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Network Working Group                                   J. Lang, Editor
Internet Draft                                         Calient Networks
Category: Standards Track                                 November 2002
Expires: May 2003


                     Link Management Protocol (LMP)

                      draft-ietf-ccamp-lmp-07.txt

 Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

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

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

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

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

 Abstract

   For scalability purposes, multiple data links can be combined to
   form a single traffic engineering (TE) link.  Furthermore, the
   management of TE links is not restricted to in-band messaging, but
   instead can be done using out-of-band techniques.  This document
   specifies a link management protocol (LMP) that runs between
   neighboring nodes and is used to manage TE links.  Specifically, LMP
   will be used to maintain control channel connectivity, verify the
   physical connectivity of the data links, correlate the link property
   information, suppress downstream alarms, and localize link failures
   for protection/restoration purposes in multiple kinds of networks.










J. Lang, Editor            Standards Track                   [Page 1]


Internet Draft       draft-ietf-ccamp-lmp-07.txt        November 2002

Table of Contents
   1  Introduction ................................................   5
      1.1 Terminology .............................................   5
   2  LMP Overview ................................................   8
   3  Control Channel Management ..................................  10
      3.1 Parameter Negotiation ...................................  11
      3.2 Hello Protocol ..........................................  12
          3.2.1  Hello Parameter Negotiation ......................  12
          3.2.2  Fast Keep-alive ..................................  13
          3.2.3  Control Channel Down .............................  13
          3.2.4  Degraded State ...................................  14
   4  Link Property Correlation ...................................  14
   5  Verifying Link Connectivity .................................  16
      5.1 Example of Link Connectivity Verification ...............  18
   6  Fault Management ............................................  20
      6.1 Fault Detection .........................................  20
      6.2 Fault Localization Procedure ............................  20
      6.3 Examples of Fault Localization ..........................  21
      6.4 Channel Activation Indication ...........................  22
      6.5 Channel Deactivation Indication .........................  22
   7  Message_Id Usage ............................................  23
   8  Graceful Restart ............................................  24
   9  Addressing ..................................................  25
   10 Exponential Back-off Procedures .............................  25
      10.1 Operation...............................................  25
      10.2 Retransmission Algorithm ...............................  26
   11 LMP Finite State Machines ...................................  27
      11.1 Control Channel FSM ....................................  27
          11.1.1  Control Channel States ..........................  27
          11.1.2  Control Channel Events ..........................  28
          11.1.3  Control Channel FSM Description .................  30
      11.2 TE Link FSM ............................................  31
          11.2.1  TE Link States ..................................  31
          11.2.2  TE Link Events ..................................  31
          11.2.3  TE Link FSM Description .........................  32
      11.3 Data Link FSM ..........................................  32
          11.3.1  Data Link States ................................  33
          11.3.2  Data Link Events ................................  33
          11.3.3  Active Data Link FSM Description ................  35
          11.3.4  Passive Data Link FSM Description ...............  36
   12 LMP Message Formats .........................................  37
      12.1 Common Header ..........................................  37
      12.2 LMP Object Format ......................................  38
      12.3 Parameter Negotiation Messages .........................  39
      12.4 Hello Message ..........................................  41
      12.5 Link Verification Messages .............................  41
      12.6 Link Summary Messages ..................................  45
      12.7 Fault Management Messages ..............................  46
   13 LMP Object Definitions ......................................  48
   14 Intellectual Property Considerations ........................  66
   15 References ..................................................  66
   16 Security Considerations .....................................  67

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      16.1 Security Requirements ..................................  67
      16.2 Security Mechanisms ....................................  68
   17 IANA Considerations .........................................  69
   18 Acknowledgements ............................................  72
   19 Contributors ................................................  73
   20 Contact Address .............................................  73
   21 Full Copyright Statement ....................................  74














































J. Lang, Editor            Standards Track                   [Page 3]


Internet Draft       draft-ietf-ccamp-lmp-07.txt        November 2002

   [Editor's note: "Changes from previous version" notes can be removed
   prior to publication as an RFC.]

   Changes from previous version:

   o  Editorial changes.
   o  Updated Error Codes.














































J. Lang, Editor            Standards Track                   [Page 4]


Internet Draft       draft-ietf-ccamp-lmp-07.txt        November 2002

1. Introduction

   Networks are being developed with routers, switches, crossconnects,
   DWDM systems, and add-drop multiplexors (ADMs) that use a common
   control plane [e.g., Generalized MPLS (GMPLS)] to dynamically
   allocate resources and to provide network survivability using
   protection and restoration techniques.  A pair of nodes may have
   thousands of interconnects, where each interconnect may consist of
   multiple data links when multiplexing (e.g., Frame Relay DLCIs at
   Layer 2, or TDM slots or WDM wavelengths at Layer 1) is used.  For
   scalability purposes, multiple data links may be combined into a
   single traffic-engineering (TE) link.

   To enable communication between nodes for routing, signaling, and
   link management, there must be a pair of IP interfaces that are
   mutually reachable.  We call such a pair of interfaces a control
   channel.  Note that "mutually reachable" does not imply that these
   two interfaces are (directly) connected by an IP link; there may be
   an IP network between the two.  Furthermore, the interface over
   which the control messages are sent/received may not be the same
   interface over which the data flows.  This document specifies a link
   management protocol (LMP) that runs between neighboring nodes and is
   used to manage TE links and verify reachability of the control
   channel.

   In GMPLS, the control channels between two adjacent nodes are no
   longer required to use the same physical medium as the data links
   between those nodes.  For example, a control channel could use a
   separate virtual circuit, wavelength, fiber, Ethernet link, an IP
   tunnel routed over a separate management network, or a multi-hop IP
   network.  A consequence of allowing the control channel(s) between
   two nodes to be logically or physically diverse from the associated
   data links is that the health of a control channel does not
   necessarily correlate to the health of the data links, and vice-
   versa.  Therefore, a clean separation between the fate of the
   control channel and data links must be made.  New mechanisms must be
   developed to manage the data links, both in terms of link
   provisioning and fault management.

   Among the tasks that LMP accomplishes is checking that the grouping
   of links into TE links as well as the properties of those links are
   the same at both end points of the links -- this is called "link
   property correlation".  Also, LMP can communicate these link
   properties to the IGP module, which can then announce them to other
   nodes in the network.  LMP can also tell the signaling module the
   mapping between TE links and control channels.  Thus, LMP performs a
   valuable "glue" function in the control plane.

   Note that while the existence of the control network (single or
   multi-hop) is necessary for enabling communication, it is by no
   means sufficient.  For example, if the two interfaces are separated
   by an IP network, faults in the IP network may result in the lack of

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   an IP path from one interface to another, and therefore in an
   interruption of communication between the two interfaces.  On the
   other hand, not every failure in the control network affects a given
   control channel, hence the need for establishing and managing
   control channels.

   For the purposes of this document, a data link may be considered by
   each node that it terminates on as either a 'port' or a 'component
   link' depending on the multiplexing capability of the endpoint on
   that link; component links are multiplex capable, whereas ports are
   not multiplex capable.  This distinction is important since the
   management of such links (including, for example, resource
   allocation, label assignment, and their physical verification) is
   different based on their multiplexing capability.  For example, a
   Frame Relay switch is able to demultiplex an interface into virtual
   circuits based on DLCIs; similarly, a SONET crossconnect with OC-192
   interfaces may be able to demultiplex the OC-192 stream into four
   OC-48 streams.  If multiple interfaces are grouped together into a
   single TE link using link bundling [BUNDLE], then the link resources
   must be identified using three levels: Link_Id, component interface
   Id, and label identifying virtual circuit, timeslot, etc.  Resource
   allocation happens at the lowest level (labels), but physical
   connectivity happens at the component link level.  As another
   example, consider the case where an optical switch (e.g., PXC)
   transparently switches OC-192 lightpaths.  If multiple interfaces
   are once again grouped together into a single TE link, then link
   bundling [BUNDLE] is not required and only two levels of
   identification are required: Link_Id and Port_Id.  In this case,
   both resource allocation and physical connectivity happen at the
   lowest level (i.e. port level).

   To ensure interworking between data links with different
   multiplexing capabilities, LMP capable devices SHOULD allow sub-
   channels of a component link to be locally configured as (logical)
   data links.  For example, if a Router with 4 OC-48 interfaces is
   connected through a 4:1 MUX to a cross-connect with OC-192
   interfaces, the cross-connect SHOULD be able to configure each sub-
   channel (e.g., STS-48c SPE if the 4:1 MUX is a SONET MUX) as a data
   link.

   LMP is designed to support aggregation of one or more data links
   into a TE link (either ports into TE links, or component links into
   TE links).  The purpose of forming a TE link is to group/map the
   information about certain physical resources (and their properties)
   into the information that is used by Constrained SPF for the purpose
   of path computation, and by GMPLS signaling.

1.1. Terminology

   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 [RFC2119].

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   The reader is assumed to be familiar with the terminology in [GMPLS-
   SIG], [GMPLS-RTG], and [BUNDLE].

   Bundled Link:

      As defined in [BUNDLE], a bundled link is a TE link such that for
      the purpose of GMPLS signaling a combination of <link identifier,
      label> is not sufficient to unambiguously identify the
      appropriate resources used by an LSP.  A bundled link is composed
      of two or more component links.

   Control Channel:

      A control channel is a pair of mutually reachable interfaces that
      are used to enable communication between nodes for routing,
      signaling, and link management.

   Component Link:

      As defined in [BUNDLE], a component link is a subset of resources
      of a TE Link such that (a) the partition is minimal, and (b)
      within each subset a label is sufficient to unambiguously
      identify the appropriate resources used by an LSP.

   Data Link:

      A data link is a pair of interfaces that are used to transfer
      user data.  Note that in GMPLS, the control channel(s) between
      two adjacent nodes are no longer required to use the same
      physical medium as the data links between those nodes.

   Link Property Correlation:

      This is a procedure to correlate the local and remote properties
      of a TE link.

   Multiplex Capability:

      The ability to multiplex/demultiplex a data stream into sub-rate
      streams for switching purposes.

   Node_Id:

       For a node running OSPF, the LMP Node_Id is the same as the
       address contained in the OSPF Router Address TLV.  For a node
       running IS-IS and advertising the TE Router ID TLV, the Node_Id
       is the same as the advertised Router ID.

   Port:

      An interface that terminates a data link.

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   TE Link:
      As defined in [GMPLS-RTG], a TE link is a logical construct that
      represents a way to group/map the information about certain
      physical resources (and their properties) that interconnect LSRs
      into the information that is used by Constrained SPF for the
      purpose of path computation, and by GMPLS signaling.

   Transparent:

      A device is called X-transparent if it forwards incoming signals
      from input to output without examining or modifying the X aspect
      of the signal.  For example, a Frame Relay switch is network-
      layer transparent; an all-optical switch is electrically
      transparent.

2. LMP Overview

   The two core procedures of LMP are control channel management and
   link property correlation.  Control channel management is used to
   establish and maintain control channels between adjacent nodes.
   This is done using a Config message exchange and a fast keep-alive
   mechanism between the nodes.  The latter is required if lower-level
   mechanisms are not available to detect control channel failures.
   Link property correlation is used to synchronize the TE link
   properties and verify the TE link configuration.

   LMP requires that a pair of nodes have at least one active bi-
   directional control channel between them.  Each direction of the
   control channel is identified by a Control Channel Id (CC_Id), and
   the two directions are coupled together using the LMP Config message
   exchange.  All LMP packets are run over UDP with an LMP port number
   [except in some cases, the Test Message which may be limited by the
   transport mechanism for in-band messaging].  The link level encoding
   of the control channel is outside the scope of this document.

   An "LMP adjacency" is formed between two nodes when at least one bi-
   directional control channel is established between them.  Multiple
   control channels may be active simultaneously for each adjacency;
   control channel parameters, however, MUST be individually negotiated
   for each control channel.  If the LMP fast keep-alive is used over a
   control channel, LMP Hello messages MUST be exchanged over the
   control channel.  Other LMP messages MAY be transmitted over any of
   the active control channels between a pair of adjacent nodes.  One
   or more active control channels may be grouped into a logical
   control channel for signaling, routing, and link property
   correlation purposes.

   The link property correlation function of LMP is designed to
   aggregate multiple data links (ports or component links) into a TE
   link and to synchronize the properties of the TE link.  As part of
   the link property correlation function, a LinkSummary message
   exchange is defined.  The LinkSummary message includes the local and

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   remote Link_Ids, a list of all data links that comprise the TE link,
   and various link properties.  A LinkSummaryAck or LinkSummaryNack
   message MUST be sent in response to the receipt of a LinkSummary
   message indicating agreement or disagreement on the link properties.

   LMP messages are transmitted reliably using Message_Ids and
   retransmissions.  Message_Ids are carried in MESSAGE_ID objects.  No
   more than one MESSAGE_ID object may be included in an LMP message.
   For control channel specific messages, the Message_Id is within the
   scope of the control channel over which the message is sent.  For TE
   link specific messages, the Message_Id is within the scope of the
   LMP adjacency.  The value of the Message_Id is monotonically
   increasing and only decreases when the value wraps.

   In this document, two additional LMP procedures are defined: link
   connectivity verification and fault management.  These procedures
   are particularly useful when the control channels are physically
   diverse from the data links.  Link connectivity verification is used
   for data plane discovery, Interface_Id exchange (Interface_Ids are
   used in GMPLS signaling, either as port labels or component link
   identifiers, depending on the configuration), and physical
   connectivity verification.  This is done by sending Test messages
   over the data links and TestStatus messages back over the control
   channel.  Note that the Test message is the only LMP message that
   must be transmitted over the data link.  The ChannelStatus message
   exchange is used between adjacent nodes for both the suppression of
   downstream alarms and the localization of faults for protection and
   restoration.

   For LMP link connectivity verification, the Test message is
   transmitted over the data links.  For X-transparent devices, this
   requires examining and modifying the X aspect of the signal.  The
   LMP link connectivity verification procedure is coordinated using a
   BeginVerify message exchange over a control channel.  To support
   various aspects of transparency, a Verify Transport Mechanism is
   included in the BeginVerify and BeginVerifyAck messages.  Note that
   there is no requirement that all data links must lose their
   transparency simultaneously, but at a minimum, it must be possible
   to terminate them one at a time.  There is also no requirement that
   the control channel and TE link use the same physical medium;
   however, the control channel MUST terminate on the same two nodes
   that the TE link spans.  Since the BeginVerify message exchange
   coordinates the Test procedure, it also naturally coordinates the
   transition of the data links in and out of the transparent mode.

   The LMP fault management procedure is based on a ChannelStatus
   message exchange using the following messages: ChannelStatus,
   ChannelStatusAck, ChannelStatusRequest, and ChannelStatusResponse.
   The ChannelStatus message is sent unsolicited and is used to notify
   an LMP neighbor about the status of one or more data channels of a
   TE link.  The ChannelStatusAck message is used to acknowledge
   receipt of the ChannelStatus message.  The ChannelStatusRequest

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   message is used to query an LMP neighbor for the status of one or
   more data channels of a TE Link.  The ChannelStatusResponse message
   is used to acknowledge receipt of the ChannelStatusRequest message
   and indicate the states of the queried data links.

3. Control Channel Management

   To initiate an LMP adjacency between two nodes, one or more bi-
   directional control channels MUST be activated.  The control
   channels can be used to exchange control-plane information such as
   link provisioning and fault management information (implemented
   using a messaging protocol such as LMP, proposed in this document),
   path management and label distribution information (implemented
   using a signaling protocol such as RSVP-TE [RFC3209]), and network
   topology and state distribution information (implemented using
   traffic engineering extensions of protocols such as OSPF [OSPF-TE]
   and IS-IS [ISIS-TE]).

   For the purposes of LMP, the exact implementation of the control
   channel is not specified; it could be, for example, a separate
   wavelength or fiber, an Ethernet link, an IP tunnel through a
   separate management network, or the overhead bytes of a data link.
   Rather, a node-wide unique 32-bit non-zero integer control channel
   identifier (CC_Id) is assigned at each end of the control channel.
   This identifier comes from the same space as the unnumbered
   interface Id.  Furthermore, LMP packets are run over UDP with an LMP
   port number.  Thus, the link level encoding of the control channel
   is not part of the LMP specification.

   To establish a control channel, the destination IP address on the
   far end of the control channel must be known.  This knowledge may be
   manually configured or automatically discovered.  Note that for in-
   band signaling, a control channel could be explicitly configured on
   a particular data link.  In this case, the Config message exchange
   can be used to dynamically learn the IP address on the far end of
   the control channel.  This is done by sending the Config message to
   the Multicast address (224.0.0.1).  The ConfigAck and ConfigNack
   messages MUST be sent to the source IP address found in the IP
   header of the received Config message.

   Control channels exist independently of TE links and multiple
   control channels may be active simultaneously between a pair of
   nodes.  Individual control channels can be realized in different
   ways; one might be implemented in-fiber while another one may be
   implemented out-of-fiber.  As such, control channel parameters MUST
   be negotiated over each individual control channel, and LMP Hello
   packets MUST be exchanged over each control channel to maintain LMP
   connectivity if other mechanisms are not available.  Since control
   channels are electrically terminated at each node, it may be
   possible to detect control channel failures using lower layers
   (e.g., SONET/SDH).


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Internet Draft       draft-ietf-ccamp-lmp-07.txt        November 2002

   There are four LMP messages that are used to manage individual
   control channels.  They are the Config, ConfigAck, ConfigNack, and
   Hello messages.  These messages MUST be transmitted on the channel
   to which they refer.  All other LMP messages may be transmitted over
   any of the active control channels between a pair of LMP adjacent
   nodes.

   In order to maintain an LMP adjacency, it is necessary to have at
   least one active control channel between a pair of adjacent nodes
   (recall that multiple control channels can be active simultaneously
   between a pair of nodes).  In the event of a control channel
   failure, alternate active control channels can be used and it may be
   possible to activate additional control channels as described below.

3.1. Parameter Negotiation

   Control channel activation begins with a parameter negotiation
   exchange using Config, ConfigAck, and ConfigNack messages.  The
   contents of these messages are built using LMP objects, which can be
   either negotiable or non-negotiable (identified by the N bit in the
   object header).  Negotiable objects can be used to let LMP peers
   agree on certain values.  Non-negotiable objects are used for the
   announcement of specific values that do not need, or do not allow,
   negotiation.

   To activate a control channel, a Config message MUST be transmitted
   to the remote node, and in response, a ConfigAck message MUST be
   received at the local node.  The Config message contains the Local
   Control Channel Id (CC_Id), the sender's Node_Id, a Message_Id for
   reliable messaging, and a CONFIG object.  It is possible that both
   the local and remote nodes initiate the configuration procedure at
   the same time.  To avoid ambiguities, the node with the higher
   Node_Id wins the contention; the node with the lower Node_Id MUST
   stop transmitting the Config message and respond to the Config
   message it received.

   The ConfigAck message is used to acknowledge receipt of the Config
   message and express agreement on ALL of the configured parameters
   (both negotiable and non-negotiable).

   The ConfigNack message is used to acknowledge receipt of the Config
   message, indicate which (if any) non-negotiable CONFIG objects are
   unacceptable, and propose alternate values for the negotiable
   parameters.

   If a node receives a ConfigNack message with acceptable alternate
   values for negotiable parameters, the node SHOULD transmit a Config
   message using these values for those parameters.

   If a node receives a ConfigNack message with unacceptable alternate
   values, the node MAY continue to retransmit Config messages.  Note
   that the problem may be solved by an operator changing parameters.

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   In the case where multiple control channels use the same physical
   interface, the parameter negotiation exchange is performed for each
   control channel.  The various LMP parameter negotiation messages are
   associated with their corresponding control channels by their node-
   wide unique identifiers (CC_Ids).

3.2. Hello Protocol

   Once a control channel is activated between two adjacent nodes, the
   LMP Hello protocol can be used to maintain control channel
   connectivity between the nodes and to detect control channel
   failures.  The LMP Hello protocol is intended to be a lightweight
   keep-alive mechanism that will react to control channel failures
   rapidly so that IGP Hellos are not lost and the associated link-
   state adjacencies are not removed unnecessarily.

3.2.1. Hello Parameter Negotiation

   Before sending Hello messages, the HelloInterval and
   HelloDeadInterval parameters MUST be agreed upon by the local and
   remote nodes.  These parameters are exchanged in the Config message.
   The HelloInterval indicates how frequently LMP Hello messages will
   be sent, and is measured in milliseconds (ms).  For example, if the
   value were 150, then the transmitting node would send the Hello
   message at least every 150ms.  The HelloDeadInterval indicates how
   long a device should wait to receive a Hello message before
   declaring a control channel dead, and is measured in milliseconds
   (ms).

   The HelloDeadInterval MUST be greater than the HelloInterval, and
   SHOULD be at least 3 times the value of HelloInterval.  If the fast
   keep-alive mechanism of LMP is not used, the HelloInterval and
   HelloDeadInterval parameters MUST be set to zero.

   Suggested default values for the HelloInterval is 150 ms and for the
   HelloDeadInterval is 500 ms.

   When a node has either sent or received a ConfigAck message, it may
   begin sending Hello messages.  Once it has sent a Hello message and
   received a valid Hello message (i.e., with expected sequence
   numbers; see Section 3.2.2), the control channel moves to the up
   state.  (It is also possible to move to the up state without sending
   Hellos if other methods are used to indicate bi-directional control-
   channel connectivity.)  If, however, a node receives a ConfigNack
   message instead of a ConfigAck message, the node MUST not send Hello
   messages and the control channel SHOULD NOT move to the up state.
   See Section 11.1 for the complete control channel FSM.





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3.2.2. Fast Keep-alive

   Each Hello message contains two sequence numbers: the first sequence
   number (TxSeqNum) is the sequence number for the Hello message being
   sent and the second sequence number (RcvSeqNum) is the sequence
   number of the last Hello message received from the adjacent node
   over this control channel.

   There are two special sequence numbers.  TxSeqNum MUST NOT ever be
   0.  TxSeqNum = 1 is used to indicate that the sender has just
   started or has restarted and has no recollection of the last
   TxSeqNum that was sent.  Thus, the first Hello sent has a TxSeqNum
   of 1 and an RxSeqNum of 0.  When TxSeqNum reaches 2^32 -1, the next
   sequence number used is 2, not 0 or 1, as these have special
   meanings.

   Under normal operation, the difference between the RcvSeqNum in a
   Hello message that is received and the local TxSeqNum that is
   generated will be at most 1.  This difference can be more than one
   only when a control channel restarts or when the values wrap.

   Since the 32-bit sequence numbers may wrap, the following expression
   may be used to test if a newly received TxSeqNum value is less than
   a previously received value:

   If ((int) old_id - (int) new_id > 0) {
      New value is less than old value;
   }

   Having sequence numbers in the Hello messages allows each node to
   verify that its peer is receiving its Hello messages.  By including
   the RcvSeqNum in Hello packets, the local node will know which Hello
   packets the remote node has received.

   The following example illustrates how the sequence numbers operate.
   Note that only the operation at one node is shown, and alternative
   scenarios are possible:

   1)  After completing the configuration stage, Node A sends Hello
       messages to Node B with {TxSeqNum=1;RcvSeqNum=0}.
   2)  When Node A receives a Hello from Node B with
       {TxSeqNum=1;RcvSeqNum=1}, it sends Hellos to Node B with
       {TxSeqNum=2;RcvSeqNum=1}.
   3)  When Node A receives a Hello from Node B with
       {TxSeqNum=2;RcvSeqNum=2}, it sends Hellos to Node B with
       {TxSeqNum=3;RcvSeqNum=2}.

3.2.3. Control Channel Down

   To allow bringing a control channel down gracefully for
   administration purposes, a ControlChannelDown flag is available in
   the Common Header of LMP packets.  When data links are still in use

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Internet Draft       draft-ietf-ccamp-lmp-07.txt        November 2002

   between a pair of nodes, a control channel SHOULD only be taken down
   administratively when there are other active control channels that
   can be used to manage the data links.

   When bringing a control channel down administratively, a node MUST
   set the ControlChannelDown flag in all LMP messages sent over the
   control channel.  The node that initiated the control channel down
   procedure may stop sending Hello messages after HelloDeadInterval
   seconds have passed, or if it receives an LMP message over the same
   control channel with the ControlChannelDown flag set.

   When a node receives an LMP packet with the ControlChannelDown flag
   set, it SHOULD send a Hello message with the ControlChannelDown flag
   set and move the control channel to the down state.

3.2.4. Degraded State

   A consequence of allowing the control channels to be physically
   diverse from the associated data links is that there may not be any
   active control channels available while the data links are still in
   use.  For many applications, it is unacceptable to tear down a link
   that is carrying user traffic simply because the control channel is
   no longer available; however, the traffic that is using the data
   links may no longer be guaranteed the same level of service.  Hence
   the TE link is in a Degraded state.

   When a TE link is in the Degraded state, routing and signaling
   SHOULD be notified so that new connections are not accepted and the
   TE link is advertised with no unreserved resources.

4. Link Property Correlation

   As part of LMP, a link property correlation exchange is defined for
   TE links using the LinkSummary, LinkSummaryAck, and LinkSummaryNack
   messages.  The contents of these messages are built using LMP
   objects, which can be either negotiable or non-negotiable
   (identified by the N flag in the object header).  Negotiable objects
   can be used to let both sides agree on certain link parameters.
   Non-negotiable objects are used for announcement of specific values
   that do not need, or do not allow, negotiation.

   Each TE link has an identifier (Link_Id) that is assigned at each
   end of the link.  These identifiers MUST be the same type (i.e,
   IPv4, IPv6, unnumbered) at both ends.  If a LinkSummary message is
   received with different local and remote TE link types, then a
   LinkSummaryNack message MUST be sent with Error Code "Bad TE Link
   Object".  Similarly, each data link is assigned an identifier
   (Interface_Id) at each end.  These identifiers MUST also be the same
   type at both ends.  If a LinkSummary message is received with
   different local and remote Interface_Id types then a LinkSummaryNack
   message MUST be sent with Error Code "Bad Data Link Object".


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   Link property correlation SHOULD be done before the link is brought
   up and MAY be done at any time a link is up and not in the
   Verification process.

   The LinkSummary message is used to verify for consistency the TE and
   data link information on both sides.  Link Summary messages are also
   used to aggregate multiple data links (either ports or component
   links) into a TE link; exchange, correlate (to determine
   inconsistencies), or change TE link parameters; and exchange,
   correlate (to determine inconsistencies), or change Interface_Ids
   (used either Port_Ids or component link identifiers).

   The LinkSummary message includes a TE_LINK object followed by one or
   more DATA_LINK objects.  The TE_LINK object identifies the TE link's
   local and remote Link_Id and indicates support for fault management
   and link verification procedures for that TE link.  The DATA_LINK
   objects are used to characterize the data links that comprise the TE
   link.  These objects include the local and remote Interface_Ids, and
   may include one or more sub-objects further describing the
   properties of the data links.

   If the LinkSummary message is received from a remote node and the
   Interface_Id mappings match those that are stored locally, then the
   two nodes have agreement on the Verification procedure (see Section
   5) and data link identification configuration.  If the verification
   procedure is not used, the LinkSummary message can be used to verify
   agreement on manual configuration.

   The LinkSummaryAck message is used to signal agreement on the
   Interface_Id mappings and link property definitions.  Otherwise, a
   LinkSummaryNack message MUST be transmitted, indicating which
   Interface mappings are not correct and/or which link properties are
   not accepted.  If a LinkSummaryNack message indicates that the
   Interface_Id mappings are not correct and the link verification
   procedure is enabled, the link verification process SHOULD be
   repeated for all mismatched free data links; if an allocated data
   link has a mapping mismatch, it SHOULD be flagged and verified when
   it becomes free.  If a LinkSummaryNack message includes negotiable
   parameters, then acceptable values for those parameters MUST be
   included.  If a LinkSummaryNack message is received and includes
   negotiable parameters, then the initiator of the LinkSummary message
   SHOULD send a new LinkSummary message.  The new LinkSummary message
   SHOULD include new values for the negotiable parameters.  These
   values SHOULD take into account the acceptable values received in
   the LinkSummaryNack message.

   It is possible that the LinkSummary message could grow quite large
   due to the number of DATA LINK objects.  An LMP implementation
   SHOULD be able to fragment when transmitting LMP messages, and MUST
   be able to re-assemble IP fragments when receiving LMP messages.



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5. Verifying Link Connectivity

   In this section, an optional procedure is described that may be used
   to verify the physical connectivity of the data links and
   dynamically learn (i.e., discover) the TE link and Interface_Id
   associations.  The procedure SHOULD be done when establishing a TE
   link, and subsequently, on a periodic basis for all unallocated
   (free) data links of the TE link.

   Support for this procedure is indicated by setting the "Link
   Verification Supported" flag in the TE_LINK object of the
   LinkSummary message.

   If a BeginVerify message is received and link verification is not
   supported for the TE link, then a BeginVerifyNack message MUST be
   transmitted with Error Code indicating, "Link Verification Procedure
   not supported for this TE Link."

   A unique characteristic of transparent devices is that the data is
   not modified or examined in normal operation.  This characteristic
   poses a challenge for validating the connectivity of the data links
   and establish the label mappings.  Therefore, to ensure proper
   verification of data link connectivity, it is required that until
   the data links are allocated for user traffic, they must be opaque
   (i.e., lose their transparency).  To support various degrees of
   opaqueness (e.g., examining overhead bytes, terminating the IP
   payload, etc.), and hence different mechanisms to transport the Test
   messages, a Verify Transport Mechanism field is included in the
   BeginVerify and BeginVerifyAck messages.

   There is no requirement that all data links be terminated
   simultaneously, but at a minimum, the data links MUST be able to be
   terminated one at a time.  Furthermore, for the link verification
   procedure it is assumed that the nodal architecture is designed so
   that messages can be sent and received over any data link.  Note
   that this requirement is trivial for opaque devices since each data
   link is electrically terminated and processed before being forwarded
   to the next opaque device, but that in transparent devices this is
   an additional requirement.

   To interconnect two nodes, a TE link is defined between them, and at
   a minimum, there MUST be at least one active control channel between
   the nodes.  For link verification, a TE link MUST include at least
   one data link.

   Once a control channel has been established between the two nodes,
   data link connectivity can be verified by exchanging Test messages
   over each of the data links specified in the TE link.  It should be
   noted that all LMP messages except the Test message are exchanged
   over the control channels and that Hello messages continue to be
   exchanged over each control channel during the data link
   verification process.  The Test message is sent over the data link

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   that is being verified.  Data links are tested in the transmit
   direction as they are unidirectional, and therefore, it may be
   possible for both nodes to (independently) exchange the Test
   messages simultaneously.

   To initiate the link verification procedure, the local node MUST
   send a BeginVerify message over a control channel.  To limit the
   scope of Link Verification to a particular TE Link, the local
   Link_Id MUST be non-zero.  If this field is zero, the data links can
   span multiple TE links and/or they may comprise a TE link that is
   yet to be configured.  For the case where the local Link_Id field is
   zero, the "Verify all Links" flag of the BEGIN_VERIFY object is used
   to distinguish between data links that span multiple TE links and
   those that have not yet been assigned to a TE link.  Specifically,
   verification of data links that span multiple TE links is indicated
   by setting the local Link_Id field to zero and setting the "Verify
   all Links" flag.  Verification of data links that have not yet been
   assigned to a TE link is indicated by setting the local Link_Id
   field to zero and clearing the "Verify all Links" flag.

   The BeginVerify message also contains the number of data links that
   are to be verified; the interval (called VerifyInterval) at which
   the Test messages will be sent; the encoding scheme and transport
   mechanisms that are supported; the data rate for Test messages; and,
   when the data links correspond to fibers, the wavelength identifier
   over which the Test messages will be transmitted.

   If the remote node receives a BeginVerify message and it is ready to
   process Test messages, it MUST send a BeginVerifyAck message back to
   the local node specifying the desired transport mechanism for the
   TEST messages.  The remote node includes a 32-bit node unique
   Verify_Id in the BeginVerifyAck message.  The Verify_Id is then used
   in all corresponding verification messages to differentiate them
   from different LMP peers and/or parallel Test procedures.  When the
   local node receives a BeginVerifyAck message from the remote node,
   it may begin testing the data links by transmitting periodic Test
   messages over each data link.  The Test message includes the
   Verify_Id and the local Interface_Id for the associated data link.
   The remote node MUST send either a TestStatusSuccess or a
   TestStatusFailure message in response for each data link.  A
   TestStatusAck message MUST be sent to confirm receipt of the
   TestStatusSuccess and TestStatusFailure messages.

   It is also permissible for the sender to terminate the Test
   procedure anytime after sending the BeginVerify message.  An
   EndVerify message SHOULD be sent for this purpose.

   Message correlation is done using message identifiers and the
   Verify_Id; this enables verification of data links, belonging to
   different link bundles or LMP sessions, in parallel.



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   When the Test message is received, the received Interface_Id (used
   in GMPLS as either a Port label or component link identifier
   depending on the configuration) is recorded and mapped to the local
   Interface_Id for that data link, and a TestStatusSuccess message
   MUST be sent.  The TestStatusSuccess message includes the local
   Interface_Id along with the Interface_Id and Verify_Id received in
   the Test message.  The receipt of a TestStatusSuccess message
   indicates that the Test message was detected at the remote node and
   the physical connectivity of the data link has been verified.  When
   the TestStatusSuccess message is received, the local node SHOULD
   mark the data link as up and send a TestStatusAck message to the
   remote node.  If, however, the Test message is not detected at the
   remote node within an observation period (specified by the
   VerifyDeadInterval), the remote node MUST send a TestStatusFailure
   message over the control channel indicating that the verification of
   the physical connectivity of the data link has failed.  When the
   local node receives a TestStatusFailure message, it SHOULD mark the
   data link as FAILED and send a TestStatusAck message to the remote
   node.  When all the data links on the list have been tested, the
   local node SHOULD send an EndVerify message to indicate that testing
   is complete on this link.

   If the local/remote data link mappings are known, then the link
   verification procedure can be optimized by testing the data links in
   a defined order known to both nodes.  The suggested criterion for
   this ordering is in increasing value of the remote Interface_Id.

   Both the local and remote nodes SHOULD maintain the complete list of
   Interface_Id mappings for correlation purposes.

5.1. Example of Link Connectivity Verification

   Figure 1 shows an example of the link verification scenario that is
   executed when a link between Node A and Node B is added.  In this
   example, the TE link consists of three free ports (each transmitted
   along a separate fiber) and is associated with a bi-directional
   control channel (indicated by a "c").  The verification process is
   as follows:
     o  A sends a BeginVerify message over the control channel to B
        indicating it will begin verifying the ports that form the TE
        link.  The LOCAL_LINK_ID object carried in the BeginVerify
        message carries the identifier (IP address or interface index)
        that A assigns to the link.
     o  Upon receipt of the BeginVerify message, B creates a Verify_Id
        and binds it to the TE Link from A.  This binding is used later
        when B receives the Test messages from A, and these messages
        carry the Verify_Id.  B discovers the identifier (IP address or
        interface index) that A assigns to the TE link by examining the
        LOCAL_LINK_ID object carried in the received BeginVerify
        message.  (If the data ports are not yet assigned to the TE
        Link, the binding is limited to the Node_Id of A.)  In response
        to the BeginVerify message, B sends to A the BeginVerifyAck

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        message.  The LOCAL_LINK_ID object carried in the
        BeginVerifyAck message is used to carry the identifier (IP
        address or interface index) that B assigns to the TE link.  The
        REMOTE_LINK_ID object carried in the BeginVerifyAck message is
        used to bind the Link_Ids assigned by both A and B.  The
        Verify_Id is returned to A in the BeginVerifyAck message over
        the control channel.
     o  When A receives the BeginVerifyAck message, it begins
        transmitting periodic Test messages over the first port
        (Interface Id=1).  The Test message includes the Interface_Id
        for the port and the Verify_Id that was assigned by B.
     o  When B receives the Test messages, it maps the received
        Interface_Id to its own local Interface_Id = 10 and transmits a
        TestStatusSuccess message over the control channel back to Node
        A.  The TestStatusSuccess message includes both the local and
        received Interface_Ids for the port as well as the Verify_Id.
        The Verify_Id is used to determine the local/remote TE link
        identifiers (IP addresses or interface indices) for which the
        data links belong.
     o  A will send a TestStatusAck message over the control channel
        back to B indicating it received the TestStatusSuccess message.
     o  The process is repeated until all of the ports are verified.
     o  At this point, A will send an EndVerify message over the
        control channel to B to indicate that testing is complete.
     o  B will respond by sending an EndVerifyAck message over the
        control channel back to A.

     Note that this procedure can be used to "discover" the
     connectivity of the data ports.

   +---------------------+                      +---------------------+
   +                     +                      +                     +
   +      Node A         +<-------- c --------->+        Node B       +
   +                     +                      +                     +
   +                     +                      +                     +
   +                   1 +--------------------->+ 10                  +
   +                     +                      +                     +
   +                     +                      +                     +
   +                   2 +                /---->+ 11                  +
   +                     +          /----/      +                     +
   +                     +     /---/            +                     +
   +                   3 +----/                 + 12                  +
   +                     +                      +                     +
   +                     +                      +                     +
   +                   4 +--------------------->+ 14                  +
   +                     +                      +                     +
   +---------------------+                      +---------------------+

    Figure 1:  Example of link connectivity between Node A and Node B.




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6. Fault Management

   In this section, an optional LMP procedure is described that is used
   to manage failures by rapid notification of the status of one or
   more data channels of a TE Link.  The scope of this procedure is
   within a TE link, and as such, the use of this procedure is
   negotiated as part of the LinkSummary exchange.  The procedure can
   be used to rapidly isolate link failures and is designed to work for
   both unidirectional and bi-directional LSPs.

   An important implication of using transparent devices is that
   traditional methods that are used to monitor the health of allocated
   data links in may no longer be appropriate.  Instead, fault
   detection is delegated to the physical layer (i.e., loss of light or
   optical monitoring of the data) instead of layer 2 or layer 3.

   Recall that a TE link connecting two nodes may consist of a number
   of data links.  If one or more data links fail between two nodes, a
   mechanism must be used for rapid failure notification so that
   appropriate protection/restoration mechanisms can be initiated.  If
   the failure is subsequently cleared, then a mechanism must be used
   to notify that the failure is clear and the channel status is OK.

6.1. Fault Detection

   Fault detection should be handled at the layer closest to the
   failure; for optical networks, this is the physical (optical) layer.
   One measure of fault detection at the physical layer is detecting
   loss of light (LOL).  Other techniques for monitoring optical
   signals are still being developed and will not be further considered
   in this document.  However, it should be clear that the mechanism
   used for fault notification in LMP is independent of the mechanism
   used to detect the failure, but simply relies on the fact that a
   failure is detected.

6.2. Fault Localization Procedure

   In some situations, a data link failure between two nodes is
   propagated downstream such that all the downstream nodes detect the
   failure without localizing the failure.  To avoid multiple alarms
   stemming from the same failure, LMP provides failure notification
   through the ChannelStatus message.  This message may be used to
   indicate that a single data channel has failed, multiple data
   channels have failed, or an entire TE link has failed.  Failure
   correlation is done locally at each node upon receipt of the failure
   notification.

   To localize a fault to a particular link between adjacent nodes, a
   downstream node (downstream in terms of data flow) that detects data
   link failures will send a ChannelStatus message to its upstream
   neighbor indicating that a failure has been detected (bundling
   together the notification of all of the failed data links).  An

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   upstream node that receives the ChannelStatus message MUST send a
   ChannelStatusAck message to the downstream node indicating it has
   received the ChannelStatus message.  The upstream node should
   correlate the failure to see if the failure is also detected locally
   for the corresponding LSP(s).  If, for example, the failure is clear
   on the input of the upstream node or internally, then the upstream
   node will have localized the failure.  Once the failure is
   correlated, the upstream node SHOULD send a ChannelStatus message to
   the downstream node indicating that the channel is failed or is ok.
   If a ChannelStatus message is not received by the downstream node,
   it SHOULD send a ChannelStatusRequest message for the channel in
   question.  Once the failure has been localized, the signaling
   protocols may be used to initiate span or path protection and
   restoration procedures.

   If all of the data links of a TE link have failed, then the upstream
   node MAY be notified of the TE link failure without specifying each
   data link of the failed TE link.  This is done by sending failure
   notification in a ChannelStatus message identifying the TE Link
   without including the Interface_Ids in the CHANNEL_STATUS object.

6.3. Examples of Fault Localization

   In Fig. 2, a sample network is shown where four nodes are connected
   in a linear array configuration.  The control channels are bi-
   directional and are labeled with a "c".  All LSPs are also bi-
   directional.

   In the first example [see Fig. 2(a)], there is a failure on one
   direction of the bi-directional LSP.  Node 4 will detect the failure
   and will send a ChannelStatus message to Node 3 indicating the
   failure (e.g., LOL) to the corresponding upstream node.  When Node 3
   receives the ChannelStatus message from Node 4, it returns a
   ChannelStatusAck message back to Node 4 and correlates the failure
   locally.  When Node 3 correlates the failure and verifies that the
   failure is clear, it has localized the failure to the data link
   between Node 3 and Node 4.  At that time, Node 3 should send a
   ChannelStatus message to Node 4 indicating that the failure has been
   localized.

   In the second example [see Fig. 2(b)], a single failure (e.g., fiber
   cut) affects both directions of the bi-directional LSP.  Node 2
   (Node 3) will detect the failure of the upstream (downstream)
   direction and send a ChannelStatus message to the upstream (in terms
   of data flow) node indicating the failure (e.g., LOL).
   Simultaneously (ignoring propagation delays), Node 1 (Node 4) will
   detect the failure on the upstream (downstream) direction, and will
   send a ChannelStatus message to the corresponding upstream (in terms
   of data flow) node indicating the failure.  Node 2 and Node 3 will
   have localized the two directions of the failure.



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       +-------+        +-------+        +-------+        +-------+
       + Node1 +        + Node2 +        + Node3 +        + Node4 +
       +       +-- c ---+       +-- c ---+       +-- c ---+       +
   ----+---\   +        +       +        +       +        +       +
   <---+---\\--+--------+-------+---\    +       +        +    /--+--->
       +    \--+--------+-------+---\\---+-------+---##---+---//--+----
       +       +        +       +    \---+-------+--------+---/   +
       +       +        +       +        +       +  (a)   +       +
   ----+-------+--------+---\   +        +       +        +       +
   <---+-------+--------+---\\--+---##---+--\    +        +       +
       +       +        +    \--+---##---+--\\   +        +       +
       +       +        +       +  (b)   +   \\--+--------+-------+--->
       +       +        +       +        +    \--+--------+-------+----
       +       +        +       +        +       +        +       +
       +-------+        +-------+        +-------+        +-------+

          Figure 2: Two types of data link failures are shown
          (indicated by ## in the figure): (A) a data link
          corresponding to the downstream direction of a bi-directional
          LSP fails, (B) two data links corresponding to both
          directions of a bi-directional LSP fail.  The control channel
          connecting two nodes is indicated with a "c".

6.4. Channel Activation Indication

   The ChannelStatus message may also be used to notify an LMP neighbor
   that the data link should be actively monitored.  This is called
   Channel Activation Indication.  This is particularly useful in
   networks with transparent nodes where the status of data links may
   need to be triggered using control channel messages.  For example,
   if a data link is pre-provisioned and the physical link fails after
   verification and before inserting user traffic, a mechanism is
   needed to indicate the data link should be active or the failure may
   not be able to be detected.

   The ChannelStatus message is used to indicate that a channel or
   group of channels are now active.  The ChannelStatusAck message MUST
   be transmitted upon receipt of a ChannelStatus message.  When a
   ChannelStatus message is received, the corresponding data link(s)
   MUST be put into the Active state.  If upon putting them into the
   Active state, a failure is detected, the ChannelStatus message
   SHOULD be transmitted as described in Section 6.2.

6.5. Channel Deactivation Indication

   The ChannelStatus message may also be used to notify an LMP neighbor
   that the data link no longer needs to be actively monitored.  This
   is the counterpart to the Channel Active Indication.

   When a ChannelStatus message is received with Channel Deactive
   Indication, the corresponding data link(s) MUST be taken out of the
   Active state.

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7. Message_Id Usage

   The MESSAGE_ID and MESSAGE_ID_ACK objects are included in LMP
   messages to support reliable message delivery.  This section
   describes the usage of these objects.  The MESSAGE_ID and
   MESSAGE_ID_ACK objects contain a Message_Id field.

   Only one MESSAGE_ID/MESSAGE_ID_ACK object may be included in any LMP
   message.

   For control channel specific messages, the Message_Id field is
   within the scope of the CC_Id.  For TE link specific messages, the
   Message_Id field is within the scope of the LMP adjacency.

   The Message_Id field of the MESSAGE_ID object contains a generator-
   selected value.  This value MUST be monotonically increasing.  A
   value is considered to be previously used when it has been sent in
   an LMP message with the same CC_Id (for control channel specific
   messages) or LMP adjacency (for TE Link specific messages).  The
   Message_Id field of the MESSAGE_ID_ACK object contains the
   Message_Id field of the message being acknowledged.

   Unacknowledged messages sent with the MESSAGE_ID object SHOULD be
   retransmitted until the message is acknowledged or until a retry
   limit is reached (see also Section 10).

   Note that the 32-bit Message_Id value MAY wrap.  The following
   expression may be used to test if a newly received Message_Id value
   is less than a previously received value:

   If ((int) old_id - (int) new_id > 0) {
      New value is less than old value;
   }

   Nodes processing incoming messages SHOULD check to see if a newly
   received message is out of order and can be ignored.  Out-of-order
   messages can be identified by examining the value in the Message_Id
   field.  If a message is determined to be out-of-order, that message
   should be silently dropped.

   If the message is a Config message, and the Message_Id value is less
   than the largest Message_Id value previously received from the
   sender for the CC_Id, then the message SHOULD be treated as being
   out-of-order.

   If the message is a LinkSummary message and the Message_Id value is
   less than the largest Message_Id value previously received from the
   sender for the TE Link, then the message SHOULD be treated as being
   out-of-order.



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   If the message is a ChannelStatus message and the Message_Id value
   is less than the largest Message_Id value previously received from
   the sender for the specified TE link, then the receiver SHOULD check
   the Message_Id value previously received for the state of each data
   channel included in the ChannelStatus message.  If the Message_Id
   value is greater than the most recently received Message_Id value
   associated with at least one of the data channels included in the
   message, the message MUST NOT be treated as out of order; otherwise
   the message SHOULD be treated as being out of order.  However, the
   state of any data channel MUST NOT be updated if the Message_Id
   value is less than the most recently received Message_Id value
   associated with the data channel.

   All other messages MUST NOT be treated as out-of-order.

8. Graceful Restart

   This section describes the mechanism to resynchronize the LMP state
   after a control plane restart.  A control plane restart may occur
   when bringing up the first control channel after a control
   communications failure.  A control communications failure may be the
   result of an LMP adjacency failure or a nodal failure wherein the
   LMP control state is lost, but the data plane is unaffected.  The
   latter is detected by setting the "LMP Restart" bit in the Common
   Header of the LMP messages.  When the control plane fails due to the
   loss of the control channel, the LMP link information should be
   retained.  It is possible that a node may be capable of retaining
   the LMP link information across a nodal failure.  However, in both
   cases the status of the data channels MUST be synchronized.

   It is assumed the Local Interface_Ids remain stable across a control
   plane restart.

   After the control plane of a node restarts, the control channel(s)
   must be re-established using the procedures of Section 3.1.

   If the control plane failure was the result of a nodal failure where
   the LMP control state is lost, then the "LMP Restart" flag MUST be
   set in LMP messages until a Hello message is received with the
   RcvSeqNum equal to the local TxSeqNum.  This indicates that the
   control channel is up and the LMP neighbor has detected the restart.

   The following assumes that the LMP component restart only occurred
   on one end of the TE Link.  If the LMP component restart occurred on
   both ends of the TE Link, the normal procedures for LinkSummary
   should be used, as described in Section 4.

   Once a control channel is up, the LMP neighbor MUST send a
   LinkSummary message for each TE Link across the adjacency.  All the
   objects of the LinkSummary message MUST have the N-bit set to 0
   indicating that the parameters are non-negotiable.  This provides
   the local/remote Link_Id and Interface_Id mappings, the associated

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   data link parameters, and indication of which data links are
   currently allocated to user traffic.  When a node receives the
   LinkSummary message, it checks its local configuration.  If the node
   is capable of retaining the LMP link information across a restart,
   it must process the LinkSummary message as described in Section 4
   with the exception that the allocated/de-allocated flag of the
   DATA_LINK object received in the LinkSummary message MUST take
   precedence over any local value.  If, however, the node was not
   capable of retaining the LMP link information across a restart, the
   node MUST accept the data link parameters of the received
   LinkSummary message and respond with a LinkSummaryAck message.

   Upon completion of the LinkSummary exchange, the node that has
   restarted the control plane SHOULD send a ChannelStatusRequest
   message for that TE link.  The node SHOULD also verify the
   connectivity of all unallocated data channels.

9. Addressing

   All LMP messages are run over UDP with an LMP port number (except,
   in some cases, the Test messages which may be limited by the
   transport mechanism for in-band messaging).  The destination address
   of the IP packet MAY be either the address learned in the
   Configuration procedure (i.e., the Source IP address found in the IP
   header of the received Config message), an IP address configured on
   the remote node, or the Node_Id.  The Config message is an exception
   as described below.

   The manner in which a Config message is addressed may depend on the
   signaling transport mechanism.  When the transport mechanism is a
   point-to-point link, Config messages SHOULD be sent to the Multicast
   address (224.0.0.1).  Otherwise, Config messages MUST be sent to an
   IP address on the neighboring node.  This may be configured at both
   ends of the control channel or may be automatically discovered.

10.  Exponential Back-off Procedures

   This section is based on [RFC2961] and provides exponential back-off
   procedures for message retransmission.  Implementations MUST use the
   described procedures or their equivalent.

10.1. Operation

   The following operation is one possible mechanism for exponential
   back-off retransmission of unacknowledged LMP messages.  The sending
   node retransmits the message until an acknowledgement message is
   received or until a retry limit is reached.  When the sending node
   receives the acknowledgement, retransmission of the message is
   stopped.  The interval between message retransmission is governed by
   a rapid retransmission timer.  The rapid retransmission timer starts
   at a small interval and increases exponentially until it reaches a
   threshold.

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   The following time parameters are useful to characterize the
   procedures:

   Rapid retransmission interval Ri:

      Ri is the initial retransmission interval for unacknowledged
      messages.  After sending the message for the first time, the
      sending node will schedule a retransmission after Ri
      milliseconds.

   Rapid retry limit Rl:

      Rl is the maximum number of times a message will be transmitted
      without being acknowledged.

   Increment value Delta:

      Delta governs the speed with which the sender increases the
      retransmission interval.  The ratio of two successive
      retransmission intervals is (1 + Delta).

   Suggested default values for an initial retransmission interval (Ri)
   of 500ms, a power of 2 exponential back-off (Delta = 1) and a retry
   limit of 3.

10.2. Retransmission Algorithm

   After a node transmits a message requiring acknowledgement, it
   should immediately schedule a retransmission after Ri seconds.  If a
   corresponding acknowledgement message is received before Ri seconds,
   then message retransmission SHOULD be canceled.  Otherwise, it will
   retransmit the message after (1+Delta)*Ri seconds.  The
   retransmission will continue until either an appropriate
   acknowledgement message is received or the rapid retry limit, Rl,
   has been reached.

   A sending node can use the following algorithm when transmitting a
   message that requires acknowledgement:

      Prior to initial transmission, initialize Rk = Ri and Rn = 0.

      while (Rn++ < Rl) {
        transmit the message;
        wake up after Rk milliseconds;
        Rk = Rk * (1 + Delta);
      }
      /* acknowledged message or no reply from receiver and Rl
      reached*/
      do any needed clean up;
      exit;


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   Asynchronously, when a sending node receives a corresponding
   acknowledgment message, it will change the retry count, Rn, to Rl.

   Note that the transmitting node does not advertise or negotiate the
   use of the described exponential back-off procedures in the Config
   or LinkSummary messages.

11. LMP Finite State Machines

11.1. Control Channel FSM

   The control channel FSM defines the states and logics of operation
   of an LMP control channel.

11.1.1. Control Channel States

   A control channel can be in one of the states described below.
   Every state corresponds to a certain condition of the control
   channel and is usually associated with a specific type of LMP
   message that is periodically transmitted to the far end.

   Down:        This is the initial control channel state.  In this
                state, no attempt is being made to bring the control
                channel up and no LMP messages are sent.  The control
                channel parameters should be set to the initial values.

   ConfSnd:     The control channel is in the parameter negotiation
                state.  In this state the node periodically sends a
                Config message, and is expecting the other side to
                reply with either a ConfigAck or ConfigNack message.
                The FSM does not transition into the Active state until
                the remote side positively acknowledges the parameters.

   ConfRcv:     The control channel is in the parameter negotiation
                state.  In this state, the node is waiting for
                acceptable configuration parameters from the remote
                side.  Once such parameters are received and
                acknowledged, the FSM can transition to the Active
                state.

   Active:      In this state the node periodically sends a Hello
                message and is waiting to receive a valid Hello
                message.  Once a valid Hello message is received, it
                can transition to the up state.

   Up:          The CC is in an operational state.  The node receives
                valid Hello messages and sends Hello messages.

   GoingDown:   A CC may go into this state because of administrative
                action.  While a CC is in this state, the node sets the
                ControlChannelDown bit in all the messages it sends.


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11.1.2. Control Channel Events

   Operation of the LMP control channel is described in terms of FSM
   states and events.  Control channel events are generated by the
   underlying protocols and software modules, as well as by the packet
   processing routines and FSMs of associated TE links.  Every event
   has its number and a symbolic name.  Description of possible control
   channel events is given below.

   1 : evBringUp:    This is an externally triggered event indicating
                     that the control channel negotiation should begin.
                     This event, for example, may be triggered by an
                     operator command, by the successful completion of
                     a control channel bootstrap procedure, or by
                     configuration.  Depending on the configuration,
                     this will trigger either
                         1a) the sending of a Config message,
                         1b) a period of waiting to receive a Config
                              message from the remote node.

   2 : evCCDn:       This event is generated when there is indication
                     that the control channel is no longer available.

   3 : evConfDone:   This event indicates a ConfigAck message has been
                     received, acknowledging the Config parameters.

   4 : evConfErr:    This event indicates a ConfigNack message has been
                     received, rejecting the Config parameters.

   5 : evNewConfOK:  New Config message was received from neighbor and
                     positively acknowledged.

   6 : evNewConfErr: New Config message was received from neighbor and
                     rejected with a ConfigNack message.

   7 : evContenWin:  New Config message was received from neighbor at
                     the same time a Config message was sent to the
                     neighbor.  The local node wins the contention.  As
                     a result, the received Config message is ignored.

   8 : evContenLost: New Config message was received from neighbor at
                     the same time a Config message was sent to the
                     neighbor.  The local node loses the contention.
                         8a) The Config message is positively
                              acknowledged.
                         8b) The Config message is negatively
                              acknowledged.

   9 : evAdminDown:  The administrator has requested that the control
                     channel is brought down administratively.



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   10: evNbrGoesDn:  A packet with ControlChannelDown flag is received
                     from the neighbor.

   11: evHelloRcvd:  A Hello packet with expected SeqNum has been
                     received.

   12: evHoldTimer:  The HelloDeadInterval timer has expired indicating
                     that no Hello packet has been received.  This
                     moves the control channel back into the
                     Negotiation state, and depending on the local
                     configuration, this will trigger either
                         12a) the sending of periodic Config messages,
                         12b) a period of waiting to receive Config
                              messages from the remote node.

   13: evSeqNumErr:  A Hello with unexpected SeqNum received and
                     discarded.

   14: evReconfig:   Control channel parameters have been reconfigured
                     and require renegotiation.

   15: evConfRet:    A retransmission timer has expired and a Config
                     message is resent.

   16: evHelloRet:   The HelloInterval timer has expired and a Hello
                     packet is sent.

   17: evDownTimer: A timer has expired and no messages have been
                     received with the ControlChannelDown flag set.
























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11.1.3. Control Channel FSM Description

   Figure 3 illustrates operation of the control channel FSM
   in a form of FSM state transition diagram.

                               +--------+
            +----------------->|        |<--------------+
            |       +--------->|  Down  |<----------+   |
            |       |+---------|        |<-------+  |   |
            |       ||         +--------+        |  |   |
            |       ||           |    ^       2,9| 2|  2|
            |       ||1b       1a|    |          |  |   |
            |       ||           v    |2,9       |  |   |
            |       ||         +--------+        |  |   |
            |       ||      +->|        |<------+|  |   |
            |       ||  4,7,|  |ConfSnd |       ||  |   |
            |       || 14,15+--|        |<----+ ||  |   |
            |       ||         +--------+     | ||  |   |
            |       ||       3,8a| |          | ||  |   |
            |       || +---------+ |8b  14,12a| ||  |   |
            |       || |           v          | ||  |   |
            |       |+-|------>+--------+     | ||  |   |
            |       |  |    +->|        |-----|-|+  |   |
            |       |  |6,14|  |ConfRcv |     | |   |   |
            |       |  |    +--|        |<--+ | |   |   |
            |       |  |       +--------+   | | |   |   |
            |       |  |          5| ^      | | |   |   |
            |       |  +---------+ | |      | | |   |   |
            |       |            | | |      | | |   |   |
            |       |            v v |6,12b | | |   |   |
            |       |10        +--------+   | | |   |   |
            |       +----------|        |   | | |   |   |
            |       |       +--| Active |---|-+ |   |   |
       10,17|       |   5,16|  |        |-------|---+   |
        +-------+ 9 |   13  +->|        |   |   |       |
        | Going |<--|----------+--------+   |   |       |
        | Down  |   |           11| ^       |   |       |
        +-------+   |             | |5      |   |       |
            ^       |             v |  6,12b|   |       |
            |9      |10        +--------+   |   |12a,14 |
            |       +----------|        |---+   |       |
            |                  |   Up   |-------+       |
            +------------------|        |---------------+
                               +--------+
                                 |   ^
                                 |   |
                                 +---+
                                11,13,16
                       Figure 3: Control Channel FSM




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   Event evCCDn always forces the FSM to the down state.  Events
   evHoldTimer evReconfig always force the FSM to the Negotiation state
   (either ConfSnd or ConfRcv).

11.2. TE Link FSM

   The TE Link FSM defines the states and logics of operation of the
   LMP TE Link.

11.2.1. TE Link States

   An LMP TE link can be in one of the states described below.  Every
   state corresponds to a certain condition of the TE link and is
   usually associated with a specific type of LMP message that is
   periodically transmitted to the far end via the associated control
   channel or in-band via the data links.

   Down:      There are no data links allocated to the TE link.

   Init:      Data links have been allocated to the TE link, but the
               configuration has not yet been synchronized with the LMP
               neighbor.

   Up:        This is the normal operational state of the TE link.  At
               least one LMP control channel is required to be
               operational between the nodes sharing the TE link.

   Degraded:  In this state, all LMP control channels are down, but
               the TE link still includes some data links that are
               allocated to user traffic.

11.2.2. TE Link Events

   Operation of the LMP TE link is described in terms of FSM states and
   events.  TE Link events are generated by the packet processing
   routines and by the FSMs of the associated control channel(s) and
   the data links.  Every event has its number and a symbolic name.
   Description of possible events is given below.

   1 : evDCUp:         One or more data channels have been enabled and
                       assigned to the TE Link.

   2 : evSumAck:       LinkSummary message received and positively
                       acknowledged.

   3 : evSumNack:      LinkSummary message received and negatively
                       acknowledged.

   4 : evRcvAck:       LinkSummaryAck message received acknowledging
                       the TE Link Configuration.

   5 : evRcvNack:      LinkSummaryNack message received.

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   6 : evSumRet:       Retransmission timer has expired and LinkSummary
                       message is resent.

   7 : evCCUp:         First active control channel goes up.

   8 : evCCDown:       Last active control channel goes down.

   9 : evDCDown:       Last data channel of TE Link has been removed.

11.2.3. TE Link FSM Description

   Figure 4 illustrates operation of the LMP TE Link FSM in a form of
   FSM state transition diagram.


                                     3,7,8
                                     +--+
                                     |  |
                                     |  v
                                  +--------+
                                  |        |
                    +------------>|  Down  |<---------+
                    |             |        |          |
                    |             +--------+          |
                    |                |  ^             |
                    |               1|  |9            |
                    |                v  |             |
                    |             +--------+          |
                    |             |        |<-+       |
                    |             |  Init  |  |3,5,6  |9
                    |             |        |--+ 7,8   |
                   9|             +--------+          |
                    |                  |              |
                    |               2,4|              |
                    |                  v              |
                 +--------+   7   +--------+          |
                 |        |------>|        |----------+
                 |  Deg   |       |   Up   |
                 |        |<------|        |
                 +--------+   8   +--------+
                                     |  ^
                                     |  |
                                     +--+
                                   2,3,4,5,6

                         Figure 4: LMP TE Link FSM

   In the above FSM, the sub-states that may be implemented when the
   link verification procedure is used have been omitted.

11.3. Data Link FSM

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   The data link FSM defines the states and logics of operation of a
   data link within an LMP TE link.  Operation of a data link is
   described in terms of FSM states and events.  Data links can either
   be in the active (transmitting) mode, where Test messages are
   transmitted from them, or the passive (receiving) mode, where Test
   messages are received through them.  For clarity, separate FSMs are
   defined for the active/passive data links; however, a single set of
   data link states and events are defined.

11.3.1. Data Link States

   Any data link can be in one of the states described below.  Every
   state corresponds to a certain condition of the data link.

   Down:          The data link has not been put in the resource pool
                  (i.e., the link is not æin serviceÆ)

   Test:          The data link is being tested.  An LMP Test message
                  is periodically sent through the link.

   PasvTest:      The data link is being checked for incoming test
                  messages.

   Up/Free:       The link has been successfully tested and is now put
                  in the pool of resources (in-service).  The link has
                  not yet been allocated to data traffic.

   Up/Alloc:      The link is up and has been allocated for data
                  traffic.

11.3.2. Data Link Events

   Data link events are generated by the packet processing routines and
   by the FSMs of the associated control channel and the TE link.
   Every event has its number and a symbolic name.  Description of
   possible data link events is given below:

   1 :evCCUp:      First active control channel goes up.

   2 :evCCDown:    LMP neighbor connectivity is lost.  This indicates
                    the last LMP control channel has failed between
                    neighboring nodes.

   3 :evStartTst:  This is an external event that triggers the sending
                    of Test messages over the data link.

   4 :evStartPsv:  This is an external event that triggers the
                    listening for Test messages over the data link.

   5 :evTestOK:    Link verification was successful and the link can
                    be used for path establishment.

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                        (a) This event indicates the Link Verification
                            procedure (see Section 5) was successful
                            for this data link and a TestStatusSuccess
                            message was received over the control
                            channel.
                        (b) This event indicates the link is ready for
                            path establishment, but the Link
                            Verification procedure was not used.  For
                            in-band signaling of the control channel,
                            the control channel establishment may be
                            sufficient to verify the link.

   6 :evTestRcv:    Test message was received over the data port and a
                    TestStatusSuccess message is transmitted over the
                    control channel.

   7 :evTestFail:   Link verification returned negative results.  This
                    could be because (a) a TestStatusFailure message
                    was received, or (b) the Verification procedure has
                    ended without receiving a TestStatusSuccess or
                    TestStatusFailure message for the data link.

   8 :evPsvTestFail:Link verification returned negative results.  This
                    indicates that a Test message was not detected and
                    either (a) the VerifyDeadInterval has expired or
                    (b) the Verification procedure has ended and the
                    VerifyDeadInterval has not yet expired.

   9 :evLnkAlloc:   The data link has been allocated.

   10:evLnkDealloc: The data link has been de-allocated.

   11:evTestRet:    A retransmission timer has expired and the Test
                    message is resent.

   12:evSummaryFail:The LinkSummary did not match for this data port.

   13:evLocalizeFail:A Failure has been localized to this data link.

   14:evdcDown:     The data channel is no longer available.













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11.3.3. Active Data Link FSM Description

   Figure 5 illustrates operation of the LMP active data link FSM in a
   form of FSM state transition diagram.

                             +------+
                             |      |<-------+
                  +--------->| Down |        |
                  |     +----|      |<-----+ |
                  |     |    +------+      | |
                  |     |5b   3|  ^        | |
                  |     |      |  |7       | |
                  |     |      v  |        | |
                  |     |    +------+      | |
                  |     |    |      |<-+   | |
                  |     |    | Test |  |11 | |
                  |     |    |      |--+   | |
                  |     |    +------+      | |
                  |     |     5a| 3^       | |
                  |     |       |  |       | |
                  |     |       v  |       | |
                  |12   |   +---------+    | |
                  |     +-->|         |14  | |
                  |         | Up/Free |----+ |
                  +---------|         |      |
                            +---------+      |
                               9| ^          |
                                | |          |
                                v |10        |
                            +---------+      |
                            |         |13    |
                            |Up/Alloc |------+
                            |         |
                            +---------+

                    Figure 5: Active LMP Data Link FSM

















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11.3.4. Passive Data Link FSM Description

   Figure 6 illustrates operation of the LMP passive data link FSM in a
   form of FSM state transition diagram.

                             +------+
                             |      |<------+
                 +---------->| Down |       |
                 |     +-----|      |<----+ |
                 |     |     +------+     | |
                 |     |5b    4|  ^       | |
                 |     |       |  |8      | |
                 |     |       v  |       | |
                 |     |    +----------+  | |
                 |     |    | PasvTest |  | |
                 |     |    +----------+  | |
                 |     |       6|  4^     | |
                 |     |        |   |     | |
                 |     |        v   |     | |
                 |12   |    +---------+   | |
                 |     +--->| Up/Free |14 | |
                 |          |         |---+ |
                 +----------|         |     |
                            +---------+     |
                                9| ^        |
                                 | |        |
                                 v |10      |
                            +---------+     |
                            |         |13   |
                            |Up/Alloc |-----+
                            |         |
                            +---------+

                    Figure 6: Passive LMP Data Link FSM



















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12. LMP Message Formats

   All LMP messages are run over UDP with an LMP port number (except,
   in some cases, the Test messages are limited by the transport
   mechanism for in-band messaging) and run over UDP with port number
   xxx - TBA (to be assigned) by IANA.

12.1. Common Header

   In addition to the UDP header and standard IP header, all LMP
   messages (except, in some cases, the Test messages which may be
   limited by the transport mechanism for in-band messaging) have the
   following 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Vers  |      (Reserved)       |    Flags      |    Msg Type   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          LMP Length           |          (Reserved)           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Reserved field should be sent as zero and ignored on receipt.

   All values are defined in network byte order (i.e., big-endian byte
   order).

   Vers: 4 bits

        Protocol version number.  This is version 1.

   Flags: 8 bits.  The following values are defined.  All other values
          are reserved and should be sent as zero and ignored on
          receipt.

        0x01: ControlChannelDown

        0x02: LMP Restart

               This bit is set to indicate that a nodal failure has
               occured and the LMP control state has been lost.  This
               flag may be reset to 0 when a Hello message is received
               with RcvSeqNum equal to the local TxSeqNum.

   Msg Type: 8 bits.  The following values are defined.  All other
             values are reserved and should be sent as zero and ignored
             on receipt.

        1  = Config

        2  = ConfigAck


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        3  = ConfigNack

        4  = Hello

        5  = BeginVerify

        6  = BeginVerifyAck

        7  = BeginVerifyNack

        8  = EndVerify

        9  = EndVerifyAck

        10 = Test

        11 = TestStatusSuccess

        12 = TestStatusFailure

        13 = TestStatusAck

        14 = LinkSummary

        15 = LinkSummaryAck

        16 = LinkSummaryNack

        17 = ChannelStatus

        18 = ChannelStatusAck

        19 = ChannelStatusRequest

        20 = ChannelStatusResponse

        All of the messages are sent over the control channel EXCEPT
        the Test message, which is sent over the data link that is
        being tested.

   LMP Length: 16 bits

        The total length of this LMP message in bytes, including the
        common header and any variable-length objects that follow.

12.2. LMP Object Format

   LMP messages are built using objects.  Each object is identified by
   its Object Class and Class-type.  Each object has a name, which is
   always capitalized in this document.  LMP objects can be either
   negotiable or non-negotiable (identified by the N bit in the object
   header).  Negotiable objects can be used to let the devices agree on

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   certain values.  Non-negotiable objects are used for announcement of
   specific values that do not need or do not allow negotiation.

   All values are defined in network byte order (i.e., big-endian byte
   order).

   The format of the LMP object is as follows:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |N|   C-Type    |     Class     |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                       (object contents)                     //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   N: 1 bit

        The N flag indicates if the object is negotiable (N=1) or non-
        negotiable (N=0).

   C-Type: 7 bits

        Class-type, unique within an Object Class.  Values are defined
        in Section 13.

   Class: 8 bits

        The Class indicates the object type.  Each object has a name,
        which is always capitalized in this document.

   Length: 16 bits

        The Length field indicates the length of the object in bytes,
        including the N, C-Type, Class, and Length fields.

12.3. Parameter Negotiation Messages

12.3.1. Config Message (Msg Type = 1)

   The Config message is used in the control channel negotiation phase
   of LMP.  The contents of the Config message are built using LMP
   objects.  The format of the Config message is as follows:

   <Config Message> ::= <Common Header> <LOCAL_CCID> <MESSAGE_ID>
                        <LOCAL_NODE_ID> <CONFIG>

   The above transmission order SHOULD be followed.

   The MESSAGE_ID object is within the scope of the LOCAL_CCID object.

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   The Config message MUST be periodically transmitted until (1) it
   receives a ConfigAck or ConfigNack message, (2) a retry limit has
   been reached and no ConfigAck or ConfigNack message has been
   received, or (3) it receives a Config message from the remote node
   and has lost the contention (e.g., the Node_Id of the remote node is
   higher than the Node_Id of the local node).  Both the retransmission
   interval and the retry limit are local configuration parameters.

12.3.2. ConfigAck Message (Msg Type = 2)

   The ConfigAck message is used to acknowledge receipt of the Config
   message and indicate agreement on all parameters.

   <ConfigAck Message> ::= <Common Header> <LOCAL_CCID> <LOCAL_NODE_ID>
                           <REMOTE_CCID> <MESSAGE_ID_ACK>
                           <REMOTE_NODE_ID>

   The above transmission order SHOULD be followed.

   The contents of the REMOTE_CCID, MESSAGE_ID_ACK, and REMOTE_NODE_ID
   objects MUST be obtained from the Config message being acknowledged.

12.3.3. ConfigNack Message (Msg Type = 3)

   The ConfigNack message is used to acknowledge receipt of the Config
   message and indicate disagreement on non-negotiable parameters or
   propose other values for negotiable parameters.  Parameters where
   agreement was reached MUST NOT be included in the ConfigNack
   Message.  The format of the ConfigNack message is as follows:

   <ConfigNack Message> ::= <Common Header> <LOCAL_CCID>
                            <LOCAL_NODE_ID>  <REMOTE_CCID>
                            <MESSAGE_ID_ACK> <REMOTE_NODE_ID> <CONFIG>

   The above transmission order SHOULD be followed.

   The contents of the REMOTE_CCID, MESSAGE_ID_ACK, and REMOTE_NODE_ID
   objects MUST be obtained from the Config message being negatively
   acknowledged.

   It is possible that multiple parameters may be invalid in the Config
   message.

   If a negotiable CONFIG object is included in the ConfigNack message,
   it MUST include acceptable values for the parameters.

   If the ConfigNack message includes CONFIG objects for non-negotiable
   parameters, they MUST be copied from the CONFIG objects received in
   the Config message.



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   If the ConfigNack message is received and only includes CONFIG
   objects that are negotiable, then a new Config message SHOULD be
   sent.  The values in the CONFIG object of the new Config message
   SHOULD take into account the acceptable values included in the
   ConfigNack message.

   If a node receives a Config message and recognizes the CONFIG object
   but does not recognize the C-Type, a ConfigNack message including
   the unknown CONFIG object MUST be sent.

12.4. Hello Message (Msg Type = 4)

   The format of the Hello message is as follows:

   <Hello Message> ::= <Common Header> <LOCAL_CCID> <HELLO>

   The above transmission order SHOULD be followed.

   The Hello message MUST be periodically transmitted at least once
   every HelloInterval msec.  If no Hello message is received within
   the HelloDeadInterval, the control channel is assumed to have
   failed.

12.5. Link Verification Messages

12.5.1. BeginVerify Message (Msg Type = 5)

   The BeginVerify message is sent over the control channel and is used
   to initiate the link verification process.  The format is as
   follows:

   <BeginVerify Message> ::= <Common Header> <LOCAL_LINK_ID>
                             <MESSAGE_ID> [<REMOTE_LINK_ID>]
                             <BEGIN_VERIFY>

   The above transmission order SHOULD be followed.

   To limit the scope of Link Verification to a particular TE Link, the
   Link_Id field of the LOCAL_LINK_ID object MUST be non-zero.  If this
   field is zero, the data links can span multiple TE links and/or they
   may comprise a TE link that is yet to be configured.  In the special
   case where the local Link_Id field is zero, the "Verify all Links"
   flag of the BEGIN_VERIFY object is used to distinguish between data
   links that span multiple TE links and those that have not yet been
   assigned to a TE link (see Section 5).

   The REMOTE_LINK_ID object may be included if the local/remote
   Link_Id mapping is known.

   The Link_Id field of the REMOTE_LINK_ID object MUST be non-zero if
   included.


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   The BeginVerify message MUST be periodically transmitted until (1)
   the node receives either a BeginVerifyAck or BeginVerifyNack message
   to accept or reject the verify process or (2) a retry limit has been
   reached and no BeginVerifyAck or BeginVerifyNack message has been
   received.  Both the retransmission interval and the retry limit are
   local configuration parameters.

12.5.2. BeginVerifyAck Message (Msg Type = 6)

   When a BeginVerify message is received and Test messages are ready
   to be processed, a BeginVerifyAck message MUST be transmitted.

   <BeginVerifyAck Message> ::= <Common Header> [<LOCAL_LINK_ID>]
                                <MESSAGE_ID_ACK> <BEGIN_VERIFY_ACK>
                                <VERIFY_ID>

   The above transmission order SHOULD be followed.

   The LOCAL_LINK_ID object may be included if the local/remote Link_Id
   mapping is known or learned through the BeginVerify message.

   The Link_Id field of the LOCAL_LINK_ID MUST be non-zero if included.

   The contents of the MESSAGE_ID_ACK object MUST be obtained from the
   BeginVerify message being acknowledged.

   The VERIFY_ID object contains a node-unique value that is assigned
   by the generator of the BeginVerifyAck message.  This value is used
   to uniquely identify the Verification process from multiple LMP
   neighbors and/or parallel Test procedures between the same LMP
   neighbors.

12.5.3. BeginVerifyNack Message (Msg Type = 7)

   If a BeginVerify message is received and a node is unwilling or
   unable to begin the Verification procedure, a BeginVerifyNack
   message MUST be transmitted.

   <BeginVerifyNack Message> ::= <Common Header> [<LOCAL_LINK_ID>]
                                 <MESSAGE_ID_ACK> <ERROR_CODE>

   The above transmission order SHOULD be followed.

   The contents of the MESSAGE_ID_ACK object MUST be obtained from the
   BeginVerify message being negatively acknowledged.

   If the Verification process is not supported, the ERROR_CODE MUST
   indicate "Link Verification Procedure not supported".

   If Verification is supported, but the node is unable to begin the
   procedure, the ERROR_CODE MUST indicate "Unwilling to verify".  If a
   BeginVerifyNack message is received with such an ERROR_CODE, the

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   node that originated the BeginVerify SHOULD schedule a BeginVerify
   retransmission after Rf seconds, where Rf is a locally defined
   parameter.

   If the Verification Transport mechanism is not supported, the
   ERROR_CODE MUST indicate, "Unsupported verification transport
   mechanism".

   If remote configuration of the Link_Id is not supported and the
   contents of the REMOTE_LINK_ID object (included in the BeginVerify
   message) does not match any configured values, the ERROR_CODE MUST
   indicate "Link_Id configuration error".

   If a node receives a BeginVerify message and recognizes the
   BEGIN_VERIFY object but does not recognize the C-Type, the
   ERROR_CODE MUST indicate, "Unknown object C-Type".

12.5.4. EndVerify Message (Msg Type = 8)

   The EndVerify message is sent over the control channel and is used
   to terminate the link verification process.  The EndVerify message
   may be sent at any time the initiating node desires to end the
   Verify procedure.  The format is as follows:

   <EndVerify Message> ::= <Common Header> <MESSAGE_ID> <VERIFY_ID>

   The above transmission order SHOULD be followed.

   The EndVerify message will be periodically transmitted until (1) an
   EndVerifyAck message has been received or (2) a retry limit has been
   reached and no EndVerifyAck message has been received.  Both the
   retransmission interval and the retry limit are local configuration
   parameters.

12.5.5. EndVerifyAck Message (Msg Type =9)

   The EndVerifyAck message is sent over the control channel and is
   used to acknowledge the termination of the link verification
   process.  The format is as follows:

   <EndVerifyAck Message> ::= <Common Header> <MESSAGE_ID_ACK>
                              <VERIFY_ID>

   The above transmission order SHOULD be followed.

   The contents of the MESSAGE_ID_ACK object MUST be obtained from the
   EndVerify message being acknowledged.

12.5.6. Test Message (Msg Type = 10)

   The Test message is transmitted over the data link and is used to
   verify its physical connectivity.  Unless explicitly stated, these

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   messages MUST be transmitted over UDP like all other LMP messages.
   The format of the Test messages is as follows:

   <Test Message> ::= <Common Header> <LOCAL_INTERFACE_ID> <VERIFY_ID>

   The above transmission order SHOULD be followed.

   Note that this message is sent over a data link and NOT over the
   control channel.  The transport mechanism for the Test message is
   negotiated using Verify Transport Mechanism field of the
   BEGIN_VERIFY object and the Verify Transport Response field of the
   BEGIN_VERIFY_ACK object (see Sections 13.8 and 13.9).

   The local (transmitting) node sends a given Test message
   periodically (at least once every VerifyInterval ms) on the
   corresponding data link until (1) it receives a correlating
   TestStatusSuccess or TestStatusFailure message on the control
   channel from the remote (receiving) node or (2) all active control
   channels between the two nodes have failed.  The remote node will
   send a given TestStatus message periodically over the control
   channel until it receives either a correlating TestStatusAck message
   or an EndVerify message is received over the control channel.

12.5.7. TestStatusSuccess Message (Msg Type = 11)

   The TestStatusSuccess message is transmitted over the control
   channel and is used to transmit the mapping between the local
   Interface_Id and the Interface_Id that was received in the Test
   message.

   <TestStatusSuccess Message> ::= <Common Header> <LOCAL_LINK_ID>
                                   <MESSAGE_ID> <LOCAL_INTERFACE_ID>
                                   <REMOTE_INTERFACE_ID> <VERIFY_ID>

   The above transmission order SHOULD be followed.

   The contents of the REMOTE_INTERFACE_ID object MUST be obtained from
   the corresponding Test message being positively acknowledged.

12.5.8. TestStatusFailure Message (Msg Type = 12)

   The TestStatusFailure message is transmitted over the control
   channel and is used to indicate that the Test message was not
   received.

   <TestStatusFailure Message> ::= <Common Header> <MESSAGE_ID>
                                   <VERIFY_ID>

   The above transmission order SHOULD be followed.




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12.5.9. TestStatusAck Message (Msg Type = 13)

   The TestStatusAck message is used to acknowledge receipt of the
   TestStatusSuccess or TestStatusFailure messages.

   <TestStatusAck Message> ::= <Common Header> <MESSAGE_ID_ACK>
                               <VERIFY_ID>

   The above transmission order SHOULD be followed.

   The contents of the MESSAGE_ID_ACK object MUST be obtained from the
   TestStatusSuccess or TestStatusFailure message being acknowledged.

12.6. Link Summary Messages

12.6.1. LinkSummary Message (Msg Type = 14)

   The LinkSummary message is used to synchronize the Interface_Ids and
   correlate the properties of the TE link.  The format of the
   LinkSummary message is as follows:

   <LinkSummary Message> ::= <Common Header> <MESSAGE_ID> <TE_LINK>
                             <DATA_LINK> [<DATA_LINK>...]

   The above transmission order SHOULD be followed.

   The LinkSummary message can be exchanged at any time a link is not
   in the Verification process.  The LinkSummary message MUST be
   periodically transmitted until (1) the node receives a
   LinkSummaryAck or LinkSummaryNack message or (2) a retry limit has
   been reached and no LinkSummaryAck or LinkSummaryNack message has
   been received.  Both the retransmission interval and the retry limit
   are local configuration parameters.

12.6.2. LinkSummaryAck Message (Msg Type = 15)

   The LinkSummaryAck message is used to indicate agreement on the
   Interface_Id synchronization and acceptance/agreement on all the
   link parameters.  It is on the reception of this message that the
   local node makes the Link_Id associations.

   <LinkSummaryAck Message> ::=  <Common Header> <MESSAGE_ID_ACK>

   The above transmission order SHOULD be followed.

12.6.3. LinkSummaryNack Message (Msg Type = 16)

   The LinkSummaryNack message is used to indicate disagreement on non-
   negotiated parameters or propose other values for negotiable
   parameters.  Parameters where agreement was reached MUST NOT be
   included in the LinkSummaryNack message.


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   <LinkSummaryNack Message> ::= <Common Header> <MESSAGE_ID_ACK>
                                 <ERROR_CODE> [<DATA_LINK>...]

   The above transmission order SHOULD be followed.

   The DATA_LINK objects MUST include acceptable values for all
   negotiable parameters.  If the LinkSummaryNack includes DATA_LINK
   objects for non-negotiable parameters, they MUST be copied from the
   DATA_LINK objects received in the LinkSummary message.

   If the LinkSummaryNack message is received and only includes
   negotiable parameters, then a new LinkSummary message SHOULD be
   sent.  The values received in the new LinkSummary message SHOULD
   take into account the acceptable parameters included in the
   LinkSummaryNack message.

   If the LinkSummary message is received with unacceptable non-
   negotiable parameters, the ERROR_CODE MUST indicate "Unacceptable
   non-netotiable LINK_SUMMARY parameters."

   If the LinkSummary message is received with unacceptable negotiable
   parameters, the ERROR_CODE MUST indicate "Renegotiate LINK_SUMMARY
   parameters."

   If the LinkSummary message is received with an invalid TE_LINK
   object, the ERROR_CODE MUST indicate "Invalid TE_LINK object."

   If the LinkSummary message is received with an invalid DATA_LINK
   object, the ERROR_CODE MUST indicate "Invalid DATA_LINK object."

   If the LinkSummary message is received with a TE_LINK object but the
   C-Type is unknown, the ERROR_CODE MUST indicate, "Unknown TE_LINK
   object C-Type."

   If the LinkSummary message is received with a DATA_LINK object but
   the C-Type is unknown, the ERROR_CODE MUST indicate, "Unknown
   DATA_LINK object C-Type."

12.7. Fault Management Messages

12.7.1. ChannelStatus Message (Msg Type = 17)

   The ChannelStatus message is sent over the control channel and is
   used to notify an LMP neighbor of the status of a data link.  A node
   that receives a ChannelStatus message MUST respond with a
   ChannelStatusAck message.  The format is as follows:

   <ChannelStatus Message> ::= <Common Header> <LOCAL_LINK_ID>
                               <MESSAGE_ID> <CHANNEL_STATUS>

   The above transmission order SHOULD be followed.


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   If the CHANNEL_STATUS object does not include any Interface_Ids,
   then this indicates the entire TE Link has failed.

12.7.2. ChannelStatusAck Message (Msg Type = 18)

   The ChannelStatusAck message is used to acknowledge receipt of the
   ChannelStatus Message.  The format is as follows:

   <ChannelStatusAck Message> ::= <Common Header> <MESSAGE_ID_ACK>

   The above transmission order SHOULD be followed.

   The contents of the MESSAGE_ID_ACK object MUST be obtained from the
   ChannelStatus message being acknowledged.

12.7.3. ChannelStatusRequest Message (Msg Type = 19)

   The ChannelStatusRequest message is sent over the control channel
   and is used to request the status of one or more data link(s).  A
   node that receives a ChannelStatusRequest message MUST respond with
   a ChannelStatusResponse message.  The format is as follows:

   <ChannelStatusRequest Message> ::= <Common Header> <LOCAL_LINK_ID>
                                      <MESSAGE_ID>
                                      [<CHANNEL_STATUS_REQUEST>]

   The above transmission order SHOULD be followed.

   If the CHANNEL_STATUS_REQUEST object is not included, then the
   ChannelStatusRequest is being used to request the status of ALL of
   the data link(s) of the TE Link.

12.7.4. ChannelStatusResponse Message (Msg Type = 20)

   The ChannelStatusResponse message is used to acknowledge receipt of
   the ChannelStatusRequest Message and notify the LMP neighbor of the
   status of the data channel(s).  The format is as follows:

   <ChannelStatusResponse Message> ::= <Common Header> <MESSAGE_ID_ACK>
                                       <CHANNEL_STATUS>

   The above transmission order SHOULD be followed.

   The contents of the MESSAGE_ID_ACK objects MUST be obtained from the
   ChannelStatusRequest message being acknowledged.








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13. LMP Object Definitions

13.1. CCID (Control Channel ID) Class

   Class = 1.

   o    C-Type = 1, LOCAL_CCID

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            CC_Id                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   CC_Id:  32 bits

        This MUST be node-wide unique and non-zero.  The CC_Id
        identifies the control channel of the sender associated with
        the message.

   This object is non-negotiable.

   o    C-Type = 2, REMOTE_CCID

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             CC_Id                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   CC_Id:  32 bits

        This identifies the remote nodeÆs CC_Id and MUST be non-zero.

   This object is non-negotiable.

13.2. NODE_ID Class

   Class = 2.

   o    C-Type = 1, LOCAL_NODE_ID

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Node_Id (4 bytes)                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Node_Id:

        This identities the node that originated the LMP packet.


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   This object is non-negotiable.

   o    C-Type = 2, REMOTE_NODE_ID

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Node_Id (4 bytes)                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Node_Id:

        This identities the remote node.

   This object is non-negotiable.

13.3. LINK_ID Class

   Class = 3

   o    C-Type = 1, IPv4 LOCAL_LINK_ID

   o    C-Type = 2, IPv4 REMOTE_LINK_ID

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Link_Id (4 bytes)                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   o    C-Type = 3, IPv6 LOCAL_LINK_ID

   o    C-Type = 4, IPv6 REMOTE_LINK_ID

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                        Link_Id (16 bytes)                     +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+








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   o    C-Type = 5, Unnumbered LOCAL_LINK_ID

   o    C-Type = 6, Unnumbered REMOTE_LINK_ID

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Link_Id (4 bytes)                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Link_Id:

        For LOCAL_LINK_ID, this identifies the senderÆs Link associated
        with the message. This value MUST be non-zero.

        For REMOTE_LINK_ID, this identifies the remote nodeÆs Link_Id
        and MUST be non-zero.

   This object is non-negotiable.

13.4. INTERFACE_ID Class

   Class = 4

   o    C-Type = 1, IPv4 LOCAL_INTERFACE_ID

   o    C-Type = 2, IPv4 REMOTE_INTERFACE_ID

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Interface_Id (4 bytes)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   o    C-Type = 3, IPv6 LOCAL_INTERFACE_ID

   o    C-Type = 4, IPv6 REMOTE_INTERFACE_ID

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                       Interface_Id (16 bytes)                 +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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   o    C-Type = 5, Unnumbered LOCAL_INTERFACE_ID

   o    C-Type = 6, Unnumbered REMOTE_INTERFACE_ID

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Interface_Id (4 bytes)                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Interface_Id:

        For the LOCAL_INTERFACE_ID, this identifies the data link.
        This value MUST be node-wide unique and non-zero.

        For the REMOTE_INTERFACE_ID, this identifies the remote nodeÆs
        data link.  The Interface_Id MUST be non-zero.

   This object is non-negotiable.

13.5. MESSAGE_ID Class

   Class = 5.

   o    C-Type=1, MessageId

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Message_Id                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Message_Id:

        The Message_Id field is used to identify a message.  This value
        is incremented and only decreases when the value wraps.  This
        is used for message acknowledgment.

   This object is non-negotiable.

   o    C-Type = 2, MessageIdAck

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Message_Id                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+






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   Message_Id:

        The Message_Id field is used to identify the message being
        acknowledged.  This value is copied from the MESSAGE_ID object
        of the message being acknowledged.

   This object is non-negotiable.

13.6. CONFIG Class

   Class = 6.

   o    C-Type = 1, HelloConfig

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         HelloInterval         |      HelloDeadInterval        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   HelloInterval:  16 bits.

        Indicates how frequently the Hello packets will be sent and is
        measured in milliseconds (ms).

   HelloDeadInterval:  16 bits.

        If no Hello packets are received within the HelloDeadInterval,
        the control channel is assumed to have failed.  The
        HelloDeadInterval is measured in milliseconds (ms).  The
        HelloDeadInterval MUST be greater than the HelloInterval, and
        SHOULD be at least 3 times the value of HelloInterval.

   If the fast keep-alive mechanism of LMP is not used, the
   HelloInterval and HelloDeadInterval MUST be set to zero.

13.7. HELLO Class

   Class = 7

   o    C-Type = 1, Hello

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           TxSeqNum                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           RcvSeqNum                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




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   TxSeqNum:  32 bits

        This is the current sequence number for this Hello message.
        This sequence number will be incremented when the sequence
        number is reflected in the RcvSeqNum of a Hello packet that is
        received over the control channel.

        TxSeqNum=0 is not allowed.

        TxSeqNum=1 is used to indicate that the this is the first Hello
        message sent over the control channel.

   RcvSeqNum:  32 bits

        This is the sequence number of the last Hello message received
        over the control channel.  RcvSeqNum=0 is used to indicate that
        a Hello message has not yet been received.

   This object is non-negotiable.

13.8. BEGIN_VERIFY Class

   Class = 8.

   o    C-Type = 1

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Flags                      |         VerifyInterval        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Number of Data Links                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    EncType    |  (Reserved)   |  Verify Transport Mechanism   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       TransmissionRate                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Wavelength                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Reserved field should be sent as zero and ignored on receipt.

   Flags:  16 bits

        The following flags are defined:

        0x01 Verify all Links
                If this bit is set, the verification process checks all
                unallocated links; else it only verifies new ports or
                component links that are to be added to this TE link.



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        0x02 Data Link Type
                If set, the data links to be verified are ports,
                otherwise they are component links

   VerifyInterval:  16 bits

        This is the interval between successive Test messages and is
        measured in milliseconds (ms).

   Number of Data Links:  32 bits

        This is the number of data links that will be verified.

   EncType:  8 bits

        This is the encoding type of the data link.  The defined
        EncType values are consistent with the LSP Encoding Type values
        of [GMPLS-SIG].

   Verify Transport Mechanism:  16 bits

        This defines the transport mechanism for the Test Messages.
        The scope of this bit mask is restricted to each encoding type.
        The local node will set the bits corresponding to the various
        mechanisms it can support for transmitting LMP test messages.
        The receiver chooses the appropriate mechanism in the
        BeginVerifyAck message.

        The following flag is defined across all Encoding Types.  All
        other flags are dependent on the Encoding Type.

        0x8000 Payload: Test Message transmitted in the payload

                Capable of transmitting Test messages in the payload.
                The Test message is sent as an IP packet as defined
                above.

   TransmissionRate:  32 bits

        This is the transmission rate of the data link over which the
        Test messages will be transmitted.  This is expressed in bytes
        per second and represented in IEEE floating-point format.

   Wavelength:  32 bits

        When a data link is assigned to a port or component link that
        is capable of transmitting multiple wavelengths (e.g., a fiber
        or waveband-capable port), it is essential to know which
        wavelength the test messages will be transmitted over.  This
        value corresponds to the wavelength at which the Test messages
        will be transmitted over and has local significance.  If there


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        is no ambiguity as to the wavelength over which the message
        will be sent, then this value SHOULD be set to 0.

13.9. BEGIN_VERIFY_ACK Class

   Class = 9.

   o    C-Type = 1

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      VerifyDeadInterval       |   Verify_Transport_Response   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   VerifyDeadInterval:  16 bits

        If a Test message is not detected within the
        VerifyDeadInterval, then a node will send the TestStatusFailure
        message for that data link.

   Verify_Transport_Response:  16 bits

        The recipient of the BeginVerify message (and the future
        recipient of the TEST messages) chooses the transport mechanism
        from the various types that are offered by the transmitter of
        the Test messages.  One and only one bit MUST be set in the
        verification transport response.

   This object is non-negotiable.

13.10.  VERIFY_ID Class

   Class = 10.

   o    C-Type = 1

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Verify_Id                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Verify_Id:  32 bits

        This is used to differentiate Test messages from different TE
        links and/or LMP peers.  This is a node-unique value that is
        assigned by the recipient of the BeginVerify message.

   This object is non-negotiable.



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13.11.  TE_LINK Class

   Class = 11.

   o    C-Type = 1, IPv4 TE_LINK

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Flags     |                   (Reserved)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Local_Link_Id (4 bytes)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Remote_Link_Id (4 bytes)                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   o    C-Type = 2, IPv6 TE_LINK

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Flags     |                   (Reserved)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                      Local_Link_Id (16 bytes)                 +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                      Remote_Link_Id (16 bytes)                +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   o    C-Type = 3, Unnumbered TE_LINK

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Flags     |                   (Reserved)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Local_Link_Id (4 bytes)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Remote_Link_Id (4 bytes)                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


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   The Reserved field should be sent as zero and ignored on receipt.

   Flags: 8 bits
        The following flags are defined.  All other values are reserved
        and should be sent as zero and ignored on receipt.

        0x01 Fault Management Supported.

        0x02 Link Verification Supported.

   Local_Link_Id:

        This identifies the nodeÆs local Link_Id and MUST be non-zero.

   Remote_Link_Id:

        This identifies the remote nodeÆs Link_Id and MUST be non-zero.

13.12.  DATA_LINK Class

   Class = 12.

   o    C-Type = 1, IPv4 DATA_LINK

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Flags     |                   (Reserved)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Local_Interface_Id (4 bytes)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Remote_Interface_Id (4 bytes)               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                        (Subobjects)                         //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
















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   o    C-Type = 2, IPv6 DATA_LINK

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Flags     |                   (Reserved)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                   Local_Interface_Id (16 bytes)               +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                   Remote_Interface_Id (16 bytes)              +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                        (Subobjects)                         //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   o    C-Type = 3, Unnumbered DATA_LINK

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Flags     |                   (Reserved)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Local_Interface_Id (4 bytes)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Remote_Interface_Id (4 bytes)               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                        (Subobjects)                         //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Reserved field should be sent as zero and ignored on receipt.

   Flags: 8 bits

        The following flags are defined.  All other values are reserved
        and should be sent as zero and ignored on receipt.



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        0x01 Interface Type: If set, the data link is a port,
                              otherwise it is a component link.
        0x02 Allocated Link: If set, the data link is currently
                              allocated for user traffic.  If a single
                              Interface_Id is used for both the
                              transmit and receive data links, then
                              this bit only applies to the transmit
                              interface.
        0x04 Failed Link: If set, the data link is failed and not
                          suitable for user traffic.

   Local_Interface_Id:

        This is the local identifier of the data link.  This MUST be
        node-wide unique and non-zero.

   Remote_Interface_Id:

        This is the remote identifier of the data link.  This MUST be
        non-zero.

   Subobjects

        The contents of the DATA_LINK object consist of a series of
        variable-length data items called subobjects.  The subobjects
        are defined in section 13.12.1 below.

   A DATA_LINK object may contain more than one subobject.  More than
   one subobject of the same Type may appear if multiple capabilities
   are supported over the data link.

13.12.1.  Data Link Subobjects

   The contents of the DATA_LINK object include a series of variable-
   length data items called subobjects.  Each subobject has the form:

    0                   1
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---------------//------------ -+
   |    Type       |    Length     |      (Subobject contents)     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--------------//---------------+

   Type: 8 bits

        The Type indicates the type of contents of the subobject.
        Currently defined values are:

        Type = 1, Interface Switching Type

        Type = 2, Wavelength



J. Lang, Editor            Standards Track                  [Page 59]


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   Length: 8 bits

        The Length contains the total length of the subobject in bytes,
        including the Type and Length fields.  The Length MUST be at
        least 4, and MUST be a multiple of 4.

13.12.1.1. Subobject Type 1: Interface Switching Type

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Type       |    Length     | Switching Type|   EncType     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Minimum Reservable Bandwidth                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Maximum Reservable Bandwidth                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Switching Type: 8 bits

        This is used to identify the local Interface Switching Type of
        the TE link as defined in [GMPLS-SIG].

   EncType:  8 bits

        This is the encoding type of the data link.  The defined
        EncType values are consistent with the LSP Encoding Type values
        of [GMPLS-SIG].

   Minimum Reservable Bandwidth: 32 bits

        This is measured in bytes per second and represented in IEEE
        floating point format.

   Maximum Reservable Bandwidth: 32 bits

        This is measured in bytes per second and represented in IEEE
        floating point format.

   If the interface only supports a fixed rate, the minimum and maximum
   bandwidth fields are set to the same value.

13.12.1.2. Subobject Type 2: Wavelength

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Type       |    Length     |         (Reserved)            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Wavelength                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


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   The Reserved field should be sent as zero and ignored on receipt.

   Wavelength: 32 bits

        This value indicates the wavelength carried over the port.
        Values used in this field only have significance between two
        neighbors.

13.13.  CHANNEL_STATUS Class

   Class = 13

   o    C-Type = 1, IPv4 INTERFACE_ID

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Interface_Id (4 bytes)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |A|D|                     Channel Status                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              :                                |
   //                             :                               //
   |                              :                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Interface_Id (4 bytes)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |A|D|                     Channel Status                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
























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   o    C-Type = 2, IPv6 INTERFACE_ID

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                       Interface_Id (16 bytes)                 +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |A|D|                     Channel Status                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              :                                |
   //                             :                               //
   |                              :                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                       Interface_Id (16 bytes)                 +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |A|D|                     Channel Status                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   o    C-Type = 3, Unnumbered INTERFACE_ID

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Interface_Id (4 bytes)                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |A|D|                     Channel Status                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              :                                |
   //                             :                               //
   |                              :                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Interface_Id (4 bytes)                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |A|D|                     Channel_Status                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Active bit: 1 bit

   This indicates that the Channel is allocated to user traffic and the
   data link should be actively monitored.

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   Direction bit: 1 bit

   This indicates the direction (transmit/receive) of the data channel
   referred to in the CHANNEL_STATUS object.  If set, this indicates
   the data channel is in the transmit direction.

   Channel_Status: 30 bits

        This indicates the status condition of a data channel.  The
        following values are defined.  All other values are reserved
        and should be sent as zero and ignored on receipt.

        1   Signal Okay (OK): Channel is operational
        2   Signal Degrade (SD): A soft failure caused by a BER
                    exceeding a preselected threshold.  The specific
                    BER used to define the threshold is configured.
        3   Signal Fail (SF): A hard signal failure including (but not
                    limited to) loss of signal (LOS), loss of frame
                    (LOF), or Line AIS.

   This object contains one or more Interface_Ids followed by a
   Channel_Status field.

   To indicate the status of the entire TE Link, there MUST only be one
   Interface_Id and it MUST be zero.

   This object is non-negotiable.

13.14.  CHANNEL_STATUS_REQUEST Class

   Class = 14

   o    C-Type = 1, IPv4 INTERFACE_ID

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Interface_Id (4 bytes)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              :                                |
   //                             :                               //
   |                              :                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Interface_Id (4 bytes)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   This object contains one or more Interface_Ids.

   The Length of this object is 4 + 4N in bytes, where N is the number
   of Interface_Ids.



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   o    C-Type = 2, IPv6 INTERFACE_ID

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                       Interface_Id (16 bytes)                 +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              :                                |
   //                             :                               //
   |                              :                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                       Interface_Id (16 bytes)                 +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   This object contains one or more Interface_Ids.

   The Length of this object is 4 + 16N in bytes, where N is the number
   of Interface_Ids.

   o    C-Type = 3, Unnumbered INTERFACE_ID

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Interface_Id (4 bytes)                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              :                                |
   //                             :                               //
   |                              :                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Interface_Id (4 bytes)                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   This object contains one or more Interface_Ids.

   The Length of this object is 4 + 4N in bytes, where N is the number
   of Interface_Ids.

   This object is non-negotiable.


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13.15.  ERROR_CODE Class

   Class = 20.

   o    C-Type = 1, BEGIN_VERIFY_ERROR

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          ERROR CODE                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        The following bit-values are defined in network byte order
        (i.e., big-endian byte order):

        0x01 = Link Verification Procedure not supported.
        0x02 = Unwilling to verify.
        0x04 = Unsupported verification transport mechanism.
        0x08 = Link_Id configuration error.
        0x10 = Unknown object C-Type.

        All other values are reserved and should be sent as zero and
        ignored on receipt.

        Multiple bits may be set to indicate multiple errors.

        This object is non-negotiable.

   If a BeginVerifyNack message is received with Error Code 2, the node
   that originated the BeginVerify SHOULD schedule a BeginVerify
   retransmission after Rf seconds, where Rf is a locally defined
   parameter.

   o    C-Type = 2, LINK_SUMMARY_ERROR

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          ERROR CODE                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        The following bit-values are defined in network byte order
        (i.e., big-endian byte order):

        0x01 = Unacceptable non-negotiable LINK_SUMMARY parameters.
        0x02 = Renegotiate LINK_SUMMARY parameters.
        0x04 = Invalid TE_LINK Object.
        0x08 = Invalid DATA_LINK Object.
        0x10 = Unknown TE_LINK object C-Type.
        0x20 = Unknown DATA_LINK object C-Type.



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        All other values are reserved and should be sent as zero and
        ignored on receipt.

        Multiple bits may be set to indicate multiple errors.

        This object is non-negotiable.

14. Intellectual Property Considerations

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights.  Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11.  Copies of
   claims of rights made available for publication and any assurances
   of licenses to be made available, or the result of an attempt made
   to obtain a general license or permission for the use of such
   proprietary rights by implementers or users of this specification
   can be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard.  Please address the information to the IETF Executive
   Director.

15. References

15.1. Normative References

   [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate
               Requirement Levels", BCP 14, RFC 2119, March 1997.
   [BUNDLE]    Kompella, K., Rekhter, Y., Berger, L., "Link Bundling in
               MPLS Traffic Engineering," (work in progress).
   [GMPLS-SIG] Ashwood-Smith, P., Banerjee, A., et al, "Generalized
               MPLS - Signaling Functional Description," (work in
               progress).
   [GMPLS-RTG] Kompella, K., Rekhter, Y. et al, "Routing Extensions in
               Support of Generalized MPLS", (work in progress).
   [RFC2961]   Berger, L., Gan, D., et al, "RSVP Refresh Overhead
               Reduction Extensions," RFC 2961, April 2001.
   [RFC2402]   Kent, S., Atkinson, R., "IP Authentication Header", RFC
               2402, November 1998
   [RFC2406]   Kent, S., Atkinson, R., "IP Encapsulating Security
               Payload (ESP)", RFC 2406, November 1998
   [RFC2407]   Piper, D., "The Internet IP Security Domain of
               Interpretation for ISAKMP", RFC 2407, November 1998
   [RFC2409]   Harkins, D., Carrel, D., "The Internet Key Exchange
               (IKE)", RFC 2409, November 1998

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15.2. Informative References

   [RFC3209]   Awduche, D. O., Berger, L, et al, "Extensions to RSVP
               for LSP Tunnels," Internet Draft, RFC3209 December 2001.
   [OSPF-TE]   Katz, D., Yeung, D., Kompella, K., "Traffic Engineering
               Extensions to OSPF," (work in progress).
   [ISIS-TE]   Li, T., Smit, H., "IS-IS extensions for Traffic
               Engineering," (work in progress).
   [RFC2401]   Kent, S., Atkinson, R., "Security Architecture for the
               Internet Protocol", RFC 2401, November 1998
   [RFC2434]   Narten, T. and Alvestrand, H., "Guidelines for Writing
               an IANA Considerations Section in RFCs," RFC 2434,
               October 1998.

16. Security Considerations

   There are number of attacks that an LMP protocol session can
   potentially experience.  Some examples include:

        o an adversary may spoof control packets

        o an adversary may modify the control packets in transit

        o an adversary may replay control packets

        o an adversary may study a number of control packets and try to
          break the key using cryptographic tools.  If the
          hash/encryption algorithm used has known weaknesses than it
          becomes easy for the adversary to discover the key using
          simple tools.

   This section specifies an IPsec-based security mechanism for LMP.

16.1. Security Requirements

   The following requirements are applied to the mechanism described in
   this section.

        o LMP security MUST be able to provide authentication, integrity
          and replay protection.

        o For LMP traffic, confidentiality is not needed.  Only
          authentication is needed to ensure the control packets
          (packets sent along the LMP Control Channel) are originating
          from the right place and have not been modified in transit.
          LMP Test packets exchanged through the data links do not need
          to be protected.

        o Security mechanism should provide for well defined key
          management schemes.  The key management schemes should be well
          analyzed to be cryptographically secure.  The key management
          schemes should be scalable.

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        o The algorithms used for authentication MUST be
          cryptographically sound.  Also the security protocol MUST
          allow for negotiating and using different authentication
          algorithms.

16.2. Security Mechanisms

   IPsec is a protocol suite that is used to secure communication at the
   network layer between two peers.  This protocol is comprised of IP
   Security architecture document [RFC2401], IKE [RFC2409], IPsec AH
   [RFC2402], and IPsec ESP [RFC2406].  IKE is the key management
   protocol for IP networks while AH and ESP are used to protect IP
   traffic.  IKE is defined specific to IP domain of interpretation.

   Considering the requirements described in Section 16.1, it is
   recommended that where security is needed for LMP, implementations
   use IPsec as described below:

   1. IPsec AH, tunnel mode SHOULD be used for packet authentication.

   2. IKE [RFC2409] SHOULD be used as the key exchange mechanism.

   Implementations of LMP over IPsec protocol MUST support manual keying
   mode and dynamic key exchange protocol using IKE.  IKE implementation
   SHOULD use the IPsec DOI [RFC2407].

   For IKE protocol, the identities of the SAs negotiated in Quick Mode
   represent the traffic that the peers agree to protect and are
   comprised of address space, protocol and port information.  For LMP
   over IPsec, it is recommended that the identity payload contain the
   following information.  The identities SHOULD be of type IP
   addresses and the value of the identities SHOULD be the IP addresses
   of the communicating peers. The protocol field SHOULD be IP protocol
   UDP (17). The port field SHOULD be set to zero to indicate port
   fields should be ignored.  In LMP exchanges, the channel identifier
   user by the peer is not known beforehand, and hence cannot be used in
   the SA.  This restriction implies that LMP authentication is
   performed on a per LMP neighbor basis rather than on a per LMP
   control channel basis between two neighbors.

   All LMP messages are expected to be sent over the IPsec channel.  The
   crypto channel (IKE SA and IPsec SAs) may be established on need
   basis or earlier.  However, all LMP messages should be sent through
   the crypto channel.

   A set of control channels can share the same crypto channel.  When
   LMP Hellos are used to monitor the status of the control channel, it
   is important to keep in mind that the keep-alive failure in a control
   channel may also be due to failure in the crypto channel.  The
   following method is recommended to ensure LMP communication path
   between two peers is working properly.

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     - If LMP Hellos detect a failure on a control channel, switch to an
      alternate (backup) control channel and/or try to bring up a new
      control channel.

     - Ensure the health of the control channels using LMP Hellos.  If
      all control channels indicate a failure and it is not possible to
      bring up a new control channel, tear down all existing control
      channels.  Also tear down the crypto channel (both the IKE SA and
      IPsec SAs).

     - Reestablish the crypto channel.  Failure to establish a crypto
      channel indicates a fatal failure for LMP communication.

     - Bring up the control channel.  Failure to bring up the control
      channel indicates a fatal failure for LMP communication.

        o When LMP peers are dynamically discovered (particularly the
          initiator), the following points should be noted if pre-shared
          key based authentication is used for setting up the crypto
          channels.  When using pre-shared key based authentication, the
          pre-shared key is required to compute the value of SKEYID
          (used for deriving keys to encrypt messages during key
          exchange).  In main mode, pre-shared key to be used has to be
          identified from information in the IP header since SKEYID is
          calculated prior to the receipt of identification payloads.
          This is not possible if the IP addresses of the peer are
          discovered dynamically.  Aggressive mode of key exchange can
          be used since identification payloads are sent in the first
          message.

   Note however that aggressive mode is prone to passive denial of
   service attacks.  We also strongly discourage using a shared secret
   (group shared secret) among a number of peers as this opens up the
   solution to man-in-the middle attacks.

   Digital signature based authentication is not prone to such problems.
   It is recommended using digital signature based authentication
   mechanism where possible.  If pre-shared key based authentication is
   required, then aggressive mode SHOULD be used.  IKE pre-shared
   authentication key values SHOULD be protected in a manner similar to
   the user's account password.

17. IANA Considerations

   LMP requires that a UDP port number be assigned.

   LMP defines the following name spaces that require management:

   - LMP Message Type.
   -  LMP Object Class.


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   -  LMP Object Class type (C-Type).  These are unique within the
     Object Class.
   -  LMP Sub-object Class type (Type).  These are unique within the
     Object Class.

   The LMP Message Type name space should be allocated as follows:
   pursuant to the policies outlined in [RFC2434], the numbers in the
   range 0-127 are allocated by Expert Review, 128-240 are allocated
   through an IETF Consensus action, and 241-255 are reserved for
   Private Use.

   The LMP Object Class name space should be allocated as follows:
   pursuant to the policies outlined in [RFC2434], the numbers in the
   range of 0-127 are allocated by Expert Review, 128-247 are allocated
   through an IETF Consensus action, and 248-255 are reserved for
   Private Use.

   The LMP Sub-object Class name space should be allocated as follows:
   pursuant to the policies outlined in [RFC2434], the numbers in the
   range of 0-127 are allocated by Expert Review, 128-247 are allocated
   through an IETF Consensus action, and 248-255 are reserved for
   Private Use.

   The LMP Object Class type name space should be allocated as follows:
   pursuant to the policies outlined in [RFC2434], the numbers in the
   range 0-111 are allocated by Expert Review, 112-119 are allocated
   through an IETF Consensus action, and 120-127 are reserved for
   Private Use.

   The following name spaces need to be assigned initially:

   [Note to RFC Editor: Please drop all text enclosed in parentheses in
   this section once the IANA assignments are made.  The values are
   included for reference only and should be considered unassigned.]

   ------------------------------------------------------------------
   LMP Message Type name space

   o Config message (suggested Message type = 1)

   o ConfigAck message (suggested Message type = 2)

   o ConfigNack message (suggested Message type = 3)

   o Hello message (suggested Message type = 4)

   o BeginVerify message (suggested Message type = 5)

   o BeginVerifyAck message (suggested Message type = 6)

   o BeginVerifyNack message (suggested Message type = 7)


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   o EndVerify message (suggested Message type = 8)

   o EndVerifyAck message (suggested Message type = 9)

   o Test message (suggested Message type = 10)

   o TestStatusSuccess message (suggested Message type = 11)

   o TestStatusFailure message (suggested Message type = 12)

   o TestStatusAck message (suggested Message type = 13)

   o LinkSummary message (suggested Message type = 14)

   o LinkSummaryAck message (suggested Message type = 15)

   o LinkSummaryNack message (suggested Message type = 16)

   o ChannelStatus message (suggested Message type = 17)

   o ChannelStatusAck message (suggested Message type = 18)

   o ChannelStatusRequest message (suggested Message type = 19)

   o ChannelStatusResponse message (suggested Message type = 20)

   ------------------------------------------------------------------
   LMP Object Class name space and Class type (C-Type)

   o CCID                  Class name (suggested = 1)
     - LOCAL_CCID                     (suggested C-Type = 1)
     - REMOTE_CCID                    (suggested C-Type = 2)

   o NODE_ID               Class name (suggested = 2)
     - LOCAL_NODE_ID                  (suggested C-Type = 1)
     - REMOTE_NODE_ID                 (suggested C-Type = 2)

   o LINK_ID               Class name (suggested = 3)
     - IPv4 LOCAL_LINK_ID             (suggested C-Type = 1)
     - IPv4 REMOTE_LINK_ID            (suggested C-Type = 2)
     - IPv6 LOCAL_LINK_ID             (suggested C-Type = 3)
     - IPv6 REMOTE_LINK_ID            (suggested C-Type = 4)
     - unnumbered LOCAL_LINK_ID        (suggested C-Type = 5)
     - unnumbered REMOTE_LINK_ID       (suggested C-Type = 6)

   o INTERFACE_ID          Class name (suggested = 4)
     - IPv4 LOCAL_INTERFACE_ID         (suggested C-Type = 1)
     - IPv4 REMOTE_INTERFACE_ID        (suggested C-Type = 2)
     - IPv6 LOCAL_INTERFACE_ID         (suggested C-Type = 3)
     - IPv6 REMOTE_INTERFACE_ID        (suggested C-Type = 4)
     - unnumbered LOCAL_INTERFACE_ID   (suggested C-Type = 5)
     - unnumbered REMOTE_INTERFACE_ID  (suggested C-Type = 6)

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   o MESSAGE_ID            Class name (suggested = 5)
     - MESSAGE_ID                     (suggested C-Type = 1)
     - MESSAGE_ID_ACK                 (suggested C-Type = 2)

   o CONFIG_ID             Class name (suggested = 6)
     - HELLO_CONFIG                   (suggested C-Type = 1)

   o HELLO                 Class name (suggested = 7)
     - HELLO                          (suggested C-Type = 1)

   o BEGIN_VERIFY          Class name (suggested = 8)
     - Type 1                         (suggested C-Type = 1)

   o BEGIN_VERIFY_ACK      Class name (suggested = 9)
     - Type 1                         (suggested C-Type = 1)

   o VERIFY_ID             Class name (suggested = 10)
     - Type 1                         (suggested C-Type = 1)

   o TE_LINK               Class name (suggested = 11)
     - IPv4 TE_LINK                   (suggested C-Type = 1)
     - IPv6 TE_LINK                   (suggested C-Type = 2)
     - unnumbered TE_LINK             (suggested C-Type = 3)

   o DATA_LINK             Class name (suggested = 12)
     - IPv4 DATA_LINK                 (suggested C-Type = 1)
     - IPv6 DATA_LINK                 (suggested C-Type = 2)
     - unnumbered DATA_LINK            (suggested C-Type = 3)

     - Interface Switching Type        (suggested sub-object Type = 1)
     - Wavelength                      (suggested sub-object Type = 2)

   o CHANNEL_STATUS        Class name (suggested = 13)
     - IPv4 INTERFACE_ID              (suggested C-Type = 1)
     - IPv6 INTERFACE_ID              (suggested C-Type = 2)
     - unnumbered INTERFACE_ID         (suggested C-Type = 3)

   o CHANNEL_STATUS_REQUEST Class name (suggested = 14)
     - IPv4 INTERFACE_ID              (suggested C-Type = 1)
     - IPv6 INTERFACE_ID              (suggested C-Type = 2)
     - unnumbered INTERFACE_ID         (suggested C-Type = 3)

   o ERROR_CODE            Class name (suggested = 20)
     - BEGIN_VERIFY_ERROR             (suggested C-Type = 1)
     - LINK_SUMMARY_ERROR               (suggested C-Type = 2)

18. Acknowledgements

   The authors would like to thank Andre Fredette for his many
   contributions to this document.  We would also like to thank Ayan
   Banerjee, George Swallow, Andre Fredette, Adrian Farrel, Vinay

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   Ravuri, and David Drysdale for their insightful comments and
   suggestions.  We would also like to thank John Yu, Suresh Katukam,
   and Greg Bernstein for their helpful suggestions for the in-band
   control channel applicability.  Finally, we would like to thank
   Dimitri Papadimitriou for his contributions to the SONET/SDH test
   procedures.

19. Contributors

   Jonathan P. Lang                        Krishna Mitra
   Calient Networks                        Independent Consultant
   25 Castilian Drive                      email: kmitra@earthlink.net
   Goleta, CA 93117
   Email: jplang@calient.net

   John Drake                              Kireeti Kompella
   Calient Networks                        Juniper Networks, Inc.
   5853 Rue Ferrari                        1194 North Mathilda Avenue
   San Jose, CA 95138                      Sunnyvale, CA 94089
   email: jdrake@calient.net               email: kireeti@juniper.net

   Yakov Rekhter                           Lou Berger
   Juniper Networks, Inc.                  Movaz Networks
   1194 North Mathilda Avenue              email: lberger@movaz.com
   Sunnyvale, CA 94089
   email: yakov@juniper.net

   Debanjan Saha                           Debashis Basak
   Tellium Optical Systems                 Accelight Networks
   2 Crescent Place                        70 Abele Road, Suite 1201
   Oceanport, NJ 07757-0901                Bridgeville, PA 15017-3470
   email: dsaha@tellium.com                email: dbasak@accelight.com

   Hal Sandick                             Alex Zinin
   Shepard M.S.                            Alcatel
   2401 Dakota Street                      email: zinin@psg.com
   Durham, NC 27705
   email: sandick@nc.rr.com

   Bala Rajagopalan                        Sankar Ramamoorthi
   Tellium Optical Systems                 Juniper Networks, Inc.
   2 Crescent Place                        1194 North Mathilda Avenue
   Oceanport, NJ 07757-0901                Sunnyvale, CA 94089
   email: braja@tellium.com                email: sankarr@juniper.net

20. Contact Address

   Jonathan P. Lang
   Calient Networks
   25 Castilian Drive
   Goleta, CA 93117
   Email: jplang@calient.net

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21. Full Copyright Statement

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

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

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

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


























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