1. Requirements and Implementations for Intra-flow/Intra-AC DiffServ
5/30/2019May 2008
November 2007
doc.: IEEE /2752r1
2019/5/30
Requirements and Implementations for Intra-flow/Intra-AC DiffServ
Date:
Authors:
Jun Li, Thomson Inc..
Peter Ecclesine, Cisco Systems

2. 5/30/2019May 2008
November 2007
doc.: IEEE /2752r1
2019/5/30
Abstract
One of the goals of VTS is to enable link layer adaptation on differentiated frames in a video stream according to channel conditions. This requires an intra-flow/intra-AC differentiated service (intra-Flow DiffServ), which is not supported in e QoS amendments. This proposal discusses the requirements on link layer intra-flow DiffServ and presents solutions accordingly.
Jun Li, Thomson Inc..
Peter Ecclesine, Cisco Systems

3. Outlines Why we need intra-flow/intra-AC DiffServ? Approach
5/30/2019May 2008
November 2007
doc.: IEEE /2752r1
2019/5/30
Outlines
Why we need intra-flow/intra-AC DiffServ?
Approach
Possible Differentiation Fields
Solution 1: Modify QoS control field
Solution 2: Add a 2-byte new field before Frame body
Compatibility to e
Management frame modifications for supporting intra-flow DiffServ
Jun Li, Thomson Inc..
Peter Ecclesine, Cisco Systems

4. Why we need intra-flow/intra-AC DiffServ?
2019/5/30
Why we need intra-flow/intra-AC DiffServ?
VTS PAR scope proposed the following MAC enhancement
Graceful degradation of audio video streams when there is insufficient channel capacity, by enabling packet discarding without any requirement for deep packet inspection.
Intra-Access Category prioritization of transport streams by modifying EDCA timing and parameter selection without any requirement for deep packet inspection.
Improved link reliability and low jitter characteristics for multicast/broadcast audio video streams
Differentiated frames have different importance in a video transport stream, e.g.,
Video content dependent MAC frames, e.g.
SVC base layer or enhance layer;
I,P,B frames in MPEG-2 or H.264
Region of interest based encoding
Frames carrying application layer FEC
Jun Li, Thomson Inc..

5. 2019/5/30
Approach
Basic idea: define new information fields in MAC frame header to enable frame differentiation without requiring deep frame inspection.
Information required:
VTS flag
For distinguishing the VTS MAC frames against legacy frames
VTS stream identification (VTS-SID)
For a pair of source and destination addresses, multiple streams may be served. Need to differentiate one stream from another, so that intra-flow (aka. intra-stream) differentiation can be done for each stream
In case of intra-AC (Access Category of EDCA), VTS-SID may not be required
VTS stream intra-flow differentiation fields
Used for frame differentiation within one video flow, e.g.,
I,P,B frames in MPEG-2 video flow;
video, audio, FEC packets in one video flow
Provide the frame priority and dropping criteria when there is insufficient channel capacity
Jun Li, Thomson Inc..

6. 802.11n MAC Frame Format 2019/5/30 Jun Li, Thomson Inc.. Octets:2
0-7955 2 6 6 6 2 6 2 4 4
Frame Control
Duration/ ID
Sequence control
QoS Control
Frame Body
Address 1
Address 2
Address 3
Address 4
HT Control
FCS
Jun Li, Thomson Inc..

7. Possible Intra-AC DiffServ Fields
2019/5/30
Possible Intra-AC DiffServ Fields
Priority
Corresponding to content dependent frames for intra-flow or intra-AC
Dropping precedence
How to drop
Frame category
Video/Audio
FEC
Jun Li, Thomson Inc..

8. Solution 1: Modify the existing fields
2019/5/30
Solution 1: Modify the existing fields
Option 1: Only modify the MAC data frame fields
Non-QoS Data
No support
QoS Data
Order sub-field in frame control field
VTS/802.11aa Flag
Intra-flow / intra-AC DiffServ Information
Non n
The order sub-field shall be set to 0 for Non n frame indication
Bit 7 (reserved) in QoS field shall be set to 1 for VTS frame indication;
0 otherwise
Bit 8-15 (overridden) in QoS control field shall be used for intra-flow / intra-AC DiffServ information
802.11n
The order sub-field shall be set to 1 for n frame indication
Sub-option 1: Bit 20 (reserved) in HT field shall be set to 1 for VTS frame indication;
Sub-option 2: Bit 25 (reserved) in HT field shall be set to 1 for VTS frame indication;
Bit (reserved) in HT field shall be used for Intra-flow / intra-AC DiffServ information
Option 2: Modify fields of TSPEC information element
Jun Li, Thomson Inc..

9. For non-802.11n QoS data frame: Modify QoS control field
2019/5/30
For non n QoS data frame: Modify QoS control field
Applicable frame
(sub) types
Bits
0–3
Bit 4
Bits 5-6
Bit 7
Bits 8–15
QoS (+)CF-Poll frames sent by HC
TID
EOSP
Ack Policy
Reserved
TXOP Limit
QoS Data, QoS Null, and QoS Data+CF-Ack frames sent by HC
QAP PS Buffer State
1(VTS flag)
Intra-flow/Intra-AC information
QoS data frames sent by non-AP QSTAs
TXOP Duration Requested 1
Queue Size
The TID subfield (4 bits) identifies the TC or TS to which the corresponding MSDU, or fragment thereof, in the Frame Body field belongs.
The EOSP subfield (1 bit) is used by the HC to indicate the end of the current service period (SP).
The Ack Policy subfield (2 bits) identifies the acknowledgement policy. 00=normal Ack, 10=No Ack, 01= No explicit acknowledgment. 11= Block Ack
Bit 7 flag indicates it is a VTS frame with intra-flow/ intra-Access Category (AC) information included. When the flag is set, intra-flow/intra-Access Category field is contained in bits When the flag is not set, other information is contained in bits 8-15.
Jun Li, Thomson Inc..

10. 2019/5/30
For n QoS data frame: Use bit 20 (reserved) in HT field (Sub-option 1)
VTS Flag
B16-B17
Link
Adaptation
Control
Bits: B0-B15
Calibration
Position
Sequence
CSI/
Steering
NDP
Announcement
Reserved AC
Constraint
RDG/
More PPDU
B18-B19
B20
B22-B23
B24
B25-B29
B30
B31
HT field in n
B21
Jun Li, Thomson Inc..

11. Intra-flow / Intra-AC DiffServ information field (Sub-option 1)
2019/5/30
Intra-flow / Intra-AC DiffServ information field (Sub-option 1)
Drop
Precedence
Priority
Reserved B8
B10
B11
B12
B15
B13
B14
Frame
category
Bit 8 to Bit15 in QoS Control field
Priority subfield (2 bits) indicates the priority of the frame in the access category.
Drop precedence subfield (2 bits) indicates how the frame is dropped.
B12B13 = 00: no special action, 01: drop if necessary, 10: drop all if necessary, 11: reserved
Frame category (1 bit) indicates if the frame is an FEC frame if it is set to 1. (We may want to combine it with Drop precedence to give more choices.)
Reserved (3 bits), however, in case of frame is “QoS Data, QoS Null, and QoS Data+CF-Ack frames sent by HC” , B9, buffer status indicator in QAP PS buffer status field should set to 0. Avoid confusion for non-VTS devices.
Jun Li, Thomson Inc..

12. 2019/5/30
For n QoS data frame: Use bit (reserved) in HT field (Sub-option 2)
VTS
Flag
B16-B17
Link
Adaptation
Control
Bits: B0-B15
Calibration
Position
Sequence
CSI/
Steering
NDP
Announcement AC
Constraint
RDG/
More PPDU
B18-B19
B20-21
B22-B23
B24
B26-B27
B30
B31
Reserved
B25
Drop
Precedence
Priority
B28-B29
HT control field in n
Jun Li, Thomson Inc..

13. A TSPEC for each flow / AC
2019/5/30
A TSPEC for each flow / AC
Drop
Precedence
Priority
Reserved B8
B10
B11
B12
B15
B13
B14
Frame
category
TID
B0-B3
intra-flow/intra-AC information TS
Info
TSPEC element
Bits: B0 B7 B8 B9
B11
B13
B18
B21
B22
B23
Access policy = 01 UP
VTS
flag
Reserved
TS Info field
TID indicates AC (0-7) or flow (8-15). For VTS, a TSPEC management frame must be used to specify parameters of a AC or a flow. B18 = 1 (VTS flag) indicates there are intra-AC / intra-flow diffServ information available in QoS control field bits 8-15 for frames with same SA+TID.
In case of TID = 8-15, a VTS frame needs to make sure Access policy = 01 (EDCA) and UP (user priority) = AC (access category), in order to compatible with EDCA.
Jun Li, Thomson Inc..

14. 2019/5/30
Alternative Solution: Add a new 2-byte VTS control field before frame body
Octets:2 2 6 6 6 2 6 2 2
2302 4
VTS control
Frame Control
Duration/ ID
Sequence control
QoS Control
VTS control information
Frame Body
Address 1
Address 2
Address 3
Address 4
FCS
B0-B3 B4
B10
B11
B12
B13
B14
B15
Drop
Precedence
Intra-Flow
Priority
TID
Frame
category
Reserved
intra-flow/intra-AC information
A 2-byte field, VTS control field, is defined and added before the frame body in the data frame. Priority, Dropping criteria, Frame category fields are defined as same as in solution 1. TID = 0-7, intra-AC only, TID = 8-15, intra-flow.
The method for setting VTS Flag shall be the same as solution 1.
Jun Li, Thomson Inc..

15. Compatibility to 802.11e Not needed for HCCA
2019/5/30
Compatibility to e
Not needed for HCCA
Intra-flow/ intra-AC priority is not required due to per flow QoS is already specified by HCCA.
Backward compatibility to EDCA
VTS devices can process EDCA frames produced by legacy devices.
If all EDCA functions are supported, it is fully compatible.
Forward compatibility to EDCA
Legacy e device can process VTS frames as normal EDCA frames.
However, a frame generated by VTS device may not contain information of QAP PS buffer status, a possible optional function for EDCA
Solution 1 is backward & forward compatible, solution 2 is backward compatible only.
Jun Li, Thomson Inc..

16. Management frame modifications for supporting intra-flow DiffServ
2019/5/30
Management frame modifications for supporting intra-flow DiffServ
Following management frames need to be modified
Beacon frame
Association request / Reassociation request
Association response / Reassociation response
Following information elements / fields contained in the above frames need to be extended
QoS capability information element
QoS info field
Jun Li, Thomson Inc..

17. 2019/5/30
Use cases
Jun Li, Thomson Inc..

18. Traffic generated from a 802.11aa STA within a BSS
2019/5/30
Traffic generated from a aa STA within a BSS
802.11aa AP
VTS diffServ Info
used at AP
VTS traffic
802.11aa STA
802.11aa STA
VTS diffServ Info
created at STA
Jun Li, Thomson Inc..

19. Traffic generated from 802.11aa STA in a more complex network
2019/5/30
Traffic generated from aa STA in a more complex network
VTS diffServ Info may not be forwarded at the last hop
VTS diffServ Info
used & forwarded
VTS diffServ info
mapped to 802.1Q
802.11aa AP
802.11aa
Mesh Node
802.11aa
& 802.1avb
Bridge
LAN
802.11aa STA
802.11aa STA
VTS diffServ Info
created at STA
Jun Li, Thomson Inc..
VTS traffic

20. Traffic mapped at edge bridge of WLAN
2019/5/30
Traffic mapped at edge bridge of WLAN
Video
Streaming
Server
Layered video
streamed as diff
flows
Or single flow is
streamed but packets
are tagged
Layered video & FEC info mapped to
802.11aa diffServ info, DPI required
VTS diffServ Info
Used (no DPI)
802.11aa AP
Edge bridge
(cross-layer
mapping)
Application
layer FEC
generation
FEC are tagged
The same device
802.11aa STA
Jun Li, Thomson Inc..

21. Traffic mapped at edge router of LAN
2019/5/30
Traffic mapped at edge router of LAN
Layered video
streamed as diff
flows
Video
streaming
Or single flow is
streamed but packets
are tagged
FEC
generation
VTS diffServ Info
used
802.11aa AP
802.11aa
& 802.1avb
Bridge
Edge router
(Cross-layer
Mapping)
FEC packets are tagged
LAN
The same device
Multi-layer video
flows mapped to
802.1 AVB (DPI)
802.1AVB mapped to
802.11aa diffServ info
802.11aa STA
Jun Li, Thomson Inc..

22. 2019/5/30
Observations
VTS intra-flow/ intra-AC diffServ info carried and used within WLAN domain without mapping required
Cross-domain requires layered video information mapped to VTS diffServ info field
If layered video information is not explicitly available, DPI (deep packet inspection) is required at the Edge
DPI is never required inside WLAN, complying to VTS PAR
Jun Li, Thomson Inc..

23. Mapping at Edge (router / bridge)
2019/5/30
Mapping at Edge (router / bridge)
No specifications in PAR/requirements is made for 802.1AVB for intra-flow / intra-AC diffServ
This feature may be less important in wired network, and may never be implemented in as well as IETF.
If VTS considers it is important regardless of corresponding wired network feature, mapping at Edge with DPI (deep packet inspection) is required. The mapping is considered an upper layer function though.
Jun Li, Thomson Inc..