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Versions: 00 01 02 03 04 05 06 07 08 09 10 RFC 4204

Internet Draft       draft-ietf-ccamp-lmp-04.txt            June 2002

Network Working Group                          Jonathan P. Lang, Editor
Internet Draft
Expiration Date: December 2002

                                                              June 2002

                     Link Management Protocol (LMP)

                      draft-ietf-ccamp-lmp-04.txt

 Status of this Memo

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

   Optical networks are being developed to include photonic switches,
   optical crossconnects, and routers that are configured with control
   channels and data links. Furthermore, multiple data links may be
   combined to form a single traffic engineering (TE) link for routing
   purposes. This draft 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-bearing
   channels, correlate the link property information, suppress
   downstream alarms, and localize link failures for
   protection/restoration purposes in both opaque and transparent
   networks.








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Internet Draft       draft-ietf-ccamp-lmp-04.txt            June 2002

Table of Contents
   1  Introduction ................................................   4
   2  LMP Overview ................................................   5
   3 Control Channel Management ...................................   7
      3.1 Parameter Negotiation ...................................   8
      3.2 Hello Protocol ...........................................  9
          3.2.1  Hello Parameter Negotiation .......................  9
          3.2.2  Fast Keep-alive ..................................  10
          3.2.3  Control Channel Down .............................  11
          3.2.4  Degraded (DEG) State .............................  11
   4  Link Property Correlation ...................................  11
   5  Verifying Link Connectivity .................................  13
      5.1 Example of Link Connectivity Verification ...............  16
   6  Fault Management ............................................  17
      6.1 Fault Detection .........................................  17
      6.2 Fault Localization Procedure ............................  18
      6.3 Examples of Fault Localization ..........................  18
      6.4 Channel Activation Indication ...........................  19
      6.5 Channel Deactivation Indication .........................  20
   7  Message_Id Usage ............................................  20
   8  Graceful Restart ............................................  21
   9  Addressing ..................................................  22
   10 Exponential Back-off Procedures .............................  23
   10.1 Operation..................................................  23
   10.2 Retransmission Algorithm ..................................  23
   11 IANA Considerations .........................................  24
   12 LMP Finite State Machines ...................................  24
      12.1 Control Channel FSM ....................................  24
          12.1.1  Control Channel States ..........................  24
          12.1.2  Control Channel Events ..........................  25
          12.1.3  Control Channel FSM Description .................  28
      12.2 TE Link FSM ............................................  29
          12.2.1  TE link States ..................................  29
          12.2.2  TE link Events ..................................  29
          12.2.3  TE link FSM Description .........................  30
      12.3 Data Link FSM ..........................................  30
          12.3.1  Data Link States ................................  31
          12.3.2  Data Link Events ................................  31
          12.3.3  Active Data Link FSM Description ................  33
          12.3.4  Passive Data Link FSM Description ...............  34
   13 LMP Message Formats .........................................  35
      13.1 Common Header ..........................................  35
      13.2 LMP Object Format ......................................  36
      13.3 Parameter Negotiation ..................................  37
      13.4 Hello ..................................................  39
      13.5 Link Verification ......................................  39
      13.6 Link Summary ...........................................  43
      13.7 Fault Management .......................................  44
   14 LMP Object Definitions ......................................  45
   15 Security Conderations .......................................  63
   16 Intellectual Property Considerations ........................  63
   17 References ..................................................  63

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   18 Acknowledgments .............................................  64
   19 Contributors ................................................  65
   20 Contact Address .............................................  65


















































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   Changes from previous version:

   o  Editorial changes.
   o  Changed LMP from running directly over IP to running over UDP.
   o  Added Section describing exponential back-off procedures.
   o  Added suggested values for timers.
   o  Merged the LOCAL/REMOTE Id classes into single class.
   o  Merged the MESSAGE_ID/MESSAGE_ID_ACK classes into single class.
   o  Removed the MD5 security option.

1. Introduction

   Optical networks are being developed with photonic switches (PXCs),
   optical crossconnects (OXCs), routers, switches, 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 (e.g., two PXCs) may be connected by
   thousands of fibers, and each fiber may be used to transmit multiple
   wavelengths if DWDM is used. Furthermore, multiple fibers and/or
   multiple wavelengths may be combined into a single traffic-
   engineering (TE) link for routing purposes. To enable communication
   between nodes for routing, signaling, and link management, control
   channels must be established between the node pair; however, the
   interface over which the control messages are sent/received may not
   be the same interface over which the data flows. This draft
   specifies a link management protocol (LMP) that runs between
   neighboring nodes and is used to manage TE links.

   In this draft, OXC is used to refer to all categories of optical
   crossconnects irrespective of the internal switching fabric.
   Furthermore, a distinction is made between crossconnects that
   require opto-electronic conversion, called digital crossconnects
   (DXCs), and those that are all-optical, called photonic switches or
   photonic crossconnects (PXCs) û often referred to as pure
   crossconnects [LAMBDA] because their transparent nature introduces
   new restrictions for monitoring and managing the data links. LMP can
   be used for any type of node, enhancing the functionality of
   traditional DXCs and routers, while enabling PXCs and DWDMs to
   intelligently interoperate in heterogeneous optical networks.

   In GMPLS, the control channels between two adjacent nodes are no
   longer required to use the same physical medium as the data-bearing
   links between those nodes. For example, a control channel could use
   a separate wavelength or fiber, an Ethernet link, an IP tunnel
   through a separate management network, or a multi-hop IP network. A
   consequence of allowing the control channel(s) between two nodes to
   be 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-bearing
   links must be made. New mechanisms must be developed to manage the

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   data-bearing links, both in terms of link provisioning and fault
   management.

   For the purposes of this document, a data-bearing link may be either
   a "port" or a "component link" depending on its multiplexing
   capability; 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
   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: TE link Id, component interface Id, and timeslot label.
   Resource allocation happens at the lowest level (timeslots), but
   physical connectivity happens at the component link level. As
   another example, consider the case where a 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:
   TE 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 an OXC with OC-192c interfaces, the
   OXC SHOULD be able to configure each OC-48 sub-channel as a data
   link.

   LMP is designed to support aggregation of one or more data-bearing
   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.

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

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   control channel is identified by a control channel id (CCId), and
   the two directions are coupled together using the LMP Config message
   exchange. All LMP messages are IP encoded [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
   remote TE 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 draft, 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-bearing 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
   Interface Ids, depending on the configuration), and physical
   connectivity verification. This is done by sending Test messages in-
   band over the data-bearing 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-bearing link. The
   ChannelStatus message exchange is used between adjacent nodes for


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   both the suppression of downstream alarms and the localization of
   faults for protection and restoration.

   For LMP link connectivity verification using a PXC, the Test message
   is generated and terminated by opaque test units that may be shared
   among multiple ports. Opaque test units are needed since the PXC
   ports are transparent. The LMP link connectivity verification
   procedure is coordinated using a BeginVerify message exchange over a
   control channel. To support various degrees of transparency (e.g.,
   examining overhead bytes, terminating the payload, etc.), and hence,
   different mechanisms to transport the Test messages, a Verify
   Transport Mechanism is included in the BeginVerify and
   BeginVerifyAck messages. Note that there is no requirement that all
   data-bearing links must be terminated 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 between opaque and
   transparent mode.

   The LMP fault management procedure is based on a ChannelStatus
   exchange using the following messages: ChannelStatus,
   ChannelStatusAck, ChannelStatusRequest, and ChannelStatusResponse.
   The ChannelStatus message is sent unsolicitated 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
   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 draft), path
   management and label distribution information (implemented using a
   signaling protocol such as RSVP-TE [RFC3209] or CR-LDP [RFC3219]),
   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-bearing
   link. Rather, a node-wide unique 32-bit non-zero integer control

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   channel identifier (CCId) 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-bearing 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).

   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.

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   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 senderÆs Node ID, a MessageId 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.

   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 (CCIds).

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

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   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.

   Suggested default values for the HelloInterval is 5 ms and for the
   HelloDeadInterval is 18 ms.

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

   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 12.1 for the complete control channel FSM.

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. Each node increments its sequence number
   when it sees its current sequence number reflected in Hellos
   received from its peer. The sequence numbers start at 1 and wrap
   around back to 2; 0 is used in the RcvSeqNum to indicate that a
   Hello has not yet been seen.

   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.

   Note that 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 û (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


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   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
   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

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   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".

   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 bearing 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 Interface Ids).

   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 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

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   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. Since the LinkSummary
   message is IP encoded, normal IP fragmentation should be used if the
   resulting PDU exceeds the MTU.

5. Verifying Link Connectivity

   In this section, an optional procedure is described that may be used
   to verify the physical connectivity of the data-bearing 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 all-optical switches is that the data-
   bearing links are transparent when allocated to user traffic. This
   characteristic poses a challenge for validating the connectivity of
   the data links. For example, shining unmodulated light through a
   link may not result in received light at the next switch because
   there may be terminating (or opaque) elements, such as DWDM
   equipment, between the PXCs. Therefore, to ensure proper
   verification of data link connectivity, it is required that until
   the links are allocated for user traffic, they must be opaque. To
   support various degrees of opaqueness (e.g., examining overhead
   bytes, terminating the payload, etc.), and hence different
   mechanisms to transport the Test messages, a Verify Transport
   Mechanism field is included in the BeginVerify and BeginVerifyAck
   messages.

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   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 DXCs (and OEO devices in general)
   since each data link is terminated and processed electronically
   before being forwarded to the next OEO device, but that in PXCs (and
   transparent devices in general) 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
   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.



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   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
   VerifyId in the BeginVerifyAck message. The VerifyId 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 VerifyId 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.

   When the Test message is received, the received Interface Id (used
   in GMPLS as either a Port/Wavelength label or Component Interface
   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 and the remote Interface Id (received in the Test
   message), along with the VerifyId 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 will 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 criteria for this
   ordering is in increasing value of the Remote_Interface_ID.


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   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 VerifyId
        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 VerifyId. 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
        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 TE link Ids assigned by both A and B. The
        VerifyId 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 VerifyId 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 PXC
        A. The TestStatusSuccess message includes both the local and
        received Interface Ids for the port as well as the VerifyId.
        The VerifyId 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.


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

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

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

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 PXCs is that traditional methods
   that are used to monitor the health of allocated data links in OEO
   nodes (e.g., DXCs) may no longer be appropriate, since PXCs are
   transparent to the bit-rate, format, and wavelength. 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

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   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

   If data links fail between two PXCs, the power monitoring system in
   all of the downstream nodes may detect LOL and indicate a failure.
   To avoid multiple alarms stemming from the same failure, LMP
   provides a 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 OXCs, 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 occurred (bundling together
   the notification of all of the failed data links). An 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 (including
   ingress side) 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.



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   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 it 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.


       +-------+        +-------+        +-------+        +-------+
       + 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

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   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.

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 CCID. 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 CCID (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:


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   If ((int) old_id û (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 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 CCID, 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.

   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 an LMP adjacency
   has failed, or as a result of an LMP component restart. 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 (rather than an LMP component restart), the LMP
   Link information should be retained. It is possible that a node may
   be capable of retaining the LMP Link information across an LMP
   component restart. 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.



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   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 an LMP component
   restart, 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 Interace Id mappings, the associated
   Link/Data channel 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/deallocated 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 Link/Data channel 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 sent directly over IP (except, in some cases,
   the Test messages are 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.

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10.    Exponential Back-off Procedures

   This section is based on [RFC2961] and provides exponential backup
   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.

   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

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   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;

   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.    IANA Considerations

   LMP defines the following name spaces that require management:

   - Msg Type Name Space.
   -  LMP Object Class name space.
   -  LMP Object Class type (C-Type). These are unique within the Object
     Class.

   Following the policies outlined in [IANA], Msg Type, Object Class,
   and Class type are allocated through an IETF Consensus action.

12.    LMP Finite State Machines

12.1.      Control Channel FSM

   The control channel FSM defines the states and logics of operation
   of an LMP control channel. The description of FSM state transitions
   and associated actions is given in Section 3.

12.1.1. 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.


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   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.

   ConfigSnd:   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.

12.1.2. 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.



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   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. Hello
                     messages (with ControlChannelDown flag set) SHOULD
                     be sent for HelloDeadInterval seconds or until an
                     LMP message is received over the control channel
                     with the ControlChannelDown flag set.

   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.

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   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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12.1.3. 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 ConfigSnd or ConfigRcv).

12.2.      TE Link FSM

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

12.2.1. 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 primary CC is required to be operational
               between the nodes sharing the TE link.

   Degraded:   In this state, all primary CCs are down, but the TE link
               still includes some data links that are allocated to
               data traffic.

12.2.2. 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 primary control
   channel(s) and the data links. Every event has its number and a
   symbolic name. Description of possible control channel 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.
   6 : evSumRet:       Retransmission timer has expired and LinkSummary
                       message is resent.
   7 : evCCUp:         First active control channel goes up.

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   8 : evCCDown:       Last active control channel goes down.
   9 : evDCDown:       Last data channel of TE Link has been removed.

12.2.3. 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.

12.3.      Data Link FSM

   The data link FSM defines the states and logics of operation of a
   port or component link within an LMP TE link. Operation of a data
   link is described in terms of FSM states and events. Data-bearing
   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

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   FSMs are defined for the active/passive data-bearing links; however,
   a single set of data link states and events are defined.

12.3.1. Data Link States

   Any data link can be in one of the states described below. Every
   state corresponds to a certain condition of the TE 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/Allocated:  The link is UP and has been allocated for data
                  traffic.

12.3.2. Data Link Events

   Data bearing 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:       CC has gone 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 bearing link.

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

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

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                            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 deallocated.
   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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12.3.3. 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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12.3.4. 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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13.    LMP Message Formats

   All LMP messages are IP encoded (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.

13.1.      Common Header

   In addition to the standard IP header, all LMP messages (except, in
   some cases, the Test messages which are 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           |           Checksum            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Vers: 4 bits

        Protocol version number. This is version 1.

   Flags: 8 bits. The following values are defined. All other values
          are reserved.

        0x01: ControlChannelDown

        0x02: LMP Restart

               This bit is set to indicate the LMP component has
               restarted. 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.

        1  = Config

        2  = ConfigAck

        3  = ConfigNack

        4  = Hello

        5  = BeginVerify

        6  = BeginVerifyAck

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        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.

   Checksum: 16 bits

        The standard IP checksum of the entire contents of the LMP
        message, starting with the LMP message header. This checksum is
        calculated as the 16-bit one's complement of the one's
        complement sum of all the 16-bit words in the packet. If the
        packet's length is not an integral number of 16-bit words, the
        packet is padded with a byte of zero before calculating the
        checksum.

13.2.      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

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

   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 14.

   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.

13.3.      Parameter Negotiation Messages

13.3.1. 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 is within the scope of the CCID.

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   The Config message MUST be periodically transmitted until (1) it
   receives a ConfigAck or ConfigNack message, (2) a timeout expires
   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
   timeout period are local configuration parameters.

13.3.2. 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.

13.3.3. 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.

13.4.      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.

13.5.      Link Verification

13.5.1. 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
   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. 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.


   The REMOTE_LINK_ID may be included if the local/remote Link Id
   mapping is known.

   The REMOTE_LINK_ID MUST be non-zero if included.

   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 timeout expires and
   no BeginVerifyAck or BeginVerifyNack message has been received. Both
   the retransmission interval and the timeout period are local
   configuration parameters.

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13.5.2. 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 may be included if the local/remote Link Id
   mapping is known or learned through the BeginVerify message.

   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.

13.5.3. 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 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
   node that originated the BeginVerify SHOULD schedule a BeginVerify
   retransmission after Rf seconds, where Rf is a locally defined
   parameter.




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

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

   The BeginVerifyNack uses BEGIN_VERIFY_ERROR_ C-Type 1.

13.5.4. 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 timeout expires and
   no EndVerifyAck message has been received. Both the retransmission
   interval and the timeout period are local configuration parameters.

13.5.5. 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.

13.5.6. 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 in the
   Verify Transport Mechanism description for the BEGIN_VERIFY class,
   this is transmitted as an IP packet with payload format as follows:

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

   The above transmission order SHOULD be followed.


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   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 14.8 and 14.9).

   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.

13.5.7. 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.

13.5.8. 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.

13.5.9. 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.

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

13.6.      Link Summary Messages

13.6.1. 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 timeout expires
   and no LinkSummaryAck or LinkSummaryNack message has been received.
   Both the retransmission interval and the timeout period are local
   configuration parameters.

13.6.2. 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 TE Link Id associations.

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

   The above transmission order SHOULD be followed.

13.6.3. 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.

   <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.

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   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.

   The LinkSummaryNack message uses LINK_SUMMARY_ERROR C-Type 2.

13.7.      Fault Management Messages

13.7.1. 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.

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

13.7.2. 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.

13.7.3. 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.



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   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.

13.7.4. 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.

14.    LMP Object Definitions

14.1.      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.


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   This object is non-negotiable.

14.2.      NODE_ID Classes

   Class = 2.

   o    C-Type = 1, LOCAL_NODE_ID Class

    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.

   This object is non-negotiable.

   o    C-Type = 2, REMOTE_NODE_ID Class

    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.

14.3.      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


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    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)                     +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   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)                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   o    C-Type = 7, Reserved for OIF

   o    C-Type = 8, Reserved for OIF

   Link_Id:

        For LOCAL_LINK_ID, this identifies the senderÆs Link associated
        with the message.

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

   This object is non-negotiable.

14.4.      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

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   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)                 +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   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
        (either port or component link). This value MUST be node-wide
        unique and non-zero.

        For the REMOTE_INTERFACE_ID, this identifies the remote nodeÆs
        data link (either port or component link). The Interface Id
        MUST be non-zero.

   This object is non-negotiable.

14.5.      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:



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        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                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   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.

14.6.      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.

14.7.      HELLO Class


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   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                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   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 reserved to indicate that the control channel has
        booted or restarted.

   RcvSeqNum:  32 bits

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

   This object is non-negotiable.

14.8.      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                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


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   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.
        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 Link 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 link 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.

        For SONET/SDH Encoding Type, the following flags are defined:

        0x01 J0-16: 16 byte J0 Test Message

                Capable of transmitting Test messages using J0 overhead
                bytes with string length of 16 bytes (with CRC-7). See
                table 4 of ITU G.707 [G707] for the 16-byte J0
                definition. The definition of CRC-7 is found in Annex B
                of ITU G.707.

                Note that Due to the byte limitation, the Test message
                is NOT sent as an IP packet and as such, no L2
                encapsulation is used. A special Test message format is
                defined as follows:


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                The Test message is a 15-byte message, where the 7 most
                significant bits (MSb) of each byte are usable. Due to
                the byte limitation, the LMP Header is not included.

                The first usable 32 bits MUST be the VerifyId that was
                received in the VERIFY_ID object of the BeginVerifyAck
                message. The second usable 32 bits MUST be the
                Interface_Id. The next usable 8 bits are used to
                determine the address type of the Interface_Id. For
                IPv4, this value is 1. For unnumbered, this value is 3.
                The remaining bits are Reserved.

                Note that this Test Message format is only valid when
                the Interface_Id is either IPv4 or unnumbered.

        0x02 J0-64: 64 byte J0 Test Message

                 Capable of transmitting Test messages using J0
                 overhead bytes with string length of 64 bytes (see GR-
                 253-CORE [GR253]). Note that this is only appropriate
                 for SONET encoding and not SDH encoding.

                The Test message is sent as an IP packet as defined
                above.

        0x04 DCCS: Test Message over the Section DCC

                Capable of transmitting Test messages using the DCC
                Section Overhead bytes with bit-oriented HDLC framing
                format.

                The Test message is sent as an IP packet as defined
                above.

        0x08 DCCL: Test Message over the Line DCC

                Capable of transmitting Test messages using the DCC
                Line Overhead bytes with bit-oriented HDLC framing
                format.

                The Test message is sent as an IP packet as defined
                above.

       0x10 Payload:  Test Message transmitted in the payload

                Capable of transmitting Test messages in the payload
                using Packet over SONET framing using the encoding type
                specified in the EncType field.

                The Test message is sent as an IP packet as defined
                above.


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        0x20 GigE:

                Capable of transmitting Test messages in the payload

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

14.9.      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.

14.10.  VERIFY_ID Class

   Class = 10.

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   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           VerifyId                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   VerifyId:  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.

14.11.  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)                +

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   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   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)                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   o    C-Type = 4, Reserved for OIF

   Flags: 8 bits
        The following flags are defined. All other values are reserved.

        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.

14.12.  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)                         //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Flags: 8 bits

        The following flags are defined. All other values are reserved.

        0x01 Interface Type: If set, the data link is a port,
                              otherwise it is a component link.

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        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 14.12.1 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.

14.12.1.        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 Capability

   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.

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14.12.1.1.      Subobject Type 1: Interface Switching Capability

    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 Cap |   EncType     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Minimum Reservable Bandwidth                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Maximum Reservable Bandwidth                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Switching Capability: 8 bits

        This is used to identify the local Interface Switching
        Capability 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 Link 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.

14.12.1.2.      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                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Wavelength: 32 bits

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

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14.13.  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|                       Channel Status                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              :                                |
   //                             :                               //
   |                              :                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Interface Id (4 bytes)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |A|                       Channel Status                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   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|                       Channel Status                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              :                                |
   //                             :                               //
   |                              :                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                       Interface Id (16 bytes)                 +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |A|                       Channel Status                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   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|                       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.

   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.

        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.

14.14.  CHANNEL_STATUS_REQUEST Class

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   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.

   o    C-Type = 2, 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 (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.

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   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.

14.15.  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:

        0x01 = Link Verification Procedure not supported for this TE
               Link.
        0x02 = Unwilling to verify at this time
        0x04 = Unsupported verification transport mechanism
        0x08 = TE Link Id configuration error

        All other values are Reserved.

        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.

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   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:

        0x01 = Unacceptable non-negotiable LINK_SUMMARY parameters
        0x02 = Renegotiate LINK_SUMMARY parameters
        0x04 = Bad Received Remote_Link_Id
        0x08 = Bad TE Link Object
        0x10 = Bad Data Link Object

        All other values are Reserved.

        Multiple bits may be set to indicate multiple errors.

        This object is non-negotiable.

15.    Security Considerations

   Security is discussed in [LMP-SEC].

16.    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.

17.    References

17.1.      Normative References

Lang et al                                                   [Page 63]


Internet Draft       draft-ietf-ccamp-lmp-04.txt            June 2002


   [RFC2026]   Bradner, S., "The Internet Standards Process -- Revision
               3," BCP 9, RFC 2026, October 1996.
   [BUNDLE]    Kompella, K., Rekhter, Y., Berger, L., "Link Bundling in
               MPLS Traffic Engineering," Internet Draft, draft-
               kompella-mpls-bundle-05.txt, (work in progress), February
               2001.
   [RFC2961]   Berger, L., Gan, D., et al, "RSVP Refresh Overhead
               Reduction Extensions," RFC 2961, April 2001.
   [GMPLS-SIG] Ashwood-Smith, P., Banerjee, A., et al, "Generalized
               MPLS - Signaling Functional Description," Internet Draft,
               draft-ietf-mpls-generalized-signaling-06.txt, (work in
               progress), October 2001.
   [G707]      ITU-T G.707, "Network node interface for the synchronous
               digital hierarchy (SDH)," March 1996.
   [GR253]     GR-253-CORE, "Synchronous Optical Network (SONET)
               Transport Systems: Common Generic Criteria," Telcordia
               Technologies, Issue 3, September 2000.
   [LMP-SEC]   Ramamoorthi,S. and Zinin, A., "LMP Security Mechanism,"
               Internet Draft, draft-sankar-lmp-sec-00.txt, (work in
               progress), Internet Draft, February 2002.

17.2.      Informative References

   [LAMBDA]    Awduche, D. O., Rekhter, Y., Drake, J., Coltun, R.,
               "Multi-Protocol Lambda Switching: Combining MPLS Traffic
               Engineering Control with Optical Crossconnects,"
               Internet Draft, draft-awduche-mpls-te-optical-03.txt,
               (work in progress), April 2001.
   [RFC3209]   Awduche, D. O., Berger, L, et al, "Extensions to RSVP
               for LSP Tunnels," Internet Draft, RFC3209 December 2001.
   [RFC3219]   Jamoussi, B., ed., "Constraint-Based LSP Setup using
               LDP," RFC3219, January 2002.
   [OSPF-TE]   Katz, D., Yeung, D., Kompella, K., "Traffic Engineering
               Extensions to OSPF," Internet Draft, draft-katz-yeung-
               ospf-traffic-04.txt, (work in progress), February 2001.
   [ISIS-TE]   Li, T., Smit, H., "IS-IS extensions for Traffic
               Engineering," Internet Draft,draft-ietf-isis-traffic-
               02.txt, (work in progress), September 2000.

18.    Acknowledgements

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


Lang et al                                                   [Page 64]


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19.    Contributors

   Jonathan P. Lang                        Krishna Mitra
   Calient Networks                        Calient Networks
   25 Castilian Drive                      5853 Rue Ferrari
   Goleta, CA 93117                        San Jose, CA 95138
   Email: jplang@calient.net               email: krishna@calient.net

   John Drake                              Kireeti Kompella
   Calient Networks                        Juniper Networks, Inc.
   5853 Rue Ferrari                        385 Ravendale Drive
   San Jose, CA 95138                      Mountain View, CA 94043
   email: jdrake@calient.net               email: kireeti@juniper.net

   Yakov Rekhter                           Lou Berger
   Juniper Networks, Inc.                  Movaz Networks
   385 Ravendale Drive                     email: lberger@movaz.com
   Mountain View, CA 94043
   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
   Tellium Optical Systems
   2 Crescent Place
   Oceanport, NJ 07757-0901
   email: braja@tellium.com

20.    Contact Address

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








Lang et al                                                   [Page 65]


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