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Versions: (draft-sratliff-manet-dlep) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 RFC 8175

Mobile Ad hoc Networks Working                                S. Ratliff
Group                                                           B. Berry
Internet-Draft                                               G. Harrison
Intended status: Standards Track                                 S. Jury
Expires: November 2, 2011                                 D. Satterwhite
                                                           Cisco Systems
                                                             May 2, 2011


                   Dynamic Link Exchange Protocol (DLEP)
                         draft-ietf-manet-dlep-01

Abstract

   When routing devices rely on modems to effect communications over
   wireless links, they need timely and accurate knowledge of the
   characteristics of the link (speed, state, etc.) in order to make
   forwarding decisions. In mobile or other environments where these
   characteristics change frequently, manual configurations or the
   inference of state through routing or transport protocols does not
   allow the router to make the best decisions. A bidirectional, event-
   driven communication channel between the router and the modem is
   necessary.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   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.

   This Internet-Draft will expire on November 2, 2011    .

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents



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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1   Requirements . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Assumptions  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Normal Session Flow  . . . . . . . . . . . . . . . . . . . . .  5
   4.  Generic DLEP Packet Definition . . . . . . . . . . . . . . . .  6
   5.  Message Header Format  . . . . . . . . . . . . . . . . . . . .  7
   6.  Message TLV Block Format . . . . . . . . . . . . . . . . . . .  7
   7.  DLEP Sub-TLVs  . . . . . . . . . . . . . . . . . . . . . . . .  8
     7.1.  Identification Sub-TLV . . . . . . . . . . . . . . . . . .  9
     7.2.  DLEP Version Sub-TLV . . . . . . . . . . . . . . . . . . . 10
     7.3.  Peer Type Sub-TLV  . . . . . . . . . . . . . . . . . . . . 11
     7.4.  MAC Address Sub-TLV  . . . . . . . . . . . . . . . . . . . 11
     7.5.  IPv4 Address Sub-TLV . . . . . . . . . . . . . . . . . . . 12
     7.6.  IPv6 Address Sub-TLV . . . . . . . . . . . . . . . . . . . 12
     7.7.  Maximum Data Rate Sub-TLV. . . . . . . . . . . . . . . . . 13
     7.8.  Current Data Rate Sub-TLV. . . . . . . . . . . . . . . . . 14
     7.9.  Latency Sub-TLV. . . . . . . . . . . . . . . . . . . . . . 14
     7.10. Resources Sub-TLV. . . . . . . . . . . . . . . . . . . . . 15
     7.11. Relative Link Quality Sub-TLV. . . . . . . . . . . . . . . 16
     7.12. Peer Termination Sub-TLV . . . . . . . . . . . . . . . . . 16
     7.13  Heartbeat Interval Sub-TLV . . . . . . . . . . . . . . . . 17
     7.14  Heartbeat Threshold Sub-TLV. . . . . . . . . . . . . . . . 17
     7.15  Link Characteristics ACK Timer Sub-TLV . . . . . . . . . . 18
   8.  DLEP Protocol Messages . . . . . . . . . . . . . . . . . . . . 19
     8.1.  Message Block TLV Values . . . . . . . . . . . . . . . . . 19
   9.  Peer Discovery Messages  . . . . . . . . . . . . . . . . . . . 20
     9.1.  Attached Peer Discovery Message  . . . . . . . . . . . . . 20
     9.2.  Detached Peer Discovery Message  . . . . . . . . . . . . . 22
   10. Peer Offer Message . . . . . . . . . . . . . . . . . . . . . . 23
   11. Peer Update Message. . . . . . . . . . . . . . . . . . . . . . 25
   12. Peer Update ACK Message. . . . . . . . . . . . . . . . . . . . 27
   13. Peer Termination Message . . . . . . . . . . . . . . . . . . . 27
   14. Peer Termination ACK Message . . . . . . . . . . . . . . . . . 28
   15. Neighbor Up Message  . . . . . . . . . . . . . . . . . . . . . 29
   16. Neighbor Up ACK Message. . . . . . . . . . . . . . . . . . . . 31
   17. Neighbor Down Message  . . . . . . . . . . . . . . . . . . . . 32
   18. Neighbor Down ACK Message. . . . . . . . . . . . . . . . . . . 33
   19. Neighbor Update Message  . . . . . . . . . . . . . . . . . . . 35
   20. Neighbor Address Update Message. . . . . . . . . . . . . . . . 36
   21. Neighbor Address Update ACK Message. . . . . . . . . . . . . . 38
   22. Heartbeat Message  . . . . . . . . . . . . . . . . . . . . . . 39
   23. Link Characteristics Message . . . . . . . . . . . . . . . . . 39
   24. Link Characteristics ACK Message . . . . . . . . . . . . . . . 41
   25. Security Considerations. . . . . . . . . . . . . . . . . . . . 42

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   26. IANA Considerations. . . . . . . . . . . . . . . . . . . . . . 42
     26.1  TLV Registrations. . . . . . . . . . . . . . . . . . . . . 43
     26.2  Expert Review: Evaluation Guidelines . . . . . . . . . . . 43
     26.3  Message TLV Type Registrations . . . . . . . . . . . . . . 43
     26.4  DLEP Order Registrations . . . . . . . . . . . . . . . . . 43
     26.5  DLEP Sub-TLV Type Registrations. . . . . . . . . . . . . . 44
   27. Appendix A . . . . . . . . . . . . . . . . . . . . . . . . . . 45

1. Introduction

   There exist today a collection of modem devices that control links of
   variable bandwidth and quality. Examples of these types of links
   include line-of-sight (LOS) radios, satellite terminals, and cable/
   DSL modems. Fluctuations in speed and quality of these links can
   occur due to configuration (in the case of cable/DSL modems), or on a
   moment-to-moment basis, due to physical phenomena like multipath
   interference, obstructions, rain fade, etc. It is also quite possible
   that link quality and bandwidth varies with respect to individual
   neighbors on a link, and with the type of traffic being sent. As an
   example, consider the case of an 802.11g access point, serving 2
   associated laptop computers. In this environment, the answer to the
   question "What is the bandwidth on the 802.11g link?" is "It depends
   on which associated laptop we're talking about, and on what kind of
   traffic is being sent." While the first laptop, being physically
   close to the access point, may have a bandwidth of 54Mbps for
   unicast traffic, the other laptop, being relatively far away, or
   obstructed by some object, can simultaneously have a bandwidth of
   only 32Mbps for unicast. However, for multicast traffic sent from the
   access point, all traffic is sent at the base transmission rate
   (which is configurable, but depending on the model of the access
   point, is usually 24Mbps or less).

   In addition to utilizing variable bandwidth links, mobile networks
   are challenged by the notion that link connectivity will come and go
   over time.  Effectively utilizing a relatively short-lived connection
   is problematic in IP routed networks, as routing protocols tend to
   rely on independent timers at OSI Layer 3 to maintain network
   convergence (e.g. HELLO messages and/or recognition of DEAD routing
   adjacencies). These short-lived connections can be better utilized
   with an event-driven paradigm, where acquisition of a new neighbor
   (or loss of an existing one) is somehow signaled, as opposed to a
   timer-driven paradigm.

   Another complicating factor for mobile networks are the different
   methods of physically connecting the modem devices to the router.
   Modems can be deployed as an interface card in a router's
   chassis, or as a standalone device connected to the router via
   Ethernet, USB, or even a serial link. In the case of Ethernet or
   serial attachment, with existing protocols and techniques, routing
   software cannot be aware of convergence events occurring on the
   radio link (e.g. acquisition or loss of a potential routing
   neighbor), nor can the router be aware of the actual capacity of
   the link. This lack of awareness, along with the variability in
   bandwidth, leads to a situation where quality of service (QoS)

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   profiles are extremely difficult to establish and properly
   maintain. This is especially true of demand-based access schemes
   such as Demand Assigned Multiple Access (DAMA) implementations
   used on some satellite systems. With a DAMA-based system,
   additional bandwidth may be available, but will not be used
   unless the network devices emit traffic at rate higher than the
   currently established rate. Increasing the traffic rate does not
   guarantee additional bandwidth will be allocated; rather, it may
   result in data loss and additional retransmissions on the link.

   In attempting to address the challenges listed above, the authors
   have developed the Data Link Exchange Protocol, or DLEP. The DLEP
   protocol runs between a router and its attached modem devices,
   allowing the modem to communicate link characteristics as they
   change, and convergence events (acquisition and loss of potential
   routing neighbors). The diagram below is used to illustrate the
   scope of DLEP sessions. When a local client (Modem device)
   detects the presence of a remote neighbor, it sends an indication
   to its local router via the DLEP session. Upon receipt of the
   indication, the local router would take appropriate action (e.g.
   initiation of discovery or HELLO protocols) to converge the
   network. After notification of the new neighbor, the modem device
   utilizes the DLEP session to report the characteristics of the
   link (bandwidth, latency, etc) to the router on an as-needed
   basis. Finally, the Modem is able to use the DLEP session to
   notify the router when the remote neighbor is lost, shortening
   the time required to re-converge the network.


   |-----Local Neighbor-----|          |-----Remote Neighbor----|
   |                        |          |     (far-end device)   |

   +--------+       +-------+          +-------+       +--------+
   | Router |=======| Modem |{~~~~~~~~}| Modem |=======| Router |
   |        |       | Device|          | Device|       |        |
   +--------+       +-------+          +-------+       +--------+

            |       |       | Link     |       |       |
            |-DLEP--|       | Protocol |       |-DLEP--|
            |       |       | (e.g.    |       |       |
            |       |       | 802.11)  |       |       |

                          Figure 1: DLEP Network


   DLEP exists as a collection of type-length-value (TLV) based messages
   using [RFC5444] formatting. The protocol can be used for both Ethernet
   attached modems (utilizing, for example, a UDP socket for transport
   of the RFC 5444 packets), or in environments where the modem is an
   interface card in a chassis (via a message passing scheme). DLEP
   utilizes a session paradigm between the modem device and its
   associated router. If multiple modem devices are attached to a
   router, a separate DLEP session MUST exist for each modem. If a modem
   device supports multiple connections to a router (via multiple

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   interfaces), or supports connections to multiple routers, a separate
   DLEP session MUST exist for each connection.


1.1  Requirements

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in BCP 14, RFC 2119
   [RFC2119].

2. Assumptions

   In order to implement discovery in the DLEP protocol (thereby
   avoiding some configuration), we have defined a first-speaker and a
   passive-listener scheme. Specifically, the router is defined as the
   passive-listener, and the modem device defined as the first-speaker
   (e.g. the initiator for discovery). Borrowing from existing
   terminology, this document refers to the first-speaker as the
   'client', even though there is no client/server relationship in the
   classic sense.

   DLEP assumes that participating modem devices appear to the router
   as a transparent bridge - specifically, the assumption is that the
   destination MAC address for data traffic in any frame emitted by
   the router should be the MAC address of the next-hop router or end-
   device, and not the MAC address of any of the intervening modem
   devices.

   DLEP assumes that security on the session (e.g. authentication of
   session partners, encryption of traffic, or both) is dealt with by
   the underlying transport mechanism for the RFC 5444 packets (e.g. by
   using a transport such as DTLS [DTLS]).

   The optional [RFC5444] message header Sequence Number MUST be
   included in all DLEP packets. Sequence Numbers start at 1 and are
   incremented by one for each original and retransmitted message.  The
   unsigned 16-bit Sequence Number rolls over at 65535 to 1.  A
   Sequence Number of 0 is not valid. Peer level Sequence Numbers are
   unique within the context of a DLEP session. Sequence numbers are
   used in DLEP to correlate a response to a request.

3. Normal Session Flow

   A session between a router and a client is established by exchanging
   the "Peer Discovery" and "Peer Offer" messages described below.

   Once that exchange has successfully occurred, the client informs the
   router of the presence of a new potential routing partner via the
   "Neighbor Up" message. The loss of a neighbor is communicated via the
   "Neighbor Down" message, and link quality is communicated via the
   "Neighbor Update" message. Note that, due to the issue of metrics
   varying depending on neighbor (discussed above), DLEP link metrics
   are expressed within the context of a neighbor relationship, instead
   of on the link as a whole.

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   Once the DLEP session has started, the session partners exchange
   heartbeat messages based on a negotiated time interval. The heartbeat
   messages are used to assure the session partners are in an
   appropriate state, and that bidirectional connectivity still exists.

   In addition to receiving metrics about the link, DLEP provides for
   the ability for the router to request a different amount of
   bandwidth, or latency, for its client via the Link Characteristics
   Message. This allows the router to deal with requisite increases
   (or decreases) of allocated bandwidth/latency in demand-based
   schemes in a more deterministic manner.


4. Generic DLEP Packet Definition

   The Generic DLEP Packet Definition follows the format for packets
   defined in [RFC5444].

   The Generic DLEP Packet Definition contains the following fields:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Version| Flags | Packet Sequence Number        | Packet TLV    |
   |       |       |                               | Block...      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Message (Contains DLEP message)...                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Version                - Version of RFC 5444 specification on
                            which the packet/messages/TLVs are
                            constructed.

   Flags                  - 4 bit field. All bits MUST be ignored
                            by DLEP implementations.

   Packet Sequence Number - If present, the packet sequence number
                            is parsed and ignored. DLEP does NOT
                            use or generate packet sequence numbers.

   Packet TLV block       - a TLV block which contains packet level
                            TLV information. DLEP implementations
                            MUST NOT use this TLV block.

   Message                - the packet MAY contain zero or more
                            messages, however, DLEP messages are
                            encoded within an RFC 5444 Message
                            TLV Block.







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5. Message Header Format


   DLEP utilizes the following format for the RFC 5444 message 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Msg Type   |Msg Flg|AddrLen|          Message Size         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Message Seq Num      |           TLV Block...        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Message Type           - an 8-bit field which specifies the type
                            of the message. For DLEP, this field
                            contains DLEP_MESSAGE (value TBD)

   Message Flags          - Set to 0x1 (bit 3, mhasseqnum bit is
                            set).  All other bits are unused and MUST
                            be set to '0'.

   Message Address Length - a 4-bit unsigned integer field encoding the
                            length of all addresses included in this
                            message. DLEP implementations do not use
                            this field; contents SHOULD be ignored.

   Message Size           - a 16-bit unsigned integer field which
                            specifies the number of octets that make up
                            the message including the message header.

   Message Sequence Number - a 16-bit unsigned integer field that
                             contains a sequence number, generated by
                             the originator of the message. Sequence
                             numbers range from 1 to 65535. Sequence
                             numbers roll over at 65535 to 1; 0 is
                             invalid.

   TLV Block               - TLV Block included in the message.


6. Message TLV Block Format

   The DLEP protocol is organized as a set of orders, each with a
   collection of Sub-TLVs. The Sub-TLVs carry information needed
   to process and/or establish context (e.g. the MAC address of a
   far-end router), and the 'tlv-type' field in the message TLV
   block carries the DLEP order itself. The DLEP orders are
   enumerated in section 8.1 of this document, and the messages
   created using these orders are documented in sections 9 through
   24.




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   DLEP uses the following settings for an RFC 5444 Message TLV
   block:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |       TLVs Length             |  TLV Type     | TLV Flags     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |    Length    |       Value...                                 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   TLVs Length - a 16-bit unsigned integer field that contains the total
                 number of octets in all of the immediately following
                 TLV elements (tlvs-length not included).

   TLV Type    - an 8-bit unsigned integer field specifying the type
                 of the TLV. DLEP uses this field to specify the DLEP
                 order. Valid DLEP orders are defined in section 8.1 of
                 this document.

   TLV Flags   - an 8-bit flags bit field. Bit 3 (thasvalue) MUST be
                 set; all other bits are not used and MUST be set
                 to '0'.

   Length      - Length of the 'Value' field of the TLV

   Value       - A field of length <Length> which contains data
                 specific to a particular TLV type. In the DLEP
                 case, this field will consist of a collection of
                 DLEP sub-TLVs appropriate for the DLEP action
                 specified in the TLV type field.


7. DLEP sub-TLVs

   DLEP protocol messages are transported in an RFC 5444 message TLV.
   All DLEP messages use the RFC 5444 DLEP_MESSAGE value (TBD). The
   protocol messages consist of a DLEP order, encoded in the 'tlv-type'
   field in the message TLV block, with the 'value' field of the TLV
   block containing a collection (1 or more) DLEP sub-TLVs.

   The format of DLEP Sub-TLVs is consistent with RFC 5444 in that the
   Sub-TLVs contain a flag field in addition to the type, length, and
   value fields. Valid DLEP Sub-TLVs are:

          TLV      TLV
          Value    Description
          =========================================
          TBD      Identification sub-TLV
          TBD      DLEP Version sub-TLV
          TBD      Peer Type sub-TLV
          TBD      MAC Address sub-TLV
          TBD      IPv4 Address sub-TLV
          TBD      IPv6 Address sub-TLV

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          TBD      Maximum Data Rate (MDR) sub-TLV
          TBD      Current Data Rate (CDR) sub-TLV
          TBD      Latency sub-TLV
          TBD      Resources sub-TLV
          TBD      Relative Link Quality (RLQ) sub-TLV
          TBD      Status sub-TLV
          TBD      Heartbeat Interval sub-TLV
          TBD      Heartbeat Threshold sub-TLV
          TBD      Neighbor down ACK timer sub-TLV
          TBD      Link Characteristics ACK timer sub-TLV


   DLEP sub-TLVs contain the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  TLV Type     |TLV Flags=0x10 | Length        | Value...      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   TLV Type    - an 8-bit unsigned integer field specifying the type
                 of the sub-TLV.

   TLV Flags   - an 8-bit flags bit field. Bit 3 (thasvalue) MUST be
                 set, all other bits are not used and MUST be set to
                 '0'.

   Length      - an 8-bit length of the value field of the sub-TLV

   Value       - A field of length <Length> which contains data
                 specific to a particular sub-TLV.


7.1  Identification Sub-TLV

   This Sub-TLV MUST exist in the TLV Block for all DLEP messages, and
   MUST be the first Sub-TLV of the message. Further, there MUST be ONLY
   one Identification Sub-TLV in an RFC 5444 message TLV block. The
   Identification sub-TLV contains client and router identification
   information used to establish the proper context for processing DLEP
   protocol messages.


   The Identification sub-TLV contains the following fields:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |TLV Type = TBD |TLV Flags=0x10 |Length = 8     | Router ID     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Router ID                  | Client ID     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Client ID                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   TLV Type      - Value TBD

   TLV Flags     - 0x10, Bit 3 (thasvalue) is set, all other bits are
                   unused and MUST be set to '0'.

   Length        - 8

   Router ID     - indicates the router ID of the DLEP session.

   Client ID     - indicates the client ID of the DLEP session.

   When the client initiates discovery (via the Peer Discovery message),
   it MUST set the Client ID to a 32-bit quantity that will be used to
   uniquely identify this session from the client-side. The client MUST
   set the Router ID to '0'. When responding to the Peer Discovery
   message, the router MUST echo the Client ID, and MUST supply its own
   unique 32-bit quantity to identify the session from the router's
   perspective. After the Peer Discovery/Peer Offer exchange, both the
   Client ID and the Router ID MUST be set to the values obtained from
   the Peer DIscovery/Peer Offer sequence.


7.2  DLEP Version Sub-TLV

   The DLEP Version Sub-TLV is an OPTIONAL TLV in both the Peer
   Discovery and Peer Offer messages. The Version Sub-TLV is used to
   indicate the client or router version of the protocol. The client
   and router MAY use this information to decide if the peer is running
   at a supported level.

   The DLEP Version Sub-TLV contains the following fields:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |TLV Type =TBD  |TLV Flags=0x10 |Length=4       | Major Version |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Major Version |       Minor Version           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   TLV Type      - TBD

   TLV Flags     - 0x10, Bit 3 (thasvalue) is set, all other bits are
                   not used and MUST be set to '0'.

   Length        - Length is 4

   Major Version - Major version of the client or router protocol.

   Minor Version - Minor version of the client or router protocol.

   Support of this draft is indicated by setting the Major Version
   to '1', and the Minor Version to '1' (e.g. Version 1.1).


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7.3  Peer Type Sub-TLV

   The Peer Type Sub-TLV is used by the router and client to give
   additional information as to its type. It is an OPTIONAL sub-TLV in
   both the Peer Discovery Message and the Peer Offer message. The peer
   type is a string and is envisioned to be used for informational
   purposes (e.g. display command).

   The Peer Type sub-TLV contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Type =TBD  |TLV Flags=0x10 |Length= peer   |Peer Type Str  |
  |               |               |type string len|Max Len = 80   |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   TLV Type         - TBD

   TLV Flags        - 0x10, Bit 3 (thasvalue) is set, all other bits
                      are not used and MUST be set to '0'.

   Length           - length of peer type string (80 bytes maximum)
   Peer Type String - Non-Null terminated peer type string, maximum
                      length of 80 bytes. For example, a satellite
                      modem might set this variable to 'Satellite
                      terminal'.


7.4  MAC Address Sub-TLV

   The MAC address Sub-TLV MUST appear in all neighbor-oriented
   messages (e.g. Neighbor Up, Neighbor Up ACK, Neighbor Down, Neighbor
   Down ACK, Neighbor Update, Link Characteristics Request, and Link
   Characteristics ACK). The MAC Address sub-TLV contains the address
   of the far-end (neighbor) router.

   The MAC Address sub-TLV contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Type =TBD  |TLV Flags=0x10 |Length = 6     |MAC Address    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                      MAC Address                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | MAC Address   |
  +-+-+-+-+-+-+-+-+

   TLV Type    - TBD

   TLV Flags   - 0x10, Bit 3 (thasvalue) is set, all other bits are not
                 used and MUST be set to '0'.


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   Length      - 6

   MAC Address - MAC Address of the far-end router.


7.5  IPv4 Address Sub-TLV

   The IPv4 Address Sub-TLV MAY be used in Neighbor Up, Neighbor Update,
   and Peer Update Messages, if the client is aware of the Layer 3
   address. When included in Neighbor messages, the IPv4 Address sub-TLV
   contains the IPv4 address of the far-end router (neighbor). In
   the Peer Update message, it contains the IPv4 address of the local
   router. In either case, the sub-TLV also contains an indication of
   whether this is a new or existing address, or is a deletion of
   a previously known address.

   The IPv4 Address Sub-TLV contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Type =TBD  |TLV Flags=0x10 |Length = 5     |   Add/Drop    |
  |               |               |               |   Indicator   |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                    IPv4 Address                               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   TLV Type     - TBD

   TLV Flags    - 0x10, Bit 3 (thasvalue) is set, all other bits are not
                  used and MUST be set to '0'.

   Length       - 5

   Add/Drop     - Value indicating whether this is a new or existing
   Indicator      address (0x01), or a withdrawal of an address (0x02).

   IPv4 Address - IPv4 Address of the far-end router.


7.6  IPv6 Address Sub-TLV

   The IPv6 Address Sub-TLV MAY be used in Neighbor Up, Neighbor Update,
   and Peer Update Messages, if the client is aware of the Layer 3
   address. When included in Neighbor messages, the IPv6 Address sub-TLV
   contains the IPv6 address of the far-end router (neighbor). In
   the Peer Update, it contains the IPv6 address of the local router.
   In either case, the sub-TLV also contains an indication of whether
   this is a new or existing address, or is a deletion of a
   previously known address.





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   The IPv6 Address sub-TLV contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Type =TBD  |TLV Flags=0x10 |Length = 17    |   Add/Drop    |
  |               |               |               |   Indicator   |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        IPv6 Address                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        IPv6 Address                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        IPv6 Address                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        IPv6 Address                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   TLV Type     - TBD

   TLV Flags    - 0x10, Bit 3 (thasvalue) is set, all other bits are not
                  used and MUST be set to '0'.

   Length       - 17

   Add/Drop     - Value indicating whether this is a new or
   Indicator      existing address (0x01), or a withdrawal of
                  an address (0x02).

   IPv6 Address - IPv6 Address of the far-end router.


7.7  Maximum Data Rate Sub-TLV

   The Maximum Data Rate (MDR) Sub-TLV is used in Neighbor Up, Neighbor
   Update, and Link Characteristics ACK Messages to indicate the
   maximum theoretical data rate, in bits per second, that can be
   achieved on the link. When metrics are reported via the messages
   listed above, the maximum data rate MUST be reported.

   The Maximum Data Rate sub-TLV contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Type =TBD  |TLV Flags=0x10 |Length = 8     |  MDR (bps)    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        MDR (bps)                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        MDR (bps)              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   TLV Type              -  TBD



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   TLV Flags             -  0x10, Bit 3 (thasvalue) is set, all other
                            bits are not used and MUST be set to '0'.

   Length                -  8

   Maximum Data Rate     -  A 64-bit unsigned number, representing the
                            maximum theoretical data rate, in bits per
                            second (bps), that can be achieved on the
                            link.


7.8  Current Data Rate Sub-TLV

   The Current Data Rate (CDR) Sub-TLV is used in Neighbor Up, Neighbor
   Update, Link Characteristics Request, and Link Characteristics ACK
   messages to indicate the rate at which the link is currently
   operating, or in the case of the Link Characteristics Request,
   the desired data rate for the link.

   The Current Data Rate sub-TLV contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Type =TBD  |TLV Flags=0x10 |Length = 8     |CDR (bps)      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        CDR (bps)                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        CDR (bps)              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   TLV Type              -  TBD

   TLV Flags             -  0x10, Bit 3 (thasvalue) is set, all other
                            bits are not used and MUST be set to '0'.

   Length                -  8

   Current Data Rate     -  A 64-bit unsigned number, representing the
                            current data rate, in bits per second (bps),
                            on the link. When reporting metrics (e.g,
                            in Neighbor Up, Neighbor Down, or Link
                            Characteristics ACK), if there is no
                            distinction between current and maximum
                            data rates, current data rate SHOULD be
                            set equal to the maximum data rate.

7.9  Latency Sub-TLV

   The Latency Sub-TLV is used in Neighbor Up, Neighbor Update, Link
   Characteristics Request, and Link Characteristics ACK messages to
   indicate the amount of latency on the link, or in the case of the
   Link Characteristics Request, to indicate the maximum latency
   required (e.g. a should-not-exeed value) on the link.

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   The Latency Sub-TLV contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Type =TBD  |TLV Flags=0x10 |Length = 2     |Latency (ms)   |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Latency (ms)   |
  +-+-+-+-+-+-+-+-+

   TLV Type              -  TBD

   TLV Flags             -  0x10, Bit 3 (thasvalue) is set, all other
                            bits are not used and MUST be set to '0'.

   Length                -  2

   Latency               -  the transmission delay that a packet
                            encounters as it is transmitted over the
                            link. In Neighbor Up, Neighbor Update,
                            and Link Characteristics ACK, this value
                            is reported in absolute delay, in
                            milliseconds. The calculation of latency
                            is modem-device dependent. For example,
                            the latency may be a running average
                            calculated from the internal queuing. If
                            the modem device cannot calculate latency,
                            it SHOULD be reported as 0. In the Link
                            Characteristics Request Message, this value
                            represents the maximum delay, in milliseconds,
                            expected on the link.


7.10  Resources Sub-TLV

   The Resources Sub-TLV is used in Neighbor Up, Neighbor Update, and Link
   Characteristics ACK messages to indicate a percentage (0-100) amount
   of resources (e.g. battery power) remaining on the modem device.

   The Resources TLV contains the following fields:
   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Type =TBD  |TLV Flags=0x10 |Length = 1     |   Resources   |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   TLV Type              -  TBD

   TLV Flags             -  0x10, Bit 3 (thasvalue) is set, all other
                            bits are not used and MUST be set to '0'.

   Length                -  1



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   Resources             -  a percentage, 0-100, representing the amount
                            of remaining resources, such as battery power.
                            If resources cannot be calculated, a value of
                            100 SHOULD be reported.


7.11  Relative Link Quality Sub-TLV

   The Relative Link Quality (RLQ) Sub-TLV is used in Neighbor Up,
   Neighbor Update, and Link Characteristics ACK messages to indicate
   the quality of the link as calculated by the modem device.

   The Relative Link Quality sub-TLV contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Type =TBD  |TLV Flags=0x10 |Length = 1     |Relative Link  |
  |               |               |               |Quality (RLQ)  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   TLV Type              -  TBD

   TLV Flags             -  0x10, Bit 3 (thasvalue) is set, all other
                            bits are not used and MUST be set to '0'.

   Length                -  1

   Relative Link Quality -  a non-dimensional number, 0-100,
                            representing the relative link quality.
                            A value of 100 represents a link of the
                            highest quality. If the RLQ cannot be
                            calculated, a value of 100 SHOULD be
                            reported.


7.12  Status Sub-TLV

   The Status Sub-TLV is sent from either the client or router to
   indicate the success or failure of a given request

   The Status Sub-TLV contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Type =TBD  |TLV Flags=0x10 |Length = 1     |     Code      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   TLV Type         - TBD

   TLV Flags        - 0x10, Bit 3 (thasvalue) is set, all other bits are
                      not used and MUST be set to '0'.


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   Length           - 1

   Termination Code - 0 = Success
                      Non-zero = Failure. Specific values of a non-
                      zero termination code depend on the operation
                      requested (e.g. Neighbor Up, Neighbor Down, etc).


7.13  Heartbeat Interval Sub-TLV

   The Heartbeat Interval Sub-TLV MAY be sent from the client during
   Peer Discovery to indicate the desired Heartbeat timeout window.
   If included in the Peer Discovery, the router MUST either accept the
   timeout interval, or reject the Peer Discovery.

   The Heartbeat Interval Sub-TLV contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Type =TBD  |TLV Flags=0x10 |Length = 1     | Interval      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   TLV Type         - TBD

   TLV Flags        - 0x10, Bit 3 (thasvalue) is set, all other bits are
                      not used and MUST be set to '0'.

   Length           - 1

   Interval         - 0 = Do NOT use heartbeats on this peer-to-peer
                      session. Non-zero = Interval, in seconds, for
                      heartbeat messages.


7.14  Heartbeat Threshold Sub-TLV

   The Heartbeat Threshold Sub-TLV MAY be sent from the client during
   Peer Discovery to indicate the desired number of windows, of time
   (Heartbeat Interval) seconds, to wait before either peer declares
   the peer-to-peer session lost. In this case, the overall amount of
   time before a peer-to-peer session is declared lost is expressed as
   (Interval * Threshold), where 'Interval' is the value in the
   Heartbeat Interval sub-TLV, documented above. If this sub-TLV is
   included by the client in the Peer Discovery, the client MUST also
   specify the Heartbeat Interval sub-TLV with a non-zero interval. If
   this sub-TLV is received during Peer Discovery, the router MUST
   either accept the threshold, or reject the Peer Discovery.







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   The Heartbeat Threshold Sub-TLV contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Type =TBD  |TLV Flags=0x10 |Length = 1     | Threshold     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   TLV Type         - TBD

   TLV Flags        - 0x10, Bit 3 (thasvalue) is set, all other bits are
                      not used and MUST be set to '0'.

   Length           - 1

   Threshold        - 0 = Do NOT use heartbeats on this peer-to-peer
                      session. Non-zero = Number of windows, of
                      Heartbeat Interval seconds, to wait before
                      declaring a peer-to-peer session to be lost.


7.15  Link Characteristics ACK Timer Sub-TLV

   The Link Characteristic ACK Timer Sub-TLV MAY be sent from the
   client during Peer Discovery to indicate the desired number of
   seconds the router should wait for a response to a Link
   Characteristics Request. If this sub-TLV is received during Peer
   Discovery, the router MUST either accept the timeout value, or
   reject the Peer Discovery.

   The Link Characteristics ACK Timer Sub-TLV contains the
   following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Type =TBD  |TLV Flags=0x10 |Length = 1     | Interval      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   TLV Type         - TBD

   TLV Flags        - 0x10, Bit 3 (thasvalue) is set, all other bits are
                      not used and MUST be set to '0'.

   Length           - 1

   Interval         - 0 = Do NOT use timeouts for Link Characteristics
                      requests on this peer-to-peer session.
                      Non-zero = Interval, in seconds, to wait before
                      considering a Link Characteristics Request has
                      been lost.




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8. DLEP Protocol Messages

   DLEP places no additional requirements on the RFC 5444 Packet
   formats, or the packet header. DLEP does require that the optional
   'msg-seq-num' in the message header exist, and defines a set of
   values for the 'tlv-type' field in the RFC 5444 TLV block. Therefore,
   a DLEP message, starting from the RFC 5444 Message header, would
   appear 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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Msg Type =   |Msg Flg|AddrLen|          Message Size         |
  | DLEP_MESSAGE  | 0x1   | 0x0   |                               |
  | (value TBD)   |       |       |                               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Message Seq Num      | TLV block length (length of   |
  |                               | DLEP order + Sub-TLVs)        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | DLEP Message  |TLV Flags=0x10 | Length        | Start of DLEP |
  | Block value   |               |               | Sub-TLVs...   |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


8.1  Message Block TLV Values

   As mentioned above, all DLEP messages utilize a single RFC 5444
   message type, the DLEP_MESSAGE (TBD). DLEP further identifies
   protocol messages by using the 'tlv-type' field in the RFC 5444
   message TLV block. DLEP defines the following Message-Type-
   specific values for the tlv-type field:

          TLV      TLV
          Value    Description
          =========================================
          TBD      Attached Peer Discovery
          TBD      Detached Peer Discovery
          TBD      Peer Offer
          TBD      Peer Update
          TBD      Peer Update ACK
          TBD      Peer Termination
          TBD      Peer Termination ACK
          TBD      Neighbor Up
          TBD      Neighbor Up ACK
          TBD      Neighbor Down
          TBD      Neighbor Down ACK
          TBD      Neighbor Update
          TBD      Neighbor Address Update
          TBD      Neighbor Address Update ACK
          TBD      Heartbeat
          TBD      Link Characteristics Request
          TBD      Link Characteristics ACK


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   In all of the diagrams following, the message layouts begin with the
   RFC 5444 message header.


9. Peer Discovery Messages

   There are two different types of Peer Discovery Messages, Attached
   and Detached.  Attached Peer Discovery Messages are sent by the
   client when it is directly attached to the router (e.g. the client
   exists as a card in the chassis, or it is connected via Ethernet with
   no intervening devices). The Detached Peer Discovery message, on the
   other hand, is sent by a "remote" client -- for example, a client at
   a satellite hub system might use a Detached Discovery Message in
   order to act as a proxy for remote ground terminals. To explain in
   another way, a detached client uses the variable link itself (the
   radio or satellite link) to establish a DLEP session with a remote
   router.

9.1  Attached Peer Discovery Message

   The Attached Peer Discovery Message is sent by an attached client
   to a router to begin a new DLEP association. The Peer Offer message
   is required to complete the discovery process. The client MAY
   implement its own retry heuristics in the event it (the client)
   determines the Attached Peer Discovery Message has timed out.

   The Attached Peer Discovery Message contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Msg Type =   |Msg Flg|AddrLen|          Message Size         |
  | DLEP_MESSAGE  | 0x1   | 0x0   |        22 + size of opt       |
  | (value TBD)   |       |       |            sub-TLV            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Message Seq Num      |TLVs Length =14 + opt sub-TLVs |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | DLEP Attached |TLV Flags=0x10 | Length =11 +  | Sub-TLV type= |
  | Peer Discovery|               | opt sub-TLVs  | Identification|
  | (Value TDB)   |               |               | sub-TLV (TBD) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |          Router ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Router ID          |          Client ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Client ID          |Sub-TLV type=  |TLV Flags=0x10 |
  |                               |DLEP Version   |               |
  |                               |sub-TLV (TBD)  |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Length = 4     |         Major Version         | Minor Version |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Minor Version |Sub-TLV type=  |TLV Flags=0x10 | Length = Len  |
  |               |Peer Type (TBD)|               |of peer string |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |               (Continued on next page)                        |
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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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |               (Continued from previous page)                  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Peer Type Str |Sub-TLV Type=  |TLV Flags=0x10 | Length = 1    |
  |MaxLen=80 bytes|Heartbeat Int. |               |               |
  |               |(TBD)          |               |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Heartbeat     |Sub-TLV Type=  |TLV Flags=0x10 | Length = 1    |
  | Interval      |HB Thresh.     |               |               |
  | (seconds)     |(TBD)          |               |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Heartbeat     |Sub-TLV Type=  |TLV FLags=0x10 | Length = 1    |
  | Threshold     |Link Char. ACK |               |               |
  |(# of windows) |Timer (TBD)    |               |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Link Char ACK  |
  |Timer (sec)    |
  +-+-+-+-+-+-+-+-+

   Message Type                    - DLEP_MESSAGE (value TBD)

   Message Flags                   - Set to 0x1 (bit 3, mhasseqnum
                                     bit is set).  No other bits are
                                     used and MUST be set to '0'.

   Message Address Length          - 0x0

   Message Size                    - 22 + size of optional sub-TLVs

   Message Sequence Number         - a 16-bit unsigned integer field
                                     containing a sequence number
                                     generated by the message
                                     originator.

   TLV Block                       - TLVs Length: 14 + size of optional
                                                  sub-TLVs.

                                     DLEP Attached Peer Disc. order
                                     Identification TLV (MANDATORY)
                                     Version Sub-TLV (OPTIONAL)
                                     Peer Type Sub-TLV (OPTIONAL)
                                     Heartbeat Int. Sub-TLV (OPTIONAL)
                                     Heartbeat Threshold Sub-TLV (OPT.)
                                     Link Characteristics ACK Timer
                                     Sub-TLV (OPTIONAL)








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9.2  Detached Peer Discovery Message

   The Detached Peer Discovery Message is sent by a detached client
   proxy to a router to begin a new DLEP session. The Peer Offer
   message is required to complete the discovery process. The client
   MAY implement its own retry heuristics in the event it (the client)
   determines the Detached Peer Discovery Message has timed out.

   The Detached Peer Discovery Message contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Msg Type =   |Msg Flg|AddrLen|          Message Size         |
  | DLEP_MESSAGE  | 0x1   | 0x0   |        22 + size of opt       |
  | (value TBD)   |       |       |            sub-TLV            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Message Seq Num      |TLVs Length =14 + opt sub-TLVs |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | DLEP Detached |TLV Flags=0x10 | Length = 11 + | Sub-TLV type= |
  | Peer Discovery|               | opt sub-TLVs  | Identification|
  | (Value TDB)   |               |               | sub-TLV (TBD) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |          Router ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Router ID          |          Client ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Client ID          |Sub-TLV type=  |TLV Flags=0x10 |
  |                               |DLEP Version   |               |
  |                               |sub-TLV (TBD)  |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Length = 4     |         Major Version         | Minor Version |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Minor Version |Sub-TLV type=  |TLV Flags=0x10 | Length = Len  |
  |               |Peer Type (TBD)|               |of peer string |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Peer Type Str |Sub-TLV Type=  |TLV Flags=0x10 | Length = 1    |
  |MaxLen=80 bytes|Heartbeat Int. |               |               |
  |               |(TBD)          |               |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Heartbeat     |Sub-TLV Type=  |TLV Flags=0x10 | Length = 1    |
  | Interval      |HB Thresh.     |               |               |
  | (seconds)     |(TBD)          |               |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Heartbeat     |Sub-TLV Type=  |TLV FLags=0x10 | Length = 1    |
  | Threshold     |Link Char. ACK |               |               |
  |(# of windows) |Timer (TBD)    |               |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Link Char ACK  |
  |Timer (sec)    |
  +-+-+-+-+-+-+-+-+

   Message Type                  - DLEP_MESSAGE (value TBD)


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   Message Flags                 - Set to 0x1 (bit 3,
                                   mhasseqnum bit is set).
                                   All other bits are not used
                                   and MUST be set to '0'.

   Message Address Length        - 0x0

   Message Size                  - 22 + size of optional
                                   sub-TLVs

   Message Sequence Number       - A 16-bit unsigned integer
                                   field containing a sequence
                                   number, generated by the
                                   message originator.

   TLV Block                     - TLVs Length: 14 + size of
                                    optional sub-TLVs.

                                   DLEP Detached Peer Discovery order
                                   Identification sub-TLV (MANDATORY)
                                   Version sub-TLV (OPTIONAL)
                                   Peer Type Sub-TLV (OPTIONAL)
                                   Heartbeat Interval Sub-TLV (OPTIONAL)
                                   Heartbeat Threshold Sub-TLV (OPTIONAL)
                                   Link Char. ACK Timer Sub-TLV(OPTIONAL)


10. Peer Offer Message

   The Peer Offer Message is sent by a router to a client or client
   proxy in response to a Peer Discovery Message. The Peer Offer
   Message is the response to either of the Peer Discovery messages
   (either Attached or Detached), and completes the DLEP session
   establishment.

   The Peer Offer Message contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Msg Type =   |Msg Flg|AddrLen|          Message Size         |
  | DLEP_MESSAGE  | 0x1   | 0x0   |        22 + size of opt       |
  | (value TBD)   |       |       |            sub-TLV            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Message Seq Num      |TLVs Length =14 + opt sub-TLVs |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |DLEP Peer Offer|TLV Flags=0x10 | Length = 11 + | Sub-TLV type= |
  | (Value TBD)   |               | opt sub-TLVs  | Identification|
  |               |               |               | sub-TLV (TBD) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |          Router ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                  (Continued on next page)                     |


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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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                  (Continued from above)                       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Router ID          |          Client ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Client ID          |Sub-TLV type=  |TLV Flags=0x10 |
  |                               |DLEP Version   |               |
  |                               |sub-TLV (TBD)  |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Length = 4    |         Major Version         | Minor Version |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Minor Version |Peer Type sub- |TLV Flags=0x10 | Length = Len  |
  |               |TLV = TDB      |               |of peer string |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Peer Type Str |DLEP IPv4 sub- |TLV Flags=0x10 | Length = 5    |
  |MaxLen=80 bytes|TLV (TBD)      |               |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Add/Drop Ind. |                 IPv4 Address                  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | IPv4 Address  |DLEP IPv6 sub- |TLV Flags=0x10 | Length = 17   |
  |               |TLV Type = TBD |               |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Add/Drop Ind. |                 IPv6 Address                  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        IPv6 Address                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        IPv6 Address                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        IPv6 Address                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |IPv6 Address   |Sub-TLV type=  |TLV Flags=0x10 | Length = 1    |
  |               |Heartbeat Int. |               |               |
  |               |(TBD)          |               |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Heartbeat    |Sub-TLV Type=  |TLV Flags=0x10 | Length = 1    |
  |  Interval     |Heartbeat      |               |               |
  |  (seconds)    |Threshold (TBD)|               |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Heartbeat    |Sub-TLV Type=  |TLV FLags=0x10 | Length = 1    |
  |  Threshold    |Link Char. ACK |               |               |
  | (# of windows)|Timer (TBD)    |               |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Link Char ACK  |Sub-TLV Type=  |TLV Flags=0x10 | Length = 1    |
  |Timer (sec)    |DLEP Status    |               |               |
  |               |(TBD)          |               |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Code          |
  +-+-+-+-+-+-+-+-+

   Message Type            - DLEP_MESSAGE (Value TBD)



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   Message Flags           - Set to 0x1 (bit 3, mhasseqnum bit
                             is set). All other bits are unused and
                             MUST be set to '0'.

   Message Address Length  - 0x0

   Message Size            - 22 + size of optional sub-TLVs

   Message Sequence Number - A 16-bit unsigned integer field containing
                             a sequence number, generated by the message
                             originator.

   TLV Block               - TLV Length: 14 + size of optional sub-TLVs
                             DLEP Peer Offer order
                             Identification sub-TLV (MANDATORY)
                             DLEP Version sub-TLV (OPTIONAL)
                             Peer Type sub-TLV (OPTIONAL)
                             IPv4 Address sub-TLV (OPTIONAL)
                             IPv6 Address sub-TLV (OPTIONAL)
                             Status sub-TLV (OPTIONAL)
                             Heartbeat Interval Sub-TLV (OPTIONAL)
                             Heartbeat Threshold Sub-TLV (OPTIONAL)
                             Link Char. ACK Timer Sub-TLV (OPTIONAL)



11. Peer Update Message

   The Peer Update message is sent by the router to indicate local
   Layer 3 address changes. For example, addition of an IPv4 address
   to the router would prompt a Peer Update message to its attached
   DLEP clients. If the modem device is capable of understanding and
   forwarding this information, the address update would prompt any
   remote DLEP clients (DLEP clients that are on the far-end of the
   variable link) to issue a "Neighbor Update" message to their local
   routers, with the address change information. Clients that do not
   track Layer 3 addresses MUST silently ignore the Peer Update
   Message. Clients that track Layer 3 addresses MUST acknowledge the
   Peer Update with a Peer Update ACK message. Routers MAY employ
   heuristics to retransmit Peer Update messages. Sending of Peer
   Update Messages SHOULD cease when a router implementation
   determines that a partner modem device does NOT support Layer 3
   address tracking.












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   The Peer Update Message contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Msg Type =   |Msg Flg|AddrLen|          Message Size         |
  | DLEP_MESSAGE  | 0x1   | 0x0   |        22 + size of opt       |
  | (value TBD)   |       |       |            sub-TLVs           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Message Seq Num      |TLVs Length =14 + opt sub-TLVs |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | DLEP Peer     |TLV Flags=0x10 | Length = 11 + | Sub-TLV type= |
  | Update        |               | opt sub-TLVs  | Identification|
  | (Value TDB)   |               |               | sub-TLV (TBD) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |          Router ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Router ID          |          Client ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Client ID          |Sub-TLV type=  |TLV Flags=0x10 |
  |                               |DLEP IPv4      |               |
  |                               |sub-TLV (TBD)  |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Length = 5     | Add/Drop Ind. |         IPv4 Address          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |         IPv4 Address          | Sub-TLV type= |TLV Flags=0x10 |
  |                               | DLEP IPv6     |               |
  |                               | sub-TLV (TBD) |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Length = 17    | Add/Drop Ind. |         IPv6 Address          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        IPv6 Address                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        IPv6 Address                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        IPv6 Address                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |        IPv6 Address           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Message Type             - DLEP_MESSAGE (Value TBD)

   Message Flags            - Set to 0x1 (bit 3, mhasseqnum bit
                              is set). All other bits are unused and
                              MUST be set to '0'.

   Message Address Length   - 0x0

   Message Size             - 22 + optional Sub-TLVs

   Message Sequence Number  - A 16-bit unsigned integer field containing
                              a sequence number generated by the message
                              originator.


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   TLV Block                - TLV Length:  14 + length of optional
                                           sub-TLVs.
                              DLEP Peer Update order
                              Identification sub-TLV (MANDATORY)
                              IPv4 Address Sub-TLV (OPTIONAL)
                              IPv6 Address Sub-TLV (OPTIONAL)


12. Peer Update ACK Message

   The client sends the Peer Update ACK Message to indicate whether a
   Peer Update Message was successfully processed.

   The Peer Update ACK message contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Msg Type =   |Msg Flg|AddrLen|          Message Size         |
  | DLEP_MESSAGE  | 0x1   | 0x0   |        22 + size of opt       |
  | (value TBD)   |       |       |            sub-TLVs           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Message Seq Num      |TLVs Length =14 + opt sub-TLVs |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | DLEP Peer     |TLV Flags=0x10 | Length = 11 + | Sub-TLV type= |
  | Update ACK    |               | opt sub-TLVs  | Identification|
  | (Value TDB)   |               |               | sub-TLV (TBD) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |          Router ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Router ID          |          Client ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Client ID          |Sub-TLV type=  |TLV Flags=0x10 |
  |                               |DLEP Status    |               |
  |                               |sub-TLV (TBD)  |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Length = 1     |      Code     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Message Type             - DLEP_MESSAGE (Value TBD)

   Message Flags            - Set to 0x1 (bit 3, mhasseqnum bit
                              is set). All other bits are unused and
                              MUST be set to '0'.

   Message Address Length   - 0x0

   Message Size             - 22 + size of optional sub-TLVs.

   Message Sequence Number  - A 16-bit unsigned integer field containing
                              the sequence number from the Neighbor Up
                              Message that is being acknowledged.



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   TLV Block                - TLV Length:  14 + optional sub-TLVs
                              DLEP Peer Update ACK order
                              Identification Sub-TLV (MANDATORY)
                              Status Sub-TLV (OPTIONAL)


13. Peer Termination Message

   The Peer Termination Message is sent by either the client or the
   router when a session needs to be terminated. Transmission of a
   Peer Termination ACK message is required to confirm the
   termination process. The sender of the Peer Termination message
   is free to define its heuristics in event of a timeout. The
   receiver of a Peer Termination Message MUST terminate all
   neighbor relationships and release associated resources. No
   Neighbor Down messages are sent.

   The Peer Termination Message contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Msg Type =   |Msg Flg|AddrLen|          Message Size         |
  | DLEP_MESSAGE  | 0x1   | 0x0   |        22 + size of opt       |
  | (value TBD)   |       |       |            sub-TLVs           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Message Seq Num      |TLVs Length =14 + opt sub-TLVs |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | DLEP Peer     |TLV Flags=0x10 | Length = 11 + | Sub-TLV type= |
  | Termination   |               | opt sub-TLVs  | Identification|
  | (Value TDB)   |               |               | sub-TLV (TBD) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |          Router ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Router ID          |          Client ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Client ID          |Sub-TLV type=  |TLV Flags=0x10 |
  |                               |DLEP Status    |               |
  |                               |sub-TLV (TBD)  |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Length = 1    | Code          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Message Type                  - DLEP_MESSAGE (Value TBD)

   Message Flags                 - Set to 0x1 (bit 3, mhasseqnum
                                   bit is set). All other bits are
                                   unused and MUST be set to '0'.

   Message Address Length        - 0x0

   Message Size                  - 22 + size of optional sub-TLVs.



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   Message Sequence Number       - A 16-bit unsigned integer field
                                   containing a sequence number
                                   generated by the message originator.

   TLV Block                     - TLV Length = 14 + optional sub-TLVs
                                   DLEP Peer Termination order
                                   Identification Sub-TLV (MANDATORY)
                                   Status Sub-TLV (OPTIONAL)



14. Peer Termination ACK Message

   The Peer Termination Message ACK is sent by either the client or
   the router when a session needs to be terminated.

   The Peer Termination ACK Message contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Msg Type =   |Msg Flg|AddrLen|          Message Size         |
  | DLEP_MESSAGE  | 0x1   | 0x0   |        22 + size of opt       |
  | (value TBD)   |       |       |            sub-TLVs           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Message Seq Num      |TLVs Length =14 + opt sub-TLVs |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | DLEP Peer Term|TLV Flags=0x10 | Length = 11 + | Sub-TLV type= |
  | ACK           |               | opt sub-TLVs  | Identification|
  | (Value TBD)   |               |               | sub-TLV (TBD) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |          Router ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Router ID          |          Client ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Client ID          |Sub-TLV type=  |TLV Flags=0x10 |
  |                               |DLEP Status    |               |
  |                               |sub-TLV (TBD)  |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Length = 1    | Code          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Message Type                  - DLEP_MESSAGE (Value TBD)

   Message Flags                 - Set to 0x1 (bit 3, mhasseqnum
                                   bit is set). All other bits are
                                   unused and MUST be set to '0'.

   Message Address Length        - 0x0

   Message Size                  - 22 + optional sub-TLVs.



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   Message Sequence Number       - A 16-bit unsigned integer field
                                   containing the sequence number in
                                   the corresponding Peer Termination
                                   Message being acknowledged.

   TLV Block                     - TLV Length = 14 + optional Sub-TLVs
                                   DLEP Peer Termination ACK order
                                   Identification Sub-TLV (MANDATORY)
                                   Status Sub-TLV (OPTIONAL)


15. Neighbor Up Message

   The client sends the Neighbor Up message to report that a new
   potential routing neighbor has been detected. A Neighbor Up
   ACK Message is required to confirm a received Neighbor Up.
   The sender of the Neighbor Up Message is free to define its
   retry heuristics in event of a timeout.

   The Neighbor Up Message contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Msg Type =   |Msg Flg|AddrLen|          Message Size         |
  | DLEP_MESSAGE  | 0x1   | 0x0   |        31 + size of opt       |
  | (value TBD)   |       |       |            sub-TLVs           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Message Seq Num      |TLVs Length =23 + opt sub-TLVs |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | DLEP Neighbor |TLV Flags=0x10 | Length =20 +  | Sub-TLV type= |
  | Up (TBD)      |               | opt sub-TLVs  | Identification|
  |               |               |               | sub-TLV (TBD) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |          Router ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Router ID          |          Client ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Client ID          |Sub-TLV type=  |TLV Flags=0x10 |
  |                               |DLEP MAC       |               |
  |                               |sub-TLV (TBD)  |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Length = 6     |                MAC Address                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |              MAC Address                      |Sub-TLV type=  |
  |                                               |DLEP IPv4 (TBD)|
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 5     | Add/Drop Ind. | IPv4 Address  |
  |               |               |               |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                IPv4 Address                   |Sub-TLV type=  |
  |                                               |DLEP IPv6 (TBD)|
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                   (Continued on next page)                    |

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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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                  (Continued from above)                       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 17    | Add/Drop Ind. | IPv6 Address  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        IPv6 Address                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        IPv6 Address                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        IPv6 Address                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                IPv6 Address                   |Sub-TLV type=  |
  |                                               |DLEP MDR (TBD) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |         MDR (bps)             |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        MDR (bps)                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |        MDR (bps)              |sub-TLV Type = |TLV Flags=0x10 |
  |                               |DLEP CDR (TBD) |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Length = 8     |                 CDR (bps)                     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        CDR (bps)                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  CDR (bps)    |sub-TLV Type = |TLV Flags=0x10 | Length = 2    |
  |               |Latency (TBD)  |               |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           Latency (ms)           |sub-TLV Type = |TLV Flags=0x10 |
  |                               |Resources(TBD) |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Length = 1    |   Resources   |sub-TLV Type = |TLV Flags=0x10 |
  |               |               |DLEP RLQ (TBD) |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Length = 1    |      RLQ      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Message Type             - DLEP_MESSAGE (Value TBD)

   Message Flags            - Set to 0x1 (bit 3, mhasseqnum bit
                              is set). All other bits are unused and
                              MUST be set to '0'.

   Message Address Length   - 0x0

   Message Size             - 31 + optional Sub-TLVs

   Message Sequence Number  - A 16-bit unsigned integer field containing
                              a sequence number generated by the message
                              originator.



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   TLV Block                - TLV Length:  23 + optional Sub-TLVs.
                              DLEP Neighbor Up order
                              Identification Sub-TLV (MANDATORY)
                              MAC Address Sub-TLV (MANDATORY)
                              IPv4 Address Sub-TLV (OPTIONAL)
                              IPv6 Address Sub-TLV (OPTIONAL)
                              Maximum Data Rate Sub-TLV (OPTIONAL)
                              Current Data Rate Sub-TLV (OPTIONAL)
                              Latency Sub-TLV (OPTIONAL)
                              Resources Sub-TLV (OPTIONAL)
                              Relative Link Factor Sub-TLV (OPTIONAL)


16. Neighbor Up ACK Message

   The router sends the Neighbor Up ACK Message to indicate whether a
   Neighbor Up Message was successfully processed.

   The Neighbor Up ACK message contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Msg Type =   |Msg Flg|AddrLen|          Message Size         |
  | DLEP_MESSAGE  | 0x1   | 0x0   |                35             |
  | (value TBD)   |       |       |                               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Message Seq Num      |TLVs Length = 27               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | DLEP Neighbor |TLV Flags=0x10 | Length = 24   | Sub-TLV type= |
  | Up ACK (TBD)  |               |               | Identification|
  |               |               |               | sub-TLV (TBD) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |          Router ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Router ID          |          Client ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Client ID          |Sub-TLV type=  |TLV Flags=0x10 |
  |                               |DLEP MAC       |               |
  |                               |sub-TLV (TBD)  |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Length = 6     |                MAC Address                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |              MAC Address                      |Sub-TLV type=  |
  |                                               |DLEP Status
  |                                               |(TBD)          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 | Length = 1    |  Code         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Message Type             - DLEP_MESSAGE (Value TBD)


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   Message Flags            - Set to 0x1 (bit 3, mhasseqnum bit
                              is set). All other bits are unused and
                              MUST be set to '0'.

   Message Address Length   - 0x0

   Message Size             - 35

   Message Sequence Number  - A 16-bit unsigned integer field containing
                              the sequence number from the Neighbor Down
                              Message that is being acknowledged.

   TLV Block                - TLV Length:  27

                              DLEP Neighbor Up ACK order
                              Identification Sub-TLV (MANDATORY)
                              MAC Address Sub-TLV (MANDATORY)
                              Status Sub-TLV (MANDATORY)


17. Neighbor Down Message

   The client sends the Neighbor Down message to report when a neighbor
   is no longer reachable from the client. The Neighbor Down message
   MUST contain a MAC Address TLV. Any other TLVs present MAY be
   ignored. A Neighbor Down ACK Message is required to confirm the
   process. The sender of the Neighbor Down message is free to define
   its retry heuristics in event of a timeout.

   The Neighbor Down Message contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Msg Type =   |Msg Flg|AddrLen|          Message Size         |
  | DLEP_MESSAGE  | 0x1   | 0x0   |         31 + optional         |
  | (value TBD)   |       |       |            sub-TLV            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Message Seq Num      |  TLVs Length = 23 + optional  |
  |                               |             Sub-TLV           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | TLV Type =    |TLV Flags=0x10 | Length = 20 + | Sub-TLV type= |
  | DLEP Neighbor |               | optional Sub- | Identification|
  | Down (TBD)    |               | TLV           | sub-TLV (TBD) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |          Router ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Router ID          |          Client ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Client ID          |Sub-TLV type=  |TLV Flags=0x10 |
  |                               |DLEP MAC       |               |
  |                               |sub-TLV (TBD)  |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                  (Continued on next page)                     |

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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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                   (Continued from above)                      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Length = 6     |                MAC Address                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |              MAC Address                      |Sub-TLV type=  |
  |                                               |DLEP Status
  |                                               |(TBD)          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 | Length = 1    |  Code         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Message Type               - DLEP_MESSAGE (Value TBD)

   Message Flags              - Set to 0x1 (bit 3, mhasseqnum bit
                                is set). All other bits are unused and
                                MUST be set to '0'.

   Message Address Length     - 0x0

   Message Size               - 31 + optional TLVs

   Message Sequence Number    - A 16-bit unsigned integer field
                                containing a sequence number generated
                                by the message originator.

   TLV Block                  - TLV Length: 23 + optional Sub-TLVs

                                DLEP Neighbor Down order
                                Identification Sub-TLV (MANDATORY)
                                MAC Address Sub-TLV (MANDATORY)
                                Status Sub-TLV (OPTIONAL)



18. Neighbor Down ACK Message

   The router sends the Neighbor Down ACK Message to indicate whether
   a Neighbor Down Message was successfully processed.













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   The Neighbor Down ACK message contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Msg Type =   |Msg Flg|AddrLen|          Message Size         |
  | DLEP_MESSAGE  | 0x1   | 0x0   |                35             |
  | (value TBD)   |       |       |                               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Message Seq Num      |TLVs Length = 27               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | DLEP Neighbor |TLV Flags=0x10 | Length = 24   | Sub-TLV type= |
  | Down ACK (TBD)|               |               | Identification|
  |               |               |               | sub-TLV (TBD) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |          Router ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Router ID          |          Client ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Client ID          |Sub-TLV type=  |TLV Flags=0x10 |
  |                               |DLEP MAC       |               |
  |                               |sub-TLV (TBD)  |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Length = 6     |                MAC Address                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |              MAC Address                      |Sub-TLV type=  |
  |                                               |DLEP Status
  |                                               |(TBD)          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 | Length = 1    |  Code         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Message Type             - DLEP_MESSAGE (Value TBD)

   Message Flags            - Set to 0x1 (bit 3, mhasseqnum bit
                              is set). All other bits are unused and
                              MUST be set to '0'.

   Message Address Length   - 0x0

   Message Size             - 35

   Message Sequence Number  - A 16-bit unsigned integer field containing
                              the sequence number from the Neighbor Down
                              Message that is being acknowledged.

   TLV Block                - TLV Length:  27

                              DLEP Neighbor Down ACK order
                              Identification Sub-TLV (MANDATORY)
                              MAC Address Sub-TLV (MANDATORY)
                              Status Sub-TLV (MANDATORY)



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19. Neighbor Update Message

   The client sends the Neighbor Update message when a change in link
   metric parameters is detected for a routing neighbor.

   The Neighbor Update Message contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Msg Type =   |Msg Flg|AddrLen|          Message Size         |
  | DLEP_MESSAGE  | 0x1   | 0x0   |         31 + optional         |
  | (value TBD)   |       |       |            sub-TLV            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Message Seq Num      |  TLVs Length = 23 + optional  |
  |                               |             Sub-TLVs          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Type =     |TLV Flags=0x10 |Length = 20 +  |Sub-TLV type = |
  |DLEP Neighbor  |               |optional Sub-  |Identification |
  |Update (TBD)   |               |TLVs           |Sub-TLV (TBD)  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |          Router ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Router ID          |          Client ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Client ID          |Sub-TLV type=  |TLV Flags=0x10 |
  |                               |DLEP MAC       |               |
  |                               |sub-TLV (TBD)  |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Length = 6     |                MAC Address                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |              MAC Address                      |Sub-TLV type=  |
  |                                               |DLEP MDR (TBD) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |           MDR (bps)           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        MDR (bps)                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |        MDR (bps)              |Sub-TLV Type = |TLV Flags=0x10 |
  |                               |DLEP CDR (TBD) |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Length = 8     |                 CDR (bps)                     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        CDR (bps)                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |   CDR (bps)   |Sub-TLV Type = |TLV Flags=0x10 | Length = 2    |
  |               |DLEP Latency   |               |               |
  |               |(TBD)          |               |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |        Latency (ms)           |Sub-TLV Type=  |TLV Flags=0x10 |
  |                               |DLEP Resources |               |
  |                               |(TBD)          |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                   (Continued on next page)                    |

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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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                    (Continued from above)                     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Length = 1    |   Resources   |Sub-TLV Type=  |TLV FLags=0x10 |
  |               |               |DLEP RLQ (TBD) |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Length = 1    |      RLQ      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Message Type                 - DLEP_MESSAGE (Value TBD)

   Message Flags                - Set to 0x1 (bit 3, mhasseqnum
                                  bit is set).  All other bits are
                                  unused and MUST be set to '0'.

   Message Address Length       - 0x0

   Message Size                 - 31 + optional TLVs

   Message Sequence Number      - A 16-bit unsigned integer field
                                  containing a sequence number,
                                  generated by the message originator.

   TLV Block                    - TLVs Length - 23 + optional Sub-TLVs.

                                  DLEP Neighbor Update order
                                  Identification Sub-TLV (MANDATORY)
                                  MAC Address Sub-TLV (MANDATORY)
                                  Maximum Data Rate Sub-TLV (OPTIONAL)
                                  Current Data Rate Sub-TLV (OPTIONAL)
                                  Latency Sub-TLV (OPTIONAL)
                                  Resources Sub-TLV (OPTIONAL)
                                  Relative Link Quality Sub-TLV
                                  (OPTIONAL)


20. Neighbor Address Update Message

   The client sends the Neighbor Address Update message when a change
   in Layer 3 addressing is detected for a routing neighbor.

   The Neighbor Address Update Message contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Msg Type =   |Msg Flg|AddrLen|          Message Size         |
  | DLEP_MESSAGE  | 0x1   | 0x0   |        31 + size of opt       |
  | (value TBD)   |       |       |            sub-TLVs           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Message Seq Num      |TLVs Length =23 + opt sub-TLVs |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                 (Continued on next page)                      |

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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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                  (Continued from above)                       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | DLEP Neighbor |TLV Flags=0x10 | Length =20 +  | Sub-TLV type= |
  | Address Update|               | opt sub-TLVs  | Identification|
  |(TBD)          |               |               | Sub-TLV (TBD) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |          Router ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Router ID          |          Client ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Client ID          |Sub-TLV type=  |TLV Flags=0x10 |
  |                               |DLEP MAC       |               |
  |                               |sub-TLV (TBD)  |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Length = 6     |                MAC Address                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |              MAC Address                      |Sub-TLV type=  |
  |                                               |DLEP IPv4 (TBD)|
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 5     | Add/Drop Ind. | IPv4 Address  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                IPv4 Address                   |Sub-TLV type=  |
  |                                               |DLEP IPv6 (TBD)|
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 17    | Add/Drop Ind. | IPv6 Address  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        IPv6 Address                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        IPv6 Address                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        IPv6 Address                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                IPv6 Address                   |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Message Type                 - DLEP_MESSAGE (Value TBD)

   Message Flags                - Set to 0x1 (bit 3, mhasseqnum bit is
                                  set).  All other bits are unused and
                                  MUST be set to '0'.

   Message Address Length       - 0x0

   Message Size                 - 31 + optional TLVs

   Message Sequence Number      - A 16-bit unsigned integer field
                                  containing a sequence number,
                                  generated by the message originator.




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   TLV Block                    - TLVs Length - 23 + optional Sub-TLVs.
                                  DLEP Neighbor Address Update order
                                  Identification Sub-TLV (MANDATORY)
                                  MAC Address Sub-TLV (MANDATORY)
                                  IPv4 Address Sub-TLV (OPTIONAL)
                                  IPv6 Address Sub-TLV (OPTIONAL)


21. Neighbor Address Update ACK Message

   The router sends the Neighbor Address Update ACK Message to
   indicate whether a Neighbor Address Update Message was
   successfully processed.

   The Neighbor Address Update ACK message contains the following
   fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Msg Type =   |Msg Flg|AddrLen|          Message Size         |
  | DLEP_MESSAGE  | 0x1   | 0x0   |                35             |
  | (value TBD)   |       |       |                               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Message Seq Num      |TLVs Length = 27               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | DLEP Neighbor |TLV Flags=0x10 | Length = 24   | Sub-TLV type= |
  | Address Update|               |               | Identification|
  | ACK (TBD)     |               |               | sub-TLV (TBD) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |          Router ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Router ID          |          Client ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Client ID          |Sub-TLV type=  |TLV Flags=0x10 |
  |                               |DLEP MAC       |               |
  |                               |sub-TLV (TBD)  |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Length = 6     |                MAC Address                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |              MAC Address                      |Sub-TLV type=  |
  |                                               |DLEP Status
  |                                               |(TBD)          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 | Length = 1    |  Code         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Message Type             - DLEP_MESSAGE (Value TBD)

   Message Flags            - Set to 0x1 (bit 3, mhasseqnum bit
                              is set). All other bits are unused and
                              MUST be set to '0'.

   Message Address Length   - 0x0

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   Message Size             - 35

   Message Sequence Number  - A 16-bit unsigned integer field containing
                              the sequence number from the Neighbor Down
                              Message that is being acknowledged.

   TLV Block                - TLV Length:  27

                              DLEP Neighbor Address Update ACK order
                              Identification Sub-TLV (MANDATORY)
                              MAC Address Sub-TLV (MANDATORY)
                              Status Sub-TLV (MANDATORY)


22. Heartbeat Message

   A Heartbeat Message is sent by a peer every N seconds, where N is
   defined in the "Heartbeat Interval" field of the discovery message.
   The message is used by peers to detect when a DLEP session partner
   is no longer communicating. Peers SHOULD allow some integral number
   of heartbeat intervals (default 4) to expire with no traffic on the
   session before initiating DLEP session termination procedures.

   The Heartbeat Message contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Msg Type =   |Msg Flg|AddrLen|          Message Size         |
  | DLEP_MESSAGE  | 0x1   | 0x0   |               22              |
  | (value TBD)   |       |       |                               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Message Seq Num      |TLVs Length = 14               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | DLEP Heartbeat|TLV Flags=0x10 | Length = 11   | Sub-TLV type= |
  | (TBD)         |               |               | Identification|
  |               |               |               | sub-TLV (TBD) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |          Router ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Router ID          |          Client ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Client ID          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Message Type            - DLEP_MESSAGE (Value TBD)

   Message Flags           - Set to 0x1 (bit 3, mhasseqnum bit is
                             set). All other bits are unused and SHOULD
                             be set to '0'.

   Message Address Length  - 0x0

   Message Size            - 22

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   Message Sequence Number - A 16-bit unsigned integer field containing
                             a sequence number generated by the message
                             originator.

   TLV Block -               TLV Length = 14

                             DLEP Heartbeat order
                             Identification Sub-TLV (MANDATORY)


23. Link Characteristics Request Message

   The Link Characteristics Request Message is sent by the router to
   the modem device when the router detects that a different set of
   transmission characteristics is necessary (or desired) for the
   type of traffic that is flowing on the link. The request contains
   either a Current Data Rate (CDR) TLV to request a different
   amount of bandwidth than what is currently allocated, a Latency
   TLV to request that traffic delay on the link not exceed the
   specified value, or both. A Link Characteristics ACK Message is
   required to complete the request. Implementations are free to
   define their retry heuristics in event of a timeout. Issuing a
   Link Characteristics Request with ONLY the MAC Address TLV is a
   mechanism a peer MAY use to request metrics (via the Link
   Characteristics ACK) from its partner.

   The Link Characteristics Request Message contains the following
   fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Msg Type =   |Msg Flg|AddrLen|          Message Size         |
  | DLEP_MESSAGE  | 0x1   | 0x0   |        31 + size of opt       |
  | (value TBD)   |       |       |            sub-TLVs           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Message Seq Num      |TLVs Length =23 + opt sub-TLVs |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | DLEP Link Char|TLV Flags=0x10 | Length =20 +  | Sub-TLV type= |
  | Request (TBD) |               | opt sub-TLVs  | Identification|
  |               |               |               | Sub-TLV (TBD) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |          Router ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Router ID          |          Client ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Client ID          |Sub-TLV type=  |TLV Flags=0x10 |
  |                               |DLEP MAC       |               |
  |                               |sub-TLV (TBD)  |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Length = 6     |                MAC Address                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                (Continued on next page)                       |


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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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                (Continued from above)                         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |              MAC Address                      |Sub-TLV type=  |
  |                                               |DLEP CDR (TBD) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |           CDR (bps)           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        CDR (bps)                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |        CDR (bps)              |Sub-TLV Type=  |TLV Flags=0x10 |
  |                               |Latency (TBD)  |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Length = 2     |         Latency (ms)          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Message Type            - DLEP_MESSAGE (Value TBD)

   Message Flags           - Set to 0x1 (bit 3, mhasseqnum bit
                             is set).  All other bits are unused and
                             MUST be set to '0'.

   Message Address Length  - 0x0

   Message Size            - 31 + length of optional (Current Data
                             Rate and/or Latency) Sub-TLVs

   Message Sequence Number - A 16-bit unsigned integer field containing
                             a sequence number generated by the message
                             originator.

   TLV Block               - Length: 23 + optional Sub-TLVs

                             DLEP Link Characteristics Request order
                             Identification Sub-TLV (MANDATORY)
                             MAC Address Sub-TLV (MANDATORY)

                             Current Data Rate Sub-TLV - if present,
                             this value represents the requested data
                             rate in bits per second (bps). (OPTIONAL)

                             Latency TLV - if present, this value
                             represents the maximum latency, in
                             milliseconds, desired on the link.
                             (OPTIONAL)

24. Link Characteristics ACK Message

   The Link Characteristics ACK Message is sent by the client to the
   router letting the router know the success (or failure) of the
   requested change in link characteristics.  The Link Characteristics
   ACK message SHOULD contain a complete set of metric TLVs. It MUST

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   contain the same TLV types as the request. The values in the
   metric TLVs in the Link Characteristics ACK message MUST reflect
   the link characteristics after the request has been processed.

   The Link Characteristics ACK Message contains the following fields:

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  Msg Type =   |Msg Flg|AddrLen|          Message Size         |
  | DLEP_MESSAGE  | 0x1   | 0x0   |        31 + size of opt       |
  | (value TBD)   |       |       |            sub-TLVs           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Message Seq Num      |TLVs Length =23 + opt sub-TLVs |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | DLEP Link Char|TLV Flags=0x10 | Length =20 +  | Sub-TLV type= |
  | ACK (TBD)     |               | opt sub-TLVs  | Identification|
  |               |               |               | Sub-TLV (TBD) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |          Router ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Router ID          |          Client ID            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Client ID          |Sub-TLV type=  |TLV Flags=0x10 |
  |                               |DLEP MAC       |               |
  |                               |sub-TLV (TBD)  |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Length = 6     |                MAC Address                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |              MAC Address                      |Sub-TLV type=  |
  |                                               |DLEP MDR (TBD) |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |TLV Flags=0x10 |Length = 8     |           MDR (bps)           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        MDR (bps)                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |        MDR (bps)              |Sub-TLV Type=  |TLV Flags=0x10 |
  |                               |DLEP CDR (TBD) |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Length = 8     |                  CDR (bps)                    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                           CDR (bps)                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  CDR (bps)    |Sub-TLV Type = |TLV Flags=0x10 | Length = 2    |
  |               |Latency (TBD)  |               |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |        Latency (ms)           |Sub-TLV Type=  |TLV Flags=0x10 |
  |                               |Resources (TBD)|               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Length = 1    |   Resources   |Sub-TLV Type=  |TLV Flags=0x10 |
  |               |               |RLQ (TBD)      |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Length = 1    |      RLQ      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   Message Type            - DLEP_MESSAGE (Value TBD)

   Message Flags           - Set to 0x1 (bit 3, mhasseqnum bit
                             is set).  All other bits are unused and
                             MUST be set to '0'.

   Message Address Length  - 0x0

   Message Size            - 31 + length of optional (Current Data
                             Rate and/or Latency) TLVs

   Message Sequence Number - A 16-bit unsigned integer field containing
                             the sequence number that appeared on the
                             corresponding Link Characteristics Request
                             message.

   TLV Block               - TLVs Length = 23 + Optional TLVs

                             DLEP Link Characteristics ACK order
                             Identification Sub-TLV (MANDATORY)
                             MAC Address Sub-TLV (MANDATORY)
                             Maximum Data Rate Sub-TLV (OPTIONAL)

                             Current Data Rate Sub-TLV - if present,
                             this value represents the NEW (or
                             unchanged, if the request is denied)
                             Current Data Rate in bits per second (bps).
                             (OPTIONAL)

                             Latency Sub-TLV - if present, this value
                             represents the NEW maximum latency (or
                             unchanged, if the request is denied),
                             expressed in milliseconds, on the link.
                             (OPTIONAL)

                             Resources Sub-TLV (OPTIONAL)

                             Relative Link Quality Sub-TLV (OPTIONAL)

25.  Security Considerations

   The protocol does not contain any mechanisms for security (e.g.
   authentication or encryption). The protocol assumes that any
   security would be implemented in the underlying transport (for
   example, by use of DTLS or some other mechanism), and is
   therefore outside the scope of this document.

26.  IANA Considerations

   This section specifies requests to IANA.




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26.1  TLV Registrations

   This specification defines:

   o  One TLV types which must be allocated from the 0-223 range
      of the "Assigned Message TLV Types" repository of [RFC5444].

   o  A new repository for DLEP orders, with seventeen values currently
      assigned.

   o  A new repository for DLEP Sub-TLV assignments with fifteen values
      currently assigned.


26.2  Expert Review: Evaluation Guidelines

   For the registries for TLV type extensions where an Expert Review is
   required, the designated expert SHOULD take the same general
   recommendations into consideration as are specified by [RFC5444].


26.3  Message TLV Type Registration

   The Message TLV specified below must be allocated from the "Message
   TLV Types" namespace of [RFC5444].

       o   DLEP_MESSAGE


26.4  DLEP Order Registration

   A new repository must be created with the values of the DLEP orders.
   Valid orders are:

       o   Attached Peer Discovery Message
       o   Detached Peer Discovery Message
       o   Peer Offer Message
       o   Peer Update Message
       o   Peer Update ACK Message
       o   Peer Termination Message
       o   Peer Termination ACK Message
       o   Neighbor Up Message
       o   Neighbor Up ACK Message
       o   Neighbor Down Message
       o   Neighbor Down ACK Message
       o   Neighbor Update Message
       o   Neighbor Address Update Message
       o   Neighbor Address Update ACK Message
       o   Heartbeat Message
       o   Link Characteristics Request Message
       o   Link Characteristics ACK Message



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   This registry should be created according to the guidelines for
   'Message-Type-Specific TLV' registration as specified in section
   6.2.1 of [RFC5444].


26.5  DLEP Sub-TLV Type Registrations

   A new repository for DLEP Sub-TLVs must be created. Valid Sub-TLVs are:

       o   Identification Sub-TLV
       o   DLEP Version Sub-TLV
       o   Peer Type Sub-TLV
       o   MAC Address Sub-TLV
       o   IPv4 Address Sub-TLV
       o   IPv6 Address Sub-TLV
       o   Maximum Data Rate Sub-TLV
       o   Current Data Rate Sub-TLV
       o   Latency Sub-TLV
       o   Resources Sub-TLV
       o   Relative Link Quality Sub-TLV
       o   Status Sub-TLV
       o   Heartbeat Interval Sub-TLV
       o   Heartbeat Threshold Sub-TLV
       o   Link Characteristics ACK Timer Sub-TLV

   It is also requested that the registry allocation contain space
   reserved for experimental sub-TLVs.




























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27. Appendix A.


Peer Level Message Flows


*Modem Device (Client) Restarts Discovery

   Router                    Client   Message Description
   ====================================================================

   <-------Peer Discovery---------    Modem initiates discovery


    ---------Peer Offer----------->   Router detects a problem, sends
      w/ Non-zero Status TLV          Peer Offer w/ Status TLV indicating
                                      the error.

                                      Modem accepts failure, restarts
                                      discovery process.

   <-------Peer Discovery---------    Modem initiates discovery


    ---------Peer Offer----------->   Router accepts, sends Peer Offer
         w/ Zero Status TLV           w/ Status TLV indicating success.

                                      Discovery completed.



*Modem Device Detects Peer Offer Timeout

   Router                    Client   Message Description
   ====================================================================

   <-------Peer Discovery---------    Modem initiates discovery,
                                      starts a guard timer.

                                      Modem guard timer expires.
                                      Modem restarts discovery process.

    <-------Peer Discovery---------   Modem initiates discovery,
                                      starts a guard timer.

    ---------Peer Offer----------->   Router accepts, sends Peer Offer
         w/ Zero Status TLV           w/ Status TLV indicating success.

                                      Discovery completed.





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*Router Peer Offer Lost

   Router                    Client   Message Description
   ====================================================================

   <-------Peer Discovery---------    Modem initiates discovery,
                                      starts a guard timer.

    ---------Peer Offer-------||      Router offers availability

                                      Modem times out on Peer Offer,
                                      restarts discovery process.

   <-------Peer Discovery---------    Modem initiates discovery

    ---------Peer Offer----------->   Router detects subsequent discovery,
                                      internally terminates the previous,
                                      accepts the new association, sends
                                      Peer Offer w/ Status TLV indicating
                                      success.


                                      Discovery completed.


*Discovery Success

   Router                    Client   Message Description
   ====================================================================

   <-------Peer Discovery---------    Modem initiates discovery

    ---------Peer Offer----------->   Router offers availability

    -------Peer Heartbeat--------->

   <-------Peer Heartbeat---------

    -------Peer Heartbeat--------->

   <==============================>   Neighbor Sessions

   <-------Peer Heartbeat---------

    -------Peer Heartbeat--------->

    --------Peer Term Req--------->   Terminate Request

   <--------Peer Term Res---------    Terminate Response





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*Router Detects a Heartbeat timeout

   Router                    Client   Message Description
   ====================================================================

   <-------Peer Heartbeat---------

    -------Peer Heartbeat--------->

      ||---Peer Heartbeat---------

           ~ ~ ~ ~ ~ ~ ~

    -------Peer Heartbeat--------->

      ||---Peer Heartbeat---------
                                      Router Heartbeat Timer expires,
                                      detects missing heartbeats. Router
                                      takes down all neighbor sessions
                                      and terminates the Peer association.

    ------Peer Terminate --------->   Peer Terminate Request

                                      Modem takes down all neighbor
                                      sessions, then acknowledges the
                                      Peer Terminate

   <----Peer Terminate ACK---------   Peer Terminate ACK




*Modem Detects a Heartbeat timeout

   Router                    Client   Message Description
   ====================================================================

   <-------Peer Heartbeat---------

    -------Peer Heartbeat------||

   <-------Peer Heartbeat---------

           ~ ~ ~ ~ ~ ~ ~

    -------Peer Heartbeat------||

   <-------Peer Heartbeat---------
                                      Modem Heartbeat Timer expires,
                                      detects missing heartbeats. Modem
                                      takes down all neighbor sessions
                                      and terminates the Peer association.


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    <-------Peer Terminate--------    Peer Terminate Request

                                      Router takes down all neighbor
                                      sessions, then acknowledges the
                                      Peer Terminate

    ------Peer Terminate ACK----->    Peer Terminate ACK




*Peer Terminate (from Modem) Lost

   Router                    Client   Message Description
   ====================================================================

     ||------Peer Terminate--------   Modem Peer Terminate Request

                                      Router Heartbeat times out,
                                      terminates association.

    --------Peer Terminate------->    Router Peer Terminate

    <-----Peer Terminate ACK------    Modem sends Peer Terminate ACK



*Peer Terminate (from router) Lost

   Router                    Client   Message Description
   ====================================================================

    -------Peer Terminate-------->    Router Peer Terminate Request

                                      Modem HB times out,
                                      terminates association.

    <------Peer Terminate--------     Modem Peer Terminate

    ------Peer Terminate ACK----->    Peer Terminate ACK














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Neighbor Level Message Flows



*Modem Neighbor Up Lost

   Router                    Client   Message Description
   ====================================================================

    ||-----Neighbor Up ------------   Modem sends Neighbor Up

                                      Modem timesout on ACK

    <------Neighbor Up ------------   Modem sends Neighbor Up

    ------Neighbor Up ACK--------->   Router accepts the neighbor
                                      session

   <------Neighbor Update---------    Modem Neighbor Metrics
          . . . . . . . .
   <------Neighbor Update---------    Modem Neighbor Metrics



*Router Detects Duplicate Neighbor Ups

   Router                    Client   Message Description
   ====================================================================

    <------Neighbor Up ------------   Modem sends Neighbor Up

    ------Neighbor Up ACK-------||    Router accepts the neighbor
                                      session

                                      Modem timesout on ACK

    <------Neighbor Up ------------   Modem resends Neighbor Up

                                      Router detects duplicate
                                      Neighbor, takes down the
                                      previous, accepts the new
                                      Neighbor.

    ------Neighbor Up ACK--------->   Router accepts the neighbor
                                      session

   <------Neighbor Update---------    Modem Neighbor Metrics
          . . . . . . . .
   <------Neighbor Update---------    Modem Neighbor Metrics





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*Neighbor Up, No Layer 3 Addresses

   Router                    Client    Message Description
   ====================================================================

    <------Neighbor Up ------------   Modem sends Neighbor Up

    ------Neighbor Up ACK--------->   Router accepts the neighbor
                                      session

                                      Router ARPs for IPv4 if defined.
                                      Router drives ND for IPv6 if
                                      defined.

   <------Neighbor Update---------    Modem Neighbor Metrics
          . . . . . . . .
   <------Neighbor Update---------    Modem Neighbor Metrics


*Neighbor Up with IPv4, No IPv6

   Router                    Client   Message Description
   ====================================================================

    <------Neighbor Up ------------   Modem sends Neighbor Up with
                                      the IPv4 TLV

    ------Neighbor Up ACK--------->   Router accepts the neighbor
                                      session

                                      Router drives ND for IPv6 if
                                      defined.

   <------Neighbor Update---------    Modem Neighbor Metrics
          . . . . . . . .
   <------Neighbor Update---------    Modem Neighbor Metrics


*Neighbor Up with IPv4 and IPv6

   Router                    Client   Message Description
   ====================================================================

    <------Neighbor Up ------------   Modem sends Neighbor Up with
                                      the IPv4 and IPv6 TLVs

    ------Neighbor Up ACK--------->   Router accepts the neighbor
                                      session

   <------Neighbor Update---------    Modem Neighbor Metrics
          . . . . . . . .
   <------Neighbor Update---------    Modem Neighbor Metrics


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*Neighbor Session Success

   Router                    Client   Message Description
   ====================================================================


    ---------Peer Offer----------->   Router offers availability

    -------Peer Heartbeat--------->


   <------Neighbor Up -----------      Modem

    ------Neighbor Up ACK-------->     Router

   <------Neighbor Update---------     Modem
          . . . . . . . .
   <------Neighbor Update---------     Modem

                                       Modem initiates the terminate

   <------Neighbor Down ----------     Modem

    ------Neighbor Down ACK------->    Router

                                       or

                                       Router initiates the terminate

    ------Neighbor Down ---------->    Router

   <------Neighbor Down ACK-------     Modem




Acknowledgements

   The authors would like to acknowledge the influence and contributions
   of Chris Olsen and Teco Boot.

Normative References

   [RFC5444] Clausen, T., Ed,. "Generalized Mobile Ad Hoc Network (MANET)
             Packet/Message Format", RFC 5444, Februar, 2009.

   [RFC5578] Berry, B., Ed., "PPPoE with Credit Flow and Metrics",
             RFC 5578, February 2010.

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", RFC 2119, March 1997.


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Informative References

   [DTLS] Rescorla, E., Ed,. "Datagram Transport Layer Security",
          RFC 4347, April 2006.





Author's Addresses

   Stan Ratliff
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134
   USA
   EMail: sratliff@cisco.com

   Bo Berry
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134
   USA
   EMail: boberry@cisco.com

   Greg Harrison
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134
   USA
   EMail: greharri@cisco.com

   Shawn Jury
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134
   USA
   Email: sjury@cisco.com

   Darryl Satterwhite
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134
   USA
   Email: dsatterw@cisco.com









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