draft-ietf-manet-dlep-multi-hop-extension.xml

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<rfc category="std" ipr="trust200902" docName="draft-ietf-manet-dlep-multi-hop-extension-04" >

<front>
<title abbrev="DLEP Multi-Hop Extension">DLEP Multi-Hop Forwarding Extension</title> 
   <author initials='B.' surname="Cheng" fullname='Bow-Nan Cheng'>
    <organization>Lincoln Laboratory</organization>
    <address>
      <postal>
        <street>Massachusetts Institute of Technology</street>
        <street>244 Wood Street</street>
        <city>Lexington</city>
        <region>MA</region>
        <code>02421-6426</code>
      </postal>
       <email>bcheng@ll.mit.edu</email>
    </address>
    </author>
   <author initials='L.' surname="Berger" fullname='Lou Berger' role='editor'>
    <organization>LabN Consulting, L.L.C.</organization>
    <address>
       <email>lberger@labn.net</email>
    </address>
    </author>

  <date/>
  <abstract>
<t>
  This document defines an extension to the DLEP protocol that enables
  the reporting and control of Multi-Hop Forwarding by DLEP capable
  modems.
</t>
</abstract>
</front>

<middle>
<section anchor="sec-1" title="Introduction">
<t>
  The Dynamic Link Exchange Protocol (DLEP) is defined in <xref
  target="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.
</t>
<t>
  Some modem technologies support connectivity to destinations via
  multi-hop forwarding. DLEP Destination messages can be used to report
  such connectivity, see <xref target="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".
</t>
<t>
  This document defines a new DLEP Extension Type Value in <xref
  target="sec-ext-type"/> which is used to indicate the use of the
  extension, and three new DLEP Data Items in <xref
  target="sec-data-items"/>.
</t>
<section anchor="sec-1.1" title="Key Words">
<t>
   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 <xref target="RFC2119"/> <xref target="RFC8174"/> when, and
   only when, they appear in all capitals, as shown here.
</t>
</section>
</section>

<section anchor="sec-ext-type" title="Extension Usage and Identification">
<t>
   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 <xref target="RFC8175"/>.
</t>
<t>
  The Multi-Hop Forwarding Extension Type Value is TBA1, see <xref
  target="sec-iana"/>.
</t>
</section>

<section anchor="sec-data-items" title="Extension Data Items">
<t>
   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.
</t>
<section anchor="sec-di-hcount" title="Hop Count">
<t>
  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. 
</t>
<t>
  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.  
</t>
<t>
  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).
</t>
<t>
  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).
</t>
<t>
  The format of the Hop Count Data Item is:
</t>
<t>
<figure>
<artwork>
     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   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
</artwork>
</figure>
</t>
<t>
  <list style="hanging">
    <t hangText="Data Item Type:">TBA2</t>
    <t hangText="Length:">4</t>
    <t hangText="P:">
      <vspace blankLines="1"/>
      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.
    </t>
    <t hangText="Reserved:">
      <vspace blankLines="1"/>
      MUST be set to zero by the sender (a modem) and ignored by the
      receiver (a router).
    </t>
    <t hangText="Hop Count:">
      <vspace blankLines="1"/>
      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.
      <vspace blankLines="1"/>
      A value of zero (0) is used to indicated that processing of a Hop
      Control action, see <xref target="sec-di-hcontrol"/>, 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. 
    </t>
  </list>
</t>
</section>

<section anchor="sec-di-hcontrol" title="Hop Control">
<t>
  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.
</t>
<t>
  The Hop Control Data Item MAY be carried in a Session Update Message
  when the control applies to the whole device, or a Link
  Characteristics Request Message when the control applies to a
  particular destination.
</t>
<t>
  A router that receives the Hop Control in a Session Update Message
  SHOULD attempt to make the change indicated by the data item for the
  whole device.  Results of any changes made are reflected 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.
</t>
<t>
  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.
</t>
<t>
  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.
</t>
<t>
  The format of the Hop Control Data Item is:
</t>
<t>
<figure>
<artwork>
     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     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
</artwork>
</figure>
</t>
<t>
  <list style="hanging">
    <t hangText="Data Item Type:">TBA3</t>
    <t hangText="Length:">4</t>
    <t hangText="Hop Control Actions:">
      <vspace blankLines="1"/>
      An unsigned 16-bit value with the following meaning:
      </t>
  </list>
</t>
<texttable anchor="table_hc" title="Hop Control Actions Values">
        <preamble></preamble>
        <ttcol>Value</ttcol><ttcol>Action</ttcol>
        <c>0</c> <c>Reset</c>
        <c>1</c> <c>Terminate</c>
        <c>2</c> <c>Direct Connection</c>
        <c>3</c> <c>Suppress Forwarding</c>
        <postamble></postamble>
      </texttable>

<section anchor="sec-di-hc-r" title="Reset">
  <t>
    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.
  </t>
</section>
<section anchor="sec-di-hc-t" title="Terminate">
  <t>
    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 in the Hop Count to the destination not
    being impacted by the processing of the request.
  </t>
</section>
<section anchor="sec-di-hc-dc" title="Direct Connection">
  <t>
    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.
  </t>
</section>
   
<section anchor="sec-di-hc-sf" title="Suppress Forwarding">
<t>
  The Suppress Forwarding Action is used by a router to indicate to
  its peer that multi-hop forwarding is to be suppressed.  A router may
  request that multi-hop forwarding may be suppressed on a device wide
  or destination specific basis.  
</t>
<t>
  A modem which receives the Suppress Forwarding Data Item in a Session
  Update Message MUST suppress multi-hop forwarding on a device wide
  basis. Impact to destination hop counts are provided to the router by
  the modem as described above.
</t>
<t>
  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. Results are provided as
  described above.
</t>
</section>
</section>
</section>
<section anchor="sec-sec" title="Security Considerations">
<t>
   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 <xref target="RFC8175"/>.
   The approach taken to Security in that document applies equally
   when running the extension defined in this document.
</t>
</section>
<section anchor="sec-iana" title="IANA Considerations">
<t>
  This document requests the assignment of 3 values by IANA.  All
  assignments are to registries defined by <xref
  target="RFC8175"/>.
  It also requests creation of one new registry.
</t>
<section anchor="sec-iana-ext" title="Extension Type Value">
<t>
  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:
</t>
<texttable anchor="table_et" title="Requested Extension Type Value">
  <preamble></preamble>
  <ttcol>Code</ttcol> <ttcol>Description</ttcol>
    <c>TBA1</c> <c>Multi-Hop Forwarding</c> 
    <postamble></postamble>
    </texttable>
</section>
<section anchor="sec-iana-di" title="Data Item Values">
<t>
  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:
</t>
<texttable anchor="table_di" title="Requested Data Item Values">
  <preamble></preamble>
  <ttcol>Type Code</ttcol> <ttcol>Description</ttcol>
    <c>TBA2</c> <c>Hop Count</c> 
    <c>TBA3</c> <c>Hop Control</c> 
    <postamble></postamble>
    </texttable>
</section>
<section anchor="sec-iana-hca" title="Hop Control Actions Registry">
  <t>
    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 <xref
   target="RFC8126"/>. defined policies that should apply to the
   registry:
</t>
<texttable anchor="table_iana_hca" title="Hop Control Actions Values">
        <preamble></preamble>
        <ttcol>Value</ttcol><ttcol>Action/Policy</ttcol>
        <c>0</c> <c>Reset</c>
        <c>1</c> <c>Terminate</c>
        <c>2</c> <c>Direct Connection</c>
        <c>3</c> <c>Suppress Forwarding</c>
        <c>4-65519</c>     <c>Specification Required</c>
        <c>65520-65534</c> <c>Private Use</c>
        <c>65535</c>       <c>Reserved</c>
        <postamble></postamble>
      </texttable>
</section>
</section>
</middle>

<?rfc needLines="20"?>
<back>
<references title="Normative References">

<?rfc include="reference.RFC.2119"?>
<?rfc include="reference.RFC.8174"?>
<?rfc include="reference.RFC.8175"?>

</references>

<references title="Informative References">

<?rfc include="reference.RFC.8126"?>

</references>
<?rfc needLines="100"?>
<section title="Acknowledgments">
  <t>
    Helpful comments were received from members of the MANET working
    grouping, including Henning Rogge, Victoria Pritchard and David
    Wiggins.
  </t>
</section> 

</back>
</rfc>

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