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Requirements and Implementations for Intra-flow/Intra-AC DiffServ

Requirements and Implementations for Intra-flow/Intra-AC DiffServ. Authors:. Date: 2008-7-14. Abstract.

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Requirements and Implementations for Intra-flow/Intra-AC DiffServ

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  1. Requirements and Implementations for Intra-flow/Intra-AC DiffServ Authors: Date: 2008-7-14 Jun Li, Thomson Inc..

  2. 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 802.11e QoS amendments. This proposal discusses the requirements on link layer intra-flow DiffServ and presents solutions accordingly. Jun Li, Thomson Inc..

  3. 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 802.11e • Management frame modifications for supporting intra-flow DiffServ Jun Li, Thomson Inc..

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

  7. 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 • Option 1: Only modify the MAC data frame fields • Option 2: Modify fields of TSPEC information element Jun Li, Thomson Inc..

  9. For non-802.11n QoS data frame: Modify QoS control field • 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 8-15. When the flag is not set, other information is contained in bits 8-15. Jun Li, Thomson Inc..

  10. For 802.11n QoS data frame: Use bit 20 (reserved) in HT field (Sub-option 1) B30 B31 Bits: B0-B15 B16-B17 B18-B19 B20 B21 B22-B23 B24 B25-B29 Link Adaptation Control VTS Flag Reserved AC Constraint RDG/ More PPDU Reserved HT field in 802.11n NDP Announcement CSI/ Steering Calibration Sequence Calibration Position Jun Li, Thomson Inc..

  11. Intra-flow / Intra-AC DiffServ information field(Sub-option 1) 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. B11 B12 B8 B10 B13 B14 B15 Drop Precedence Reserved Frame category Priority Bit 8 to Bit15 in QoS Control field Jun Li, Thomson Inc..

  12. For 802.11n QoS data frame: Use bit 25-29 (reserved) in HT field (Sub-option 2) B31 Bits: B0-B15 B16-B17 B18-B19 B20-21 B22-B23 B24 B25 B26-B27 B28-B29 B30 Link Adaptation Control Drop Precedence VTS Flag Reserved RDG/ More PPDU AC Constraint Priority NDP Announcement CSI/ Steering Calibration Sequence Calibration Position HT control field in 802.11n Jun Li, Thomson Inc..

  13. A TSPEC for each flow / AC 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. B11 B12 B0-B3 B8 B10 B13 B14 B15 TID Drop Precedence Reserved Frame category Priority intra-flow/intra-AC information TS Info TSPEC element Bits: B0 B7 B8 B9 B11 B13 B18 B21 B22 B23 UP VTS flag Reserved Access policy = 01 TS Info field Jun Li, Thomson Inc..

  14. Alternative Solution: Add a new 2-byte VTS control field before frame body 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. 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 B4 B11 B12 B0-B3 B10 B13 B14 B15 Drop Precedence Intra-Flow Priority Frame category TID Reserved intra-flow/intra-AC information Jun Li, Thomson Inc..

  15. Compatibility to 802.11e 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 802.11e 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 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. Use cases Jun Li, Thomson Inc..

  18. Traffic generated from a 802.11aa 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 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 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 Layered video streamed as diff flows Video streaming Or single flow is streamed but packets are tagged FEC generation VTS diffServ Info used Edge router (Cross-layer Mapping) 802.11aa AP 802.11aa & 802.1avb Bridge 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. 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) 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 802.1 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..

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