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Versions: (draft-cheng-manet-dlep-multi-hop-extension) 00 01 02 03 04 05 06 07

Network Working Group                                           B. Cheng
Internet-Draft                                    MIT Lincoln Laboratory
Intended status: Standards Track                          L. Berger, Ed.
Expires: November 6, 2019                        LabN Consulting, L.L.C.
                                                             May 5, 2019


  Dynamic Link Exchange Protocol (DLEP) Multi-Hop Forwarding Extension
              draft-ietf-manet-dlep-multi-hop-extension-07

Abstract

   This document defines an extension to the Dynamic Link Exchange
   Protocol (DLEP) that enables the reporting and control of Multi-Hop
   Forwarding by DLEP capable modems.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 6, 2019.

Copyright Notice

   Copyright (c) 2019 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
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   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 Simplified BSD License.




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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 . . . . . . . . . . . . . . . . . . . . . .   7
       3.2.3.  Direct Connection . . . . . . . . . . . . . . . . . .   7
       3.2.4.  Suppress Forwarding . . . . . . . . . . . . . . . . .   7
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
     5.1.  Extension Type Value  . . . . . . . . . . . . . . . . . .   8
     5.2.  Data Item Values  . . . . . . . . . . . . . . . . . . . .   9
     5.3.  Hop Control Actions Registry  . . . . . . . . . . . . . .   9
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   The Dynamic Link Exchange Protocol (DLEP) is defined in [RFC8175].
   It provides the exchange of link related control information between
   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 mobile ad hoc network (MANET)
   forwarding where connectivity to destinations is provided via
   forwarding in intermediate modems.  This document refers to
   forwarding by intermediate modems as 'multi-hop forwarding'.  DLEP
   Destination messages can be used to report such reachable
   destinations, 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", where each modem
   that transmits/sends data to reach a particular destination is
   counted as a hop.

   It is important to note that the use of the hop control mechanism
   defined in this document can result in connectivity changes and even
   loss of the ability to reach one or more destinations.  The defined



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   mechanism will report such connectivity changes, but the details of
   what a router does or how it reacts to such are out scope of this
   document.

   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.

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.
   Per [RFC8175], to indicate that the extension is to be used, an
   implementation includes 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 modem 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
   modems that transmit/send data to reach a particular destination,
   i.e., 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.





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   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
   directly 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).

   A router receiving a Hop Count Data Item can use this information in
   its forwarding and routing decisions, and specific use is out of
   scope of this document.  When using this extension, 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:  2

   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.  This field MUST be ignored when the value
      contained in the Hop Count field is one (1).

   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 modem 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



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      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 indicate that processing of a Hop
      Control action, see Section 3.2, has resulted in the destination
      no longer being reachable.  A zero value MUST NOT be used in any
      message other than a Link Characteristics Response Message.

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 that a 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 take whatever actions are
   needed 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 not identified in the Link Characteristics Response Message and is
   no longer reachable via a Destination Down Message.  The modem MUST
   also notify the router of each impacted destination that is not
   identified in the Link Characteristics Response Message via a
   Destination Update Message.

   Failures may occur for multiple reasons, for example, the
   transmission characteristics of the link don't support the one-hop
   connection at the time of the request.  Requests can be rejected by
   local policy.

   A modem that receives the Hop Control Data Item in a Session Update
   Message SHOULD take whatever actions are needed 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.



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   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:

        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:  2

   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 MUST 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 MUST clear all
   control actions that have previously been processed for the
   destination indicated in the message.



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

3.2.3.  Direct Connection

   The Direct Connection Action 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.

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 can request that multi-hop forwarding may be
   suppressed on a device wide or destination specific basis.

   A modem that 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 that 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 can be forwarded by
   the modem per its normal processing.  Results are provided as
   described above.





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

   This extension does define one mechanism that is worth particular
   note.  This extension includes a Hop Control mechanism, see
   Section 3.2, that is similar to the Link Characteristics Request
   Message defined in [RFC8175] in that it can impact the set of
   destinations reported as reachable.  With the Link Characteristics
   Request Message, this risk is implicit.  With the Hop Control
   mechanism defined in this document it is more likely.  From a
   security perspective, implementations should be aware of this
   increased risk and may choose to implement additional configuration
   control mechanisms to ensure that the Hop Control mechanism is only
   used under conditions intended by the network operator.

   Implementations of the extension defined in this document MUST
   support configuration of TLS usage, as describe in [RFC8175], in
   order to protect configurations where injection attacks are possible,
   i.e., when the link between a modem and router is not otherwise
   protected.

   Note that this extension does allow a compromised or impersonating
   modem to suppress transmission by the router or a switch that
   interconnects the modem and router.  Similar attacks are generally
   possible base DLEP, for example an impersonating modem may cause a
   session reset or a compromised modem simply can drop all traffic
   destined to, or sent by a router.  [RFC8175] defines the use of TLS
   to protect against the impersonating attacker.

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:





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                      +------+----------------------+
                      | 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
   MIT 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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