1. Guidelines for DiffServ to IEEE 802.11 Mapping
draft-szigeti-tsvwg-ieee e-01
Tim Szigeti Fred Baker
July 23, 2015

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

3. 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

4. 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

5. 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

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

7. 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

8. Downstream DSCP-to-UP Mapping Model
Proposal
RFC 4594-Based Model
DSCP
IEEE Model
Remark / Drop
if not in use
Pros
Endeavors to align RFC 4594 recommendations into the IEEE 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

9. Upstream UP-to-DSCP Default Mapping
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

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

11. Appendix A: WLAN QoS Considerations and Implementation Models

12. 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

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

14. 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%

15. IEEE Figure 9-19

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

17. Appendix B: Related Mapping Models

18. IEEE
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 UP
UP determines access-category

19. IEEE
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

20. 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