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Versions: (draft-cheng-manet-dlep-pause-extension) 00 01 02 03

Network Working Group                                           B. Cheng
Internet-Draft                                                D. Wiggins
Intended status: Standards Track                      Lincoln Laboratory
Expires: September 2, 2018                                L. Berger, Ed.
                                                 LabN Consulting, L.L.C.
                                                           March 1, 2018


                DLEP Control Plane Based Pause Extension
                draft-ietf-manet-dlep-pause-extension-03

Abstract

   This document defines an extension to the DLEP protocol that enables
   a modem to use DLEP messages to pause and resume data traffic coming
   from its peer router.

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

   This Internet-Draft will expire on September 2, 2018.

Copyright Notice

   Copyright (c) 2018 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
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   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.  Queue Parameters  . . . . . . . . . . . . . . . . . . . .   3
       3.1.1.  Queue Parameter Sub Data Item . . . . . . . . . . . .   5
     3.2.  Pause . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.3.  Restart . . . . . . . . . . . . . . . . . . . . . . . . .   7
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
     5.1.  Extension Type Value  . . . . . . . . . . . . . . . . . .   9
     5.2.  Data Item Values  . . . . . . . . . . . . . . . . . . . .   9
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .  10
   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.

   The base DLEP specification does not include any data plane flow
   control capability.  Various flow control methods are possible, e.g.,
   see [I-D.ietf-manet-credit-window].  The extension defined in this
   document supports flow control of data traffic based on explicit
   messages sent via DLEP by a modem to indicate when a router should
   hold off sending traffic, and when it should resume.  The extension
   also optionally supports DSCP (differentiated services codepoint)
   aware, see [RFC2475], flow control.  The extension defined in this
   document is referred to as "Control Plane Based Pause".  Note that
   this mechanism only controls traffic that is to be transmitted on the
   modem's attached data channel and not to DLEP control messages
   themselves.

   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 Control Plane Based Pause Extension SHOULD be
   configurable.  To indicate that the Control Plane Based Pause
   Extension is to be used, an implementation MUST include the Control
   Plane Based Pause Extension Type Value in the Extensions Supported
   Data Item.  The Extensions Supported Data Item is sent and processed
   according to [RFC8175].

   The Control Plane Based Pause Extension Type Value is TBA1, see
   Section 5.

3.  Extension Data Items

   Three data items are defined by this extension.  The Queue Parameters
   Data Item is used by a modem to provide information on the DSCPs it
   uses in forwarding.  The Pause Data Item is used by a modem to
   indicate when a router should cease sending packets and the Restart
   Data Item is used by a modem to indicate when a router can resume
   sending packets.

3.1.  Queue Parameters

   The Queue Parameters Data Item is used by a modem to indicate DSCP
   values that may be independently paused.  This data item MUST be
   included in a Session Initialization Response Message that also
   contains the Control Plane Based Pause Extension Type Value in the
   Extensions Supported Data Item.  Updates to these parameters MAY be
   sent by a modem by including the data item in Session Update
   Messages.

   The Queue Parameters Data Item identifies DSCPs based on groups of
   logical queues, each of which is referred to via a "Queue Index".
   The number of logical queues, or queue indexes, is variable as is the
   number of DSCPs associated with each queue.  A queue size (in bytes)
   is provided for informational purposes.  Queue Indexes are numbered
   sequentially from zero, where queue index zero is a special case
   covering DSCPs which are not otherwise associated with Queue Index.





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   An implementation that does not support DSCPs would indicate 1 queue
   with 0 DSCPs, and the number of bytes that may be in its associated
   link transmit queue.  Additional logical queues are represented in a
   variable series of Queue Parameter sub-data items.

   The format of the Queue Parameters 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                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   Num Queues  | Scale |              Reserved                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Reserved     |             Queue Size Q0                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |               Queue Parameter Sub Data Item 1                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       :                                ...                            :
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |               Queue Parameter Sub Data Item n                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Data Item Type:  TBA2

   Length:  Variable

      Per [RFC8175] Length is the number of octets in the data item,
      excluding the Type and Length fields.

   Num Queues:

      An 8-bit unsigned integer indicating the number of queues
      represented in the data item.  This field MUST contain a value of
      at least one (1), and is equal to one greater than the number of
      included Queue Parameter Sub Data Items.

   Scale:

      An 4-bit unsigned integer indicating the scale used in the Queue
      Size fields.  The valid values are:

         Value  Scale
         ------------
             0   B - Bytes     (Octets)
             1  KB - Kilobytes (B/1024)
             2  MB - Megabytes (KB/1024)
             3  GB - Gigabytes (MB/1024)



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   Reserved:

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

   Queue Size Q0:

      A 24-bit unsigned integer representing the size, in the octet
      scale indicated by the Scale field, of queue index zero.

3.1.1.  Queue Parameter Sub Data Item

   Queue Parameter Sub Data Items are an ordered list composed of sub
   data items with a common format.  The first sub data item is assigned
   a Queue Index value of 1, and subsequent data items are numbered
   incrementally.  The format of the Queue Parameter Sub Data Item is
   patterned after the standard DLEP data item format, see [RFC8175]
   Section 11.3.  Any errors or inconsistencies encountered in parsing
   Sub Data Items are handled in the same fashion as any other Data Item
   parsing error encountered in DLEP.

   The format of the Queue Parameter Sub 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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Must be one (1)               | Length                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                           Value...                            :
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   and Value has the format:

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Num DSCPs Qn  |             Queue Size Qn                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  DS Field Qn  |  DS Field Qn  |              ...              :
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       :                          ...                  |  DS Field Qn  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Length:  Variable

      Copying [RFC8175], Length is the number of octets in the sub data
      item, excluding the Type and Length fields.




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   Num DSCPs Qn:

      An 8-bit unsigned integer indicating the number of DSCPs
      associated with the queue index associated with the sub data item.
      This field MUST contain a value of at least one (1).

   Queue Size Qn:

      A 24-bit unsigned integer representing the size, in the octet
      scale indicated by the Scale field, of the queue supporting
      traffic with the DSCPs associated with the queue index.

   DS Field Qn:

      The data item contains a sequence of 8 bit DS Fields.  The
      position in the sequence identifies the associated queue index.
      The number of DS Fields present should equal the sum of all Num
      DSCPs field values.

      The DS Field structure is the same as [RFC2474].

           0   1   2   3   4   5   6   7
         +---+---+---+---+---+---+---+---+
         |         DSCP          |  CU   |
         +---+---+---+---+---+---+---+---+

           DSCP: differentiated services codepoint
           CU:   currently unused, MUST be zero

3.2.  Pause

   The Pause Data Item is used by a modem to indicate to its peer that
   traffic is to be suppressed.  An example of when a modem might send
   this data item is when an internal queue length exceeds a particular
   threshold.

   A modem may indicate that traffic is to be suppressed on a device
   wide or destination specific basis.  An example of when a modem might
   use device wide indications is when output queues are shared across
   all destinations, and destination specific might be used when per
   destination queuing is used.  To indicate that suppression applies to
   all destinations, a modem MAY send the Pause Data Item in a Session
   Update Message.  To indicate that suppression applies to a particular
   destination a modem MAY send the Pause Data Item in a Destination
   Update Message.

   Each Pause Data Item identifies the traffic to be suppressed by the
   Queue Index defined by Section 3.1, which in turn indicates a set of



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   traffic identified by DSCPs.  The special value of 255 is used to
   indicate that all traffic is to be suppressed.

   While there is no restriction on the number of Messages containing
   Pause Data Item that may be sent by a modem, a modem SHOULD include
   multiple queue indexes in the same message when possible.

   A router which receives the Pause Data Item MUST cease sending the
   identified traffic to the modem.  This may of course translate into
   the router's queues exceeding their own thresholds.  If a received
   Pause Data Item contains a Queue Index value other than 0, 255, or a
   queue index established by a Session Initialization or Session Update
   Message, the router MUST terminate the session with a Status Data
   Item indicating Invalid Data.

   The format of the Pause 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                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Queue Index  |               ...                             :
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       :                                ...            |  Queue Index  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Data Item Type:  TBA3

   Length:  Variable

      Per [RFC8175] Length is the number of octets in the data item,
      excluding the Type and Length fields.  It will equal the number of
      Queue Index fields carried in the data item.

   Queue Index:

      One or more 8-bit fields used to indicate a queue index defined by
      a Queue Parameters Data Item.  The special value of 255 indicates
      all traffic is to be suppressed to the modem, when the data item
      is carried in a Session Update Message, or a destination, when the
      data item is carried in Destination Update Message.

3.3.  Restart

   The Restart Data Item is used by a modem to indicate to its peer that
   transmission of previously suppressed traffic may be resumed.  An




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   example of when a modem might send this data item is when an internal
   queue length drops below a particular threshold.

   The sending of this data item parallels the Pause Data Item, see the
   previous section, and follows the same rules.  This includes that to
   indicate that transmission can resume to all destinations, a modem
   MAY send the Restart Data Item in a Session Update Message.  It also
   includes that to indicate that transmission can resume to a
   particular destination a modem MAY send the Pause Restart Item in a
   Destination Update Message.  Finally, the same rules apply to queue
   indexes.

   A router which receives the Restart Data Item SHOULD resume
   transmission of the identified traffic to the modem.

   The format of the Restart Data Item matches the Pause Data Item and
   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                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Queue Index  |               ...                             :
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       :                                ...            |  Queue Index  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Data Item Type:  TBA4

   Length:  See Section 3.2.

   Queue Index:  See Section 3.2.

4.  Security Considerations

   The extension introduces a new mechanism for flow control between a
   router and modem using the DLEP protocol.  The extension does not
   inherently introduce any additional threats above those documented in
   [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 4 values by IANA.  All
   assignments are to registries defined by [RFC8175].





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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 | Control Plane Based Pause |
                   +------+---------------------------+

                  Table 1: Requested Extension Type Value

5.2.  Data Item Values

   This document requests 3 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      | Queue Parameters |
                     |           |                  |
                     | TBA3      | Pause            |
                     |           |                  |
                     | TBA4      | Restart          |
                     +-----------+------------------+

                    Table 2: Requested Data Item 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>.






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   [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

   [I-D.ietf-manet-credit-window]
              Ratliff, S., "Credit Windowing extension for DLEP", draft-
              ietf-manet-credit-window-07 (work in progress), November
              2016.

   [RFC2474]  Nichols, K., Blake, S., Baker, F., and D. Black,
              "Definition of the Differentiated Services Field (DS
              Field) in the IPv4 and IPv6 Headers", RFC 2474,
              DOI 10.17487/RFC2474, December 1998,
              <https://www.rfc-editor.org/info/rfc2474>.

   [RFC2475]  Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
              and W. Weiss, "An Architecture for Differentiated
              Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
              <https://www.rfc-editor.org/info/rfc2475>.

Appendix A.  Acknowledgments

   The sub data item format was inspired by Rick Taylor's "Data Item
   Containers".

Authors' Addresses

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

   Email: bcheng@ll.mit.edu


   David Wiggins
   Lincoln Laboratory
   Massachusetts Institute of Technology
   244 Wood Street
   Lexington, MA  02420-9108

   Email: David.Wiggins@ll.mit.edu





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

   Email: lberger@labn.net















































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