' and
                    'RedirectTap' for packet redirect.
                    An LFB in FE called 'RedirectSink' is responsible to
                    collect data packets that need to be redirected to
                    CE.  From the perspective of the FE LFB topology,
                    the 'RedirectSink' LFB is an LFB with only one input
                    port and without any output port, and the input port
                    can then be connected to any other LFB in FE model
                    by means of a datapath in the forwarding plane.
                    From the perspective of the ForCES protocol layer,
                    the 'RedirectSink' LFB will generate the Packet
                    Redirect Messages when it receives data packets from
                    forwarding plane.


                    An LFB in FE called 'RedirectTap' is responsible to
                    receive data packets that are redirected from CE.
                    From the perspective of the FE LFB topology, the
                    'RedirectTap' LFB is an LFB with only one output
                    port and without any input port, and the output port
                    can then be connected to any other LFB in FE model
                    by means of a datapath in the forwarding plane.
                    From the perspective of ForCES protocol layer, the
                    'RedirectTap' LFB can receive the Packet Redirect
                    Messages from CE, and un-encapsulate the data
                    packets from the message and put them to datapaths




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                    in the forwarding plane.  Actually the 'RecirectTap'
                    LFB acts more like a transcoder that transfers the
                    ForCES protocol messages to normal data packets in
                    IP forwarding plane.  As a result, if we need to
                    have redirected packets connected to some LFB (say a
                    Scheduler) in FE model, we only need to connect the
                    'RedirectTap LFB to the Scheduler LFB directly via a
                    datapath as follows:



                             +-----------------+       +-----------+
                             | RedirectTap LFB |------>|           |
                             +-----------------+       |           |
                                                       | Scheduler |
                                 From other LFB   ---->|    LFB    |
                                                       |           |
                                                       +-----------+


                               Figure 24



                    By use of several 'RedirectSink' LFBs and several
                    'RedirectTap' LFBs that connect to several different
                    datapaths in FE forwarding plane, multiple packet
                    redirect paths between CE and FE can be constructed.


        Thought 2:  There might be another way a packet could be
                    redirected: directly by a forwarding path, e.g., by
                    FPGA/ASIC/NP microcode.  In such a case we do not
                    need to put in a lot of smartness.  Probably a link
                    layer or even network level header is enough.  The
                    receiver demuxes it only based on some protocol type
                    in the link layer or network transport layer.  The
                    pros for this appraoch is it may provide a fast and
                    cost-effective path for packet redirect.  The cons
                    for this is it may more or less confuses the Fp
                    reference point definition in ForCES framework.



   We describe the Packet Redirect Message data format in details as
   follows:
   Message Direction:
      CE to FE or FE to CE
   Message Header:
      The Message Type in the header is set to MessageType=
      'PacketRedirect'.  The ACK flags in the header SHOULD be set
      'NoACK', meaning no response is expected by this message.  If the
      ACK flag is set other values, the meanings will be ignored.




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   Message Body:
      Consists of one or more TLVs, with every TLV having the following
      data format:


        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
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |        Type = LFBselect       |               Length          |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                          LFB Class ID                         |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        LFB Instance ID                        |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        Operation TLV                          |
        .                                                               .
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        ~                           ...                                 ~
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        Operation TLV                          |
        .                                                               .
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                               Figure 25


   LFB class ID:
      There are only two possible LFB classes here, the 'RedirectSink'
      LFB or the 'RedirectTap' LFB.  If the message is from FE to CE,
      the LFB class should be 'RedirectSink'.  If the message is from CE
      to FE, the LFB class should be 'RedirectTap'.
   Instance ID:
      Instance ID for the 'RedirectSink' LFB or 'RedirectTap' LFB.
   Operation TLV:
      This is a TLV describing one packet of data to be directed via the
      specified LFB above.  The order of the data number is also the
      order the data packet arrives the redirector LFB, that is, the
      Redirected Data #1 should arrive earlier than the Redirected Data
      #2 in this redirector LFB.  The TLV format is as follows:


        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |    Type = PAYLOAD             |               Length          |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        Path(or Sequence Number?)              |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        ~                        Redirected Data                        ~
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                               Figure 26





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   Path(or Sequence Number?):
      [Under discussion and TBD]
   Type:
      [TBD]
   Redirected Data:
      This field will make a detailed description of the data to be
      redirected as well as the data itself.  The encoding of the
      description is based on the ForCES FE model if the redirector LFB
      is defined by FE model, or based on vendor specifications if the
      redirector LFB is defined by vendors.  The description will
      usually include the name (or the name ID) of the redirected packet
      data (such as 'IPv4 Packet', 'IPv6 Packet'), and the packet data
      itself.  It may also include some metadata (metadata name (or name
      ID) and its value)associated with the redirected data packet.


6.7  Heartbeat Message


   The Heartbeat (HB) Message is used for one ForCES element (FE or CE)
   to asynchronously notify one or more other ForCES elements in the
   same ForCES NE on its liveness.


   A Heartbeat Message is sent by a ForCES element periodically.  The
   time interval to send the message is set by the Association Setup
   Message described in Section 6.1.1.  A little different from other
   protocol messages, a Heartbeat message is only composed of a common
   header, withe the message body left empty.  Detailed description of
   the message is as below.
   Message Transfer Direction:
       FE to CE, or CE to FE
   Message Header:
       The Message Type in the message header is set to MessageType =
       'Heartbeat'.  The ACK flag in the header SHOULD be set to
       'NoACK', meaning no response from receiver(s) is expected by the
       message sender.  Other values of the ACK flag will always be
       ignored by the message receiver.
   Message Body:
       The message body is empty for the Heartbeat Message.


6.8  Operation Summary


   The following tables summarize the operations and their applicabiity
   to the messages.


   No Operations for the following messages:
      Assoc-Setup
      Assoc-Setup-Resp
      Assoc-Teardown





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      Heartbeat


   +-------------------+-------+------------+--------+-------------+
   |     Operation     | Query | Query-Resp | Config | config-Resp |
   +-------------------+-------+------------+--------+-------------+
   |        Set        |       |            |    X   |      X      |
   |                   |       |            |        |             |
   |       Delete      |       |            |    X   |      X      |
   |                   |       |            |        |             |
   |       Update      |       |            |    X   |      X      |
   |                   |       |            |        |             |
   |        Get        |   X   |      X     |        |             |
   |                   |       |            |        |             |
   |  Event subscribe  |       |            |    X   |      X      |
   |                   |       |            |        |             |
   | Event unsubscribe |       |            |    X   |      X      |
   +-------------------+-------+------------+--------+-------------+


     +-----------+--------------+-------------+------------------+
     | Operation | Packet-Redir | Event-Notif | Event-Notif-Resp |
     +-----------+--------------+-------------+------------------+
     |  Payload  |       X      |             |                  |
     |           |              |             |                  |
     |   Event   |              |      X      |         X        |
     +-----------+--------------+-------------+------------------+



























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7.  Protocol Scenarios


7.1  Association Setup state


   The associations among CEs and FEs are initiated via Association
   setup message from the FE.  If a setup request is granted by the CE,
   a successful setup response message is sent to the FE.  If CEs and
   FEs are operating in an insecure environment then the security
   association have to be established between them before any
   association messages can be exchanged.  The TML will take care of
   establishing any security associations.


   This is followed by capability query, topology query.  When the FE is
   ready to start forwarding data traffic, it sends a FE UP Event
   message to the CE.  The CE responds with a FE ACTIVATE State
   Maintenance message to ask the FE to go active and start forwarding
   data traffic.  At this point the association establishment is
   complete.  These sequences of messages are illustrated in the Figure
   below.

































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                      FE PL                  CE PL


                        |                       |
                        |   Asso Setup Req      |
                        |---------------------->|
                        |                       |
                        |   Asso Setup Resp     |
                        |<----------------------|
                        |                       |
                        |    Capability Query   |
                        |<----------------------|
                        |                       |
                        |      Query Resp       |
                        |---------------------->|
                        |                       |
                        |       Topo Query      |
                        |<----------------------|
                        |                       |
                        |   Topo Query Resp     |
                        |---------------------->|
                        |                       |
                        |       FE UP Event     |
                        |---------------------->|
                        |                       |
                        |  Config-Activate FE   |
                        |<----------------------|
                        |                       |



    Figure 27: Message exchange between CE and FE to establish an NE
                              association


   On successful completion of this state, the FE joins the NE and is
   moved to the Established State or Steady state.


7.2  Association Established state or Steady State


   In this state the FE is continously updated or queried.  The FE may
   also send asynchronous event notifications to the CE or synchronous
   heartbeat messages.  This continues until a termination (or
   deactivation) is initiated by either the CE or FE.  Figure below
   helps illustrate this state.




                      FE PL                   CE PL


                        |                       |




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                        |    Heart Beat         |
                        |<----------------------|
                        |                       |
                        |   Heart Beat          |
                        |---------------------->|
                        |                       |
                        |  Config-Subscribe Ev  |
                        |<----------------------|
                        |                       |
                        |     Config Resp       |
                        |---------------------->|
                        |                       |
                        |  Config-Add LFB Attr  |
                        |<----------------------|
                        |                       |
                        |     Config Resp       |
                        |---------------------->|
                        |                       |
                        |   Query LFB Stats     |
                        |<----------------------|
                        |                       |
                        |    Query Resp         |
                        |---------------------->|
                        |                       |
                        |    FE Event Report    |
                        |---------------------->|
                        |                       |
                        |  Config-Del LFB Attr  |
                        |<----------------------|
                        |                       |
                        |     Config Resp       |
                        |---------------------->|
                        |                       |
                        |    Packet Redirect    |
                        |---------------------->|
                        |                       |
                        |    Heart Beat         |
                        |<----------------------|
                        .                       .
                        .                       .
                        |                       |
                        |  Config-Activate FE   |
                        |<----------------------|
                        |                       |


   Figure 28: Message exchange between CE and FE during steady-state
                             communication





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   Note that the sequence of messages shown in the figure serve only as
   examples and the messages exchange sequences could be different from
   what is shown in the figure.  Also, note that the protocol scenarios
   described in this section do not include all the different message
   exchanges which would take place during failover.  That is described
   in the HA section 8.














































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8.  High Availability Support



   The ForCES protocol provides mechanisms for CE redundancy and
   failover, in order to support High Availability as defined in
   [RFC3654].  FE redundancy and FE to FE interaction is currently out
   of scope of this draft.  There can be multiple redundant CEs and FEs
   in a ForCES NE.  However, at any time there can only be one Primary
   CE controlling the FEs and there can be multiple secondary CEs.  The
   FE and the CE PL are aware of the primary and secondary CEs.  This
   information (primary, secondary CEs) is configured in the FE, CE PLs
   during pre-association by FEM, CEM respectively.  Only the primary CE
   sends Control messages to the FEs.  The FE may send its event
   reports, redirection packets to only the Primary CE (Report Primary
   Mode) or it may send these to both primary and secondary CEs (Report
   All Mode).  (The latter helps with keeping state between CEs
   synchronized, although it does not guarantee synchronization.) This
   behavior or HA Modes are configured during Association setup phase
   but can be changed by the CE anytime during protocol operation.  A
   CE-to-CE synchronization protocol will be needed in most cases to
   support fast failover, however this will not be defined by the ForCES
   protocol.


   During a communication failure between the FE and CE (which is caused
   due to CE or link reasons, i.e.  not FE related), the TML on the FE
   will trigger the FE PL regarding this failure.  This can also be
   detected using the HB messages between FEs and CEs.  The FE PL will
   send a message (Event Report) to the Secondary CEs to indicate this
   failure or the CE PL will detect this and one of the Secondary CEs
   takes over as the primary CE for the FE.  During this phase, if the
   original primary CE comes alive and starts sending any commands to
   the FE, the FE should ignore those messages and send an Event to all
   CEs indicating its change in Primary CE.  Thus the FE only has one
   primary CE at a time.


   An explicit message (Config message- Move command) from the primary
   CE, can also be used to change the Primary CE for an FE during normal
   protocol operation.  In order to support fast failover, the FE will
   establish association (setup msg) as well as complete the capability
   exchange with the Primary as well as all the Secondary CEs (in all
   scenarios/modes).











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   These two scenarios (Report All, Report Primary) have been
   illustrated in the figures below.



                     FE                      CE Primary         CE Secondary
                        |                       |                    |
                        | Asso Estb,Caps exchg  |                    |
                      1 |<--------------------->|                    |
                        |                       |                    |
                        |         Asso Estb,Caps|exchange            |
                      2 |<----------------------|------------------->|
                        |                       |                    |
                        |     All msgs          |                    |
                      3 |<--------------------->|                    |
                        |                       |                    |
                        |    packet redirection,|events, HBs         |
                      4 |-----------------------|------------------->|
                        |                       |                    |
                        |                   FAILURE                  |
                        |                                            |
                        |             Event Report (pri CE down)     |
                      5 |------------------------------------------->|
                        |                                            |
                        |                  All Msgs                  |
                      6 |------------------------------------------->|



               Figure 29: CE Failover for Report All mode
























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                        FE                   CE Primary        CE Secondary
                        |                       |                    |
                        |  Asso Estb,Caps exchg |                    |
                      1 |<--------------------->|                    |
                        |                       |                    |
                        |         Asso Estb,Caps|exchange            |
                      2 |<----------------------|------------------->|
                        |                       |                    |
                        |       All msgs        |                    |
                      3 |<--------------------->|                    |
                        |                       |                    |
                        |            (HeartBeats| only)              |
                      4 |-----------------------|------------------->|
                        |                       |                    |
                        |                   FAILURE                  |
                        |                                            |
                        |              Event Report (pri CE down)    |
                      5 |------------------------------------------->|
                        |                                            |
                        |                   All Msgs                 |
                      6 |------------------------------------------->|



             Figure 30: CE Failover for Report Primary Mode



8.1  Responsibilities for HA


   TML level - Transport level:
   1.  The TML controls logical connection availability and failover.
   2.  The TML also controls peer HA managements.


   At this level, control of all lower layers, for example transport
   level (such as IP addresses, MAC addresses etc) and associated links
   going down are the role of the TML.


   PL Level:
   All the other functionality including configuring the HA behavior
   during setup, the CEIDs are used to identify primary, secondary CEs,
   protocol Messages used to report CE failure (Event Report), Heartbeat
   messages used to detect association failure, messages to change
   primary CE (config - move), and other HA related operations described
   before are the PL responsibility.


   To put the two together, if a path to a primary CE is down, the TML
   would take care of failing over to a backup path, if one is
   available.  If the CE is totally unreachable then the PL would be
   informed and it will take the appropriate actions described before.




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9.  Security Considerations


   ForCES architecture identified several [Reference Arch] levels of
   security.  ForCES PL uses security services provided by the ForCES
   TML layer.  TML layer provides security services such as endpoint
   authentication service, message authentication service and
   confidentiality service.  Endpoint authentication service is invoked
   at the time of pre-association connection establishment phase and
   message authentication is performed whenever FE or CE receives a
   packet from its peer.


   Following are the general security mechanism that needs to be in
   place for ForCES PL layer.
   o  Security mechanism are session controlled that is once the
      security is turned ON depending upon the chosen security level (No
      Security, Authentication only, Confidentiality), it will be in
      effect for the entire duration of the session.
   o  Operator should configure the same security policies for both
      primary and backup FE's and CE's (if available).  This will ensure
      uniform operations, and to avoid unnecessary complexity in policy
      configuration.
   o  ForCES PL endpoints SHOULD pre-established connections with both
      primary and backup CE's.  This will reduce the security messages
      and enable rapid switchover operations for HA.


9.1  No Security


   When No security is chosen for ForCES protocol communication, both
   endpoint authentication and message authentication service needs be
   performed by ForCES PL layer.  Both these mechanism are weak and does
   not involve cryptographic operation.  Operator can choose "No
   security" level when the ForCES protocol endpoints are within an
   single box.


   In order to have interoperable and uniform implementation across
   various security levels, each CE and FE endpoint MUST implement this
   level.  The operations that are being performed for "No security"
   level is required even if lower TML security services are being used.


9.1.1  Endpoint Authentication


   Each CE and FE PL layer maintain set of associations list as part of
   configuration.  This is done via CEM and FEM interfaces.  FE MUST
   connect to only those CE's that are configured via FEM similarly CE
   should accept the connection and establish associations for the FE's
   which are configured via CEM.  CE should validate the FE identifier
   before accepting the connection during the pre-association phase.





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9.1.2  Message authentication


   When CE or FE generates initiates a message, the receiving endpoint
   MUST validate the initiator of the message by checking the common
   header CE or FE identifiers.  This will ensure proper protocol
   functioning.  We recommend this extra step processing even if the
   underlying TLM layer security services.


9.2  ForCES PL and TML security service


   This section is applicable if operator wishes to use the TML security
   services.  ForCES TML layer MUST support one or more security service
   such as endpoint authentication service, message authentication
   service, confidentiality service as part of TML security layer
   functions.  It is the responsibility of the operator to select
   appropriate security service and configure security policies
   accordingly.  The details of such configuration is outside the scope
   of ForCES PL and is depending upon the type of transport protocol,
   nature of connection.


   All these configurations should be done prior to starting the CE and
   FE.


   When certificates-based authentication is being used at TML layer,
   the certificate can use ForCES specific naming structure as
   certificate names and accordingly the security policies can be
   configured at CE and FE.


9.2.1  Endpoint authentication service


   When TML security services are enabled.  ForCES TML layer performs
   endpoint authentication.  Security association is established between
   CE and FE and is transparent to the ForCES PL layer.


   We recommend that FE after establishing the connection with the
   primary CE, should establish the security association with the backup
   CE (if available).  During the switchover operation CE's security
   state associated with each SA's are not transferred.  SA between
   primary CE and FE and backup CE and FE are treated as two separate
   SA's.


9.2.2  Message authentication service


   This is TML specific operation and is transparent to ForCES PL
   layer[TML document].







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9.2.3  Confidentiality service


   This is TML specific operation and is transparent to ForCES PL
   layer.[TML document]
















































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10.  Acknowledgments


   The authors of this draft would like to acknowledge and thank the
   following: Alex Audu, Steven Blake, Allan DeKok, Ellen M.  Deleganes,
   Yunfei Guo, Joel M.  Halpern, Zsolt Haraszti, Jeff Pickering,
   Guangming Wang, Chaoping Wu, and Lily L.  Yang for their
   contributions.  We would also like to thank David Putzolu, and
   Patrick Droz for their comments and suggestions on the protocol.












































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11.  References


11.1  Normative References


   [RFC2629]  Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
              June 1999.


   [RFC3654]  Khosravi, H. and T. Anderson, "Requirements for Separation
              of IP Control and Forwarding", RFC 3654, November 2003.


   [RFC3746]  Yang, L., Dantu, R., Anderson, T. and R. Gopal,
              "Forwarding and Control Element Separation (ForCES)
              Framework", RFC 3746, April 2004.


11.2  Informational References


   [FE-MODEL]
              Yang, L., "ForCES Forwarding Element Model", Feb. 2004.



Author's Address


   Avri Doria
   ETRI


   Phone: +1 401 663 5024
   EMail: avri@acm.org

























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Appendix A.  Individual Authors/Editors Contact


      Ligang Dong
      Zhejiang Gongshang University
      149 Jiaogong Road
      Hangzhou  310035
      P.R.China
      Phone: +86-571-88071024
      EMail: donglg@mail.hzic.edu.cn



      Avri Doria
      ETRI
      EMail: avri@acm.org



      Ram Gopal
      Nokia
      5, Wayside Road
      Burlington  MA 01803
      USA
      Phone: 1-781-993-3685
      EMail: ram.gopal@nokia.com



      Robert Haas
      IBM
      Saumerstrasse 4
      8803 Ruschlikon
      Switzerland
      EMail: rha@zurich.ibm.com



      Jamal Hadi Salim
      Znyx
      Ottawa, Ontario
      Canada
      EMail: hadi@znyx.com



      Hormuzd M Khosravi
      Intel
      2111 NE 25th Avenue
      Hillsboro, OR  97124
      USA
      Phone: +1 503 264 0334
      EMail: hormuzd.m.khosravi@intel.com





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      Weiming Wang
      Zhejiang Gongshang University
      149 Jiaogong Road
      Hangzhou  310035
      P.R.China
      Phone: +86-571-88057712
      EMail: wmwang@mail.hzic.edu.cn













































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Appendix B.  IANA considerations


   tbd

















































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Appendix C.  Implementation Notes


C.1  TML considerations


   Having separated the PL from the TML layer, it became clear that the
   TML layer needed to understand the desires of the PL layer to service
   it.  Example: How does the TML layer map prioritization or
   reliability needs of a PL message? To see the challenge involved,
   assume that all of the FE TML, FE PL, CE TML and CE PL are
   implemented by different authors probably belonging to different
   organizations.  Three implementation alternatives were discussed.


   As an example, consider a TML which defines that PL messages needing
   reliability get sent over a TCP connection; then TML-PL interfaces
   are:
   o  PL to call a special API: example send_reliable(msg) which is
      translated by the TML to mean send via TCP.
   o  PL to call a generic API: example send(msg) with explicit msg
      flags turned to say "reliability needed" and the TML translates
      this to mean send via TCP.
   o  PL sends the Forces Messages such a message is inferred to mean
      send via TCP by the TML.


   in #1 and #2 the msg includes a ForCES msg with metadata flags which
   are consumed by the TML layer.


   #3 is a technique that will be referred as inference-by-TML
   technique.  It simplifies the standardization effort since both #1
   and #2 will require standardization of an API.  Two ideas discussed
   for TML inference of PL messages are:
   1.  Looking at the flags in the header.
   2.  Looking at the message type.


   #1 and #2 can still be used if a single organization implements both
   (PL and TML) layers.  It is also reasonable that one organization
   implements the TML and provides an abstraction to another
   organization to implement a PL layer on.


C.1.1  PL Flag inference by TML
   1.  Reliability
       This could be "signalled" from the PL to the TML via the ACK
       flag.  The message type as well could be used to indicate this.
   2.  No reliability
       Could be signalled via missing ACK flag.  The message type as
       well could be used to indicate this.
   3.  Priorities
       A remapping to be defined via the FEM or the CEM interface
       depending on the number of TML priorities available.




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   4.  Addressing
       This is TML specific.  For example a TML that is capable of
       multicast transport may map a multicast PL ID to a multicast
       transport address.
   5.  Event notifications
       The TML must be able to send to the PL notifications.
       1.  The TML should be able to send Transport level congestion
           notifications to the PL.
       2.  Link events for HA purposes if configuration requires it
       3.  Events that will trigger PL layer events from the TML.
           As an example, an HA event at the TML layer like a failure of
           CE detected at TML on the FE may belong to this.  In this
           case, a PL event msg will be triggered and sent to CE.
       4.  Events that are intrinsic to the same CE or FE a TML is
           located.  These will not trigger any PL msg, instead, they
           just act as notification to PL core (FE object).  The
           congestion event generated at the transmission source side
           may belong to this, because it usually only needs to tell the
           upper PL at the same side rather than the opposite side that
           congestion has happened along the path.  E.g., a congestion
           event at CE TML layer only need to tell CE PL of this, rather
           than the opposite FE via a PL msg.


C.1.2  Message type inference to Mapping at the TML


   In this case one would define the desires of the different message
   types and what they expect from the TML.  For example:
   1.  Association Setup, Teardown, Config, Query the PL will expect the
       following services from TML: Reliable delivery and highest
       prioritization.
   2.  Packet Redirect, HB Message Types, and  Event Reports the PL will
       require the following services from TML: Medium Prioritization,
       and notifications when excessive losses are reached.



















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Appendix D.  Changes between -00 and -01
   1.  Major Protocol changes
       *  Restructured message format to apply operation to LFB as
          opposed to having operation be the primary organizing
          principle
       *  Worked with model team to bring the draft into harmony with
          their model approach
   2.  Document changes
       *  Replaced FE protocol Object and FE Object sections with
          combined section on FE, CE and FE protocol LFBs
       *  Removed minor version id
       *  Added Header flags
       *  Added BNF description of message structure
       *  Added tree structure description of PDUs
       *  Added section on each type of LFB
       *  Added structural description of each message
       *  Moved query messages section to come after config message
          section
       *  Replace state maintenance section
       *  Added section with tables showing the operations relevant to
          particular messages
       *  Many spelling and grammatical corrections






























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Copyright Statement


   Copyright (C) The Internet Society (2004).  This document is subject
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Acknowledgment


   Funding for the RFC Editor function is currently provided by the
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Doria (co-editor)        Expires April 25, 2005                [Page 65]


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