DLEP DiffServ Aware Credit Window Extension
draft-ietf-manet-dlep-da-credit-extension-21

MANET                                                           B. Cheng
Internet-Draft                                    MIT Lincoln Laboratory
Intended status: Standards Track                              D. Wiggins
Expires: 4 September 2025                                               
                                                               L. Berger
                                                 LabN Consulting, L.L.C.
                                                        D. Eastlake, Ed.
                                                             Independent
                                                            3 March 2025

              DLEP DiffServ Aware Credit Window Extension
              draft-ietf-manet-dlep-da-credit-extension-21

Abstract

   This document defines an extension to the Dynamic Link Exchange
   Protocol (DLEP) that enables a DiffServ aware credit-window scheme
   for destination-specific and shared flow control.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on 4 September 2025.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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 carefully, as they describe your rights
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Key Words . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Extension Usage and Identification  . . . . . . . . . . . . .   3
   3.  Management Considerations . . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   The Dynamic Link Exchange Protocol (DLEP) is defined in [RFC8175].
   The protocol provides the exchange of link related control
   information between DLEP peers.  DLEP peers consist 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 DLEP specification does not include any flow control capability.
   There are various flow control techniques theoretically possible with
   DLEP.  This document defines a DLEP extension which provides a
   DiffServ-based flow control mechanism for traffic sent from a router
   to a modem.  Flow control is provided using one or more logical
   "Credit Windows", each of which will typically be supported by an
   associated virtual or physical queue.  A router will use traffic flow
   classification information provided by the modem to identify which
   traffic is associated with each credit window.  Credit windows may be
   shared or dedicated on a per-flow basis.  See
   [I-D.ietf-manet-dlep-ether-credit-extension] for an Ethernet-based
   version of credit window flow control.  As specified in Section 2.3.1
   of [I-D.ietf-manet-dlep-traffic-classification], when both DiffServ
   and Ethernet traffic classification are specified for a flow, the
   Ethernet information takes precedence.

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   This document uses the traffic classification and credit window
   control mechanisms defined in
   [I-D.ietf-manet-dlep-traffic-classification] and
   [I-D.ietf-manet-dlep-credit-flow-control] to provide credit window
   based flow control based on DLEP destinations and DiffServ [RFC2475]
   DSCPs (differentiated services codepoints).  The defined mechanism
   allows for credit windows to be shared across traffic sent to
   multiple DLEP destinations and DSCPs, or used exclusively for traffic
   sent to a particular destination and/or DSCP.  The extension also
   supports the "wildcard" matching of any DSCP.

   The extension defined in this document is referred to as "DiffServ
   Aware Credit Window" or, more simply, the "DA Credit" extension.  The
   reader should be familiar with both the traffic classification and
   credit window control mechanisms defined in
   [I-D.ietf-manet-dlep-traffic-classification] and
   [I-D.ietf-manet-dlep-credit-flow-control].

   This document defines a new DLEP Extension Type Value in Section 2
   which is used to indicate support for the extension.

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 extension defined in this document is composed of the mechanisms
   and processing defined in
   [I-D.ietf-manet-dlep-traffic-classification] and
   [I-D.ietf-manet-dlep-credit-flow-control].  To indicate that the
   DiffServ Aware Credit Window Extension is to be used, an
   implementation MUST include the DiffServ Aware Credit Window Type
   Value in the Extensions Supported Data Item (see Section 13.6 of
   [RFC8175]).  The Extensions Supported Data Item is sent and processed
   according to [RFC8175].  Any implementation that indicates use of the
   DiffServ Aware Credit Window Extension MUST support all Messages,
   Data Items, the DiffServ Traffic Classification Sub-Data Item, and
   all related processing defined in
   [I-D.ietf-manet-dlep-traffic-classification] and
   [I-D.ietf-manet-dlep-credit-flow-control].

   The DiffServ Aware Credit Window Extension Type Value is TBA1, see
   Section 5.

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3.  Management Considerations

   This section provides several network management guidelines to
   implementations supporting the DiffServ Aware Credit Window
   Extension.

   If this extension is supported, that support MUST be declared using
   the Extensions Supported Data Item (see Section 13.6 of [RFC8175]).
   DiffServ Aware Credit Window Extension Data Items MUST NOT be emitted
   by a DLEP participant unless such support was specified in the
   initialization message received from its peer.  The use of the
   extension defined in this document SHOULD be configurable on both
   modems and routers.  That configuration can be implemented using a
   proprietary CLI or by implementing a YANG module.  The definition of
   the YANG module is out of the scope of this document.

   Modems SHOULD support the configuration of DSCP to credit window
   (queue) mapping.

   Modems MAY support the configuration of the number of credit windows
   (queues) to advertise to a router.

   Routers may have limits on the number of queues that they can support
   and limits on supported credit window combinations.  Per destination
   queues might not be supported at all.  When modem-provided credit
   window information exceeds the capabilities of a router, the router
   SHOULD use a subset of the provided credit windows.  Alternatively, a
   router MAY reset the session and indicate that the extension is not
   supported.  In either case, the mismatch of capabilities SHOULD be
   reported to the user via normal network management mechanisms such as
   user interface messages or error logging.

   In all cases, if credit windows are in use, traffic for which credits
   are not available MUST NOT be sent to the modem by the router.

4.  Security Considerations

   This document defines a DLEP extension that uses DLEP mechanisms and
   the credit window control and flow mechanisms defined in
   [I-D.ietf-manet-dlep-traffic-classification] and
   [I-D.ietf-manet-dlep-credit-flow-control].  See also the Security
   Considerations sections of those documents.

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   The defined extension is exposed to vulnerabilities similar to
   existing DLEP messages and discussed in the Security Considerations
   section of [RFC8175] such as an injected message resizing a credit
   window to a value that results in a denial of service.  The security
   mechanisms documented in [RFC8175] can be applied equally to the
   mechanism defined in this document.

   Wildcards for matching Priority Code point (PCP) and VLAN ID (VID)
   fields (see [I-D.ietf-manet-dlep-ether-credit-extension]) are
   provided which may be convenient to match a number of packet flows
   but could inadvertently match unexpected flows or new flows that
   appear after the wildcard matching has been set up.  It is therefore
   RECOMMENDED that wildcards not be used unless needed.

5.  IANA Considerations

   IANA is requested to assign one code point in the "Extension Type
   Values" registry in the "Dynamic Link Exchange Protocol (DLEP)
   Parameters" registry group as follows:

                  +======+==============================+
                  | Code | Description                  |
                  +======+==============================+
                  | TBA1 | DiffServ Aware Credit Window |
                  +------+------------------------------+

                  Table 1: Requested Extension Type Value

6.  References

6.1.  Normative References

   [I-D.ietf-manet-dlep-credit-flow-control]
              Cheng, B., Wiggins, D., Berger, L., Ratliff, S., and E.
              Kinzie, "Dynamic Link Exchange Protocol (DLEP) Credit-
              Based Flow Control Messages and Data Items", Work in
              Progress, Internet-Draft, draft-ietf-manet-dlep-credit-
              flow-control, 3 January 2025,
              <https://datatracker.ietf.org/doc/draft-ietf-manet-dlep-
              credit-flow-control>.

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   [I-D.ietf-manet-dlep-traffic-classification]
              Cheng, B., Wiggins, D., Berger, L., and D. Fedyk, "Dynamic
              Link Exchange Protocol (DLEP) Traffic Classification Data
              Item", Work in Progress, Internet-Draft, draft-ietf-manet-
              dlep-traffic-classification, 19 November 2024,
              <https://datatracker.ietf.org/doc/draft-ietf-manet-dlep-
              traffic-classification>.

   [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-ether-credit-extension]
              Wiggins, D., Berger, L., and D. E. Eastlake, "DLEP IEEE
              802.1Q Aware Credit Window Extension", Work in Progress,
              Internet-Draft, draft-ietf-manet-dlep-ether-credit-
              extension, 15 December 2024,
              <https://datatracker.ietf.org/doc/draft-ietf-manet-dlep-
              ether-credit-extension/>.

   [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".  He also proposed the separation of credit windows from
   traffic classification at IETF 98.  Many useful comments were
   received from contributors to the MANET working group, notably Ronald
   in't Velt.

   We had the honor of working too briefly with David Wiggins on this
   and related DLEP work.  His contribution to the IETF and publication
   of the first and definitive open source DLEP implementation have been

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   critical to the acceptance of DLEP.  We mourn his passing on November
   23, 2023.  We wish to recognize his guidance, leadership and
   professional excellence.  We were fortunate to benefit from his
   leadership and friendship.  He shall be missed.

Authors' Addresses

   Bow-Nan Cheng
   MIT Lincoln Laboratory
   Massachusetts Institute of Technology
   244 Wood Street
   Lexington
   Email: bcheng@ll.mit.edu

   David Wiggins
   Email: david@none.org

   Lou Berger
   LabN Consulting, L.L.C.
   Email: lberger@labn.net

   Donald E. Eastlake 3rd (editor)
   Independent
   2386 Panoramic Circle
   Apopka, Florida 32703
   United States of America
   Phone: +1-508-333-2270
   Email: d3e3e3@gmail.com

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