DLEP IEEE 802.1Q Aware Credit Window Extension
draft-ietf-manet-dlep-ether-credit-extension-09

MANET                                                         D. Wiggins
Internet-Draft                                                          
Intended status: Standards Track                               L. Berger
Expires: 25 September 2025                       LabN Consulting, L.L.C.
                                                        D. Eastlake, Ed.
                                                             Independent
                                                           24 March 2025

             DLEP IEEE 802.1Q Aware Credit Window Extension
            draft-ietf-manet-dlep-ether-credit-extension-09

Abstract

   This document defines an extension to the Dynamic Link Exchange
   Protocol (DLEP) that enables an Ethernet IEEE 802.1Q aware credit-
   window scheme for destination-specific and shared flow control.

Status of This Memo

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   This Internet-Draft will expire on 25 September 2025.

Copyright Notice

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Key Words . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Extension Usage and Identification  . . . . . . . . . . . . .   3
   3.  Management Considerations . . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .   7
   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 define any flow control mechanisms.
   While various flow control techniques could be theoretically
   implemented with DLEP, this document specifies a DLEP extension that
   introduces an Ethernet-based flow control mechanism for traffic
   transmitted from a router to a modem.  This mechanism utilizes one or
   more logical "Credit Windows", each of which is typically associated
   with a virtual or physical queue.  The router leverages traffic flow
   classification information provided by the modem to determine the
   appropriate credit window for a given traffic flow.  Credit windows
   may be allocated on either a shared or a per-flow basis.  For a
   DiffServ-based approach to credit window flow control, refer to
   [I-D.ietf-manet-dlep-da-credit-extension].  As specified in
   Section 2.3.1 of [I-D.ietf-manet-dlep-traffic-classification], when
   both DiffServ and Ethernet traffic classification are applied to a
   flow, Ethernet-based classification takes precedence.

   This document leverages 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 enable credit window-
   based flow control based on DLEP destinations, Ethernet VLANs, and
   Priority Code Points (PCPs).  Ethernet PCP support is specified as
   part of the IEEE 802.1Q [IEEE8021Q] tag format, which includes a
   3-bit "PCP" field.  The tag format also incorporates a 12-bit "VLAN
   Identifier (VID)" field.

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   The defined mechanism allows credit windows to be shared across
   traffic destined for multiple DLEP destinations, Virtual Local Area
   Networks (VLANs), and PCPs, or to be dedicated exclusively to traffic
   associated with a specific destination, VLAN, and/or PCP.
   Additionally, this extension supports "wildcard" matching for any PCP
   or VID.

   The extension defined in this document is referred to as "IEEE 802.1Q
   Aware Credit Window" or, more simply, the "Ethernet 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 IEEE
   802.1Q Aware Credit Window Extension is to be used, an implementation
   MUST include the IEEE 802.1Q Aware Credit Window Type Value in the
   Extensions Supported Data Item.  The Extensions Supported Data Item
   is sent and processed according to [RFC8175].  Any implementation
   that indicates use of the IEEE 802.1Q Aware Credit Window Extension
   MUST support all Messages, Data Items, the Ethernet 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 IEEE 802.1Q 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 IEEE 802.1Q 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])
   which is configurable on both modems and routers.  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.

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

   Modems MAY support the configuration of PCP to credit window (queue)
   mapping on a per VLAN basis.  VID value zero (0) is used by
   [I-D.ietf-manet-dlep-traffic-classification] to indicate that VID is
   ignored and any VID value is used in traffic classification.

   When VLANs are supported by a modem without support from PCPs, the
   modem SHOULD support the configuration of VLAN to credit window
   (queue) mapping.

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

   Routers may impose limitations on the number of queues they can
   support and on the allowable credit window configurations.  In some
   cases, per-destination queues may not be supported.  If the credit
   window information provided by the modem exceeds the router's
   capabilities, the router SHOULD utilize a subset of the advertised
   credit windows.  Alternatively, the router MAY reset the session and
   indicate that the extension is not supported.  In either case, any
   mismatch in capabilities SHOULD be reported to the user through
   standard network management mechanisms, such as user interface
   notifications or error logging.

   Regardless of implementation, if credit windows are in use, the
   router MUST NOT send traffic to the modem unless sufficient credits
   are available.

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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.

   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 PCP and VID fields 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 clearly 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 | IEEE 802.1Q Aware Credit Window |
                +------+---------------------------------+

                 Table 1: Requested Extension Type Value

6.  References

6.1.  Normative References

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   [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>.

   [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>.

   [IEEE8021Q]
              IEEE, "IEEE Standard for Local and Metropolitan Area
              Networks--Bridges and Bridged Networks",
              DOI 10.1109/IEEESTD.2022.10004498, IEEE 802.1Q-2022, July
              2022, <https://ieeexplore.ieee.org/document/8403927>.

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

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Appendix A.  Acknowledgments

   The document was motivated by discussions in the MANET working group.
   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
   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

   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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