1. Requirements and Implementations for Intra-flow/Intra-AC DiffServ
11/20/2018May 2008
November 2007
doc.: IEEE /2752r1
2018/11/20
Requirements and Implementations for Intra-flow/Intra-AC DiffServ
Date:
Authors:
Jun Li, Thomson Inc..
Peter Ecclesine, Cisco Systems

2. 11/20/2018May 2008
November 2007
doc.: IEEE /2752r1
2018/11/20
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
11/20/2018May 2008
November 2007
doc.: IEEE /2752r1
2018/11/20
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?
2018/11/20
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
Channel coding frames, e.g.
FEC and/or ARQ
Jun Li, Thomson Inc..

5. 2018/11/20
Approach
Basic idea: define new information fields in MAC frame to realize 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 dropping criteria when there is insufficient channel capacity
Jun Li, Thomson Inc..

6. Possible Differentiation Fields
2018/11/20
Possible Differentiation 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..

7. Solution 1: Modify QoS control field
2018/11/20
Solution 1: 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 (Cannot use Bit 7 due to confliction with TGn A-MPDU indicator). However, bits 8-15 is still used for intra-flow/intra-AC info, VTS-flag is set in the TSPEC associated with a TC or TS.
Jun Li, Thomson Inc..

8. Intra-flow / Intra-AC diffServ information field
2018/11/20
Intra-flow / Intra-AC diffServ information field B8
B10
B11
B12
B13
B14
B15
Reserved
Frame
category
Drop
Precedence
Priority
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..

9. A TSPEC for each flow / AC
2018/11/20
A TSPEC for each flow / AC
B0-B3 B8
B10
B11
B12
B13
B14
B15
TID
Reserved
Frame
category
Drop
Precedence
Priority
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..

10. Solution 2: Add a 2-type new field before Frame body
2018/11/20
Solution 2: Add a 2-type new field before Frame body
Frame Control
Octets:2 2
Address 1
Duration/ ID
Address 2
Address 3
Sequence control 6
Address 4
QoS Control
VTS control information
Frame Body
2302
FCS 4
VTS control
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 bit 7 in QoS control field (see the following figure) shall be set to 1, based on which the VTS MAC frame can be distinguished by a VTS station. (cannot be used due to conflict with TGn A-MPDU, management frame to be used???)
TID
Bits: B0 B3 B4 B5 B6 B7 B8
B15
VTS
Flag =1
B11
B12
QoS control field in MAC frame
Jun Li, Thomson Inc..

11. Compatibility to 802.11e Not needed for HCCA
2018/11/20
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..

12. Management frame modifications for supporting intra-flow DiffServ
2018/11/20
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..

13. 2018/11/20
Use cases
Jun Li, Thomson Inc..

14. Traffic generated from 802.11aa STA
2018/11/20
Traffic generated from aa STA
VTS diffServ Info
created at STA
802.11aa STA
802.11aa STA
VTS traffic
802.11aa AP
802.11aa
Mesh Node
802.11aa
& 802.1avb
Bridge
LAN
VTS diffServ Info
used & forwarded
VTS diffServ Info may be NOT forwarded at the last hop
VTS diffServ info
mapped to 802.1Q
Jun Li, Thomson Inc..

15. Traffic mapped at edge bridge of WLAN
2018/11/20
Traffic mapped at edge bridge of WLAN
Layered video
streamed as diff
flows
802.11aa STA
Video
streaming
Or single flow is
streamed but RTP
packet is tagged
802.11aa AP
VTS traffic
Edge bridge
(cross-layer
mapping)
FEC
generation
VTS diffServ Info
used
Layered video & FEC info mapped to
802.11aa diffServ info, DPI required
FEC per flow,
as diff new flow
or DPI & tag FEC
as well at RTP
Jun Li, Thomson Inc..

16. Traffic mapped at edge router of LAN
2018/11/20
Traffic mapped at edge router of LAN
FEC per flow
or DPI
Layered video
streamed as diff
flows
Video
streaming
802.11aa STA
Or single flow is
streamed but RTP
packet is tagged
FEC
generation
802.11aa AP
VTS traffic
802.11aa
& 802.1avb
Bridge
Edge router
(Cross-layer
Mapping)
FEC is tagged
LAN
VTS diffServ Info
used
802.1AVB mapped to
802.11aa diffServ info
Multi-layer video
flows mapped to
802.1 AVB or DPI
Jun Li, Thomson Inc..

17. 2018/11/20
Observations
VTS intra-flow/ intra-AC diffServ info observed 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..

18. Mapping at Edge (router / bridge)
2018/11/20
Mapping at Edge (router / bridge)
No specifications in PAR/requirements is made for 802.1AVB to ask for intra-flow / intra-AC diffServ
This need is 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..

19. 2018/11/20
Straw Poll 1
Do you think solution 1 in document 0529/r1 a favorable solution of graceful degradation and intra-access category prioritization for TGaa (further refinement may be required) ?
Yes No
Jun Li, Thomson Inc..

20. 2018/11/20
Straw Poll 2
Do you think solution 2 in document 0529/r1 a favorable solution of graceful degradation and intra-access category prioritization for TGaa (further refinement may be required) ?
Yes No
Jun Li, Thomson Inc..