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
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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and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
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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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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