path: root/doc/rfc/rfc8325.txt

Internet Engineering Task Force (IETF)                        T. Szigeti
Request for Comments: 8325                                      J. Henry
Category: Standards Track                                  Cisco Systems
ISSN: 2070-1721                                                 F. Baker
                                                           February 2018


                    Mapping Diffserv to IEEE 802.11

Abstract

   As Internet traffic is increasingly sourced from and destined to
   wireless endpoints, it is crucial that Quality of Service (QoS) be
   aligned between wired and wireless networks; however, this is not
   always the case by default.  This document specifies a set of
   mappings from Differentiated Services Code Point (DSCP) to IEEE
   802.11 User Priority (UP) to reconcile the marking recommendations
   offered by the IETF and the IEEE so as to maintain consistent QoS
   treatment between wired and IEEE 802.11 wireless networks.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8325.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   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 and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Related Work  . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Interaction with RFC 7561 . . . . . . . . . . . . . . . .   4
     1.3.  Applicability Statement . . . . . . . . . . . . . . . . .   4
     1.4.  Document Organization . . . . . . . . . . . . . . . . . .   5
     1.5.  Requirements Language . . . . . . . . . . . . . . . . . .   5
     1.6.  Terminology Used in This Document . . . . . . . . . . . .   6
   2.  Service Comparison and Default Interoperation of Diffserv and
       IEEE 802.11 . . . . . . . . . . . . . . . . . . . . . . . . .   9
     2.1.  Diffserv Domain Boundaries  . . . . . . . . . . . . . . .   9
     2.2.  EDCF Queuing  . . . . . . . . . . . . . . . . . . . . . .  10
     2.3.  Default DSCP-to-UP Mappings and Conflicts . . . . . . . .  10
     2.4.  Default UP-to-DSCP Mappings and Conflicts . . . . . . . .  11
   3.  Recommendations for Capabilities of Wireless Device Marking
       and Mapping . . . . . . . . . . . . . . . . . . . . . . . . .  13
   4.  Recommendations for DSCP-to-UP Mapping  . . . . . . . . . . .  13
     4.1.  Network Control Traffic . . . . . . . . . . . . . . . . .  14
       4.1.1.  Network Control Protocols . . . . . . . . . . . . . .  14
       4.1.2.  Operations, Administration, and  Maintenance (OAM)  .  15
     4.2.  User Traffic  . . . . . . . . . . . . . . . . . . . . . .  15
       4.2.1.  Telephony . . . . . . . . . . . . . . . . . . . . . .  15
       4.2.2.  Signaling . . . . . . . . . . . . . . . . . . . . . .  16
       4.2.3.  Multimedia Conferencing . . . . . . . . . . . . . . .  17
       4.2.4.  Real-Time Interactive . . . . . . . . . . . . . . . .  17
       4.2.5.  Multimedia Streaming  . . . . . . . . . . . . . . . .  17
       4.2.6.  Broadcast Video . . . . . . . . . . . . . . . . . . .  18
       4.2.7.  Low-Latency Data  . . . . . . . . . . . . . . . . . .  18
       4.2.8.  High-Throughput Data  . . . . . . . . . . . . . . . .  18
       4.2.9.  Standard  . . . . . . . . . . . . . . . . . . . . . .  19
       4.2.10. Low-Priority Data . . . . . . . . . . . . . . . . . .  20
     4.3.  Summary of Recommendations for DSCP-to-UP Mapping . . . .  20
   5.  Recommendations for Upstream Mapping and Marking  . . . . . .  21
     5.1.  Upstream DSCP-to-UP Mapping within the Wireless Client
           Operating System  . . . . . . . . . . . . . . . . . . . .  22
     5.2.  Upstream UP-to-DSCP Mapping at the Wireless AP  . . . . .  22
     5.3.  Upstream DSCP-Passthrough at the Wireless AP  . . . . . .  23
     5.4.  Upstream DSCP Marking at the Wireless AP  . . . . . . . .  24
   6.  Overview of IEEE 802.11 QoS . . . . . . . . . . . . . . . . .  24
     6.1.  Distributed Coordination Function (DCF) . . . . . . . . .  25
       6.1.1.  Slot Time . . . . . . . . . . . . . . . . . . . . . .  25
       6.1.2.  Interframe Space (IFS)  . . . . . . . . . . . . . . .  26
       6.1.3.  Contention Window (CW)  . . . . . . . . . . . . . . .  26
     6.2.  Hybrid Coordination Function (HCF)  . . . . . . . . . . .  27
       6.2.1.  User Priority (UP)  . . . . . . . . . . . . . . . . .  27
       6.2.2.  Access Category (AC)  . . . . . . . . . . . . . . . .  28
       6.2.3.  Arbitration Interframe Space (AIFS) . . . . . . . . .  29



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       6.2.4.  Access Category CWs . . . . . . . . . . . . . . . . .  29
     6.3.  IEEE 802.11u QoS Map Set  . . . . . . . . . . . . . . . .  30
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  31
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  31
     8.1.  Security Recommendations for General QoS  . . . . . . . .  31
     8.2.  Security Recommendations for WLAN QoS . . . . . . . . . .  32
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  34
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  34
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  35
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  37
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  37

1.  Introduction

   The wireless medium defined by IEEE 802.11 [IEEE.802.11-2016] has
   become the preferred medium for endpoints connecting to business and
   private networks.  However, it presents several design challenges for
   ensuring end-to-end QoS.  Some of these challenges relate to the
   nature of the IEEE 802.11 Radio Frequency (RF) medium itself, being a
   half-duplex and shared medium, while other challenges relate to the
   fact that the IEEE 802.11 standard is not administered by the same
   standards body as IP networking standards.  While the IEEE has
   developed tools to enable QoS over wireless networks, little guidance
   exists on how to maintain consistent QoS treatment between wired IP
   networks and wireless IEEE 802.11 networks.  The purpose of this
   document is to provide such guidance.

1.1.  Related Work

   Several RFCs outline Diffserv QoS recommendations over IP networks,
   including:

   RFC 2474    Specifies the Diffserv Codepoint Field.  This RFC also
               details Class Selectors, as well as the Default
               Forwarding (DF) PHB for best effort traffic.  The Default
               Forwarding PHB is referred to as the Default PHB in RFC
               2474.

   RFC 2475    Defines a Diffserv architecture.

   RFC 3246    Specifies the Expedited Forwarding (EF) Per-Hop Behavior
               (PHB).

   RFC 2597    Specifies the Assured Forwarding (AF) PHB.

   RFC 3662    Specifies a Lower-Effort Per-Domain Behavior (PDB).





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   RFC 4594    Presents configuration guidelines for Diffserv service
               classes.

   RFC 5127    Presents the aggregation of Diffserv service classes.

   RFC 5865    Specifies a DSCP for capacity-admitted traffic.

   Note: [RFC4594] is intended to be viewed as a framework for
   supporting Diffserv in any network, including wireless networks;
   thus, it describes different types of traffic expected in IP networks
   and provides guidance as to what DSCP marking(s) should be associated
   with each traffic type.  As such, this document draws heavily on
   [RFC4594], as well as [RFC5127], and [RFC8100].

   In turn, the relevant standard for wireless QoS is IEEE 802.11, which
   is being progressively updated; at the time of writing, the current
   version of which is [IEEE.802.11-2016].

1.2.  Interaction with RFC 7561

   There is also a recommendation from the Global System for Mobile
   Communications Association (GSMA) on DSCP-to-UP Mapping for IP Packet
   eXchange (IPX), specifically their Guidelines for IPX Provider
   networks [GSMA-IPX_Guidelines].  These GSMA Guidelines were developed
   without reference to existing IETF specifications for various
   services, referenced in Section 1.1.  In turn, [RFC7561] was written
   based on these GSMA Guidelines, as explicitly called out in
   [RFC7561], Section 4.2.  Thus, [RFC7561] conflicts with the overall
   Diffserv traffic-conditioning service plan, both in the services
   specified and the codepoints specified for them.  As such, these two
   plans cannot be normalized.  Rather, as discussed in [RFC2474],
   Section 2, the two domains (IEEE 802.11 and GSMA) are different
   Differentiated Services Domains separated by a Differentiated
   Services Boundary.  At that boundary, codepoints from one domain are
   translated to codepoints for the other, and maybe to Default (zero)
   if there is no corresponding service to translate to.

1.3.  Applicability Statement

   This document is applicable to the use of Differentiated Services
   that interconnect with IEEE 802.11 wireless LANs (referred to as
   Wi-Fi, throughout this document, for simplicity).  These guidelines
   are applicable whether the wireless access points (APs) are deployed
   in an autonomous manner, managed by (centralized or distributed) WLAN
   controllers, or some hybrid deployment option.  This is because, in
   all these cases, the wireless AP is the bridge between wired and
   wireless media.




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   This document applies to IP networks using Wi-Fi infrastructure at
   the link layer.  Such networks typically include wired LANs with
   wireless APs at their edges; however, such networks can also include
   Wi-Fi backhaul, wireless mesh solutions, or any other type of AP-to-
   AP wireless network that extends the wired-network infrastructure.

1.4.  Document Organization

   This document is organized as follows:

   Section 1 introduces the wired-to-wireless QoS challenge, references
   related work, outlines the organization of the document, and
   specifies both the requirements language and the terminology used in
   this document.

   Section 2 begins the discussion with a comparison of IETF Diffserv
   QoS and Wi-Fi QoS standards and highlights discrepancies between
   these that require reconciliation.

   Section 3 presents the marking and mapping capabilities that wireless
   APs and wireless endpoint devices are recommended to support.

   Section 4 presents DSCP-to-UP mapping recommendations for each of the
   [RFC4594] service classes, which are primarily applicable in the
   downstream (wired-to-wireless) direction.

   Section 5, in turn, considers upstream (wireless-to-wired) QoS
   options, their respective merits and recommendations.

   Section 6 (in the form of an Appendix) presents a brief overview of
   how QoS is achieved over IEEE 802.11 wireless networks, given the
   shared, half-duplex nature of the wireless medium.

   Section 7 contains IANA considerations.

   Section 8 presents security considerations relative to DSCP-to-UP
   mapping, UP-to-DSCP mapping, and re-marking.

1.5.  Requirements Language

   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.






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1.6.  Terminology Used in This Document

   Key terminology used in this document includes:

   AC:  Access Category.  A label for the common set of enhanced
      distributed channel access (EDCA) parameters that are used by a
      QoS station (STA) to contend for the channel in order to transmit
      medium access control (MAC) service data units (MSDUs) with
      certain priorities; see [IEEE.802.11-2016], Section 3.2.

   AIFS:  Arbitration Interframe Space.  Interframe space used by QoS
      stations before transmission of data and other frame types defined
      by [IEEE.802.11-2016], Section 10.3.2.3.6.

   AP:  Access Point.  An entity that contains one station (STA) and
      provides access to the distribution services, via the wireless
      medium (WM) for associated STAs.  An AP comprises a STA and a
      distribution system access function (DSAF); see
      [IEEE.802.11-2016], Section 3.1.

   BSS:  Basic Service Set. Informally, a wireless cell; formally, a set
      of stations that have successfully synchronized using the JOIN
      service primitives and one STA that has used the START primitive.
      Alternatively, a set of STAs that have used the START primitive
      specifying matching mesh profiles where the match of the mesh
      profiles has been verified via the scanning procedure.  Membership
      in a BSS does not imply that wireless communication with all other
      members of the BSS is possible.  See the definition in
      [IEEE.802.11-2016], Section 3.1.

   Contention Window:  See CW.

   CSMA/CA:  Carrier Sense Multiple Access with Collision Avoidance.  A
      MAC method in which carrier sensing is used, but nodes attempt to
      avoid collisions by transmitting only when the channel is sensed
      to be "idle".  When these do transmit, nodes transmit their packet
      data in its entirety.

   CSMA/CD:  Carrier Sense Multiple Access with Collision Detection.  A
      MAC method (used most notably in early Ethernet technology) for
      local area networking.  It uses a carrier-sensing scheme in which
      a transmitting station detects collisions by sensing transmissions
      from other stations while transmitting a frame.  When this
      collision condition is detected, the station stops transmitting
      that frame, transmits a jam signal, and then waits for a random
      time interval before trying to resend the frame.





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   CW:  Contention Window.  Limits a CWMin and CWMax, from which a
      random backoff is computed.

   CWMax:  Contention Window Maximum.  The maximum value (in units of
      Slot Time) that a CW can take.

   CWMin:  Contention Window Minimum.  The minimum value that a CW can
      take.

   DCF:  Distributed Coordinated Function.  A class of coordination
      function where the same coordination function logic is active in
      every station (STA) in the BSS whenever the network is in
      operation.

   DIFS:  Distributed (Coordination Function) Interframe Space.  A unit
      of time during which the medium has to be detected as idle before
      a station should attempt to send frames, as per
      [IEEE.802.11-2016], Section 10.3.2.3.5.

   DSCP:  Differentiated Service Code Point [RFC2474] and [RFC2475].
      The DSCP is carried in the first 6 bits of the IPv4 Type of
      Service (TOS) field and the IPv6 Traffic Class field (the
      remaining 2 bits are used for IP Explicit Congestion Notification
      (ECN) [RFC3168]).

   EIFS:  Extended Interframe Space.  A unit of time that a station has
      to defer before transmitting a frame if the previous frame
      contained an error, as per [IEEE.802.11-2016], Section 10.3.2.3.7.

   HCF:  Hybrid Coordination Function.  A coordination function that
      combines and enhances aspects of the contention-based and
      contention-free access methods to provide QoS stations (STAs) with
      prioritized and parameterized QoS access to the WM, while
      continuing to support non-QoS STAs for best-effort transfer; see
      [IEEE.802.11-2016], Section 3.1.

   IFS:  Interframe Space.  Period of silence between transmissions over
      IEEE 802.11 networks.  [IEEE.802.11-2016] describes several types
      of Interframe Spaces.

   Random Backoff Timer:  A pseudorandom integer period of time (in
      units of Slot Time) over the interval (0,CW), where CWmin is less
      than or equal to CW, which in turn is less than or equal to CWMax.
      Stations desiring to initiate transfer of data frames and/or
      management frames using the DCF shall invoke the carrier sense
      mechanism to determine the busy-or-idle state of the medium.  If
      the medium is busy, the STA shall defer until the medium is
      determined to be idle without interruption for a period of time



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      equal to DIFS when the last frame detected on the medium was
      received correctly or after the medium is determined to be idle
      without interruption for a period of time equal to EIFS when the
      last frame detected on the medium was not received correctly.
      After this DIFS or EIFS medium idle time, the STA shall then
      generate a random backoff period for an additional deferral time
      before transmitting.  See [IEEE.802.11-2016], Section 10.3.3.

   RF:  Radio Frequency.

   SIFS:  Short Interframe Space.  An IFS used before transmission of
      specific frames as defined in [IEEE.802.11-2016],
      Section 10.3.2.3.3.

   Slot Time:  A unit of time used to count time intervals in IEEE
      802.11 networks; it is defined in [IEEE.802.11-2016],
      Section 10.3.2.13.

   Trust:  From a QoS-perspective, "trust" refers to the accepting of
      the QoS markings of a packet by a network device.  Trust is
      typically extended at Layer 3 (by accepting the DSCP), but may
      also be extended at lower layers, such as at Layer 2 by accepting
      UP markings.  For example, if an AP is configured to trust DSCP
      markings and it receives a packet marked EF, then it would treat
      the packet with the Expedite Forwarding PHB and propagate the EF
      marking value (DSCP 46) as it transmits the packet.
      Alternatively, if a network device is configured to operate in an
      untrusted manner, then it would re-mark packets as these entered
      the device, typically to DF (or to a different marking value at
      the network administrator's preference).  Note: The terms
      "trusted" and "untrusted" are used extensively in [RFC4594].

   UP:  User Priority.  A value associated with an MSDU that indicates
      how the MSDU is to be handled.  The UP is assigned to an MSDU in
      the layers above the MAC; see [IEEE.802.11-2016], Section 3.1.
      The UP defines a level of priority for the associated frame, on a
      scale of 0 to 7.

   Wi-Fi:  An interoperability certification defined by the Wi-Fi
      Alliance.  However, this term is commonly used, including in the
      present document, to be the equivalent of IEEE 802.11.

   Wireless:  In the context of this document, "wireless" refers to the
      media defined in IEEE 802.11 [IEEE.802.11-2016], and not 3G/4G LTE
      or any other radio telecommunications specification.






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2.  Service Comparison and Default Interoperation of Diffserv and
    IEEE 802.11

   (Section 6 provides a brief overview of IEEE 802.11 QoS.)

   The following comparisons between IEEE 802.11 and Diffserv services
   should be noted:

      [IEEE.802.11-2016] does not support an EF PHB service [RFC3246],
      as it is not possible to assure that a given access category will
      be serviced with strict priority over another (due to the random
      element within the contention process)

      [IEEE.802.11-2016] does not support an AF PHB service [RFC2597],
      again because it is not possible to assure that a given access
      category will be serviced with a minimum amount of assured
      bandwidth (due to the non-deterministic nature of the contention
      process)

      [IEEE.802.11-2016] loosely supports a Default PHB ([RFC2474]) via
      the Best Effort Access Category (AC_BE)

      [IEEE.802.11-2016] loosely supports a Lower Effort PDB service
      ([RFC3662]) via the Background Access Category (AC_BK)

   As such, these high-level considerations should be kept in mind when
   mapping from Diffserv to [IEEE.802.11-2016] (and vice versa);
   however, APs may or may not always be positioned at Diffserv domain
   boundaries, as will be discussed next.

2.1.  Diffserv Domain Boundaries

   It is important to recognize that the wired-to-wireless edge may or
   may not function as an edge of a Diffserv domain or a domain
   boundary.

   In most commonly deployed WLAN models, the wireless AP represents not
   only the edge of the Diffserv domain, but also the edge of the
   network infrastructure itself.  As such, only client endpoint devices
   (and no network infrastructure devices) are downstream from the
   access points in these deployment models.  Note: security
   considerations and recommendations for hardening such Wi-Fi-at-the-
   edge deployment models are detailed in Section 8; these
   recommendations include mapping network control protocols (which are
   not used downstream from the AP in this deployment model) to UP 0.






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   Alternatively, in other deployment models, such as Wi-Fi backhaul,
   wireless mesh infrastructures, wireless AP-to-AP deployments, or in
   cases where a Wi-Fi link connects to a device providing service via
   another technology (e.g., Wi-Fi to Bluetooth or Zigbee router), the
   wireless AP extends the network infrastructure and thus, typically,
   the Diffserv domain.  In such deployments, both client devices and
   infrastructure devices may be expected downstream from the APs, and,
   as such, network control protocols are RECOMMENDED to be mapped to UP
   7 in this deployment model, as is discussed in Section 4.1.1.

   Thus, as can be seen from these two examples, the QoS treatment of
   packets at the AP will depend on the position of the AP in the
   network infrastructure and on the WLAN deployment model.

   However, regardless of whether or not the AP is at the Diffserv
   boundary, marking-specific incompatibilities exist from Diffserv to
   802.11 (and vice versa) that must be reconciled, as will be discussed
   next.

2.2.  EDCF Queuing

   [IEEE.802.11-2016] displays a reference implementation queuing model
   in Figure 10-24, which depicts four transmit queues, one per access
   category.

   However, in practical implementations, it is common for WLAN network
   equipment vendors to implement dedicated transmit queues on a per-UP
   (versus a per-AC) basis, which are then dequeued into their
   associated AC in a preferred (or even in a strict priority manner).
   For example, it is common for vendors to dequeue UP 5 ahead of UP 4
   to the hardware performing the EDCA function (EDCAF) for the Video
   Access Category (AC_VI).

   Some of the recommendations made in Section 4 make reference to this
   common implementation model of queuing per UP.

2.3.  Default DSCP-to-UP Mappings and Conflicts

   While no explicit guidance is offered in mapping (6-Bit) Layer 3 DSCP
   values to (3-Bit) Layer 2 markings (such as IEEE 802.1D, 802.1p or
   802.11e), a common practice in the networking industry is to map
   these by what we will refer to as "default DSCP-to-UP mapping" (for
   lack of a better term), wherein the three Most Significant Bits
   (MSBs) of the DSCP are used as the corresponding L2 markings.







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   Note: There are mappings provided in [IEEE.802.11-2016], Annex V
   Tables V-1 and V2, but it bears mentioning that these mappings are
   provided as examples (as opposed to explicit recommendations).
   Furthermore, some of these mappings do not align with the intent and
   recommendations expressed in [RFC4594], as will be discussed in this
   and the following section (Section 2.4).

   However, when this default DSCP-to-UP mapping method is applied to
   packets marked per recommendations in [RFC4594] and destined to
   802.11 WLAN clients, it will yield a number of inconsistent QoS
   mappings, specifically:

   o  Voice (EF-101110) will be mapped to UP 5 (101), and treated in the
      Video Access Category (AC_VI) rather than the Voice Access
      Category (AC_VO), for which it is intended

   o  Multimedia Streaming (AF3-011xx0) will be mapped to UP 3 (011) and
      treated in the Best Effort Access Category (AC_BE) rather than the
      Video Access Category (AC_VI), for which it is intended

   o  Broadcast Video (CS3-011000) will be mapped to UP 3 (011) and
      treated in the Best Effort Access Category (AC_BE) rather than the
      Video Access Category (AC_VI), for which it is intended

   o  OAM traffic (CS2-010000) will be mapped to UP 2 (010) and treated
      in the Background Access Category (AC_BK), which is not the intent
      expressed in [RFC4594] for this service class

   It should also be noted that while [IEEE.802.11-2016] defines an
   intended use for each access category through the AC naming
   convention (for example, UP 6 and UP 7 belong to AC_VO, the Voice
   Access Category), [IEEE.802.11-2016] does not:

   o  define how upper-layer markings (such as DSCP) should map to UPs
      (and, hence, to ACs)

   o  define how UPs should translate to other mediums' Layer 2 QoS
      markings

   o  strictly restrict each access category to applications reflected
      in the AC name

2.4.  Default UP-to-DSCP Mappings and Conflicts

   In the opposite direction of flow (the upstream direction, that is,
   from wireless-to-wired), many APs use what we will refer to as
   "default UP-to-DSCP mapping" (for lack of a better term), wherein
   DSCP values are derived from UP values by multiplying the UP values



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   by 8 (i.e., shifting the three UP bits to the left and adding three
   additional zeros to generate a DSCP value).  This derived DSCP value
   is then used for QoS treatment between the wireless AP and the
   nearest classification and marking policy enforcement point (which
   may be the centralized wireless LAN controller, relatively deep
   within the network).  Alternatively, in the case where there is no
   other classification and marking policy enforcement point, then this
   derived DSCP value will be used on the remainder of the Internet
   path.

   It goes without saying that when six bits of marking granularity are
   derived from three, then information is lost in translation.
   Servicing differentiation cannot be made for 12 classes of traffic
   (as recommended in [RFC4594]), but for only eight (with one of these
   classes being reserved for future use (i.e., UP 7, which maps to DSCP
   CS7).

   Such default upstream mapping can also yield several inconsistencies
   with [RFC4594], including:

   o  Mapping UP 6 (which would include Voice or Telephony traffic, see
      [RFC4594]) to CS6, which [RFC4594] recommends for Network Control

   o  Mapping UP 4 (which would include Multimedia Conferencing and/or
      Real-Time Interactive traffic, see [RFC4594]) to CS4, thus losing
      the ability to differentiate between these two distinct service
      classes, as recommended in [RFC4594], Sections 4.3 and 4.4

   o  Mapping UP 3 (which would include Multimedia Streaming and/or
      Broadcast Video traffic, see [RFC4594]) to CS3, thus losing the
      ability to differentiate between these two distinct service
      classes, as recommended in [RFC4594], Sections 4.5 and 4.6

   o  Mapping UP 2 (which would include Low-Latency Data and/or OAM
      traffic, see [RFC4594]) to CS2, thus losing the ability to
      differentiate between these two distinct service classes, as
      recommended in [RFC4594], Sections 4.7 and 3.3, and possibly
      overwhelming the queues provisioned for OAM (which is typically
      lower in capacity (being Network Control Traffic), as compared to
      Low-Latency Data queues (being user traffic))

   o  Mapping UP 1 (which would include High-Throughput Data and/or Low-
      Priority Data traffic, see [RFC4594]) to CS1, thus losing the
      ability to differentiate between these two distinct service
      classes, as recommended in [RFC4594], Sections 4.8 and 4.10, and
      causing legitimate business-relevant High-Throughput Data to
      receive a [RFC3662] Lower-Effort PDB, for which it is not intended




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   The following sections address these limitations and concerns in
   order to reconcile [RFC4594] and [IEEE.802.11-2016].  First
   downstream (wired-to-wireless) DSCP-to-UP mappings will be aligned
   and then upstream (wireless-to-wired) models will be addressed.

3.  Recommendations for Capabilities of Wireless Device Marking and
    Mapping

   This document assumes and RECOMMENDS that all wireless APs (as the
   interconnects between wired-and-wireless networks) support the
   ability to:

   o  mark DSCP, per Diffserv standards

   o  mark UP, per the [IEEE.802.11-2016] standard

   o  support fully configurable mappings between DSCP and UP

   o  process DSCP markings set by wireless endpoint devices

   This document further assumes and RECOMMENDS that all wireless
   endpoint devices support the ability to:

   o  mark DSCP, per Diffserv standards

   o  mark UP, per the [IEEE.802.11-2016] standard

   o  support fully configurable mappings between DSCP (set by
      applications in software) and UP (set by the operating system and/
      or wireless network interface hardware drivers)

   Having made the assumptions and recommendations above, it bears
   mentioning that, while the mappings presented in this document are
   RECOMMENDED to replace the current common default practices (as
   discussed in Sections 2.3 and 2.4), these mapping recommendations are
   not expected to fit every last deployment model; as such, they MAY be
   overridden by network administrators, as needed.

4.  Recommendations for DSCP-to-UP Mapping

   The following section specifies downstream (wired-to-wireless)
   mappings between [RFC4594], "Configuration Guidelines for Diffserv
   Service Classes" and [IEEE.802.11-2016].  As such, this section draws
   heavily from [RFC4594], including service class definitions and
   recommendations.






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   This section assumes [IEEE.802.11-2016] wireless APs and/or WLAN
   controllers that support customizable, non-default DSCP-to-UP mapping
   schemes.

   This section also assumes that [IEEE.802.11-2016] APs and endpoint
   devices differentiate UP markings with corresponding queuing and
   dequeuing treatments, as described in Section 2.2.

4.1.  Network Control Traffic

   Network Control Traffic is defined as packet flows that are essential
   for stable operation of the administered network [RFC4594],
   Section 3.  Network Control Traffic is different from user
   application control (signaling) that may be generated by some
   applications or services.  Network Control Traffic MAY be split into
   two service classes:

   o  Network Control, and

   o  Operations, Administration, and Maintenance (OAM)

4.1.1.  Network Control Protocols

   The Network Control service class is used for transmitting packets
   between network devices (e.g., routers) that require control
   (routing) information to be exchanged between nodes within the
   administrative domain, as well as across a peering point between
   different administrative domains.

   [RFC4594], Section 3.2, recommends that Network Control Traffic be
   marked CS6 DSCP.  Additionally, as stated in [RFC4594], Section 3.1:
   "CS7 DSCP value SHOULD be reserved for future use, potentially for
   future routing or control protocols."

   By default (as described in Section 2.4), packets marked DSCP CS7
   will be mapped to UP 7 and serviced within the Voice Access Category
   (AC_VO).  This represents the RECOMMENDED mapping for CS7, that is,
   packets marked to CS7 DSCP are RECOMMENDED to be mapped to UP 7.

   However, by default (as described in Section 2.4), packets marked
   DSCP CS6 will be mapped to UP 6 and serviced within the Voice Access
   Category (AC_VO); such mapping and servicing is a contradiction to
   the intent expressed in [RFC4594], Section 3.2.  As such, it is
   RECOMMENDED to map Network Control Traffic marked CS6 to UP 7 (per
   [IEEE.802.11-2016], Section 10.2.4.2, Table 10-1), thereby admitting
   it to the Voice Access Category (AC_VO), albeit with a marking
   distinguishing it from (data-plane) voice traffic.




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   It should be noted that encapsulated routing protocols for
   encapsulated or overlay networks (e.g., VPN, Network Virtualization
   Overlays, etc.) are not Network Control Traffic for any physical
   network at the AP; hence, they SHOULD NOT be marked with CS6 in the
   first place.

   Additionally, and as previously noted, the Security Considerations
   section (Section 8) contains additional recommendations for hardening
   Wi-Fi-at-the-edge deployment models, where, for example, network
   control protocols are not expected to be sent nor received between
   APs and client endpoint devices that are downstream.

4.1.2.  Operations, Administration, and Maintenance (OAM)

   The OAM (Operations, Administration, and Maintenance) service class
   is recommended for OAM&P (Operations, Administration, and Maintenance
   and Provisioning).  The OAM service class can include network
   management protocols, such as SNMP, Secure Shell (SSH), TFTP, Syslog,
   etc., as well as network services, such as NTP, DNS, DHCP, etc.
   [RFC4594], Section 3.3, recommends that OAM traffic be marked CS2
   DSCP.

   By default (as described in Section 2.3), packets marked DSCP CS2
   will be mapped to UP 2 and serviced with the Background Access
   Category (AC_BK).  Such servicing is a contradiction to the intent
   expressed in [RFC4594], Section 3.3.  As such, it is RECOMMENDED that
   a non-default mapping be applied to OAM traffic, such that CS2 DSCP
   is mapped to UP 0, thereby admitting it to the Best Effort Access
   Category (AC_BE).

4.2.  User Traffic

   User traffic is defined as packet flows between different users or
   subscribers.  It is the traffic that is sent to or from end-terminals
   and that supports a very wide variety of applications and services
   [RFC4594], Section 4.

   Network administrators can categorize their applications according to
   the type of behavior that they require and MAY choose to support all
   or a subset of the defined service classes.

4.2.1.  Telephony

   The Telephony service class is recommended for applications that
   require real-time, very low delay, very low jitter, and very low
   packet loss for relatively constant-rate traffic sources (inelastic
   traffic sources).  This service class SHOULD be used for IP telephony
   service.  The fundamental service offered to traffic in the Telephony



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   service class is minimum jitter, delay, and packet loss service up to
   a specified upper bound.  [RFC4594], Section 4.1, recommends that
   Telephony traffic be marked EF DSCP.

   Traffic marked to DSCP EF will map by default (as described in
   Section 2.3) to UP 5 and, thus, to the Video Access Category (AC_VI)
   rather than to the Voice Access Category (AC_VO), for which it is
   intended.  Therefore, a non-default DSCP-to-UP mapping is
   RECOMMENDED, such that EF DSCP is mapped to UP 6, thereby admitting
   it into the Voice Access Category (AC_VO).

   Similarly, the VOICE-ADMIT DSCP (44 decimal / 101100 binary)
   described in [RFC5865] is RECOMMENDED to be mapped to UP 6, thereby
   admitting it also into the Voice Access Category (AC_VO).

4.2.2.  Signaling

   The Signaling service class is recommended for delay-sensitive
   client-server (e.g., traditional telephony) and peer-to-peer
   application signaling.  Telephony signaling includes signaling
   between 1) IP phone and soft-switch, 2) soft-client and soft-switch,
   and 3) media gateway and soft-switch as well as peer-to-peer using
   various protocols.  This service class is intended to be used for
   control of sessions and applications.  [RFC4594], Section 4.2,
   recommends that Signaling traffic be marked CS5 DSCP.

   While Signaling is recommended to receive a superior level of service
   relative to the default class (i.e., AC_BE), it does not require the
   highest level of service (i.e., AC_VO).  This leaves only the Video
   Access Category (AC_VI), which it will map to by default (as
   described in Section 2.3).  Therefore, it is RECOMMENDED to map
   Signaling traffic marked CS5 DSCP to UP 5, thereby admitting it to
   the Video Access Category (AC_VI).

   Note: Signaling traffic is not control-plane traffic from the
   perspective of the network (but rather is data-plane traffic); as
   such, it does not merit provisioning in the Network Control service
   class (marked CS6 and mapped to UP 6).  However, Signaling traffic is
   control-plane traffic from the perspective of the voice/video
   telephony overlay-infrastructure.  As such, Signaling should be
   treated with preferential servicing versus other data-plane flows.
   This may be achieved in common WLAN deployments by mapping Signaling
   traffic marked CS5 to UP 5.  On APs supporting per-UP EDCAF queuing
   logic (as described in Section 2.2), this will result in preferential
   treatment for Signaling traffic versus other video flows in the same
   access category (AC_VI), which are marked to UP 4, as well as
   preferred treatment over flows in the Best Effort (AC_BE) and
   Background (AC_BK) Access Categories.



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4.2.3.  Multimedia Conferencing

   The Multimedia Conferencing service class is recommended for
   applications that require real-time service for rate-adaptive
   traffic.  [RFC4594], Section 4.3, recommends Multimedia Conferencing
   traffic be marked AF4x (that is, AF41, AF42, and AF43, according to
   the rules defined in [RFC2475]).

   The primary media type typically carried within the Multimedia
   Conferencing service class is video; as such, it is RECOMMENDED to
   map this class into the Video Access Category (AC_VI), which it does
   by default (as described in Section 2.3).  Specifically, it is
   RECOMMENDED to map AF41, AF42, and AF43 to UP 4, thereby admitting
   Multimedia Conferencing into the Video Access Category (AC_VI).

4.2.4.  Real-Time Interactive

   The Real-Time Interactive service class is recommended for
   applications that require low loss and jitter and very low delay for
   variable-rate inelastic traffic sources.  Such applications may
   include inelastic video-conferencing applications, but may also
   include gaming applications (as pointed out in [RFC4594], Sections
   2.1 through 2.3 and Section 4.4).  [RFC4594], Section 4.4, recommends
   Real-Time Interactive traffic be marked CS4 DSCP.

   The primary media type typically carried within the Real-Time
   Interactive service class is video; as such, it is RECOMMENDED to map
   this class into the Video Access Category (AC_VI), which it does by
   default (as described in Section 2.3).  Specifically, it is
   RECOMMENDED to map CS4 to UP 4, thereby admitting Real-Time
   Interactive traffic into the Video Access Category (AC_VI).

4.2.5.  Multimedia Streaming

   The Multimedia Streaming service class is recommended for
   applications that require near-real-time packet forwarding of
   variable-rate elastic traffic sources.  Typically, these flows are
   unidirectional.  [RFC4594], Section 4.5, recommends Multimedia
   Streaming traffic be marked AF3x (that is, AF31, AF32, and AF33,
   according to the rules defined in [RFC2475]).

   The primary media type typically carried within the Multimedia
   Streaming service class is video; as such, it is RECOMMENDED to map
   this class into the Video Access Category (AC_VI), which it will by
   default (as described in Section 2.3).  Specifically, it is
   RECOMMENDED to map AF31, AF32, and AF33 to UP 4, thereby admitting
   Multimedia Streaming into the Video Access Category (AC_VI).




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4.2.6.  Broadcast Video

   The Broadcast Video service class is recommended for applications
   that require near-real-time packet forwarding with very low packet
   loss of constant rate and variable-rate inelastic traffic sources.
   Typically these flows are unidirectional.  [RFC4594] Section 4.6
   recommends Broadcast Video traffic be marked CS3 DSCP.

   As directly implied by the name, the primary media type typically
   carried within the Broadcast Video service class is video; as such,
   it is RECOMMENDED to map this class into the Video Access Category
   (AC_VI); however, by default (as described in Section 2.3), this
   service class will map to UP 3 and, thus, the Best Effort Access
   Category (AC_BE).  Therefore, a non-default mapping is RECOMMENDED,
   such that CS4 maps to UP 4, thereby admitting Broadcast Video into
   the Video Access Category (AC_VI).

4.2.7.  Low-Latency Data

   The Low-Latency Data service class is recommended for elastic and
   time-sensitive data applications, often of a transactional nature,
   where a user is waiting for a response via the network in order to
   continue with a task at hand.  As such, these flows are considered
   foreground traffic, with delays or drops to such traffic directly
   impacting user productivity.  [RFC4594], Section 4.7, recommends
   Low-Latency Data be marked AF2x (that is, AF21, AF22, and AF23,
   according to the rules defined in [RFC2475]).

   By default (as described in Section 2.3), Low-Latency Data will map
   to UP 2 and, thus, to the Background Access Category (AC_BK), which
   is contrary to the intent expressed in [RFC4594].

   Mapping Low-Latency Data to UP 3 may allow targeted traffic to
   receive a superior level of service via per-UP transmit queues
   servicing the EDCAF hardware for the Best Effort Access Category
   (AC_BE), as described in Section 2.2.  Therefore it is RECOMMENDED to
   map Low-Latency Data traffic marked AF2x DSCP to UP 3, thereby
   admitting it to the Best Effort Access Category (AC_BE).

4.2.8.  High-Throughput Data

   The High-Throughput Data service class is recommended for elastic
   applications that require timely packet forwarding of variable-rate
   traffic sources and, more specifically, is configured to provide
   efficient, yet constrained (when necessary) throughput for TCP
   longer-lived flows.  These flows are typically not user interactive.
   According to [RFC4594], Section 4.8, it can be assumed that this
   class will consume any available bandwidth and that packets



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   traversing congested links may experience higher queuing delays or
   packet loss.  It is also assumed that this traffic is elastic and
   responds dynamically to packet loss.  [RFC4594], Section 4.8,
   recommends High-Throughput Data be marked AF1x (that is, AF11, AF12,
   and AF13, according to the rules defined in [RFC2475]).

   By default (as described in Section 2.3), High-Throughput Data will
   map to UP 1 and, thus, to the Background Access Category (AC_BK),
   which is contrary to the intent expressed in [RFC4594].

   Unfortunately, there really is no corresponding fit for the High-
   Throughput Data service class within the constrained 4 Access
   Category [IEEE.802.11-2016] model.  If the High-Throughput Data
   service class is assigned to the Best Effort Access Category (AC_BE),
   then it would contend with Low-Latency Data (while [RFC4594]
   recommends a distinction in servicing between these service classes)
   as well as with the default service class; alternatively, if it is
   assigned to the Background Access Category (AC_BK), then it would
   receive a less-then-best-effort service and contend with Low-Priority
   Data (as discussed in Section 4.2.10).

   As such, since there is no directly corresponding fit for the High-
   Throughout Data service class within the [IEEE.802.11-2016] model, it
   is generally RECOMMENDED to map High-Throughput Data to UP 0, thereby
   admitting it to the Best Effort Access Category (AC_BE).

4.2.9.  Standard

   The Standard service class is recommended for traffic that has not
   been classified into one of the other supported forwarding service
   classes in the Diffserv network domain.  This service class provides
   the Internet's "best-effort" forwarding behavior.  [RFC4594],
   Section 4.9, states that the "Standard service class MUST use the
   Default Forwarding (DF) PHB".

   The Standard service class loosely corresponds to the
   [IEEE.802.11-2016] Best Effort Access Category (AC_BE); therefore, it
   is RECOMMENDED to map Standard service class traffic marked DF DSCP
   to UP 0, thereby admitting it to the Best Effort Access Category
   (AC_BE).  This happens to correspond to the default mapping (as
   described in Section 2.3).










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4.2.10.  Low-Priority Data

   The Low-Priority Data service class serves applications that the user
   is willing to accept without service assurances.  This service class
   is specified in [RFC3662] and [LE-PHB].

   [RFC3662] and [RFC4594] both recommend Low-Priority Data be marked
   CS1 DSCP.

   Note: This marking recommendation may change in the future, as
   [LE-PHB] defines a Lower Effort (LE) PHB for Low-Priority Data
   traffic and recommends an additional DSCP for this traffic.

   The Low-Priority Data service class loosely corresponds to the
   [IEEE.802.11-2016] Background Access Category (AC_BK); therefore, it
   is RECOMMENDED to map Low-Priority Data traffic marked CS1 DSCP to UP
   1, thereby admitting it to the Background Access Category (AC_BK).
   This happens to correspond to the default mapping (as described in
   Section 2.3).

4.3.  Summary of Recommendations for DSCP-to-UP Mapping

   Figure 1 summarizes the [RFC4594] DSCP marking recommendations mapped
   to [IEEE.802.11-2016] UP and Access Categories applied in the
   downstream direction (i.e., from wired-to-wireless networks).

  +-------------------------------------------------------------------+
  | IETF Diffserv | PHB  |Reference |         IEEE 802.11              |
  | Service Class |      |   RFC    |User Priority|  Access Category   |
  |===============+======+==========+=============+====================|
  |               |      |          |     7       |    AC_VO (Voice)   |
  |Network Control| CS7  | RFC 2474 |            OR                    |
  |(reserved for  |      |          |     0       | AC_BE (Best Effort)|
  | future use)   |      |          |See Security Considerations-Sec.8 |
  +---------------+------+----------+-------------+--------------------+
  |               |      |          |     7       |    AC_VO (Voice)   |
  |Network Control| CS6  | RFC 2474 |            OR                    |
  |               |      |          |     0       | AC_BE (Best Effort)|
  |               |      |          |    See Security Considerations   |
  +---------------+------+----------+-------------+--------------------+
  |   Telephony   |  EF  | RFC 3246 |     6       |    AC_VO (Voice)   |
  +---------------+------+----------+-------------+--------------------+
  |  VOICE-ADMIT  |  VA  | RFC 5865 |     6       |    AC_VO (Voice)   |
  |               |      |          |             |                    |
  +---------------+------+----------+-------------+--------------------+
  |   Signaling   | CS5  | RFC 2474 |     5       |    AC_VI (Video)   |





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  +---------------+------+----------+-------------+--------------------+
  |   Multimedia  | AF41 |          |             |                    |
  | Conferencing  | AF42 | RFC 2597 |     4       |    AC_VI (Video)   |
  |               | AF43 |          |             |                    |
  +---------------+------+----------+-------------+--------------------+
  |   Real-Time   | CS4  | RFC 2474 |     4       |    AC_VI (Video)   |
  |  Interactive  |      |          |             |                    |
  +---------------+------+----------+-------------+--------------------+
  |  Multimedia   | AF31 |          |             |                    |
  |  Streaming    | AF32 | RFC 2597 |     4       |    AC_VI (Video)   |
  |               | AF33 |          |             |                    |
  +---------------+------+----------+-------------+--------------------+
  |Broadcast Video| CS3  | RFC 2474 |     4       |    AC_VI (Video)   |
  +---------------+------+----------+-------------+--------------------+
  |    Low-       | AF21 |          |             |                    |
  |    Latency    | AF22 | RFC 2597 |     3       | AC_BE (Best Effort)|
  |    Data       | AF23 |          |             |                    |
  +---------------+------+----------+-------------+--------------------+
  |     OAM       | CS2  | RFC 2474 |     0       | AC_BE (Best Effort)|
  +---------------+------+----------+-------------+--------------------+
  |    High-      | AF11 |          |             |                    |
  |  Throughput   | AF12 | RFC 2597 |     0       | AC_BE (Best Effort)|
  |    Data       | AF13 |          |             |                    |
  +---------------+------+----------+-------------+--------------------+
  |   Standard    | DF   | RFC 2474 |     0       | AC_BE (Best Effort)|
  +---------------+------+----------+-------------+--------------------+
  | Low-Priority  | CS1  | RFC 3662 |     1       | AC_BK (Background) |
  |     Data      |      |          |             |                    |
  +--------------------------------------------------------------------+

  Note: All unused codepoints are RECOMMENDED to be mapped to UP 0
  (See Security Considerations below)

       Figure 1: Summary of Mapping Recommendations from Downstream
                       DSCP to IEEE 802.11 UP and AC

5.  Recommendations for Upstream Mapping and Marking

   In the upstream direction (i.e., wireless-to-wired), there are three
   types of mapping that may be implemented:

   o  DSCP-to-UP mapping within the wireless client operating system,
      and

   o  UP-to-DSCP mapping at the wireless AP, or

   o  DSCP-Passthrough at the wireless AP (effectively a 1:1 DSCP-to-
      DSCP mapping)



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   As an alternative to the latter two options, the network
   administrator MAY choose to use the wireless-to-wired edge as a
   Diffserv boundary and explicitly set (or reset) DSCP markings
   according to administrative policy, thus making the wireless edge a
   Diffserv policy enforcement point; this approach is RECOMMENDED
   whenever the APs support the required classification and marking
   capabilities.

   Each of these options will now be considered.

5.1.  Upstream DSCP-to-UP Mapping within the Wireless Client Operating
      System

   Some operating systems on wireless client devices utilize a similar
   default DSCP-to-UP mapping scheme as that described in Section 2.3.
   As such, this can lead to the same conflicts as described in that
   section, but in the upstream direction.

   Therefore, to improve on these default mappings, and to achieve
   parity and consistency with downstream QoS, it is RECOMMENDED that
   wireless client operating systems instead utilize the same DSCP-to-UP
   mapping recommendations presented in Section 4.  Note that it is
   explicitly stated that packets requesting a marking of CS6 or CS7
   DSCP SHOULD be mapped to UP 0 (and not to UP 7).  Furthermore, in
   such cases, the wireless client operating system SHOULD re-mark such
   packets to DSCP 0.  This is because CS6 and CS7 DSCP, as well as UP 7
   markings, are intended for network control protocols, and these
   SHOULD NOT be sourced from wireless client endpoint devices.  This
   recommendation is detailed in the Security Considerations section
   (Section 8).

5.2.  Upstream UP-to-DSCP Mapping at the Wireless AP

   UP-to-DSCP mapping generates a DSCP value for the IP packet (either
   an unencapsulated IP packet or an IP packet encapsulated within a
   tunneling protocol such as Control and Provisioning of Wireless
   Access Points (CAPWAP) -- and destined towards a wireless LAN
   controller for decapsulation and forwarding) from the Layer 2
   [IEEE.802.11-2016] UP marking.  This is typically done in the manner
   described in Section 2.4.

   It should be noted that any explicit re-marking policy to be
   performed on such a packet generally takes place at the nearest
   classification and marking policy enforcement point, which may be:

   o  At the wireless AP, and/or





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   o  At the wired network switch port, and/or

   o  At the wireless LAN controller

   Note: Multiple classification and marking policy enforcement points
   may exist, as some devices have the capability to re-mark at only
   Layer 2 or Layer 3, while other devices can re-mark at either/both
   layers.

   As such, UP-to-DSCP mapping allows for wireless L2 markings to affect
   the QoS treatment of a packet over the wired IP network (that is,
   until the packet reaches the nearest classification and marking
   policy enforcement point).

   It should be further noted that nowhere in the [IEEE.802.11-2016]
   specification is there an intent expressed for UP markings to be used
   to influence QoS treatment over wired IP networks.  Furthermore,
   [RFC2474], [RFC2475], and [RFC8100] all allow for the host to set
   DSCP markings for end-to-end QoS treatment over IP networks.
   Therefore, wireless APs MUST NOT leverage Layer 2 [IEEE.802.11-2016]
   UP markings as set by wireless hosts and subsequently perform a
   UP-to-DSCP mapping in the upstream direction.  But rather, if
   wireless host markings are to be leveraged (as per business
   requirements, technical constraints, and administrative policies),
   then it is RECOMMENDED to pass through the Layer 3 DSCP markings set
   by these wireless hosts instead, as is discussed in the next section.

5.3.  Upstream DSCP-Passthrough at the Wireless AP

   It is generally NOT RECOMMENDED to pass through DSCP markings from
   unauthenticated and unauthorized devices, as these are typically
   considered untrusted sources.

   When business requirements and/or technical constraints and/or
   administrative policies require QoS markings to be passed through at
   the wireless edge, then it is RECOMMENDED to pass through Layer 3
   DSCP markings (over Layer 2 [IEEE.802.11-2016] UP markings) in the
   upstream direction, with the exception of CS6 and CS7 (as will be
   discussed further), for the following reasons:

   o  [RFC2474], [RFC2475], and [RFC8100] all allow for hosts to set
      DSCP markings to achieve an end-to-end differentiated service

   o  [IEEE.802.11-2016] does not specify that UP markings are to be
      used to affect QoS treatment over wired IP networks






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   o  Most present wireless device operating systems generate UP values
      by the same method as described in Section 2.3 (i.e., by using the
      3 MSBs of the encapsulated 6-bit DSCP); then, at the AP, these
      3-bit markings are converted back into DSCP values, typically in
      the default manner described in Section 2.4; as such, information
      is lost in the translation from a 6-bit marking to a 3-bit marking
      (which is then subsequently translated back to a 6-bit marking);
      passing through the original (encapsulated) DSCP marking prevents
      such loss of information

   o  A practical implementation benefit is also realized by passing
      through the DSCP set by wireless client devices, as enabling
      applications to mark DSCP is much more prevalent and accessible to
      programmers of applications running on wireless device platforms,
      vis-a-vis trying to explicitly set UP values, which requires
      special hooks into the wireless device operating system and/or
      hardware device drivers, many of which do not support such
      functionality

   CS6 and CS7 are exceptions to this passthrough recommendation because
   wireless hosts SHOULD NOT use them (see Section 5.1) and traffic with
   those two markings poses a threat to operation of the wired network
   (see Section 8.2).  CS6 and CS7 SHOULD NOT be passed through to the
   wired network in the upstream direction unless the AP has been
   specifically configured to do that by a network administrator or
   operator.

5.4.  Upstream DSCP Marking at the Wireless AP

   An alternative option to mapping is for the administrator to treat
   the wireless edge as the edge of the Diffserv domain and explicitly
   set (or reset) DSCP markings in the upstream direction according to
   administrative policy.  This option is RECOMMENDED over mapping, as
   this typically is the most secure solution because the network
   administrator directly enforces the Diffserv policy across the IP
   network (versus an application developer and/or the developer of the
   operating system of the wireless endpoint device, who may be
   functioning completely independently of the network administrator).

6.  Overview of IEEE 802.11 QoS

   QoS is enabled on wireless networks by means of the Hybrid
   Coordination Function (HCF).  To give better context to the
   enhancements in HCF that enable QoS, it may be helpful to begin with
   a review of the original Distributed Coordination Function (DCF).






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6.1.  Distributed Coordination Function (DCF)

   As has been noted, the Wi-Fi medium is a shared medium, with each
   station -- including the wireless AP -- contending for the medium on
   equal terms.  As such, it shares the same challenge as any other
   shared medium in requiring a mechanism to prevent (or avoid)
   collisions, which can occur when two (or more) stations attempt
   simultaneous transmission.

   The IEEE Ethernet Working Group solved this challenge by implementing
   a Carrier Sense Multiple Access/Collision Detection (CSMA/CD)
   mechanism that could detect collisions over the shared physical cable
   (as collisions could be detected as reflected energy pulses over the
   physical wire).  Once a collision was detected, then a predefined set
   of rules was invoked that required stations to back off and wait
   random periods of time before reattempting transmission.  While CSMA/
   CD improved the usage of Ethernet as a shared medium, it should be
   noted the ultimate solution to solving Ethernet collisions was the
   advance of switching technologies, which treated each Ethernet cable
   as a dedicated collision domain.

   However, unlike Ethernet (which uses physical cables), collisions
   cannot be directly detected over the wireless medium, as RF energy is
   radiated over the air and colliding bursts are not necessarily
   reflected back to the transmitting stations.  Therefore, a different
   mechanism is required for this medium.

   As such, the IEEE modified the CSMA/CD mechanism to adapt it to
   wireless networks to provide Carrier Sense Multiple Access/Collision
   Avoidance (CSMA/CA).  The original CSMA/CA mechanism used in IEEE
   802.11 was the Distributed Coordination Function.  DCF is a timer-
   based system that leverages three key sets of timers, the slot time,
   interframe spaces and CWs.

6.1.1.  Slot Time

   The slot time is the basic unit of time measure for both DCF and HCF,
   on which all other timers are based.  The slot-time duration varies
   with the different generations of data rates and performances
   described by [IEEE.802.11-2016].  For example, [IEEE.802.11-2016]
   specifies the slot time to be 20 microseconds ([IEEE.802.11-2016],
   Table 15-5) for legacy implementations (such as IEEE 802.11b,
   supporting 1, 2, 5.5, and 11 Mbps data rates), while newer
   implementations (including IEEE 802.11g, 802.11a, 802.11n, and
   802.11ac, supporting data rates from 6.5 Mbps to over 2 Gbps per
   spatial stream) define a shorter slot time of 9 microseconds
   ([IEEE.802.11-2016], Section 17.4.4, Table 17-21).




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6.1.2.  Interframe Space (IFS)

   The time interval between frames that are transmitted over the air is
   called the Interframe Space (IFS).  Several IFSs are defined in
   [IEEE.802.11-2016], with the most relevant to DCF being the Short
   Interframe Space (SIFS), the DCF Interframe Space (DIFS), and the
   Extended Interframe Space (EIFS).

   The SIFS is the amount of time in microseconds required for a
   wireless interface to process a received RF signal and its associated
   frame (as specified in [IEEE.802.11-2016]) and to generate a response
   frame.  Like slot times, the SIFS can vary according to the
   performance implementation of [IEEE.802.11-2016].  The SIFS for IEEE
   802.11a, 802.11n, and 802.11ac (in 5 GHz) is 16 microseconds
   ([IEEE.802.11-2016], Section 17.4.4, Table 17-21).

   Additionally, a station must sense the status of the wireless medium
   before transmitting.  If it finds that the medium is continuously
   idle for the duration of a DIFS, then it is permitted to attempt
   transmission of a frame (after waiting an additional random backoff
   period, as will be discussed in the next section).  If the channel is
   found busy during the DIFS interval, the station must defer its
   transmission until the medium is found to be idle for the duration of
   a DIFS interval.  The DIFS is calculated as:

      DIFS = SIFS + (2 * Slot time)

   However, if all stations waited only a fixed amount of time before
   attempting transmission, then collisions would be frequent.  To
   offset this, each station must wait, not only a fixed amount of time
   (the DIFS), but also a random amount of time (the random backoff)
   prior to transmission.  The range of the generated random backoff
   timer is bounded by the CW.

6.1.3.  Contention Window (CW)

   Contention windows bound the range of the generated random backoff
   timer that each station must wait (in addition to the DIFS) before
   attempting transmission.  The initial range is set between 0 and the
   CW minimum value (CWmin), inclusive.  The CWmin for DCF (in 5 GHz) is
   specified as 15 slot times ([IEEE.802.11-2016], Section 17.4.4,
   Table 17-21).

   However, it is possible that two (or more) stations happen to pick
   the exact same random value within this range.  If this happens, then
   a collision may occur.  At this point, the stations effectively begin
   the process again, waiting a DIFS and generate a new random backoff
   value.  However, a key difference is that for this subsequent



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   attempt, the CW approximately doubles in size (thus, exponentially
   increasing the range of the random value).  This process repeats as
   often as necessary if collisions continue to occur, until the maximum
   CW size (CWmax) is reached.  The CWmax for DCF is specified as 1023
   slot times ([IEEE.802.11-2016], Section 17.4.4, Table 17-21).

   At this point, transmission attempts may still continue (until some
   other predefined limit is reached), but the CW sizes are fixed at the
   CWmax value.

   Incidentally it may be observed that a significant amount of jitter
   can be introduced by this contention process for wireless
   transmission access.  For example, the incremental transmission delay
   of 1023 slot times (CWmax) using 9-microsecond slot times may be as
   high as 9 ms of jitter per attempt.  And, as previously noted,
   multiple attempts can be made at CWmax.

6.2.  Hybrid Coordination Function (HCF)

   Therefore, as can be seen from the preceding description of DCF,
   there is no preferential treatment of one station over another when
   contending for the shared wireless media; nor is there any
   preferential treatment of one type of traffic over another during the
   same contention process.  To support the latter requirement, the IEEE
   enhanced DCF in 2005 to support QoS, specifying HCF in IEEE 802.11,
   which was integrated into the main IEEE 802.11 standard in 2007.

6.2.1.  User Priority (UP)

   One of the key changes to the frame format in [IEEE.802.11-2016] is
   the inclusion of a QoS Control field, with 3 bits dedicated for QoS
   markings.  These bits are referred to the User Priority (UP) bits and
   these support eight distinct marking values: 0-7, inclusive.

   While such markings allow for frame differentiation, these alone do
   not directly affect over-the-air treatment.  Rather, it is the
   non-configurable and standard-specified mapping of UP markings to the
   Access Categories (ACs) from [IEEE.802.11-2016] that generate
   differentiated treatment over wireless media.












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6.2.2.  Access Category (AC)

   Pairs of UP values are mapped to four defined access categories that
   correspondingly specify different treatments of frames over the air.
   These access categories (in order of relative priority from the top
   down) and their corresponding UP mappings are shown in Figure 2
   (adapted from [IEEE.802.11-2016], Section 10.2.4.2, Table 10-1).

                +-----------------------------------------+
                |   User    |   Access   | Designative    |
                | Priority  |  Category  | (informative)  |
                |===========+============+================|
                |     7     |    AC_VO   |     Voice      |
                +-----------+------------+----------------+
                |     6     |    AC_VO   |     Voice      |
                +-----------+------------+----------------+
                |     5     |    AC_VI   |     Video      |
                +-----------+------------+----------------+
                |     4     |    AC_VI   |     Video      |
                +-----------+------------+----------------+
                |     3     |    AC_BE   |   Best Effort  |
                +-----------+------------+----------------+
                |     0     |    AC_BE   |   Best Effort  |
                +-----------+------------+----------------+
                |     2     |    AC_BK   |   Background   |
                +-----------+------------+----------------+
                |     1     |    AC_BK   |   Background   |
                +-----------------------------------------+

                  Figure 2: Mappings between IEEE 802.11
                    Access Categories and User Priority

   The manner in which these four access categories achieve
   differentiated service over-the-air is primarily by tuning the fixed
   and random timers that stations have to wait before sending their
   respective types of traffic, as will be discussed next.















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6.2.3.  Arbitration Interframe Space (AIFS)

   As previously mentioned, each station must wait a fixed amount of
   time to ensure the medium is idle before attempting transmission.
   With DCF, the DIFS is constant for all types of traffic.  However,
   with [IEEE.802.11-2016], the fixed amount of time that a station has
   to wait will depend on the access category and is referred to as an
   Arbitration Interframe Space (AIFS).  AIFSs are defined in slot times
   and the AIFSs per access category are shown in Figure 3 (adapted from
   [IEEE.802.11-2016], Section 9.4.2.29, Table 9-137).

               +-------------------------------------------+
               |   Access   | Designative     |   AIFS     |
               |  Category  | (informative)   |(slot times)|
               |============+=================+============|
               |   AC_VO    |     Voice       |     2      |
               +------------+-----------------+------------+
               |   AC_VI    |     Video       |     2      |
               +------------+-----------------+------------+
               |   AC_BE    |   Best Effort   |     3      |
               +------------+-----------------+------------+
               |   AC_BK    |   Background    |     7      |
               +------------+-----------------+------------+

        Figure 3: Arbitration Interframe Spaces by Access Category

6.2.4.  Access Category CWs

   Not only is the fixed amount of time that a station has to wait
   skewed according to its [IEEE.802.11-2016] access category, but so
   are the relative sizes of the CWs that bound the random backoff
   timers, as shown in Figure 4 (adapted from [IEEE.802.11-2016],
   Section 9.4.2.29, Table 9-137).

         +-------------------------------------------------------+
         |   Access  |  Designative    |   CWmin    |   CWmax    |
         |  Category |  (informative)  |(slot times)|(slot times)|
         |===========+=================+============|============|
         |   AC_VO   |     Voice       |     3      |     7      |
         +-----------+-----------------+------------+------------+
         |   AC_VI   |     Video       |     7      |     15     |
         +-----------+-----------------+------------+------------+
         |   AC_BE   |   Best Effort   |     15     |    1023    |
         +-----------+-----------------+------------+------------+
         |   AC_BK   |   Background    |     15     |    1023    |
         +-----------+-----------------+------------+------------+

                   Figure 4: CW Sizes by Access Category



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   When the fixed and randomly generated timers are added together on a
   per-access-category basis, then traffic assigned to the Voice Access
   Category (i.e., traffic marked to UP 6 or 7) will receive a
   statistically superior service relative to traffic assigned to the
   Video Access Category (i.e., traffic marked UP 5 and 4), which, in
   turn, will receive a statistically superior service relative to
   traffic assigned to the Best Effort Access Category traffic (i.e.,
   traffic marked UP 3 and 0), which finally will receive a
   statistically superior service relative to traffic assigned to the
   Background Access Category traffic (i.e., traffic marked to UP 2 and
   1).

6.3.  IEEE 802.11u QoS Map Set

   IEEE 802.11u [IEEE.802-11u-2011] is an addendum that has now been
   included within the main standard ([IEEE.802.11-2016]), and which
   includes, among other enhancements, a mechanism by which wireless APs
   can communicate DSCP to/from UP mappings that have been configured on
   the wired IP network.  Specifically, a QoS Map Set information
   element (described in [IEEE.802.11-2016], Section 9.4.2.95, and
   commonly referred to as the "QoS Map element") is transmitted from an
   AP to a wireless endpoint device in an association / re-association
   Response frame (or within a special QoS Map Configure frame).

   The purpose of the QoS Map element is to provide the mapping of
   higher-layer QoS constructs (i.e., DSCP) to User Priorities.  One
   intended effect of receiving such a map is for the wireless endpoint
   device (that supports this function and is administratively
   configured to enable it) to perform corresponding DSCP-to-UP mapping
   within the device (i.e., between applications and the operating
   system / wireless network interface hardware drivers) to align with
   what the APs are mapping in the downstream direction, so as to
   achieve consistent end-to-end QoS in both directions.

   The QoS Map element includes two key components:

   1)  each of the eight UP values (0-7) is associated with a range of
       DSCP values, and

   2)  (up to 21) exceptions from these range-based DSCP to/from UP
       mapping associations may be optionally and explicitly specified.










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   In line with the recommendations put forward in this document, the
   following recommendations apply when the QoS Map element is enabled:

   1)  each of the eight UP values (0-7) are RECOMMENDED to be mapped to
       DSCP 0 (as a baseline, so as to meet the recommendation made in
       Section 8.2, and

   2)  (up to 21) exceptions from this baseline mapping are RECOMMENDED
       to be made in line with Section 4.3, to correspond to the
       Diffserv Codepoints that are in use over the IP network.

   It is important to note that the QoS Map element is intended to be
   transmitted from a wireless AP to a non-AP station.  As such, the
   model where this element is used is that of a network where the AP is
   the edge of the Diffserv domain.  Networks where the AP extends the
   Diffserv domain by connecting other APs and infrastructure devices
   through the IEEE 802.11 medium are not included in the cases covered
   by the presence of the QoS Map element, and therefore are not
   included in the present recommendation.

7.  IANA Considerations

   This document has no IANA actions.

8.  Security Considerations

   The recommendations in this document concern widely deployed wired
   and wireless network functionality, and, for that reason, do not
   present additional security concerns that do not already exist in
   these networks.  In fact, several of the recommendations made in this
   document serve to protect wired and wireless networks from potential
   abuse, as is discussed further in this section.

8.1.  Security Recommendations for General QoS

   It may be possible for a wired or wireless device (which could be
   either a host or a network device) to mark packets (or map packet
   markings) in a manner that interferes with or degrades existing QoS
   policies.  Such marking or mapping may be done intentionally or
   unintentionally by developers and/or users and/or administrators of
   such devices.

   To illustrate: A gaming application designed to run on a smartphone
   or tablet may request that all its packets be marked DSCP EF and/or
   UP 6.  However, if the traffic from such an application is forwarded
   without change over a business network, then this could interfere
   with QoS policies intended to provide priority services for business
   voice applications.



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   To mitigate such scenarios, it is RECOMMENDED to implement general
   QoS security measures, including:

   o  Setting a traffic conditioning policy reflective of business
      objectives and policy, such that traffic from authorized users
      and/or applications and/or endpoints will be accepted by the
      network; otherwise, packet markings will be "bleached" (i.e.,
      re-marked to DSCP DF and/or UP 0).  Additionally, Section 5.3 made
      it clear that it is generally NOT RECOMMENDED to pass through DSCP
      markings from unauthorized and/or unauthenticated devices, as
      these are typically considered untrusted sources.  This is
      especially relevant for Internet of Things (IoT) deployments,
      where tens of billions of devices are being connected to IP
      networks with little or no security capabilities, leaving them
      vulnerable to be utilized as agents for DDoS attacks.  These
      attacks can be amplified with preferential QoS treatments, should
      the packet markings of such devices be trusted.

   o  Policing EF marked packet flows, as detailed in [RFC2474],
      Section 7, and [RFC3246], Section 3.

   In addition to these general QoS security recommendations, WLAN-
   specific QoS security recommendations can serve to further mitigate
   attacks and potential network abuse.

8.2.  Security Recommendations for WLAN QoS

   The wireless LAN presents a unique DoS attack vector, as endpoint
   devices contend for the shared media on a completely egalitarian
   basis with the network (as represented by the AP).  This means that
   any wireless client could potentially monopolize the air by sending
   packets marked to preferred UP values (i.e., UP values 4-7) in the
   upstream direction.  Similarly, airtime could be monopolized if
   excessive amounts of downstream traffic were marked/mapped to these
   same preferred UP values.  As such, the ability to mark/map to these
   preferred UP values (of UP 4-7) should be controlled.

   If such marking/mapping were not controlled, then, for example, a
   malicious user could cause WLAN DoS by flooding traffic marked CS7
   DSCP downstream.  This codepoint would map by default (as described
   in Section 2.3) to UP 7 and would be assigned to the Voice Access
   Category (AC_VO).  Such a flood could cause Denial-of-Service to not
   only wireless voice applications, but also to all other traffic
   classes.  Similarly, an uninformed application developer may request
   all traffic from his/her application be marked CS7 or CS6, thinking
   this would achieve the best overall servicing of their application
   traffic, while not realizing that such a marking (if honored by the
   client operating system) could cause not only WLAN DoS, but also IP



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   network instability, as the traffic marked CS7 or CS6 finds its way
   into queues intended for servicing (relatively low-bandwidth) network
   control protocols, potentially starving legitimate network control
   protocols in the process.

   Therefore, to mitigate such an attack, it is RECOMMENDED that all
   packets marked to Diffserv Codepoints not authorized or explicitly
   provisioned for use over the wireless network by the network
   administrator be mapped to UP 0; this recommendation applies both at
   the AP (in the downstream direction) and within the operating system
   of the wireless endpoint device (in the upstream direction).

   Such a policy of mapping unused codepoints to UP 0 would also prevent
   an attack where non-standard codepoints were used to cause WLAN DoS.
   Consider the case where codepoints are mapped to UP values using a
   range function (e.g., DSCP values 48-55 all map to UP 6), then an
   attacker could flood packets marked, for example, to DSCP 49, in
   either the upstream or downstream direction over the WLAN, causing
   DoS to all other traffic classes in the process.

   In the majority of WLAN deployments, the AP represents not only the
   edge of the Diffserv domain, but also the edge of the network
   infrastructure itself; that is, only wireless client endpoint devices
   are downstream from the AP.  In such a deployment model, CS6 and CS7
   also fall into the category of codepoints that are not in use over
   the wireless LAN (since only wireless client endpoint devices are
   downstream from the AP in this model and these devices do not
   (legitimately) participate in network control protocol exchanges).
   As such, it is RECOMMENDED that CS6 and CS7 DSCP be mapped to UP 0 in
   these Wi-Fi-at-the-edge deployment models.  Otherwise, it would be
   easy for a malicious application developer, or even an inadvertently
   poorly programmed IoT device, to cause WLAN DoS and even wired IP
   network instability by flooding traffic marked CS6 DSCP, which would,
   by default (as described in Section 2.3), be mapped to UP 6, causing
   all other traffic classes on the WLAN to be starved, as well as
   hijacking queues on the wired IP network that are intended for the
   servicing of routing protocols.  To this point, it was also
   recommended in Section 5.1 that packets requesting a marking of CS6
   or CS7 DSCP SHOULD be re-marked to DSCP 0 and mapped to UP 0 by the
   wireless client operating system.

   Finally, it should be noted that the recommendations put forward in
   this document are not intended to address all attack vectors
   leveraging QoS marking abuse.  Mechanisms that may further help
   mitigate security risks of both wired and wireless networks deploying
   QoS include strong device- and/or user-authentication, access-
   control, rate-limiting, control-plane policing, encryption, and other
   techniques; however, the implementation recommendations for such



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   mechanisms are beyond the scope of this document to address in
   detail.  Suffice it to say that the security of the devices and
   networks implementing QoS, including QoS mapping between wired and
   wireless networks, merits consideration in actual deployments.

9.  References

9.1.  Normative References

   [IEEE.802.11-2016]
              IEEE, "IEEE Standard for Information technology -
              Telecommunications and information exchange between
              systems - Local and metropolitan area networks - Specific
              requirements - Part 11: Wireless LAN Medium Access Control
              (MAC) and Physical Layer (PHY) Specifications",
              IEEE 802.11, DOI 10.1109/IEEESTD.2016.7786995, December
              2016, <https://standards.ieee.org/findstds/
              standard/802.11-2016.html>.

   [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>.

   [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>.

   [RFC2597]  Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski,
              "Assured Forwarding PHB Group", RFC 2597,
              DOI 10.17487/RFC2597, June 1999,
              <https://www.rfc-editor.org/info/rfc2597>.

   [RFC3168]  Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
              of Explicit Congestion Notification (ECN) to IP",
              RFC 3168, DOI 10.17487/RFC3168, September 2001,
              <https://www.rfc-editor.org/info/rfc3168>.

   [RFC3246]  Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec,
              J., Courtney, W., Davari, S., Firoiu, V., and D.
              Stiliadis, "An Expedited Forwarding PHB (Per-Hop
              Behavior)", RFC 3246, DOI 10.17487/RFC3246, March 2002,
              <https://www.rfc-editor.org/info/rfc3246>.






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   [RFC3662]  Bless, R., Nichols, K., and K. Wehrle, "A Lower Effort
              Per-Domain Behavior (PDB) for Differentiated Services",
              RFC 3662, DOI 10.17487/RFC3662, December 2003,
              <https://www.rfc-editor.org/info/rfc3662>.

   [RFC4594]  Babiarz, J., Chan, K., and F. Baker, "Configuration
              Guidelines for DiffServ Service Classes", RFC 4594,
              DOI 10.17487/RFC4594, August 2006,
              <https://www.rfc-editor.org/info/rfc4594>.

   [RFC5865]  Baker, F., Polk, J., and M. Dolly, "A Differentiated
              Services Code Point (DSCP) for Capacity-Admitted Traffic",
              RFC 5865, DOI 10.17487/RFC5865, May 2010,
              <https://www.rfc-editor.org/info/rfc5865>.

   [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>.

9.2.  Informative References

   [GSMA-IPX_Guidelines]
              GSM Association, "Guidelines for IPX Provider networks
              (Previously Inter-Service Provider IP Backbone Guidelines)
              Version 11.0", Official Document IR.34, November 2014,
              <https://www.gsma.com/newsroom/wp-content/uploads/
              IR.34-v11.0.pdf>.

   [IEEE.802-11u-2011]
              IEEE, "IEEE Standard for Information technology -
              Telecommunications and information exchange between
              systems - Local and metropolitan area networks - Specific
              requirements - Part 11: Wireless LAN Medium Access Control
              (MAC) and Physical Layer (PHY) specifications: Amendment
              9: Interworking with External Networks", IEEE 802.11,
              DO 10.1109/IEEESTD.2011.5721908, February 2011,
              <http://standards.ieee.org/getieee802/
              download/802.11u-2011.pdf>.

   [LE-PHB]   Bless, R., "A Lower Effort Per-Hop Behavior (LE PHB)",
              Work in Progress, draft-ietf-tsvwg-le-phb-02, June 2017.

   [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>.





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   [RFC5127]  Chan, K., Babiarz, J., and F. Baker, "Aggregation of
              Diffserv Service Classes", RFC 5127, DOI 10.17487/RFC5127,
              February 2008, <https://www.rfc-editor.org/info/rfc5127>.

   [RFC7561]  Kaippallimalil, J., Pazhyannur, R., and P. Yegani,
              "Mapping Quality of Service (QoS) Procedures of Proxy
              Mobile IPv6 (PMIPv6) and WLAN", RFC 7561,
              DOI 10.17487/RFC7561, June 2015,
              <https://www.rfc-editor.org/info/rfc7561>.

   [RFC8100]  Geib, R., Ed. and D. Black, "Diffserv-Interconnection
              Classes and Practice", RFC 8100, DOI 10.17487/RFC8100,
              March 2017, <https://www.rfc-editor.org/info/rfc8100>.






































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Acknowledgements

   The authors wish to thank David Black, Gorry Fairhurst, Ruediger
   Geib, Vincent Roca, Brian Carpenter, David Blake, Cullen Jennings,
   David Benham, and the TSVWG.

   The authors also acknowledge a great many inputs, notably from David
   Kloper, Mark Montanez, Glen Lavers, Michael Fingleton, Sarav
   Radhakrishnan, Karthik Dakshinamoorthy, Simone Arena, Ranga Marathe,
   Ramachandra Murthy, and many others.

Authors' Addresses

   Tim Szigeti
   Cisco Systems
   Vancouver, British Columbia  V6K 3L4
   Canada

   Email: szigeti@cisco.com


   Jerome Henry
   Cisco Systems
   Research Triangle Park, North Carolina  27709
   United States of America

   Email: jerhenry@cisco.com


   Fred Baker
   Santa Barbara, California  93117
   United States of America

   Email: FredBaker.IETF@gmail.com

















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