Guidelines for DiffServ to IEEE 802.11 Mapping draft-szigeti-tsvwg-ieee-802-11e-01 Tim Szigeti Fred Baker szigeti@cisco.com fred@cisco.com July 23, 2015

IEEE 802.11 User Priority (UP) 3 Bit Field allows for UP values 0-7

IEEE 802.11 UP Values and Access Categories Access Category WMM Designation 7 AC_VO Voice 6 5 AC_VI Video 4 3 AC_BE Best Effort 2 AC_BK Background 1

IEEE 802.11 Arbitration Inter-Frame Space (AIFS) and Contention Windows (CW) due to the nature of wireless as a shared media, a Congestion Avoidance algorithm (CSMA/CA) must be utilized wireless senders have to wait a fixed amount of time (the AIFS) wireless senders also have to wait a random amount of time (bounded by the Contention Window) AIFS and Contention Window timers vary by Access Category Access Category AIFS (Slot Times) Voice 2 Video Best Effort 3 Background 7 Access Category CWmin (Slot Times) CWmax Voice 3 7 Video 15 Best-Effort 1023 Background

EDCF Operation Round 1 Round 2 Round 3 2+1=3 3+1=4 7+1=8 2+3=5 2+7=9 Voice Voice Voice 2+1=3 3+1=4 7+1=8 2+3=5 2+7=9 3+15=3 7+15=22 2+2=4 2+1=3 3+15=18 7+15=22 Video Video Video Best Effort Best Effort Best Effort Background Background Background Collision Voice Video

Downstream DSCP-to-UP Default Mapping 6-Bit DSCP 3-Bit UP UP 802.11 Frame DSCP DSCP CAPWAP Packet DSCP IP Packet

Default DSCP-to-UP Mapping 802.11 User Priority Access Category 56-63 7 Voice (AC_VO) 48-55 6 40-47 5 Video (AC_VI) 32-39 4 24-31 3 Best Effort (AC_BE) 0-7 16-23 2 Background (AC_BK) 8-15 1 IETF PHB for VoIP: EF 46 Per RFC 4594 & 3246

Downstream DSCP-to-UP Mapping Model Proposal RFC 4594-Based Model DSCP IEEE 802.11 Model Remark / Drop if not in use Pros Endeavors to align RFC 4594 recommendations into the IEEE 802.11 model Provides distinction between elastic and inelastic video classes Plugs potential security vulnerabilities Cons Requires several custom DSCP-to-UP mappings Network Control (CS7) Voice Access Category Best Effort Video Background UP 7 Internetwork Control CS6 UP 6 Voice + DSCP-Admit EF + 44 Broadcast Video CS5 Multimedia Conferencing AF4 UP 5 Realtime Interactive CS4 UP 4 Multimedia Streaming AF3 Signaling CS3 UP 3 Transactional Data AF2 UP 0 OAM CS2 Bulk Data AF1 UP 2 Scavenger CS1 Best Effort DF UP 1

Upstream UP-to-DSCP Default Mapping 802.11 Frame DSCP DSCP CAPWAP Packet DSCP IP Packet 6-Bit DSCP 3-Bit UP Last 3 Bits are zeroed-out First 3 Bits are copied

Upstream DSCP Trust Model 802.11 Frame DSCP DSCP CAPWAP Packet DSCP IP Packet 6-Bit DSCP 6-Bit DSCP Inner DSCP becomes outer (e.g. CAPWAP) DSCP

Appendix A: WLAN QoS Considerations and Implementation Models

Why Consider Wireless QoS? QoS is like a chain It’s only as strong as its weakest link the WLAN is one of the weakest links in enterprise QoS designs for three primary reasons: 1) Typical downshift in speed 2) Shift from full-duplex to half-duplex media 3) Shift from a dedicated media to a shared media WLAN QoS policies control both jitter and packet loss

Wireless QoS-Specific Limitations No EF PHB No AF PHB Non-deterministic media access Only 4 levels of service IP QoS WLAN QoS

WLAN QoS Improvements Quantified Application Original Metric Improved Metric Percentage Improvement Voice 15 ms max jitter 5 ms max jitter 300% 3.92 MOS (Cellular Quality) 4.2 MOS (Toll Quality) Video 9 fps 14 fps 55% Visual MOS: Good Visual MOS: Excellent Transactional Data 14 ms latency 2 ms latency 700% http://www.cisco.com/en/US/prod/collateral/wireless/cisco_avc_application_improvement.pdf

IEEE 802.11-Figure 9-19

Practical Implementation Models Per User-Priority Queues Per Client Queues Per-Radio Queues

Appendix B: Related Mapping Models

IEEE 802.11-2012 Annex V.3.3—Table V-2 Example Enterprise DSCP to UP/AC Mapping These are examples; not recommendations Several examples seem out-of-alignment with RFC 4594 intent 802.1d UP is different from 802.11 UP 802.11 UP determines access-category

IEEE 802.11-2012 Annex V.3.3—Table V-3 UP to DSCP Range Mapping Example Notable PHB Inclusions DF These are examples; not recommendations Several examples seem out-of-alignment with RFC 4594 intent CS1 AF1-CS2 AF2 CS3-AF3 CS4-AF4-CS5 EF CS6-CS7

DiffServ Interconnection Classes and Practice SP Interconnection Approach Summary (Includes Recommendations from RFC 5127—shown as dotted lines) Proposes a simplified model for interconnecting SPs “Draws heavily” on RFC 5127 Is intended for MPLS, but “is applicable to other technologies” This approach “is not intended for use within the interconnected (or other) networks” DSCPs may be remarked at the interconnection Traffic Class DSCP SP Interconnect Model Special Case Section 3.2 Network Control CS6 Telephony Service Treatment Aggregate Assured Forwarding Bulk Real-Time Default / Elastic Voice EF EF Voice-Admit (RFC 5685) 44 44 Broadcast Video CS5 Multimedia Conferencing AF4 AF41 Realtime Interactive CS4 Multimedia Streaming AF3 Signaling CS3 AF31 Transactional Data AF2 Network Management CS2 Bulk Data AF1 Scavenger CS1 Best Effort DF DF https://tools.ietf.org/pdf/draft-ietf-tsvwg-diffserv-intercon-01.pdf