DLEP Multi-Hop Forwarding Extension
draft-ietf-manet-dlep-multi-hop-extension-04

Network Working Group                                           B. Cheng
Internet-Draft                                        Lincoln Laboratory
Intended status: Standards Track                          L. Berger, Ed.
Expires: August 19, 2018                         LabN Consulting, L.L.C.
                                                       February 15, 2018

                  DLEP Multi-Hop Forwarding Extension
              draft-ietf-manet-dlep-multi-hop-extension-04

Abstract

   This document defines an extension to the DLEP protocol that enables
   the reporting and control of Multi-Hop Forwarding by DLEP capable
   modems.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Key Words . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Extension Usage and Identification  . . . . . . . . . . . . .   3
   3.  Extension Data Items  . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Hop Count . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  Hop Control . . . . . . . . . . . . . . . . . . . . . . .   5
       3.2.1.  Reset . . . . . . . . . . . . . . . . . . . . . . . .   6
       3.2.2.  Terminate . . . . . . . . . . . . . . . . . . . . . .   6
       3.2.3.  Direct Connection . . . . . . . . . . . . . . . . . .   7
       3.2.4.  Suppress Forwarding . . . . . . . . . . . . . . . . .   7
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
     5.1.  Extension Type Value  . . . . . . . . . . . . . . . . . .   8
     5.2.  Data Item Values  . . . . . . . . . . . . . . . . . . . .   8
     5.3.  Hop Control Actions Registry  . . . . . . . . . . . . . .   8
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   The Dynamic Link Exchange Protocol (DLEP) is defined in [RFC8175].
   It provides the exchange of link related control information between
   DLEP peers.  DLEP peers are comprised of a modem and a router.  DLEP
   defines a base set of mechanisms as well as support for possible
   extensions.  This document defines one such extension.

   Some modem technologies support connectivity to destinations via
   multi-hop forwarding.  DLEP Destination messages can be used to
   report such connectivity, see [RFC8175], but do not provide any
   information related to the number or capacity of the hops.  The
   extension defined in this document enables modems to inform routers
   when multi-hop forwarding is being used, and routers to request that
   modems change multi-hop forwarding behavior.  The extension defined
   in this document is referred to as "Multi-Hop Forwarding".

   This document defines a new DLEP Extension Type Value in Section 2
   which is used to indicate the use of the extension, and three new
   DLEP Data Items in Section 3.

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1.1.  Key Words

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Extension Usage and Identification

   The use of the Multi-Hop Forwarding Extension SHOULD be configurable.
   To indicate that the extension is to be used, an implementation MUST
   include the Multi-Hop Forwarding Extension Type Value in the
   Extensions Supported Data Item.  The Extensions Supported Data Item
   is sent and processed according to [RFC8175].

   The Multi-Hop Forwarding Extension Type Value is TBA1, see Section 5.

3.  Extension Data Items

   Three data items are defined by this extension.  The Hop Count Data
   Item is used by a modem to provide the number of network hops
   traversed to reach a particular destination.  The Hop Control Data
   Item is used by a router to request that a modem alter connectivity
   to a particular destination.  The Suppress Forwarding Data Item is
   used by a router to request that a modem disable multi-hop forwarding
   on either a device or destination basis.

3.1.  Hop Count

   The Hop Count Data Item is used by a modem to indicate the number of
   physical hops between the modem and a specific destination.  In other
   words, each hop represents a transmission and the number of hops is
   equal to the number of transmissions required to go from a router
   connected modem to the destination's connected modem.  The minimum
   number of hops is 1, which represents transmission to destinations
   that are directly reachable via the router's locally connected modem.

   The data item also contains an indication of when a destination which
   currently has a hop count of greater than one (1) could be made
   direcly reachable by a modem, e.g., by re-aiming an antenna.

   The Hop Count Data Item SHOULD be carried in the Destination Up,
   Destination Update, Destination Announce Response, and Link
   Characteristics Response Messages when the Hop Count to a destination
   is greater than one (1).

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   A router receiving a Hop Count Data Item MAY use this information in
   its forwarding and routing decisions, and specific use is out of
   scope of this document.  The absence of the Hop Count Data Item MUST
   be interpreted by the router as a Hop Count value of one (1).

   The format of the Hop Count Data Item is:

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Data Item Type                | Length                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |P|  Reserved   |   Hop Count   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Data Item Type:  TBA2

   Length:  4

   P:

      The P-bit indicates that a destination is potentially directly
      reachable.  When the P-bit is set, the router MAY request a direct
      link to the associated destination using the Hop Control Data Item
      described below.

   Reserved:

      MUST be set to zero by the sender (a modem) and ignored by the
      receiver (a router).

   Hop Count:

      An unsigned 8-bit integer indicating the number of network hops
      required (i.e., number of times a packet will be transmitted) to
      reach the destination indicated in the message.  The special value
      of 255 (0xFF) is used to indicate that the number of hops is an
      unknown number greater than one (1).  This field MUST contain a
      value of at least one (1) if the associated destination is
      reachable.

      A value of zero (0) is used to indicated that processing of a Hop
      Control action, see Section 3.2, has resulted in a destination no
      longer being reachable.  A zero value MUST NOT be used in any
      message other then a Link Characteristics Response Message.

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3.2.  Hop Control

   The Hop Control Data Item is used by a router to request a change in
   connectivity to a particular destination, or in multi-hop processing
   on a device wide basis.  A router can request multi-hop reachable
   destination be changed to a single hop.  A router can also indicate
   that the modem terminates a previous direct connectivity request to a
   particular destination.

   The Hop Control Data Item MAY be carried in a Session Update Message
   sent by a router when the control applies to the whole device, or a
   Link Characteristics Request Message when the control applies to a
   particular destination.

   A modem that receives the Hop Control Data Item in a Link
   Characteristics Request Message SHOULD attempt to make the change
   indicated by the data item for the associated destination MAC
   address.  Once the change is made, fails or is rejected, the modem
   MUST respond with a Link Characteristics Response Message containing
   an updated Hop Count Data Item.  Note that other destinations can be
   impacted as a result of the change and such changes are reported in
   Destination Down and Destination Update Messages.  The modem MUST
   notify the router of each destination that is no longer reachable via
   a Destination Down Message.  The modem MUST notify the router of any
   changes in Hop Counts via Destination Update Messages.  Note that
   neither Destination Down or Update Message SHOULD NOT be sent for the
   destination MAC address contained in the Link Characteristics
   Response Message.

   A modem that receives the Hop Control Data Item in a Session Update
   Message SHOULD attempt to make the change indicated by the data item
   for all known destinations.  Once the change is made, or fails or is
   rejected, the modem MUST respond with a Session Update Response
   Message with an appropriate Status Code.  Destination specific impact
   resulting from the processing of a Hop Control Data Item in a Session
   Update Message is provided via Destination Down and Destination
   Update Messages.  The modem MUST notify the router of each
   destination that is no longer reachable via a Destination Down
   Message.  The modem MUST notify the router of any changes in Hop
   Counts via Destination Update Messages.

   The format of the Hop Control Data Item is:

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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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Data Item Type                | Length                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |       Hop Control Actions     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Data Item Type:  TBA3

   Length:  4

   Hop Control Actions:

      An unsigned 16-bit value with the following meaning:

                      +-------+---------------------+
                      | Value | Action              |
                      +-------+---------------------+
                      | 0     | Reset               |
                      |       |                     |
                      | 1     | Terminate           |
                      |       |                     |
                      | 2     | Direct Connection   |
                      |       |                     |
                      | 3     | Suppress Forwarding |
                      +-------+---------------------+

                    Table 1: Hop Control Actions Values

3.2.1.  Reset

   The Reset Action requests that the default behavior be restored.
   When received in a Session Update Message message, a modem SHOULD
   clear all control actions that have previously been processed on a
   device wide basis, and revert to its configured behavior.  When
   received in a Link Characteristics Request Message, a modem SHOULD
   clear all control actions that have previously been processed for the
   destination indicated in the message.

3.2.2.  Terminate

   The Terminate Action is only valid on a per destination basis and
   MUST NOT be sent in a Session Update Message message.  It indicates
   that a direct connection is no longer needed with the destination
   identified in the message.  This request has no impact for multi-hop
   destinations and may fail even in a single hop case, i.e. MAY result

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   in the Hop Count to the destination not being impacted by the
   processing of the request.

3.2.3.  Direct Connection

   The Direct Connection is only valid on a per destination basis and
   MUST NOT be sent in a Session Update Message message.  It indicates
   that the modem SHOULD attempt to establish a direct connection with
   the destination identified in the message.  This action SHOULD only
   be sent for destinations for which the Hop Count is greater than 1
   and has the P-Bit set in the previously received Hop Count Data Item.
   Results of the request for the destination identified in the message
   are provided as described above.  If any other destination is
   impacted in the processing of this action, the modem MUST send a
   Destination Update Message for each impacted destination.

3.2.4.  Suppress Forwarding

   The Suppress Forwarding Action is used by a router to indicate to its
   peer that multi-hop forwarding performed by the modem is to be
   suppressed.  A router may request that multi-hop forwarding may be
   suppressed on a device wide or destination specific basis.

   A modem which receives the Suppress Forwarding Data Item in a Session
   Update Message MUST suppress multi-hop forwarding on a device wide
   basis.  This means that data traffic originating from the modem's
   peer router SHALL only be sent by the modem to destinations that are
   one modem hop away, and that any data traffic received by the modem
   from another modem that is not destined to the peer router SHALL be
   dropped.  Impact to destination hop counts are provided to the router
   by the modem as described above.

   A modem which receives the Suppress Forwarding Data Item in a Link
   Characteristics Request Message MUST suppress multi-hop forwarding
   for only the destination indicated in the message.  This means that
   data traffic originating from the modem's peer router SHALL be sent
   by the modem to the destination indicated in the Link Characteristics
   Request Message only when it is one modem hop away.  Notably, data
   traffic received by the modem from another modem MAY be forwarded by
   the modem per its normal processing.  Results are provided as
   described above.

4.  Security Considerations

   The extension enables the reporting and control of forwarding
   information by DLEP capable modems.  The extension does not
   inherently introduce any additional threats above those documented in

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   [RFC8175].  The approach taken to Security in that document applies
   equally when running the extension defined in this document.

5.  IANA Considerations

   This document requests the assignment of 3 values by IANA.  All
   assignments are to registries defined by [RFC8175].  It also requests
   creation of one new registry.

5.1.  Extension Type Value

   This document requests 1 new assignment to the DLEP Extensions
   Registry named "Extension Type Values" in the range with the
   "Specification Required" policy.  The requested value is as follows:

                      +------+----------------------+
                      | Code | Description          |
                      +------+----------------------+
                      | TBA1 | Multi-Hop Forwarding |
                      +------+----------------------+

                  Table 2: Requested Extension Type Value

5.2.  Data Item Values

   This document requests 2 new assignments to the DLEP Data Item
   Registry named "Data Item Type Values" in the range with the
   "Specification Required" policy.  The requested values are as
   follows:

                        +-----------+-------------+
                        | Type Code | Description |
                        +-----------+-------------+
                        | TBA2      | Hop Count   |
                        |           |             |
                        | TBA3      | Hop Control |
                        +-----------+-------------+

                    Table 3: Requested Data Item Values

5.3.  Hop Control Actions Registry

   Upon approval of this document, IANA is requested to create a new
   DLEP registry, named "Hop Control Actions Values".  The following
   table provides initial registry values and the [RFC8126]. defined
   policies that should apply to the registry:

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                 +-------------+------------------------+
                 | Value       | Action/Policy          |
                 +-------------+------------------------+
                 | 0           | Reset                  |
                 |             |                        |
                 | 1           | Terminate              |
                 |             |                        |
                 | 2           | Direct Connection      |
                 |             |                        |
                 | 3           | Suppress Forwarding    |
                 |             |                        |
                 | 4-65519     | Specification Required |
                 |             |                        |
                 | 65520-65534 | Private Use            |
                 |             |                        |
                 | 65535       | Reserved               |
                 +-------------+------------------------+

                    Table 4: Hop Control Actions Values

6.  References

6.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8175]  Ratliff, S., Jury, S., Satterwhite, D., Taylor, R., and B.
              Berry, "Dynamic Link Exchange Protocol (DLEP)", RFC 8175,
              DOI 10.17487/RFC8175, June 2017,
              <https://www.rfc-editor.org/info/rfc8175>.

6.2.  Informative References

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

Appendix A.  Acknowledgments

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   Helpful comments were received from members of the MANET working
   grouping, including Henning Rogge, Victoria Pritchard and David
   Wiggins.

Authors' Addresses

   Bow-Nan Cheng
   Lincoln Laboratory
   Massachusetts Institute of Technology
   244 Wood Street
   Lexington, MA  02421-6426

   Email: bcheng@ll.mit.edu

   Lou Berger (editor)
   LabN Consulting, L.L.C.

   Email: lberger@labn.net

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