1. Introduction

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1.  Introduction

   The Dynamic Link Exchange Protocol (DLEP) is defined in [RFC8175].
   This protocol 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.  DLEP defines Data Items, which are
   sets of information that can be reused in DLEP messaging.  The DLEP
   specification does not include any flow identification beyond DLEP
   endpoints, i.e., flows are identified based on their DLEP endpoint.

   This document defines DLEP Data Item formats that provide flow
   identification on a more granular basis.  Specifically, it enables a
   router to use traffic flow classification information provided by the
   modem to identify traffic flows based on a combination of information
   found in a data plane header.  (For general background on traffic
   classification, see Section 2.3 of [RFC2475].)  The Data Item is
   structured to allow for the use of the defined traffic classification
   information with applications such as credit window flow control as
   specified in [RFC9893].  [RFC9893] provides an example of combining
   traffic classification and credit window flow control.

   This document defines traffic classification based on a DLEP
   destination and flows identified by either Differentiated Services
   Code Points (DSCPs) [RFC2475] or IEEE 802.1Q Ethernet Priority Code
   Points (PCPs) [IEEE8021Q].  The defined mechanism allows for flows to
   be described in a flexible fashion and, when combined with
   applications such as credit window flow control, allows credit
   windows to be (1) shared across traffic sent to multiple DLEP
   destinations and as part of multiple flows or (2) used exclusively
   for traffic sent to a particular destination and/or belonging to a
   particular flow.  The extension also supports the "wildcard" matching
   of any flow (DSCP or PCP).  Traffic classification information is
   provided such that it can be readily extended to support other
   traffic classification techniques or can be used by extensions that
   are not related to credit windows, such as the extension defined in
   [RFC8651] or even 5-tuple IP flows.

   This document defines support for traffic classification using a
   single new Data Item (see Section 2.1) for general support and
   defines two new Sub-Data Items to support identification of flows
   based on DSCPs and PCPs (see Sections 2.2 and 2.3).