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Versions: (draft-szigeti-tsvwg-ieee-802-11) 00 01 02 03 04 05 06 07 08 09 10 11 RFC 8325

Transport Working Group                                       T. Szigeti
Internet-Draft                                             Cisco Systems
Intended status: Standards Track                                F. Baker
Expires: May 19, 2017                                  November 15, 2016


                    DiffServ to IEEE 802.11 Mapping
                    draft-ietf-tsvwg-ieee-802-11-01

Abstract

   As internet traffic is increasingly sourced-from and destined-to
   wireless endpoints, it is crucial that Quality of Service be aligned
   between wired and wireless networks; however, this is not always the
   case by default.  This is due to the fact that two independent
   standards bodies provide QoS guidance on wired and wireless networks:
   specifically, the IETF specifies standards and design recommendations
   for wired IP networks, while a separate and autonomous standards-
   body, the IEEE, administers the standards for wireless 802.11
   networks.  The purpose of this document is to propose a set
   Differentiated Services Code Point (DSCP) to IEEE 802.11 User
   Priority (UP) mappings to reconcile the marking recommendations
   offered by these two standards bodies, and, as such, to optimize
   wired-and-wireless interconnect QoS.

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 19, 2017.

Copyright Notice

   Copyright (c) 2016 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
   (http://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.

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
   2.  Comparison and Default Interoperation of DiffServ and IEEE
       802.11  . . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     2.1.  Default DSCP-to-UP Mappings and Conflicts . . . . . . . .   6
     2.2.  Default UP-to-DSCP Mappings and Conflicts . . . . . . . .   7
   3.  Wireless Device Marking and Mapping Capability
       Recommendations . . . . . . . . . . . . . . . . . . . . . . .   8
   4.  DSCP-to-UP Mapping Recommendations  . . . . . . . . . . . . .   9
     4.1.  Network Control Traffic . . . . . . . . . . . . . . . . .   9
       4.1.1.  Network Control Protocols . . . . . . . . . . . . . .   9
       4.1.2.  Operations Administration Management (OAM)  . . . . .  10
     4.2.  User Traffic  . . . . . . . . . . . . . . . . . . . . . .  10
       4.2.1.  Telephony . . . . . . . . . . . . . . . . . . . . . .  11
       4.2.2.  Signaling . . . . . . . . . . . . . . . . . . . . . .  11
       4.2.3.  Multimedia Conferencing . . . . . . . . . . . . . . .  12
       4.2.4.  Real-Time Interactive . . . . . . . . . . . . . . . .  12
       4.2.5.  Multimedia-Streaming  . . . . . . . . . . . . . . . .  13
       4.2.6.  Broadcast Video . . . . . . . . . . . . . . . . . . .  13
       4.2.7.  Low-Latency Data  . . . . . . . . . . . . . . . . . .  13
       4.2.8.  High-Throughput Data  . . . . . . . . . . . . . . . .  14
       4.2.9.  Standard Service Class  . . . . . . . . . . . . . . .  14
       4.2.10. Low-Priority Data . . . . . . . . . . . . . . . . . .  14
     4.3.  DSCP-to-UP Mapping Recommendations Summary  . . . . . . .  15
   5.  Upstream Mapping Recommendations  . . . . . . . . . . . . . .  17
     5.1.  Upstream DSCP-to-UP Mapping within the Wireless Client
           Operating System  . . . . . . . . . . . . . . . . . . . .  17
     5.2.  UP-to-DSCP Mapping at the Wireless Access Point . . . . .  17
     5.3.  DSCP-Trust at the Wireless Access Point . . . . . . . . .  18
   6.  Appendix: IEEE 802.11 QoS Overview  . . . . . . . . . . . . .  18
     6.1.  Distributed Coordination Function (DCF) . . . . . . . . .  19
       6.1.1.  Slot Time . . . . . . . . . . . . . . . . . . . . . .  19



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       6.1.2.  Interframe Spaces . . . . . . . . . . . . . . . . . .  20
       6.1.3.  Contention Windows  . . . . . . . . . . . . . . . . .  20
     6.2.  Hybrid Coordination Function (HCF)  . . . . . . . . . . .  21
       6.2.1.  User Priority (UP)  . . . . . . . . . . . . . . . . .  21
       6.2.2.  Access Category (AC)  . . . . . . . . . . . . . . . .  21
       6.2.3.  Arbitration Inter-Frame Space (AIFS)  . . . . . . . .  22
       6.2.4.  Access Category Contention Windows (CW) . . . . . . .  23
     6.3.  IEEE 802.11u QoS Map Set  . . . . . . . . . . . . . . . .  24
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  25
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  25
     8.1.  Privacy Considerations  . . . . . . . . . . . . . . . . .  25
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  25
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  25
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  25
     10.2.  Informative References . . . . . . . . . . . . . . . . .  26
   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .  27
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  27

1.  Introduction

   Wireless has become the medium of choice for endpoints connecting to
   business and private networks.  However, the wireless medium defined
   by IEEE 802.11 [IEEE.802-11.2012] presents several design challenges
   for ensuring end-to-end quality of service.  Some of these challenges
   relate to the nature of 802.11 RF medium itself, being a half-duplex
   and shared media, while other challenges relate to the fact that the
   802.11 standard is not administered by the standards body that
   administers the rest of the IP network.  While the IEEE has developed
   tools to enable QoS over wireless networks, little guidance exists on
   how to optimally interconnect wired IP and wireless 802.11 networks,
   which is the aim of this document.

1.1.  Related work

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

   o  [RFC2474] specifies the DiffServ Codepoint Field.  This RFC also
      details Class Selectors, as well as the Default Forwarding (DF)
      treatment.

   o  [RFC2475] defines a DiffServ architecture

   o  [RFC3246] specifies the Expedited Forwarding (EF) Per-Hop Behavior
      (PHB)

   o  [RFC2597] details the Assured Forwarding (AF) PHB.




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   o  [RFC3662] outlines a Lower Effort Per-Domain Behavior (PDB)

   o  [RFC4594] presents Configuration Guidelines for DiffServ Service
      Classes

   o  [RFC5127] discusses the Aggregation of Diffserv Service Classes

   o  [RFC5865] introduces a DSCP for Capacity Admitted Traffic

   This draft draws heavily on [RFC4594], [RFC5127], and
   [I-D.ietf-tsvwg-diffserv-intercon].

   In turn, the relevant standard for wireless QoS is IEEE 802.11, which
   is being progressively updated; the current version of which (at the
   time of writing) is IEEE 802.11-2012.

1.2.  Interaction with RFC 7561

   There is also a recommendation from GSMA, Mapping Quality of Service
   (QoS) Procedures of Proxy Mobile IPv6 (PMIPv6) and WLAN [RFC7561].
   The GSMA specification was developed without reference to the service
   plan documented in Section 1.1, and conflicts both in the services
   specified and the code points specified for them.  As such, the two
   plans cannot be normalized.  Rather, as discussed in [RFC2474]
   section 2, the two domains (802.11 and GSMA) are different
   Differentiated Services Domains separated by a Differentiated
   Services Boundary.  At that boundary, code points from one domain are
   translated to code points 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 access point is the bridge between wired
   and wireless media.

   This document primarily applies to wired IP networks that have
   wireless access points at their edges, but can also be applied to Wi-
   Fi backhaul, wireless mesh solutions or any other type of AP-to-AP
   wireless network that serves to extend the IP network infrastructure.






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1.4.  Document Organization

   This document is organized as follows:

   o  Section 1 outlines the abstract, related work, organization and
      the requirements language of this document.

   o  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.

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

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

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

   o  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.

   o  Section 7 on notes IANA considerations, security considerations,
      acknowledgements and references, respectively

1.5.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", "OPTIONAL", and "NOT
   RECOMMENDED" in this document are to be interpreted as described in
   [RFC2119].

2.  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 should be
   noted:

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




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   o  802.11 does not support a [RFC2597] AF PHB service, again because
      it is not possible to guarantee 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)

   o  802.11 loosely supports a [RFC2474] Default Forwarding service via
      the Best Effort Access Category (AC_BE)

   o  802.11 loosely supports a [RFC3662] Lower PDB service via the
      Background Access Category (AC_BK)

   As such, these are high-level considerations that need to be kept in
   mind when mapping from DiffServ to 802.11 (and vice-versa); however,
   some additional marking-specific incompatibilities must also be
   reconciled, as will be discussed next.

2.1.  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 3 Most Significant Bits (MSB) of
   the DSCP are transcribed to generate the corresponding L2 markings.

   Note: There are example mappings in IEEE 802.11 (in the Annex V
   Tables V-1 and V2), but these mappings are provided as examples (vs.
   as recommendations).  Furthermore, some of these mappings do not
   align with the intent and recommendations expressed in [RFC4594], as
   will be discussed in the following section.

   However, when this default DSCP-to-UP mapping method is applied to
   packets marked per [RFC4594] recommendations and destined to 802.11
   WLAN clients, it will yield a number of sub-optimal 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 UP3 (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 traffic class




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   It should also be noted that while IEEE 802.11 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),
   802.11 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 medium Layer 2 QoS
      markings

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

2.2.  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
   by 8 (i.e. shifting the 3 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 access point and
   the nearest classification and marking policy enforcement point
   (which may be the centralized wireless LAN controller, relatively
   deep within the network).

   It goes without saying that when 6 bits of marking granularity are
   derived from 3, then information is lost in translation.  Servicing
   differentiation cannot be made for 12 classes of traffic (as
   recommended in [RFC4594]), but for only 8 (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 (Voice) to CS6, which [RFC4594] recommends for
      Network Control

   o  Mapping UP 4 (Multimedia Conferencing and/or Real-Time
      Interactive) to CS4, thus losing the ability to distinguish
      between these two distinct traffic classes

   o  Mapping UP 3 (Multimedia Streaming and/or Broadcast Video) to CS3,
      thus losing the ability to distinguish between these two distinct
      traffic classes





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   o  Mapping UP 2 (Low-Latency Data and/or OAM) to CS2, thus losing the
      ability to distinguish between these two distinct traffic classes,
      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 (High-Throughput Data and/or Low-Priority Data) to
      CS1, thus losing the ability to distinguish between these two
      distinct traffic classes and causing legitimate business-relevant
      High-Throughput Data to receive a [RFC3662] Lower PDB, for which
      it is not intended

   Thus, the next sections of this draft seek to address these
   limitations and concerns and reconcile the intents of [RFC4594] and
   IEEE 802.11.  First the downstream (wired-to-wireless) DSCP-to-UP
   mappings will be aligned and then upstream (wireless-to-wired) models
   will be addressed.

3.  Wireless Device Marking and Mapping Capability Recommendations

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

   o  mark DSCP, per DiffServ standards

   o  mark UP, per the 802.11 standard

   o  support fully-configurable mappings between DSCP and UP

   o  trust the DSCP markings set by wireless endpoint devices (as
      discussed in Section 5.3)

   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 802.11 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 while the mappings presented in this document are
   RECOMMENDED to replace the current common default practices (as
   discussed in Section 2.1 and Section 2.2), these mapping



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   recommendations are not expected to fit every last deployment model,
   and as such may be overridden by network administrators, as needed.

4.  DSCP-to-UP Mapping Recommendations

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

   This section assumes wireless access points and/or WLAN controllers
   that support customizable, non-default DSCP-to-UP mapping schemes.

4.1.  Network Control Traffic

   Network control traffic is defined as packet flows that are essential
   for stable operation of the administered network.  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 Management (OAM)

4.1.1.  Network Control Protocols

   The Network Control service class is used for transmitting packets
   between network devices (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.  The RECOMMENDED DSCP marking for Network
   Control is CS6.

   Before discussing a mapping recommendation for Network Control
   traffic marked CS6 DSCP, it is interesting to note a relevant
   recommendation from [RFC4594] pertaining to traffic marked CS7 DSCP:
   in [RFC4594] Section 3.1 it is RECOMMENDED that packets marked CS7
   DSCP (a codepoint that SHOULD be reserved for future use) be dropped
   or remarked at the edge of the DiffServ domain.

   Following this recommendation, it is RECOMMENDED that all packets
   marked to DiffServ Codepoints not in use over the wireless network be
   dropped or remarked at the edge of the DiffServ domain.






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   It is important to note that the wired-to-wireless edge may or may
   not equate to the edge of the DiffServ domain; as such, this
   recommendation may or may not apply at the wired-to-wireless edge.

   For example, in most commonly deployed models, the wireless access
   point represents not only the edge of the DiffServ domain, but also
   the edge of the network infrastructure itself.  As such, and in line
   with the above recommendation, traffic marked CS7 DSCP SHOULD be
   dropped or remarked at this edge (as it is typically unused, as CS7
   SHOULD be reserved for future use).  So too SHOULD Network Control
   traffic marked CS6 DSCP, considering that only client devices (and no
   network infrastructure devices) are downstream from the wireless
   access points in these deployment models.  In such cases, no Network
   Control traffic would be (legitimately) expected to be sent or
   received from wireless client endpoint devices, and thus this
   recommendation would apply.

   Alternatively, in other deployment models, such as Wi-Fi backhaul,
   wireless mesh infrastructures, or any other type of wireless AP-to-AP
   deployments, the wireless access point extends the network
   infrastructure and thus, typically, the DiffServ domain.  In such
   cases, the above recommendation would not apply, as the wired-to-
   wireless edge does not represent the edge of the DiffServ domain.
   Furthermore, as these deployment models require Network Control
   traffic to be propagated across the wireless network, it is
   RECOMMENDED to map Network Control traffic marked CS6 to UP 7 (per
   IEEE 802.11-2012, Section 9.2.4.2, Table 9-1), thereby admitting it
   to the Voice Access Category (AC_VO).

4.1.2.  Operations Administration Management (OAM)

   The OAM (Operations, Administration, and Management) service class is
   RECOMMENDED for OAM&P (Operations, Administration, and Management and
   Provisioning).  The RECOMMENDED DSCP marking for OAM is CS2.

   By default, 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.
   Network administrators can categorize their applications according to



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   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
   service class is minimum jitter, delay, and packet loss service up to
   a specified upper bound.  The RECOMMENDED DSCP marking for Telephony
   is EF.

   Traffic marked to DSCP EF will map by default 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 [RFC5865] VOICE-ADMIT DSCP (44/101100) 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 (traditional telephony) and peer-to-peer application
   signaling.  Telephony signaling includes signaling between IP phone
   and soft-switch, soft-client and soft-switch, and 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.  The RECOMMENDED DSCP marking for Signaling is CS5.

   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.  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 vs. other data plane flows.  One



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   way this may be achieved in certain WLAN deployments is by mapping
   Signaling traffic marked CS5 to UP 5 (as recommended above).  To
   illustrate: IEEE 802.11-2012 displays a reference implementation
   model in Figure 9-19 which depicts four transmit queues, one per
   access category.  In practical implementation, however, it is common
   for WLAN network equipment vendors to actually implement dedicated
   transmit queues on a per-UP basis, which are then dequeued into their
   associated access category in a preferred (or even strict priority
   manner).  For example, (and specific to this point): 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).  As
   such, Signaling traffic may benefit from such treatment vs. other
   video flows in the same access category (as well as vs. data flows in
   the Best Effort and Background Access Categories) due to this
   differentiation in servicing under such implementations.

4.2.3.  Multimedia Conferencing

   The Multimedia Conferencing service class is RECOMMENDED for
   applications that require real-time service for rate-adaptive
   traffic.  The RECOMMENDED DSCP markings for Multimedia Conferencing
   are AF41, AF42 and AF43.

   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 (which it does by
   default).  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 traffic 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).  The RECOMMENDED DSCP marking for
   Real-Time Interactive traffic is CS4.

   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 (which it does by default).
   Specifically, it is RECOMMENDED to map CS4 to UP 4, thereby admitting
   Real-Time Interactive traffic into the Video Access Category (AC_VI).






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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.  The RECOMMENDED DSCP markings for Multimedia
   Streaming are AF31, AF32 and AF33.

   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.  Specifically, it is
   RECOMMENDED to map AF31, AF32 and AF33 to UP 4, thereby admitting
   Multimedia Streaming into the Video Access Category (AC_VI).

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.  The RECOMMENDED DSCP
   marking for Broadcast Video is CS3.

   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.
   Specifically, it is RECOMMENDED to map CS4 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 may be considered
   foreground traffic, with delays or drops to such traffic directly
   impacting user-productivity.  The RECOMMENDED DSCP markings for Low-
   Latency Data are AF21, AF22 and AF23.

   In line with the recommendations made in Section 4.2.2, mapping Low-
   Latency Data to UP 3 may allow such to receive a superior level of
   service via transmit queues servicing the EDCAF hardware for the Best
   Effort Access Category (AC_BE).  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).







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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 non-user-interactive.
   Per [RFC4594]-Section 4.8, it can be assumed that this class will
   consume any available bandwidth and that packets 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.  The RECOMMENDED DSCP markings for High-Throughput Data
   are AF11, AF12 and AF13.

   Unfortunately, there really is no corresponding fit for the High-
   Throughput Data traffic class within the constrained 4 Access
   Category 802.11 model.  If the High-Throughput Data traffic 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 traffic classes) as well as
   with the default traffic 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 802.11 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 Service Class

   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.  The RECOMMENDED
   DSCP marking for the Standard Service Class is DF.

   The Standard Service Class loosely corresponds to the 802.11 Best
   Effort Access Category (AC_BK) and 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).

4.2.10.  Low-Priority Data

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



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   The Low-Priority Data service class loosely corresponds to the 802.11
   Background Access Category (AC_BK) and 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).

4.3.  DSCP-to-UP Mapping Recommendations Summary

   Figure 1 summarizes the [RFC4594] DSCP marking recommendations mapped
   to IEEE 802.11 UP and access categories applied in the downstream
   direction (from wired-to-wireless networks).









































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   +------------------------------------------------------------------+
   | IETF DiffServ | PHB  |Reference|         IEEE 802.11             |
   | Service Class |      |   RFC   |User Priority|  Access Category  |
   |===============+======+=========+=============+===================|
   |Network Control| CS6  | RFC2474 |    (See Section 4.1.1)          |
   +---------------+------+---------+-------------+-------------------+
   |   Telephony   | EF   | RFC3246 |     6       |   AC_VO (Voice)   |
   +---------------+------+---------+-------------+-------------------+
   |  VOICE-ADMIT  |VOICE-| RFC5865 |     6       |   AC_VO (Voice)   |
   |               |ADMIT |         |             |                   |
   +---------------+------+---------+-------------+-------------------+
   |   Signaling   | CS5  | RFC2474 |     5       |   AC_VI (Video)   |
   +---------------+------+---------+-------------+-------------------+
   |   Multimedia  | AF41 |         |             |                   |
   | Conferencing  | AF42 | RFC2597 |     4       |   AC_VI (Video)   |
   |               | AF43 |         |             |                   |
   +---------------+------+---------+-------------+-------------------+
   |   Real-Time   | CS4  | RFC2474 |     4       |   AC_VI (Video)   |
   |  Interactive  |      |         |             |                   |
   +---------------+------+---------+-------------+-------------------+
   |  Multimedia   | AF31 |         |             |                   |
   |  Streaming    | AF32 | RFC2597 |     4       |   AC_VI (Video)   |
   |               | AF33 |         |             |                   |
   +---------------+------+---------+-------------+-------------------+
   |Broadcast Video| CS3  | RFC2474 |     4       |   AC_VI (Video)   |
   +---------------+------+---------+-------------+-------------------+
   |    Low-       | AF21 |         |             |                   |
   |    Latency    | AF22 | RFC2597 |     3       |AC_BE (Best Effort)|
   |    Data       | AF23 |         |             |                   |
   +---------------+------+---------+-------------+-------------------+
   |     OAM       | CS2  | RFC2474 |     0       |AC_BE (Best Effort)|
   +---------------+------+---------+-------------+-------------------+
   |    High-      | AF11 |         |             |                   |
   |  Throughput   | AF12 | RFC2597 |     0       |AC_BE (Best Effort)|
   |    Data       | AF13 |         |             |                   |
   +---------------+------+---------+-------------+-------------------+
   |   Standard    | DF   | RFC2474 |     0       |AC_BE (Best Effort)|
   +---------------+------+---------+-------------+-------------------+
   | Low-Priority  | CS1  | RFC3662 |     1       | AC_BK (Background)|
   |     Data      |      |         |             |                   |
   +------------------------------------------------------------------+


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






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5.  Upstream Mapping Recommendations

   In the upstream direction, there are three types of mapping that may
   occur:

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

   o  UP-to-DSCP mapping at the wireless access point

   o  DSCP-Trust at the wireless access point

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 described in Section 2.1.  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
   such wireless client operating systems utilize instead the same DSCP-
   to-UP mapping recommendations presented in Section 4 and/or fully
   customizable UP markings.

5.2.  UP-to-DSCP Mapping at the Wireless Access Point

   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 CAPWAP - and destined towards a wireless
   LAN controller for decapsulation and forwarding) from the Layer 2
   IEEE UP markings of the wireless frame.

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

   o  At the wireless access point

   o  At the wired network switch port

   o  At the wireless LAN controller

   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).




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   It should be noted that nowhere in the IEEE 802.11 specifications is
   there an intent expressed for 802.11 UP to be used to influence QoS
   treatment over wired IP networks.  Furthermore, both [RFC2474] and
   [RFC2475] allow for the host to set DSCP markings for QoS treatment
   over IP networks.  Therefore, it is NOT RECOMMENDED that wireless
   access points trust UP markings as set by these hosts and
   subsequently perform a UP-to-DSCP mapping in the upstream direction,
   but rather, if wireless host markings are to be trusted (as per
   business requirements, technical constraints and administrative
   preference), then it is RECOMMENDED to trust the DSCP markings set by
   these wireless hosts.

5.3.  DSCP-Trust at the Wireless Access Point

   On wireless access points that can trust DSCP markings of packets
   encapsulated within wireless frames it is RECOMMENDED to trust DSCP
   markings in the upstream direction, for the following reasons:

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

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

   o  Most wireless device operating systems generate UP values by the
      same method as described in Section 3.1 (i.e. by using the 3 MSB
      of the encapsulated 6-bit DSCP); then, at the access point, these
      3-bit mappings are converted back into DSCP values, either by the
      default operation described in Section 3.2 or by a customized
      mapping as described in Section 4; in either case, information is
      lost in the transitions from 6-bit marking to 3-bit marking and
      then back to 6-bit marking; trusting the encapsulated DSCP
      prevents this loss of information

   o  A practical implementation benefit is also realized by trusting
      the DSCP set by wireless client devices, as enabling applications
      to mark DSCP is much more prevalent and accessible to programmers
      of wireless applications 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 (at
      the time of writing) have little or no resources to support such
      functionality

6.  Appendix: IEEE 802.11 QoS Overview

   QoS is enabled on wireless networks by means of the Hybrid
   Coordination Function (HCF).  To give better context to the




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   enhancements in HCF that enable QoS, it may be helpful to begin with
   a review of the original Distributed Coordination Function (DCF).

6.1.  Distributed Coordination Function (DCF)

   As has been noted, the Wi-Fi medium is a shared medium, with each
   station-including the wireless access point-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 pre-defined
   set of rules was invoked that required stations to back off and wait
   random periods of time before re-attempting 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 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 contention windows.

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 the 802.11 standard.  For example, the IEEE 802.11-2012
   standard specifies the slot time to be 20 us (IEEE 802.11-2012
   Table 16-2) for legacy implementations (such as 802.11b, supporting
   1, 2, 5.5 and 11 Mbps data rates), while newer implementations
   (including 802.11g, 80.11a, 802.11n and 802.11ac, supporting data




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   rates from 500 Mbps to over 1 Gbps) define a shorter slot time of 9
   us (IEEE 802.11-2012, Section 18.4.4, Table 18-17).

6.1.2.  Interframe Spaces

   The time interval between frames that are transmitted over the air is
   called the Interframe Space (IFS).  Several IFS are defined in
   802.11, with the two most relevant to DCF being the Short Interframe
   Space (SIFS) and the DCF Interframe Space (DIFS).

   The SIFS is the amount of time in microseconds required for a
   wireless interface to process a received RF signal and its associated
   802.11 frame and to generate a response frame.  Like slot times, the
   SIFS can vary according to the performance implementation of the
   802.11 standard.  The SIFS for 802.11a, 802.11n and 802.11ac (in 5
   Ghz) is 16 us (IEEE 802.11-2012, Section 18.4.4, Table 18-17).

   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 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 Contention Window.

6.1.3.  Contention Windows

   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
   Contention Window minimum value (CWmin), inclusive.  The CWmin for
   DCF (in 5 GHz) is specified as 15 slot times (IEEE 802.11- 2012,
   Section 18.4.4, Table 18-17).

   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 will occur.  At this point, the stations effectively
   begin the process again, waiting a DIFS and generate a new random



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   backoff value.  However, a key difference is that for this subsequent
   attempt, the Contention Window approximatively 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 Contention Window size (CWmax) is reached.
   The CWmax for DCF is specified as 1023 slot times (IEEE 802.11-2012,
   Section 18.4.4, Table 18-17).

   At this point, transmission attempts may still continue (until some
   other pre-defined limit is reached), but the Contention Window 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 us 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 802.11, which
   was integrated into the main 802.11 standard in 2007.

6.2.1.  User Priority (UP)

   One of the key changes to the 802.11 frame format 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 802.11
   Access Categories (AC) that generate differentiated treatment over
   wireless media.

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




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   down) and their corresponding UP mappings are shown in Figure 2
   (adapted from IEEE 802.11-2012, Section 9.2.4.2, Table 9-1).


                +-----------------------------------------+
                |   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: IEEE 802.11 Access Categories and User Priority Mappings

   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.

6.2.3.  Arbitration Inter-Frame Space (AIFS)

   As previously mentioned, each station must wait a fixed amount of
   time to ensure the air is clear before attempting transmission.  With
   DCF, the DIFS is constant for all types of traffic.  However, with
   802.11 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).  AIFS are defined in slot times and the AIFS
   per access category are shown in Figure 3 (adapted from IEEE
   802.11-2012, Section 8.4.2.31, Table 8-105).








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               +------------------------------------------+
               |   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 Contention Windows (CW)

   Not only is the fixed amount of time that a station has to wait
   skewed according to 802.11 access category, but so are the relative
   sizes of the Contention Windows that bound the random backoff timers,
   as shown in Figure 4 (adapted from IEEE 802.11-2012,
   Section 8.4.2.31, Table 8-105).


         +-------------------------------------------------------+
         |   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: Contention Window Sizes by Access Category

   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.



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   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 proposed addendum to the IEEE
   802.11 standard which includes, among other enhancements, a mechanism
   by which wireless access points 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
   802.11u-2011 Section 7.3.2.95) 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 Set information element is to provide the mapping of
   higher layer Quality of Service constructs (i.e.  DSCP) to User
   Priorities so that a wireless endpoint device (that supports this
   function and is administratively configured to enable it) can 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.

   The QoS Map Set information element includes two key components:

   1) each of the eight UP values (0-7) are 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.

   In line with the recommendations put forward in this document, the
   following recommendations apply when the this QoS Map Set information
   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 4.1.1 (that packets marked to unused DiffServ Codepoints be
   remarked at the edge of the DiffServ domain), and

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







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7.  IANA Considerations

   This memo asks the IANA for no new parameters.

8.  Security Considerations

   The recommendation offered in Section 4.1.1 (of dropping or remarking
   packets marked with DiffServ Codepoints not in use at the edge of the
   DiffServ domain) is to address a Denial-of-Service attack vector that
   exists at wired-to-wireless edges due to the requirement of trusting
   traffic markings to ensure end-to-end QoS.  For example, consider a
   malicious user flooding traffic marked CS7 or CS6 DSCP toward the
   WLAN.  These codepoints would map by default to UP 7 and UP 6
   (respectively), both of which would be assigned to the Voice Access
   Category (AC_VO).  Such a flood could cause a Denial-of-Service to
   wireless voice applications.

8.1.  Privacy Considerations

9.  Acknowledgements

   The authors wish to thank TSVWG reviewers.

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

10.  References

10.1.  Normative References

   [IEEE.802-11.2012]
              "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 Standard 802.11, 2012,
              <http://standards.ieee.org/getieee802/
              download/802.11-2012.pdf>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.






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   [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,
              <http://www.rfc-editor.org/info/rfc2474>.

   [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,
              <http://www.rfc-editor.org/info/rfc2475>.

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

   [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,
              <http://www.rfc-editor.org/info/rfc3246>.

   [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,
              <http://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,
              <http://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,
              <http://www.rfc-editor.org/info/rfc5865>.

10.2.  Informative References

   [I-D.ietf-tsvwg-diffserv-intercon]
              Geib, R. and D. Black, "Diffserv-Interconnection classes
              and practice", draft-ietf-tsvwg-diffserv-intercon-12 (work
              in progress), October 2016.








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   [IEEE.802-11u.2011]
              "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 Standard 802.11, 2011,
              <http://standards.ieee.org/getieee802/
              download/802.11u-2011.pdf>.

   [RFC5127]  Chan, K., Babiarz, J., and F. Baker, "Aggregation of
              Diffserv Service Classes", RFC 5127, DOI 10.17487/RFC5127,
              February 2008, <http://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,
              <http://www.rfc-editor.org/info/rfc7561>.

Appendix A.  Change Log

   Initial Version:  July 2015

Authors' Addresses

   Tim Szigeti
   Cisco Systems
   Vancouver, British Columbia  V7X 1J1
   Canada

   Email: szigeti@cisco.com


   Fred Baker
   Santa Barbara, California  93117
   USA

   Email: FredBaker.IETF@gmail.com













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