DLEP Control Plane Based Pause Extension
draft-ietf-manet-dlep-pause-extension-07

Network Working Group                                           B. Cheng
Internet-Draft                                                D. Wiggins
Intended status: Standards Track                  MIT Lincoln Laboratory
Expires: November 7, 2019                                 L. Berger, Ed.
                                                 LabN Consulting, L.L.C.
                                                             May 6, 2019

                DLEP Control Plane Based Pause Extension
                draft-ietf-manet-dlep-pause-extension-07

Abstract

   This document defines an extension to the Dynamic Link Exchange
   Protocol (DLEP) 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
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   This Internet-Draft will expire on November 7, 2019.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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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 . . . . . . . . . . . . . . . . . . . . . . . . . .   7
     3.3.  Restart . . . . . . . . . . . . . . . . . . . . . . . . .   8
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
     5.1.  Extension Type Value  . . . . . . . . . . . . . . . . . .   9
     5.2.  Data Item Values  . . . . . . . . . . . . . . . . . . . .  10
     5.3.  Queue Parameters Sub Data Item Values . . . . . . . . . .  10
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

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.

   The base DLEP specification does not include any data plane flow
   control capability.  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.  This functionality parallels the flow
   control mechanism found in PPP over Ethernet (PPPoE) per [RFC5578].
   The extension also optionally supports DSCP (differentiated services
   codepoint) aware flow control for use by DiffServ-aware modems.  (For
   general background on Differentiated Services see [RFC2475].)  This
   functionality is very similar to that provided by Ethernet Priority
   flow control, see [IEEE.802.1Q_2014].  The extension defined in this
   document is referred to as "Control Plane Based Pause".  Other flow
   control methods are possible with DLEP, e.g., see
   [I-D.ietf-manet-dlep-da-credit-extension] and
   [I-D.ietf-manet-dlep-credit-flow-control].

   Note that this mechanism only applies to traffic that is to be
   transmitted on the modem's attached data channel and not to DLEP
   control messages themselves.  Furthermore it applies only to the

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   single sub-network that is used to connect a modem and a router, and
   for traffic sent from a router to a modem.

   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 Control Plane Based Pause Extension SHOULD be
   configurable.  To indicate that the implementation supports use of
   the Control Plane Based Pause Extension, 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 about 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 sent by a modem to to a router 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 groups DSCPs into logical queues, each
   of which is identified by a "Queue Index".  The number of logical

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   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 a Queue Index.

   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                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |               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:

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

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         Value  Scale
         ------------
             0    B - Bytes     (Octets)
             1  KiB - Kilobytes (1024 B)
             2  MiB - Megabytes (1024 KiB)
             3  GiB - Gigabytes (1024 MiB)

   Reserved:

      A 20-bit field that MUST be set to zero by the sender (a modem)
      and ignored by the receiver (a router).

3.1.1.  Queue Parameter Sub Data Item

   Queue Parameter Sub Data Items are an unordered list composed of sub
   data items with a common format.  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.  In
   particular, the receiving implementation MUST issue a Session
   Termination Message containing a Status Data Item with status code
   set to 130 'Invalid Data' and transition to the Session Termination
   state.

   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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Sub Data Item Type (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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Queue Index  |             Queue Size Qn                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Num DSCPs Qn  |  DS Field Qn  |              ...              :
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       :                          ...                  |  DS Field Qn  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Sub Data Item Type:

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      A 16-bit unsigned integer that indicates the type and
      corresponding format of the Sub Data Item's Value field.  Sub Data
      Item Types are scoped within the Data Item in which they are
      carried, i.e., the Sub Data Item Type field MUST be used together
      with the Queue Parameters Data Item Type to identify the format of
      the Sub Data Item.  This field MUST be set to one (1) for the
      Queue Parameter Sub Data Item.

   Length:  Variable

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

   Queue Index:

      An 8-bit field indicating the queue index of the queue parameter
      represented in the sub data item.  Only the first instance of a
      particular Queue Index value is meaningful.  Subsequent sub data
      items containing the same Queue Index values, if present, MAY be
      logged via a management interface and MUST otherwise be ignored.
      Note that the value 255 is reserved and MUST NOT be used in this
      field.

   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.

   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).

   DS Field Qn:

      The data item contains a sequence of 8 bit DS Fields.  The number
      of DS Fields present MUST equal the sum of all Num DSCPs field
      values.

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

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           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 sent by a modem to a router to indicate to its
   peer that traffic is to be suppressed, i.e., paused.  The motivating
   use case for this data item is when a modem's internal queue length
   exceeds a particular threshold.  Other use cases are possible, e.g.,
   when there are non queue related congestion points within a modem.
   Such cases are not explicitly described in this document.

   A modem can 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 MUST send the Pause Data Item in a Session
   Update Message.  To indicate that suppression applies to a particular
   destination a modem MUST 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
   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 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:

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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                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  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 is to be suppressed to
      a destination, when the data item is carried in Destination Update
      Message.

3.3.  Restart

   The Restart Data Item is sent by a modem to a router to indicate to
   its peer that transmission of previously suppressed traffic may be
   resumed.  An 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.  As above, to indicate
   that transmission can resume to all destinations, a modem MUST 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 MUST send the Pause Restart Item in a Destination
   Update Message.  Finally, queue indexes are interpreted in the same
   way as in the Pause Data Item..

   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:

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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                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  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 DLEP.  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.

   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 4 values by IANA.  All
   assignments are to registries defined by [RFC8175].

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 | 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

5.3.  Queue Parameters Sub Data Item Values

   Upon approval of this document, IANA is requested to create a new
   DLEP registry, named "Queue Parameters Sub Data Item Type Values".

   The following table provides initial registry values and the
   [RFC8126] defined policies that should apply to the registry:

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                 +-------------+------------------------+
                 | Type Code   | Description/Policy     |
                 +-------------+------------------------+
                 | 0           | Reserved               |
                 |             |                        |
                 | 1           | Queue Parameter        |
                 |             |                        |
                 | 2-65407     | Specification Required |
                 |             |                        |
                 | 65408-65534 | Private Use            |
                 |             |                        |
                 | 65535       | Reserved               |
                 +-------------+------------------------+

                                  Table 3

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

   [I-D.ietf-manet-dlep-credit-flow-control]
              Cheng, B., Wiggins, D., Berger, L., and S. Ratliff, "DLEP
              Credit-Based Flow Control Messages and Data Items", draft-
              ietf-manet-dlep-credit-flow-control-04 (work in progress),
              March 2019.

   [I-D.ietf-manet-dlep-da-credit-extension]
              Cheng, B., Wiggins, D., and L. Berger, "DLEP DiffServ
              Aware Credit Window Extension", draft-ietf-manet-dlep-da-
              credit-extension-07 (work in progress), March 2019.

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   [IEEE.802.1Q_2014]
              IEEE, "IEEE Standard for Local and metropolitan area
              networks--Bridges and Bridged Networks", IEEE 802.1Q-2014,
              DOI 10.1109/ieeestd.2014.6991462, December 2014,
              <http://ieeexplore.ieee.org/servlet/
              opac?punumber=6991460>.

   [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>.

   [RFC5578]  Berry, B., Ed., Ratliff, S., Paradise, E., Kaiser, T., and
              M. Adams, "PPP over Ethernet (PPPoE) Extensions for Credit
              Flow and Link Metrics", RFC 5578, DOI 10.17487/RFC5578,
              February 2010, <https://www.rfc-editor.org/info/rfc5578>.

   [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

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

Authors' Addresses

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

   Email: bcheng@ll.mit.edu

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

   Email: David.Wiggins@ll.mit.edu

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

   Email: lberger@labn.net

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