Hormuzd Khosravi
   Internet Draft                                         Shuchi Chawla
   Document: draft-ietf-forces-tcptml-00.txt draft-ietf-forces-tcptml-01.txt                Intel Corp.
   Expires: August 2005 January 2006                                 Furquan Ansari
   Working Group: ForCES                                   Lucent Tech.
                                                              Jon Maloy
                                                               Ericsson

                                                         February

                                                         July 2005

        TCP/IP based TML (Transport Mapping Layer) for ForCES protocol

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Copyright Notice

   Copyright (C) The Internet Society (2005).

  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in
   this document are to be interpreted as described in [2].

   Abstract

   This document defines the TCP/IP based TML (Transport Mapping Layer)
   for the ForCES protocol. It explains the rationale for choosing the
   transport protocols and also describes how this TML addresses all
   the requirements described in the Forces [3] requirements and ForCES
   protocol [7] document.

                             Table of Contents

   1. Definitions.....................................................3 Definitions.....................................................2
   2. Introduction....................................................3
   3. Protocol Framework Overview.....................................4 Overview.....................................3
   3.1.1. The PL layer................................................5
   3.1.2. The TML layer...............................................5
   4. TCP/IP TML Overview.............................................5
   4.1. Rationale for using TCP/IP....................................6 TCP/IP....................................5
   4.2. Separate Control and Data channels............................6
   4.3. Reliability...................................................7
   4.4. Congestion Control............................................8
   4.5. Security......................................................8
   4.6. Addressing....................................................8
   4.7. Prioritization................................................8
   4.8. HA Decisions..................................................8
   4.9. Encapsulations Used...........................................8 Used...........................................9
   5. TML Messaging...................................................8
   5.1. TML Message Header............................................9
   5.1.1. Version (version)...........................................9
   5.1.2. Upper Layer Protocol Flag (f)...............................9
   5.1.3. Message Type (msgType)......................................9
   5.1.4. TML Message Length (tmlMsgLength)...........................9
   5.1.5. TML Message Body...........................................10
   5.2. TML Messages.................................................10
   5.2.1. Channel Close..............................................10
   5.2.2. Heartbeat..................................................10
   5.2.3. Multicast Group Join Request...............................10
   5.2.4. Multicast Group Join Response..............................10
   5.2.5. Multicast Group Leave Request..............................11
   5.2.6. Multicast Group Leave Response.............................11 Messaging...................................................9
   6. TML Interface to Upper layer Protocol..........................11 Protocol...........................9
   6.1. TML API......................................................11 Service Interface........................................10
   6.1.1. TML Initialize.............................................11 Initialize.............................................10
   6.1.2. TML Channel Open...........................................12 Open...........................................11
   6.1.3. TML Channel Close..........................................13 Close..........................................12
   6.1.4. TML Channel Write..........................................14 Write..........................................13
   6.1.5. TML Channel Read...........................................15 Read...........................................14
   6.1.6. TML Multicast Group Join...................................16 Join...................................15
   6.1.7. TML Multicast Group Leave..................................16
   6.2. Protocol Initialization and Shutdown Model...................17
   6.2.1. Protocol Initialization....................................17
   6.2.2. Protocol Shutdown..........................................18 Shutdown..........................................19
   6.3. Multicast Model..............................................20
   6.4. Broadcast Model..............................................22
   7. Security Considerations........................................22
   7.1. TLS Usage for this TML.......................................22 TML.......................................23
   8. IANA Considerations............................................23
   9. References.....................................................23
   9.1. Manageability..................................................23
   10. References....................................................23
   10.1. Normative References.........................................23
   9.2. References........................................23
   10.2. Informative References.......................................23
   10. Acknowledgments...............................................24 References......................................24
   11. Acknowledgments...............................................25
   12. Authors' Addresses............................................24 Addresses............................................25

1.   Definitions
   The following definitions are taken from [3], [5]

   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.

   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.  This document defines a TCP/IP based
   ForCES TML.

2.   Introduction

   The ForCES (Forwarding and Control Element Separation) working group
   in the IETF is defining the architecture and protocol for separation
   of control and forwarding elements in network elements such as
   routers.  [3],  [4]  define  both  architectural  and  protocol
   requirements for the communication between CE and FE. The ForCES
   protocol layer [7] describes the protocol specification. It is
   envisioned that the ForCES protocol would be independent of the
   interconnect technology between the CE and FE and can run over
   multiple  transport  technologies  and  protocol.  Thus  a  Transport
   Mapping Layer (TML) has been defined in the protocol framework that
   will  take  care  of  mapping  the  protocol  messages  to  specific
   transports. This document defines the TCP/IP based TML for the
   ForCES protocol layer. It also addresses all the requirements for
   the TML including security, reliability, etc.

3.   Protocol Framework Overview
   The reader is referred to the Framework document [4], and in
   particular sections 3 and 4, for architectural overview and where
   and how the ForCES protocol fits in.  There may be some content
   overlap between the ForCES protocol draft [7] and this section in
   order to provide clarity.

   The ForCES protocol constitutes two pieces: the PL and TML layer.
   This is depicted in Figure 1 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 1: ForCES Interface

   The PL layer is in fact the ForCES protocol.  Its semantics and
   message layout are defined in [7].  The TML Layer is necessary to
   connect two ForCES PL layers as shown in Figure 1 above.

   Both the PL and 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 be of 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 reception, 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 by the IETF [7].  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 itĂs HA parameterization, subscribe to
   specific events etc.

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.

4.    TCP/IP TML Overview

   [TBD: Update this section based on the protocol selected for the
   data channel.]
   The TCP/IP TML consists of two TCP connections between the CE and FE
   over which the protocol messages are exchanged. One of the
   connections is called the control channel, over which control
   messages are exchanged, the other is called data channel over which
   external protocol packets, such as routing packets will be
   exchanged. The TCP connections will use unique server port numbers
   for each of the channels. In addition to this, this TML will provide
   mechanisms to prioritize the messages over the different channels.

   Some of the rationale for choosing this transport mechanism as well
   as explanation of how it meets the TML requirements is explained
   below.

4.1.Rationale for using TCP/IP
   TCP meets all the reliability requirements (no losses, no data
   corruption, no re-ordering of data) for the ForCES protocol/TML and
   also provides congestion control mechanism, which is important to
   meet the scalability requirement. In addition, it helps with
   interoperability since TCP is a well-understood, widely deployed
   transport protocol. Using TCP also enables this TML and the protocol
   to work seamlessly in single hop and multihop scenarios.

4.2.Separate Control and Data channels

   The ForCES NEs are subject to Denial of Service (DoS) attacks
   [Requirements Section 7 #15]. A malicious system in the network can
   flood a ForCES NE with bogus control packets such as spurious RIP or
   OSPF packets in an attempt to disrupt the operation of and the
   communication between the CEs and FEs. In order to protect against
   this situation, the TML uses separate control and data channels for
   communication between the CEs and FEs. Figure 2 below illustrates
   the different communication channels between the CEs and the FEs; FEs. As
   an example, the communication channels for support of High
   Availability with redundant CEs are also included.  The setup of
   these channels would be dependent on the High Availability model
   used in the NE.

                           ACTIVE CE              STANDBY CE
                    +-------------------+  +-------------------+
                    | CE: PL            |  | CE: PL            |
                    +-------------------+  +-------------------+
                    | CE: TML           |  | CE: TML           |
                    +-------------------+  +-------------------+
                    | CE: TCP           |  | CE: TCP           |
                    +-------------------+  +-------------------+
                      | |   | |    | |       |  |     |  |
                      | .   | .    | .       |  .     |  .
                      | |   | |    | |       |  |     |  |
                      | .   | .    | .       |  .     |  .
                      | |   | |    | |    Cc1Ă Cd1Ă Cc2Ă Cd2ÓCcnĂ CdnĂ
                      | .   | .    | .
            +-Cc1-----+ |   | |    | +-.-.-.-.-.Cdn.-+
            |  +-Cd1-.-.+   | .    +--------Ccn---+  |
            |  |            | |                   |  .
            |  .        +Cc2+ .                   |  |
            |  |        | +Cd2+                   |  .
            |  .        | |                       |  |
         +-----------+ +-----------+          +-----------+
         | FE: TCP   | | FE: TCP   |   . . .  | FE: TCP   |
         +-----------+ +-----------+          +-----------+
         | FE: TML   | | FE: TML   |          | FE: TML   |
         +-----------+ +-----------+          +-----------+
         | FE: PL    | | FE: PL    |          | FE: PL    |
         +-----------+ +-----------+          +-----------+
           FE1            FE2                    FEn
        \-------------V------------/
                 FE 1+1 Redundancy

   Legend:
       ---- Cc# : Unicast Control Channel between Active CE and FE#
       -.-. Cd# : Unicast Data Channel between Active CE and FE#

       ---- Cc#Ă: Unicast Control Channel between Standby CE and FE#
       -.-. Cd#Ă: Unicast Data Channel between Standby CE and FE#

                          Figure 2: CE-FE Communication Channels

   The data channel carries the control protocol packets such as RIP,
   OSPF messages as outlined in Requirements [3] Section 7 #10, which
   are carried in ForCES Packet Redirect messages [7], between the CEs
   and FEs. All the other ForCES messages, which are used for
   configuration/capability exchanges, event notification, etc, are
   carried over the control channel. The data channel is set up only
   after the control channel is set up. By default, the data channel is
   established on the CE control channel port number +1.

   The reliability requirements for the data channel messages are
   different from that of the control messages [Reqs] i.e. they donĂt
   require strict reliability in terms of retransmission, etc. However
   congestion control is important for the data channel because in case
   of DoS attacks, if an unreliable transport such as UDP is used for
   the data traffic, it can more easily overflow the physical
   connection, overwhelming the control traffic with congestion. Thus
   we need a transport protocol that provides congestion control but
   does not necessarily provide full reliability. Datagram Congestion
   Control Protocol (DCCP) [11], which is currently being defined, is a
   transport protocol that exactly meets this requirement. However
   since it is currently not an IETF standard RFC, and the authors are
   unaware of any existing implementations, this TML uses TCP as
   transport protocol for the data channel (for IP interconnect). TCP
   provides the congestion control mechanism required for the data
   channel and its wide deployment eases interoperability.

4.3.Reliability

   TCP provides the reliability (no losses, no data corruption, no re-
   ordering of data) required for ForCES protocol control messages.

4.4.Congestion Control

   TCP provides congestion control needed to satisfy this requirement.

4.5.Security

   This TML uses TLS [8] to provide security in insecure environments.
   Please see section 7 on security considerations for more details.
   [TBD: Update based on IPSec/TLS decision.]

4.6.Addressing

   This TML uses addressing provided by IP layer. For unicast
   addressing/delivery, it uses the TCP connection between the CE and
   FE.
   FE for control messaging. For multicast/broadcast addressing/delivery,
   addressing/delivery of control messages, this TML uses multiple TCP
   connections between the CE and FEs.

   Additionally, the TML layer maintains the mapping between the PL
   layer addresses and the channel descriptors assigned by the TML
   layer.  The PL layer is unaware of these descriptors; the PL layer
   only uses the PL layer addresses for all communication with the TML
   layer.

   [TBD: Add any information on addressing for data channel.]

4.7.Prioritization

   This TML provides prioritization of messages sent over control
   channel as compared to the data channel. This has also been found to
   be useful in face of DoS attacks on the protocol. The details Additionally it
   supports multiple levels of
   this are TBD. prioritization for control messages. The
   scheduling algorithm used at the TML layer gives preferential
   treatment to higher priority messages.  The scheduling algorithm
   used in the TML layer is implementation dependent.

4.8.HA Decisions

   The TML layer supports heartbeat messages between peer TML layers to
   indicate liveness of the entity generating it.  The frequency of the
   heartbeat message may be specified at protocol initialization time.

4.9.Encapsulations Used

   TML adds its own header on all ForCES protocol messages that it
   receives, and additionally on messages it generates. The ForCES
   protocol and TML messages are further encapsulated with a TCP/IP
   header.  The format of the TML header is specified in Section 5.

5. TML Messaging

   TML adds on a TML header to all messages that it either receives
   from

   [TBD: Remove this? Use liveliness message at TCP layer?  What about
   for the PL layer or those messages that it generates.  The TML
   header is followed by data channel?  What if the message body.  The message body may
   comprise protocol doesnĂt support such a PL message or it may be
   message?  If a heartbeat message generated by is required at the TML layer for communicating with its peer.  A flag in the TML header
   specifies whether the message is associated with the PL layer. The
   next section details the TML header.

5.1.TML Message Header

   Figure 3 below shows the format of the TCP TML message header.
   NOTE: The header may undergo some modifications in the next revision
   of this draft.

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |version|reserved |f|  msgType  |         tmlMsgLength          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      TBD: message body                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                          Figure 3: TCP TML Message Header Format
5.1.1.Version (version)

   The version field (4 bits) specifies the version of the TML layer
   protocol supported by the implementation.  An entity implementing
   the TML layer protocol should be backward compatible with previous
   versions of the protocol.

5.1.2.Upper Layer Protocol Flag (f)

   The upper layer protocol flag (1 bit) specifies if
   the data channel, does that imply that TML layer is
   carrying a message sent by the PL Layer.  If the protocol flag is
   set, the message body comprises of a PL message which messaging is not
   interpreted by the peer TML layer; the rest of the TML header required?
   See updates to Section 4.9 and
   message is ignored by the peer 5.]
   TML layer. If the protocol flag is
   not set, the message body carries a TML message; hence, the rest of
   the TML header needs to be read by responsible for keeping the peer TML layer control and the
   message body appropriately processed.

5.1.3.Message Type (msgType)

   The message type (6 bits) field is applicable only if the protocol
   flag field is not set. data communication
   channels up.  It specifies the TML message being sent
   between peer TML layers.

5.1.4.TML Message Length (tmlMsgLength)

   The TML message length field is applicable only if the protocol flag
   field is however does not set.  It specifies the length of the TML message in
   octets inclusive of the TML header.

5.1.5.TML Message Body

    Format of this is TBD.

5.2.TML Messages

5.2.1.Channel Close

   The channel close message is generated by the TML layer in response
   to a request to close a specified channel.  This message is sent to
   the peer TML layer to notify it of have the closure.  This provides
   information authority to the peer TML layer so it can either close its end of
   the channel also or drop any messages received by the upper layer
   protocol.

   ForCES protocol usage: This message may be sent from either the CE
   or the FE TML layer depending on decide which entity initiated the close.

5.2.2.Heartbeat

   A heartbeat message is exchanged between peer TML layers to
   communicate liveness of the entity generating the message.

   ForCES protocol usage: This message may be sent from either the
   CE to an FE or vice-versa.

5.2.3.Multicast Group Join Request

   The multicast group join request message is triggered by a request
   from the PL layer to join a specific multicast group. The peer TML
   layer on receiving this request creates the specified multicast
   group if it didnĂt previously exist.  It updates the membership of
   the group to include the entity requesting the join.

   ForCES protocol usage: Since only FEs may be set up the leaves in channels with.  That is outside its control.

   If a
   multicast group, this message FE-CE communication channel goes down or connectivity is sent lost,
   the following steps are taken by the TML layer:
   - FE TML attempts to reestablish the CE TML,
   due to a join request from communication channel
   - If the FE PL.

5.2.4.Multicast Group Join Response

   The multicast group join response message is generated by the TML
   Layer in response is unable to a join request message.

   ForCES protocol usage: If only FEs may be reestablish the leaves in a multicast
   group, this message is generated by channel (after some
     configured number of retries/timeout), it notifies the FE PL that
     the channel is down.
   - CE TML and sent waits for the channel to be reestablished (since only the
     FE
   TML, in response can reestablish it) for some configured timeout prior to
     notifying the join request message received from CE PL that the FE
   TML.

5.2.5.Multicast Group Leave Request

   The multicast group leave request message channel is triggered by a request
   from down.

   TBD: Since the PL layer to leave a specific multicast group. The peer TML
   layer on receiving this request removes is unaware of the specified multicast
   group number of channels etc.,
   what if only one channel goes down, but the entity requesting to leave other is up?  The TML
   layer notifies the only member PL layer of the
   group.  Else, which channel (control/data) is down?

   If an FE goes down and a standby FE exists for it, and it updates has
   communication channels set up with the membership of CE, the group CE PL may start to exclude
   use the
   entity requesting channels associated with the leave.

   ForCES protocol usage: standby FE.  This is not within
   the scope of TML itself, but falls in the scope of High
   Availability.

   TBD: If only FEs may an FE goes down and a standby FE exists for it, but it does
   not have communication channels set up with the CE, how should it be
   notified to set up the leaves channels?  This is not within the scope of
   TML itself, but falls in a multicast
   group, the scope of High Availability.  Do we need
   this message mentioned here?

4.9.Encapsulations Used

   There is sent by no further message encapsulation of control and data
   messages done at the FE TML to the CE TML, due to a
   leave request from the FE PL.

5.2.6.Multicast Group Leave Response layer.  The multicast group leave response message is PL generated control messages
   are transported as is by the TML
   Layer in response to a leave request message. layer. The ForCES protocol usage: If only FEs may be the leaves in control
   messages are encapsulated with a multicast
   group, this message TCP/IP header. [TBD: Encapsulation
   of data messages is generated by dependent on the CE TML and sent to protocol that will be used for
   the FE
   TML, in response to data channel (TCP is only for the leave request message received control channel). If DCCP is
   used for the data channel, then a DCCP header will be added.]

5.   TML Messaging

   There is no TML layer messaging.  TML only transports messages from
   the FE
   TML. PL layer.

6.   TML Interface to Upper layer Protocol
   ForCES TML interfaces with an upper layer protocol, the PL Layer and
   a lower layer protocol, TCP (in the case of TCP TML).  This section
   defines the interface to the upper layer protocol.  This interface
   should be used only as a guideline in implementing the API.
   Additionally, although the current interface is defined mainly as a
   synchronous interface, the interface may be implemented to be
   asynchronous if desired.

6.1.TML API Service Interface

6.1.1.TML Initialize

   status tmlInit(
     in  channelType,
     in  initAttributes)

   Input Parameters:
     channelType: control versus data channel
     initAttributes: initialization parameters

   Output Parameters:
     none

   Returns:
     status: SUCCESS
             Errors TBD

   Synopsis:
   tmlInit() enables establishment of communication channels on the
   entity that this API is invoked.  Optionally specifies attributes if
   any, for initialization. This call does not however result in the
   setup of any channels.

   ForCES Usage Model:
   In the case of ForCES which follows a client-server model, this API
   would be invoked on the CE, which functions as the server. It is
   invoked once for every class of TML channels on a per channel type
   basis (control channel versus data channel).  For example, say for
   control messaging, the CE communicates with five FEs using TCP TML
   and with another two FEs, using UDP TML.  tmlInit() will need to be
   invoked twice, once for the TCP TML attributes and once for the UDP
   TML attributes for the control channel setup with all of the FEs.
   The same holds true for the data channel setup in the above case.

   [TBD: TBD: Should tmlInit() be invoked by the PL Layer at all since
   we have now said the PL Layer is oblivious of the number of
   channels, their attributes etc.  Currently, we had specified that
   tmlInit() would specify the attributes for the channels to be setup.
   It seems like due to the change in the connection setup model this
   information should be fed to the TML Layer via some other means.
   The CE functions as the server, so the server should be up and
   running however prior to the clients (FEs) coming up and trying to
   connect to the server (CE).  The other option is that the mechanism
   to specify attributes for the channels is distinct from the process
   that uses those attributes to start up the server.  In that case,
   tmlInit() could be used mainly to start the server.]

6.1.2.TML Channel Open

   status tmlOpen(
     in  channelType,
     in  elementId,
     in  channelMode,
     in  channelAttributes,  ctrlChannelAttributes,
     in  eventHandlerCallBack,
     out channelDescriptor)  dataChannelAttributes,
     in  eventHandlerCallBack)

   Input Parameters:
     channelType: control channel or data channel
     elementId: Specific CE for which channel needs to be setup
     channelMode: unicast versus multicast
     channelAttributes:
     ctrlChannelAttributes: control channel establishment parameters
     dataChannelAttributes: data channel establishment parameters
     eventHandlerCallback: Callback function to be invoked on event
   generation

   Output Parameters:
     channelDescriptor: handle to communication channel
     none

   Returns:
     status: SUCCESS
             Errors TBD

   Synopsis:
   tmlOpen() results in a one or more communication channel of type channelType
   (control versus data), channels for control
   and data messaging being established with the specified elementId.
   It is up to the TML layer implementation whether to setup a single
   channel for both control and data messaging or distinct channels for
   each. The channel may be specified as unicast or multicast via
   channelMode.  This call may either trigger the establishment of the
   channel,
   channel(s), or if the channel is channel(s) are already established, it only
   results in a registration for that channel. the channel(s).  In either case, if
   successful,
   a handle status is returned to indicate successful
   creation/registration of the open channel is control and data channels.  No
   descriptors are returned via a channelDescriptor. to the PL layer since the TML layer
   maintains the mapping between the PL provided elementId and the
   descriptors it allocates. If this call triggers the establishment of
   the channel, control and data channels, the channel
   is channels are established using
   the channelAttributes parameter ctrlChannelAttributes and dataChannelAttributes parameters
   respectively, specified to the call.  Once the channel is channel(s) are setup
   (or if already setup prior to this call), the caller of this API is
   also capable of receiving TML events via the specified event
   handling callback function. If this call is invoked multiple times
   on a channel that has already been opened and registered, a return
   status of ALREADY_REGISTERED is returned, with no change to
   registration.

   ForCES Usage Model:
   In the case of ForCES which follows a client-server model, this API
   would be invoked on the FE by FE PL, which functions as the client.
   On each FE, it is invoked once per channel for both control and data channels
   that the FE wishes to setup with the CE.

   Notes:
   In the case of TCP TML, since there is no inherent support for
   multicast, regardless of the channelMode specified, the specified
   channel would be setup as a unicast channel; however, the unicast
   channel would be able to support pseudo multicast.  Hence, there is TCP TML
   has no need to set up a distinct channel channels for unicast and a distinct
   channel for multicast in
   communication; they are both mapped to the case of same TCP TML (as may be the case for
   UDP TML). connection.

6.1.3. TML Channel Close

   status tmlClose(
     in  channelDescriptor  elementId,
     in  mode)

   Input Parameters:
     channelDescriptor: handle to
     elementId: address of element with which communication channel is
   to be terminated
     mode: mode of operation for the close ű forced versus controlled

   Output Parameters:
     none

   Returns:
     status: SUCCESS
             Errors TBD

   Synopsis:
   Tears down/terminates specified communication channel. channels connecting to the
   specified elementId.  This API closes both control and data channels
   (regardless of whether they are implemented as a single channel or
   distinct channels in the TML layer); it is not possible to close
   just one of them.   No further CE PL ű FE PL messaging is possible
   after this.  If the mode is specified as controlled, current
   messages that are pending in the TML layer shall be sent, but no new
   messages shall be accepted by the TML layer on this channel.  In the
   forced model, mode, messages pending in the TML layer shall be discarded.
   Since the channel was terminated, a subsequent tmlOpen() will
   trigger establishment of the channel.

   ForCES Usage Model:
   This API may be invoked by either the CE or the FE.  If the FE PL
   invokes it, the FE TML sends it specifies a message to the CE TML informing it
   that the channel has been shutdown, which results in an upcall to ID for the CE PL.  This will result in elementId.  If the CE PL also shutting down its end
   of
   invokes it, it specifies an FE ID for the channel. elementId.

6.1.4.TML Channel Write

   status tmlWrite(
     in  channelDescriptor,  elementId,
     in  msgType,
     in  msg,
     in  msgSize,
     in  timeout,
     out bytesWritten)

   Input Parameters:
     channelDescriptor: handle to communication channel
     elementId: address of element to be written
   to to; may be a unicast,
   multicast or broadcast address
     msgType: control versus data message
     msg: message to be sent
     msgSize: size of message to be sent
     timeout: specifies blocking or non-blocking write.  Value of -1
   implies blocking write (wait forever), value of 0 implies non-
   blocking write

   Output Parameters:
     bytesWritten: number of bytes actually transmitted

   Returns:
     status: SUCCESS
             Errors TBD

   Synopsis:
   Sends message over to the address specified channel. by elementId.  If the
   specified
   channelDescriptor elementId is associated with a multicast group, the
   message will be sent to all members of the group.  This does not imply that  Similarly, if the
   elementId specified is a broadcast address, the message has actually been transmitted. is sent to
   all elements associated with the broadcast address.  The msgType
   parameter is used to specify whether the message is a control or
   data type of message.  Based on the message type, the TML will send
   the message over the appropriate channel.  The TML layer uses the
   address specified by elementId and the msgType to map to the
   appropriate channel to be used for sending the message.  The message
   is queued in the appropriate queue for transmission.  Once this call
   returns, the message buffer may be freed.  If TMLĂs message queues
   are full, the timeout will be used to determine how long to wait
   prior to returning; if the specified timeout expires, and no message
   buffer becomes available, the API returns with an error.

   ForCES Usage Model:
   This API may be invoked by either the FE PL or the CE PL.  If the FE
   PL invokes it, it specifies a CE ID for the elementId.  If the CE PL
   invokes it, it specifies an (unicast/multicast/broadcast) FE ID for
   the elementId.
   In the case of TCP TML since there is a single channel used for
   unicast, multicast and broadcast messaging, the same channel is used
   for sending messages regardless of the address specified.  In other
   cases where there are distinct channels for unicast versus
   multicast, the channel to be written to will differ based on the
   address specified.

6.1.5.TML Channel Read

   status tmlRead(
     in  channelDescriptor,  elementId,
     in  msgType,
     in  msgBuf,
     in  timeout,
     out bytesRead)

   Input Parameters:
     channelDescriptor: handle to communication channel
     elementId: address of element to be read from from; may be a unicast,
   multicast or broadcast address
     msgType: control versus data message
     msgBuf: buffer into which message is to be read
     timeout: specifies blocking or non-blocking read.  Value of -1
   implies blocking read (wait forever), value of 0 implies non-
   blocking read

   Output Parameters:
     bytesRead: number of bytes actually read

   Returns:
     status: SUCCESS
             Errors TBD
   Synopsis:
   Reads message on from the specified channel. address. The msgType parameter is
   used to specify whether the message to be read is a control or data
   type of message.  The TML layer uses the address specified by
   elementId and the msgType to map to the appropriate channel to be
   used for reading the message.  Once the message is copied into
   msgBuf specified by the call, the TML message buffer may be freed.
   If TMLĂs message queues are empty (no message is available), the
   timeout will be used to determine how long to wait prior to
   returning; if the specified timeout expires, and no message becomes
   available, the API returns with an error.
   If a non-blocking read is executed, the caller of the API is
   notified via an upcall when a message becomes available.
   TBD:

   ForCES Usage Model:
   This API may be invoked by either the CE or the FE.  If the channelDescriptor specified is associated with FE PL
   invokes it, it specifies a
   multicast group, CE ID for the elementId.  If the CE PL
   invokes it, it should be considered invalid specifies an (unicast/multicast/broadcast) FE ID for
   the elementId.

   In the case of TCP TML since multicast there is
   only supported on a write; a read single channel used for
   unicast, multicast and broadcast messaging, the same channel is always associated with used
   for reading messages regardless of the address specified.  In other
   cases where there are distinct channels for unicast versus
   multicast, the channel to be read from a single channel. will differ based on the
   address specified.

6.1.6.TML Multicast Group Join

   status tmlMulticastGroupJoin(
     in  groupId,
     in  groupAttributes)

   Input Parameters:
     groupId: address of multicast group to join
     groupAttributes: Attributes attributes associated with the multicast group to
   be joined

   Output Parameters:
     none

   Returns:
     status: SUCCESS
             Errors TBD

   Synopsis:

   Joins the specified multicast group specified by groupId as leaf node in the
   group. If
   this is the first join request being received for this group, it
   results in the creation of the group and the allocation of a
   groupDescriptor (which is equivalent to a channelDescriptor). Once a member of this group, the entity calling this API will
   be capable of receiving messages addressed to this multicast group.

   ForCES Usage Model:
   If
   The TML layer on each end (CE/FE) maintains the intent mapping between the
   PL layer multicast address and the descriptors.  The TML layer on
   the element which is the root of the multicast updates the set of
   elements that only FEs can be are members of a multicast the group specified by groupId.

   ForCES Usage Model:
   This API would be invoked on both the CE and the FE.  Initially, the
   intent is to only support FE multicast.  In such a CE can be case. on the FE
   the source of a multicast, this API would be is invoked once the PL layer on the FE that wishes receives a request
   from the PL layer on the CE to join a specified multicast group. On
   the CE it is invoked after the FE has successfully joined the
   multicast group.

6.1.7.TML Multicast Group Leave

   status tmlMulticastGroupLeave(
     in  groupAttributes)  groupId)

   Input Parameters:
     groupAttributes: Attributes associated with the
     groupId: address of multicast group to leave

   Output Parameters:
     none

   Returns:
     status: SUCCESS
             Errors TBD

   Synopsis:
   Leaves the specified multicast group specified by groupId it had previously
   joined. Once an entity is not a member of the multicast group, it is
   no longer capable of receiving messages addressed to group.  If this leave
   request   The
   TML layer on each end (CE/FE) updates the mapping between the PL
   layer multicast address and the descriptors.  The TML layer on the
   element which is associated with the only member root of the multicast updates the set of
   elements that are members of the group, the
   multicast group is removed, and its associated groupDescriptor
   invalidated. specified by groupId.

   ForCES Usage Model:
   If the intention is that only FEs can
   This API would be members of a multicast
   group invoked on both the CE and the FE.  Initially, the
   intent is to only support FE multicast.  In such a CE can be case, on the FE
   the source of a multicast, this API would
   be is invoked once the PL layer on the FE that wishes receives a request
   from the PL layer on the CE to leave a group specified multicast group. On
   the CE it had previously
   joined. is invoked after the FE has successfully left the
   multicast group.

6.2.Protocol Initialization and Shutdown Model

   In order for the peer PL Layers to communicate, the control and data
   channels must be setup.  This section defines a model for the setup
   of the channels, using the TML interface defined above. In this
   model, the peer TML Layers may establish the control and data
   channels between the FE FE and the CE without the involvement of the PL
   Layers, or if desired, the PL Layer may trigger the setup of the
   channels; this is left as an implementation decision.  Both modes
   may also be supported within an implementation.

6.2.1.Protocol Initialization

   The control channel must be established between the FE TML and the
   CE TML for establishment of association to proceed.  This channel
   will be used for messages related to the association setup and
   capability query.  The data channel must be established no later
   than the response from the FE to the CE Topology query message.  The
   following are the significant aspects associated with channel setup:
   - A single call by the PL layer sets up the communication channels
     for both control and data messaging to a specific FE.  The call
     specifies Unicast CE Id and attributes for control and data
     channels.
   - It is up to the TML layer whether to set up a single channel for
     both control and data or distinct channels for control and data
   - TML sets up the appropriate channels and allocates required
     descriptors for the channels.  TML layer maintains a mapping
     between the Unicast FE/CE Id and the CE without the involvement of channel descriptors and
     channel type (control versus data) it creates.
   - There is no need for channel descriptors to be returned to the PL
   Layers,
     layer at either the FE or if desired, the CE.  PL Layer may trigger the setup of the
   channels; this is left as an implementation decision.  Both modes
   may also be supported within an implementation.

6.2.1.Protocol Initialization

   The control channel must be established between only uses the FE TML Unicast
     FE/CE Id for read/write calls and specifies the
   CE TML for establishment type of association message
     (control versus data) to proceed.  This channel
   will be used for messages related to read/written.
   - If only one of the association channels is setup and
   capability query.  The data channel must be established no later
   than successfully, the response from the FE TML layer
     will have to the CE Topology query message. return appropriate status that specifies which
     channel is setup successfully and which isnĂt.

   Figure 4 illustrates the initialization model where the PL layer via
   an interface provided by the TML Layer, triggers the setup of the
   control and data channels.

        FE

     FE1 PL           FE           FE1 TML                  CE TML          CE PL
           |               |                       |               | \
        /  |               |                       | tmlInit(Cc) TBD:tmlInit() | |
   FE   |  |               |                       |<--------------| > CE Init/
 Init/  <  |               |                       | tmlInit(Cd)               | | Bootup
 Bootup |  |               |                       |<--------------|                       |               | /
        \  |               |                       |               |
           | tmlOpen(Cc) tmlOpen(CeId) |                       |               |
           |-------------->|                       |               | \
           |               |TCP CtrlChan(Cc)               |CtrlChan(Cc) Setup     |               | |
           |               |~~~~~~~~~~~~~~~~~~~~~~>|               | | Setup control
           |               |CtrlChann(Cc) Setup Rsp|               |~~~~~~~~~~~~~~~~~~~~~~>|               | | > channel if not
           |               |<~~~~~~~~~~~~~~~~~~~~~~|               |                FeId . [CcDes<ctrl>]  | already |  <-- CcDes setup. TML
           |               |                       |               | setup
           |tmlEvent(CcUp) > has mapping
           |               |CtrlChan(Cc) Setup Rsp |                       |tmlEvent(CcUp)               | /
           |<--.--.--.--.--|                       |--.--.--.--.-->| | from PL Layer
           |               |<~~~~~~~~~~~~~~~~~~~~~~|               | |     CcDes Id to channel
           |        CeId . [CcDes<ctrl>]          | tmlOpen(Cd)               | | descriptor and
           |
           |-------------->|                                       |               | \ / channel type.
           |               |                       |               |
           |               |DataChan(Cd) Setup     |               |TCP DataChann(Cd) Setup|               | | Setup data
           |               |~~~~~~~~~~~~~~~~~~~~~~>|               | | channel if not channel if not
           |               |                FeId . [CcDes<ctrl>,  | | setup. TML
           |               |                         CdDes<data>]  | | updates
           |               |                       |               | > mapping from
           |               |DataChan(Cd) Setup Rsp |               | | PL Layer
           |               |<~~~~~~~~~~~~~~~~~~~~~~|               | | Id to channel
           |        CeId . [CdDes<data>]          |               | | descriptor and
           |               |                       |               |DataChann(Cd) Setup Rsp|               | > / channel if not type.
           |               |               |<~~~~~~~~~~~~~~~~~~~~~~|                       |               | already
           |  <-- CdDes status   |                       |               |
           | setup
           |tmlEvent(CdUp)               |                       |tmlEvent(CdUp)                       | /               |
           |tmlEvent(ChUp) |                       |tmlEvent(ChUp) |
           |<--.--.--.--.--|                       |--.--.--.--.-->|
           |               |                       |     CdDes               |
           |               |   Asso Setup Req      |               |
           |---------------|-----------------------|-------------->|
           |               |   Asso Setup Rsp      |               |
           |<--------------|-----------------------|---------------|
           |               |                       |               |
           |               |    Capability Query   |               |
           |<--------------|-----------------------|---------------|
           |               | Capability Query Rsp  |               |
           |---------------|-----------------------|-------------->|
           |               |                       |               |
           |               |   Topology Query      |               |
           |<--------------|-----------------------|---------------|
           |               | Topology Query Rsp    |               |
           |---------------|-----------------------|-------------->|
           |               |                       |               |
           |               |STEADY STATE OPERATION |               |
           |<--------------|-----------------------|-------------->|
           |               |                       |               |
Legend:
 PL  --------> PL : Protocol layer messaging
 PL  --------> TML: TML API
 TML ========> TML: Messaging between TML Layers
 TML --.--.--> PL : Events/Notifications/Upcalls
 TML ~~~~~~~~> TML: Internal protocol communication

                      Figure 4: Protocol Initialization (Channel Setup)

6.2.2.Protocol Shutdown

The control channel teardown must occur only after the association
teardown has occurred.  The data channel teardown may occur no earlier
than the association teardown.

The PL Layer may completely shutdown a channel control and data channels via invocation of
the tmlClose() API.  When the PL layer shuts down a channel, the channel is channels, the
channels are torn down; hence ForCES messaging between the CE and FE is
no longer possible over that channel. those channels.  A tmlClose() results in both
control and data channels (regardless of whether they are implemented
as a single channel or distinct channels in the TML layer) being
shutdown; it is not possible to close just one of them. A subsequent
tmlOpen() triggers establishment of the channel.  This scenario  The channel(s) may be
shutdown by either the FE or the CE. If an FE initiates the shutdown,
it specifies the CE Id associated with the channel(s) to be shutdown.
If a CE initiates the shutdown, it specifies the FE Id associated with
the channel(s) to be shutdown.  A channel shutdown by the FE is
illustrated in Figure
5. 5 and a channel shutdown by the CE is illustrated
in Figure 6.

        FE PL           FE TML                  CE TML          CE PL
           |               |                       |               |
           |               |STEADY STATE OPERATION |               |
           |<--------------|-----------------------|-------------->|
           |               | Config Request        |               |
           |<--------------|-----------------------|---------------|
           |               | Config Response       |               |
           |---------------|-----------------------|-------------->|
           |               |                       |               |
           |               | Association Teardown  |               |
           |<--------------|-----------------------|---------------|
           |               |                       |               |
           |               |                       |               |
           |tmlClose(CdDes)|                       |               | \
           |-------------->|                       |               |
           |tmlClose(CeId) | Data Channel
           |               |DataChan(Cd) Close                       |               | | teardown; it no FE initiated:
           |-------------->|                       |               |======================>|               | > longer exists.
           |<-- Cd Close OK|                       |tmlCloseUpcall | | PL Layer can no
           |               |                       |--.--.--.--.-->| | longer use Cd; FE specifies CE
           | <-- status    |                       |               | | TML msging also Id associated
           |               |                       |               | / not possible.
           |               |                       |               |
           |tmlClose(CcDes)|                       |               | \
           |-------------->|                       |               | | Control Channel
           |               |CtrlChan(Cc) Close     |               | | teardown; it no
           |               |======================>|               | > longer exists.
           |<-- Cc Close OK|                       |tmlCloseUpcall | | with channel.

Legend:
 PL  --------> PL : Protocol layer messaging
 PL  --------> TML: TML API
 TML --.--.--> PL : Events/Notifications/Upcalls
 TML ~~~~~~~~> TML: Internal protocol communication

                       Figure 5: Protocol Shutdown: FE Initiated

        FE PL           FE TML                  CE TML          CE PL Layer can no
           |
           |                       |--.--.--.--.-->|               | longer use Cc;                       |               |
           |               |STEADY STATE OPERATION |               | TML msging also
           |<--------------|-----------------------|-------------->|
           |               | Config Request        |               | / not possible.
           ~               ~                       ~               ~
           ~               ~                       ~               ~
           |<--------------|-----------------------|---------------|
           |               | Config Response       |               |
           |---------------|-----------------------|-------------->|
           | tmlOpen(Cc)               |                       |               | \
           |-------------->|
           |               | Association Teardown  | Subsequent open               |               |TCP CtrlChan(Cc) Setup
           |<--------------|-----------------------|---------------|
           |               |                       | needs to launch               |               |~~~~~~~~~~~~~~~~~~~~~~>|
           | > setup of the               |               |CtrlChann(Cc) Setup Rsp|                       |               | channel since \
           |               |<~~~~~~~~~~~~~~~~~~~~~~|               |                       |tmlClose(FeId) | shutdown had |   <-- CcDes CE initiated:
           |               |                       |<--------------| > FE specifies CE
           | <-- status    | torn the
           |tmlEvent(CcUp)                       |                       |tmlEvent(CcUp) status -->    | | channel down
           |<--.--.--.--.--|                       |--.--.--.--.-->| / Id associated
           |               |                       |     CcDes               | / with channel.

Legend:
 PL  --------> PL : Protocol layer messaging
 PL  --------> TML: TML API
 TML ========> TML: Messaging between TML Layers
 TML --.--.--> PL : Events/Notifications/Upcalls
 TML ~~~~~~~~> TML: Internal protocol communication

                       Figure 5: 6: Protocol Shutdown Shutdown: CE Initiated

6.3.Multicast Model

   The TML layer provides support for multicast.  In the ForCES model,
   support is required to multicast to the FEs from a CE; in this case,
   the CE is the source or root of the multicast and the FEs are the
   leaves.

   Support for multicast requires that a channel for supporting
   multicast be opened between an FE and the CE.  In the case of TCP
   TML, the same channel is used for both unicast and multicast
   messaging since multicast mode is simulated using unicast channels
   in this case. Once the channel is open, FEs a CE may request FEs to join
   and leave specified multicast groups.  The first ˘multicast  Multicast support is CE-
   initiated.  FEs can join a multicast group join÷
   request from an FE only if the CE requests
   them to join the group.  TML maintains mapping between PL layer IDs
   and channel descriptors for multicast.  The following is the
   significant steps for adding or removing members from a multicast
   group:

   - CE PL communicates with FE PL for requesting the FE to join or
     leave a specific multicast group.
   - FE PL informs FE TML regarding the join or leave request.
   - FE TML updates the multicast group results in information.  It updates the
     mapping between the FE Multicast Id and the channel descriptor to
     be used for multicast for that FE.  This mapping may be from
     [Multicast FE Id] . [FE Id] . [Channel descriptor] or directly
     from [Multicast FE Id] . [Channel descriptor].  This is
     implementation dependent.
   - FE PL responds to CE PL informing it of the creation status of the join or
     leave request.
   - If the join or leave request was successful, CE PL informs CETML
     regarding the update to the multicast group membership.
   - CE TML updates the multicast group membership.  It updates the
     mapping between the FE Multicast Id and an allocation the set of a group descriptor
   (which is similar channel
     descriptors to a be used for multicast to the FEs that are members
     of this group.  This mapping may be from [Multicast FE Id] . [Set
     of FE Ids] . [Set of channel descriptors] or directly from
     [Multicast FE Id] . [Set of channel descriptor) descriptors].  This is
     implementation dependent.
   - There is no need for any descriptors to be returned to the PL
     layer at either the group.  The
   ˘multicast group leave÷ request from an FE to or the CE on a multicast
   group with just that one member results in CE.  PL Layer only uses the group being removed
     Multicast FE Id for write calls and specifies the descriptor deallocated. type of message
     (control versus data) to be written.

   A tmlWrite() on a unicast channel
   descriptor FE Id results in a unicast message being
   sent to the FE associated with the channel.  A tmlWrite() on a group descriptor
   multicast FE Id results in multicast messaging. Figure 6 illustrates a Figures 7 and 8
   illustrate multicast
   scenario scenarios with 2 FEs, FE1 and FE2.  In Figure
   7, the first case, CE requests FE1 joins to join a multicast group.  In the second case,  Although not
   shown as a separate figure, if FE2 joins were to join the same multicast group, and leaves the
   join procedure would be the same as in Figure 7; it would result in
   the multicast group some time later. membership being updated at the TML layer on the
   CE to include FE2 in the group.  In Figure 8, the CE requests FE1 to
   leave the multicast group, thus resulting in only FE2 being a member
   of the multicast group.

   Multicast Scenario with FE1: FE1 joining group: New group created

       FE1 PL        FE1 TML              CE TML           CE PL
         |               |                   |               |
         |               |STEADY STATE OPERATION |               | \ Channel for
           |<--------------|-----------------------|-------------->| > multicast msgs
           |               |                       |               | | already exists
           |               |                       |               | /  via tmlOpen()
           ~               ~                       ~               ~
           ~               ~                       ~               ~
           |tmlMcstGrpJoin               |                   |               | \
           |-------------->|
         |               | | FE1 joins
           |               |Mcst Group               MC Grp Join Req (McId)              | |
         |<--------------|-------------------|---------------| | Multicast                                                                  st           |               |======================>| CE:PL Level multicast group
[TML     | > Group. 1 join tmlJoin(McId) |                   |                       |tmlJoinUpcall               | | join request for
           |               |                       |--.--.--.--.-->| | group, hence sent to each
updates  |-------------->|                   |               |Mcst Group Join Rsp    |grp X={FE1}               | | FE:PL that needs to be part
MC grp with grpDes
           |               |<======================|               | / X created   |  <-- Join OK        McId = {FE1_ChDes}         |               | > of a multicast group, McId,
info]    |               |                   |               | | where McId specifies a
         |  <-- status   |                       |tmlWrite(grp X)| \                   |               |                       |<--------------| | Write to multicast group Id at the
         |               |                   |               | > Multicast Grp.
           ~               ~                       ~               ~ | Msg sent to FE1
           ~               ~                       ~               ~ / only

   Multicast Scenario with FE2:
        FE2 PL          FE2 TML                  CE TML          CE PL layer.
         |              MC Grp Join Rsp (status)             | |
         |---------------|-------------------|-------------->| /
         |               |                   |               |STEADY STATE OPERATION               |
         |
           |<--------------|-----------------------|-------------->|               |                   |               | \
         |               |                   |tmlJoin(McId)  | | TML updates multicast
         |
           ~               ~                       ~               ~
           ~               ~                       ~               ~
           |tmlMcstGrpJoin               |                   |<--------------| | group membership.  PL is
         | \
           |-------------->|               |              McId = {FE1_ChDes}   | > only aware of PL layer
         | FE2 joins               |               |Mcst Group Join Req                   |               | > Multicast |               |======================>| multicast group Id, that is,
         |               | Group. Grp                   |  status -->   |                       |tmlJoinUpcall | McId]
          | already exists.               |                   |                       |--.--.--.--.-->|               | /

                       Figure 7: Multicast Support: FE1 Joins Group members
           |               |Mcst

   Multicast Scenario with FE1 leaving group: Group Join Rsp    |grp X={FE1,FE2}| membership updated
   to exclude FE1

        FE1 PL        FE1 TML              CE TML           CE PL
         | updated.               |               |<======================|                   | /               |  <-- Join OK
         |               |                   |               | \
         |               MC Grp Leave Req (McId, FE1)        | |
         |<--------------|-------------------|---------------| | CE:PL Level multicast group
[TML     |                       |tmlWrite(grp X)| \ tmlLeave(McId)|                   |               |                       |<--------------| | Write leave request sent to FE1:PL
removes  |-------------->|                   |               | | that needs to be removed
MC grp   |        McId = {}                  |               | > Multicast Grp. from multicast group, McId,
info]    |               |                   |               | | Msg sent to FE1
           ~               ~                       ~               ~ / and FE2.
           ~               ~                       ~               ~ where McId specifies a
         |  <-- status   |                   |               |
           |tmlMcstGrpLeave| | multicast group Id at the
         | \
           |-------------->|               |                   |               | FE2 leaves |               |Mcst Group PL layer.
         |              MC Grp Leave Req Rsp (status)            | | > Multicast
         |---------------|-------------------|-------------->| /
         |               |======================>|               |                   | Group. Grp               |
         |                       |tmlLeaveUpcall               |                   | membership               | \
         |                       |--.--.--.--.-->|               | updated.                   |tmlLeave(McId) |               |Mcst Group Leave Rsp   |grp X={FE1} | TML removes FE1 from
         |               |               |<======================|                   |<--------------| | / multicast group McId.
         | <-- Leave OK               |              McId = {FE2_ChDes}   | > That leaves only FE2
         |
           ~               ~                       ~               ~
           ~               ~                       ~               ~               |                   |               | | in the group.
         |               |                       |tmlWrite(grp X)| \                   |  status -->   |                       |<--------------| | Write to
         |               |                   |               | > /

                       Figure 8: Multicast Grp.
           ~               ~                       ~               ~ | Msg sent to Support: FE1
           ~               ~                       ~               ~ /  only

Legend:
 PL  --------> PL : Protocol Leaves Group

6.4.Broadcast Model

   The TML layer provides support for broadcast.  In the ForCES model,
   support is required to broadcast to the FEs from a CE.  The
   broadcast model is just a special case of multicast, where all FEs
   are included.  TBD: Is there anything else to be added/discussed
   here.  Join/Leave messaging
 PL  --------> TML: TML API
 TML ========> TML: Messaging between TML Layers
 TML --.--.--> PL : Events/Notifications/Upcalls
 TML ~~~~~~~~> TML: Internal protocol communication

                       Figure 6: Support also used for Multicast broadcast?  ForCES draft
   also talks of CE broadcast and NE broadcast.

7.   Security Considerations

   If the CE or FE are in a single box and network operator is running
   under a secured environment then it is up to the network
   administrator to turn off all the security functions. This is
   configured during the pre-association phase of the protocol.

   When the CEs, FEs are running over IP networks or in an insecure
   environment, this TML uses TLS [8] to provide security. The security
   association between the CEs and FEs MUST be established before any
   ForCES protocol messages are exchanged between the CEs and FEs.

7.1.TLS Usage for this TML
   [TBD: Update based on inclusion of IPSec for security.]

   This section is applicable for CE or FE endpoints that use the TML
   with TLS [8] to secure communication.

   Since CE is master and FEs are slaves, the FEs are TLS clients and
   CEs are TLS server. The endpoints that implement TLS MUST perform
   mutual authentication during TLS session establishment process. CE
   must request certificate from FE and FE needs to pass the requested
   information.

   We recommend ˘TLS-RSA-with-AES-128-CBC-SHA÷ cipher suite, but CE or
   FE may negotiate other TLS cipher suites. TLS must be used for all
   control channel messages. TLS is optional for the data channel since
   data channel packets are not encrypted externally to the NE.

   This TML uses TLS to provide security when the NE is in an insecure
   environment. This is because IPsec provides less flexibility when
   configuring trust anchors since it is transparent to the application
   and use of Port identifiers is prohibited within IKE Phase 1. This
   provides restriction for IPsec to configure trust anchors for each
   application separately and policy configuration is common for all
   applications.

8.   IANA Considerations

   The TCP/IP TML needs to have a two one well-defined TCP port numbers, number,
   which needs to be assigned by IANA.  The control port is referred to
   as the TCP_TML_CONTROL_PORT.  The  [TBD: Add information for data channel
   port is referred to as if required based on the
   TCP TML DATA PORT. protocol for the data channel.]

9.   Manageability

   TBD

10.    References
9.1.Normative
10.1.Normative References

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

  2. S. Bradner, "Keywords for use in RFCs to Indicate Requirement
     Levels", RFC2119 (BCP), IETF, March 1997.

  3. Khosravi, et al., ÷Requirements for Separation of IP Control and
     Forwarding÷, RFC 3654, November 2003.

  4. L. Yang, et al., ÷ ForCES Architectural Framework÷, RFC 3746,
     April 2004.

  5. L. Yang, et al., ÷ ForCES Forwarding Element Functional Model÷,
     work in progress÷, July 2004,<draft-ietf-forces-model-03.txt>

  6. A. Audu, et al., ˘ Forwarding and Control Element protocol (FACT)"
     draft-gopal-forces-fact-06.txt, February 2004.

  7. A. Doria, et al., ÷ForCES protocol specification÷, draft-ietf-
     forces-protocol-00.txt, September 2004.

9.2.Informative

10.2.Informative References

  8. Dierks, T., Allen, C., Treese, W., Karlton, P., Freier, A. and P.
     Kocher, "The TLS Protocol Version 1.0", RFC 2246, January 1999.

  9. Jungmaier, A., Rescorla, E. and M. Tuexen, "Transport Layer
     Security over Stream Control Transmission Protocol", RFC 3436,
     December 2002.

  10.  R. Stewart, et al., ˘Stream Control Transmission Protocol
     (SCTP)÷, RFC 2960, October 2000.

  11.  E. Kohler, M. Handley, S. Floyd, J. Padhye, ˘Datagram
     Congestion Control Protocol (DCCP)÷, draft-ietf-dccp-spec-04.txt,
     June 2003.

  12.  Floyd, S., ˘Congestion Control Principles÷, RFC 2914, September
     2000.

  13.  A. Doria, F. Hellstrand, K. Sundell, T. Worster, ˘General
     Switch Management Protocol (GSMP) V3÷, RFC 3292, June 2002.

  14.  H. Balakrishnan, et al. ˘The Congestion Manager÷, RFC 3124,
     June 2001.

  15.  H. Khosravi, S. Lakkavali, ˘Analysis of protocol design issues
     for open standards based programmable routers and switches÷
     [SoftCOM 2004]

  16.  S. Lakkavali, H. Khosravi, ˘ForCES protocol design analysis for
     protection against DoS attacks÷ [ICCCN 2004]

10. Acknowledgments

11.    Acknowledgments

12.    Authors' Addresses

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

   Furquan Ansari
   101 Crawfords Corner Road
   Holmdel, NJ 07733
   USA
   Phone: +1 732-949-5249
   Email: furquan@lucent.com

   Jon Maloy
   Ericsson Research Canada
   8400 Boul Decarie
   Ville Mont-Royal, Quebec H4P 2N2
   Canada
   Phone: 1-514-345-7900
   Email: jon.maloy@ericsson.com

   Shuchi Chawla
   Intel
   2111 NE 25th Avenue
   Hillsboro, OR 97124
   Phone: 1-503-712-4539
   Email: shuchi.chawla@intel.com

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