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Stream Classification Service

Stream Classification Service. Authors:. Date: 2009-07-06. Abstract. This proposal fulfils two of the PAR objectives of the 11aa task group:

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Stream Classification Service

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  1. Stream Classification Service Authors: Date: 2009-07-06 Alex Ashley, NDS Ltd

  2. Abstract This proposal fulfils two of the PAR objectives of the 11aa task group: • 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 This proposal allows the creation of up to 4 extra EDCA parameter sets to facilitate intra-access category prioritization and a method to subdivide AIFS. This proposal also creates a new service called the “stream classification service” that allows the establishment of streams with higher layer signaling of packet drop eligibility and allows classification of streams in to an access category. Alex Ashley, NDS Ltd

  3. Use Cases • Prioritize all packets in a video stream above/below another video stream • In EDCA and EDCA-AC modes • The higher priority video has a greater chance of channel access • Allow some packets in a flow to be tagged as drop eligible • Not all packets, as some packets are more important than others • In EDCA, EDCA-AC and HCCA modes • Both of the above at the same time • And in combination with 802.1AVB • Allows AVB flows to use these prioritisation features Alex Ashley, NDS Ltd

  4. History • Implementation for Intra-AC Differentiated Services • IEEE 802.11-09/0022r0 • Using packet drop precedence for graceful degradation • IEEE 802.11-08/0764r1 • Drop Precedence in wireless, wired-wireless networks • IEEE 802.11-09/0264r0 • Thursday March 12 TGaa + 802.1AVB meeting • IEEE 802.11-09/0371r0 Alex Ashley, NDS Ltd

  5. Feedback from 802.1* Q: How many priority levels? A: There is a difference between number of supported priorities and the maximum number of priorities that can be signalled. There is not much point in having more than 8 priority signalling levels, as this is the number of priorities provided by 802.1. The minimum number of supported priorities is two, so that AV traffic can be prioritised over best effort traffic. Q: How many drop precedence levels? A: Drop precedence is a planned for the next version of the AVB spec. You could reserve two stream IDs and use one for the lower priority (droppable) packets. You could reserve more stream IDs if you wanted more levels of drop priority. *See IEEE 802.11-09/0371r0 – TGaa minutes from Vancouver Alex Ashley, NDS Ltd

  6. Drop Eligibility indicator “The DEI subfield is 1 bit in length and is used by the STA to indicate that the corresponding MSDU, or fragment thereof, is eligible for discarding if there are insufficient resources at the destination STA” • Placeholder text in QoS Control field clause until we know what other signalling bits 11aa requires. • Two extra retry limits, to allow for less retries when DEI=1 • dot11ShortDEIRetryLimit , dot11LongDEIRetryLimit Alex Ashley, NDS Ltd

  7. Intra-Access Category prioritization “Intra-Access Category prioritization of transport streams by modifying EDCA timing and parameter selection” • We cannot break current EDCA (WMM) timing and parameter selection. • We cannot do intra-AC prioritization just using the 4 existing EDCA parameter records. Alex Ashley, NDS Ltd

  8. Alternate EDCA Parameter Set • Up to four extra EDCA parameter records • AAC_BK, AAC_BE, AAC_VI, AAC_VO • Signalled in beacon, probe response, (re)association response • Identical structure to existing EDCA (WMM) Parameter Set • Reserved octet in EDCA PS used to indicate presence of AAC_?? Alex Ashley, NDS Ltd

  9. Alternate EDCA Parameter Set • User Priority -> AC mapping expanded to use these extra EDCA parameters, when supported [1] Support for an alternate AC is defined as dot11RobustAVStreamingAlternateEDCAEnabled set to true and the appropriate Alternate AC_?? Present bit it is set in the Alternate Priority Info field of the Alternate EDCA Parameter Set element (see 7.3.2.94aa). Alex Ashley, NDS Ltd

  10. Fractional AIFS • AIFS must be a multiple of slot time • but AIFSN for AC_VI is 2 and AC_BE is 3* • It would be useful if we could have an AIFSN of 2½ • We can achieve a mean AIFSN of 2½ without breaking slot times • E.g. AIFSN = 2,3,2,3,2,3 • AIFS[AC] = (AIFSN[AC] - (AIFSF[AC] &dot11QosTransmittedFrameCount [AC])) × aSlotTime + aSIFSTime Reserved field in baseline & WMM * Default parameters for EDCA and WMM Alex Ashley, NDS Ltd

  11. Simulation Parameters • 802.11 parameters • 11n at 5GHz in Europe • 20MHz channel • 2x2 MIMO STBC • Building • Height 4.8m • Width 5.5m • Depth 8m • 2 floors • Brick outer construction, drywall internal walls • Traffic • 2 x 14mbps video streams • 1 VOIP call (30ms samples) • 1 HTTP BE stream • Streams start after 10 seconds, shutdown after 50 seconds Alex Ashley, NDS Ltd

  12. STA 105 Simulation HTTP traffic Voice call AP AV stream 1 AV stream 2 HTTP traffic AV stream 1 STA 104 AV stream 2 STA 102 STA 103 Alex Ashley, NDS Ltd

  13. Simulation Results – 4ACs Packets per second Alex Ashley, NDS Ltd

  14. Simulation Results – 5ACs Packets per second Alex Ashley, NDS Ltd

  15. Intra-Access Priority IE • Intra-Access Priority IE can be used in ADDTSPEC and QosMap Configure frames to signal use of drop eligibility and EDCA alternate priority • However, only defines one priority level per TID/UP • Stream Classification Service can be used to select packets within a TS Alex Ashley, NDS Ltd

  16. Stream Classification Service (SCS) • An optional service implemented by an AP that allows a stream to be classified to a User Priority, EDCA AC and Drop Eligibility • Uses existing TCLAS processing used by TS, FMS, DMS, TFS • Each stream is assigned an ID (SCSID) by non-AP STA requesting classification • Used by AP in responding to request and by STA to modify/delete stream • Using two SCSIDs (or TS + SCSID) allows a flow to be configured with selected frames drop eligible Alex Ashley, NDS Ltd

  17. Stream Classification Service (SCS) Overview STA advertises Stream Classification Service (SCS) Capability Non-AP STA sends a request to specify traffic classes for classification and the priority to assign to matching frames AP may accept or reject the traffic class specified by the non-AP STA If the service is accepted by the AP, the AP shall process subsequent unicast MSDUs that match the classifier specified in the SCS Descriptor. The processing of matching MSDUs depends upon the access policy assigned to the MSDU: For MSDUs that are not part of a TS, the User Priority subfield of the Intra-Access Priority element is used as the UP of these MSDUs. For MSDUs that are not part of a TS, or MSDUs that are part of a TS that uses EDCA or HEMM as the Access Policy, the Alternate Priority subfield of the Intra-Access Priority element is used to select the EDCA Parameter Set for these MSDUs, if the MIB attribute dot11RobustAVStreamingAlternateEDCAEnabled is true. All matching MSDUs are tagged with their drop eligibility using the value from the Drop Eligibility subfield of the Intra-Access Priority element See doc 09/0726r0 Slide 17 Alex Ashley, NDS Ltd

  18. Non-AP STA AP SME MLME MLME SME MLME-SCS.request SCS Request Frame MLME-SCS.indication Process SCS Request MLME-SCS.confirm SCS Response Frame MLME-SCS.response SCS Frame Exchange Sequence • Non-AP STA request SCS Alex Ashley, NDS Ltd

  19. SCS Frame Exchange Sequence • AP can terminate SCS at any time Non-AP STA AP SME MLME MLME SME AP decides to terminate SCS MLME-SCS.termination SCS Response Frame MLME-SCS.termrequest Alex Ashley, NDS Ltd

  20. TSPEC + SCS • Intra-Access Priority IE can be used in ADD TSPEC request to signal UP, EDCA AC and DEI of the stream • A subsequent SCS can be used to select some packets in the TS • E.g. to select packets for DEI=1 MLME-SCS.request SCS Request Frame MLME-SCS.indication Process SCS Request MLME-SCS.confirm SCS Response Frame MLME-SCS.response Alex Ashley, NDS Ltd

  21. SCS Request and Response frames • SCS Request frame: SCS Descriptor • SCS Response frame: SCS Status Alex Ashley, NDS Ltd

  22. AP Pure 802.11 Example, no SCS AV stream AV stream UP & DEI passed via MAC-SAP interface The AP can use the UP value to choose EDCA AC and the DEI tagging to choose packets to discard if conditions deteriorate. Alex Ashley, NDS Ltd

  23. AP Mixed Wired/Wireless Example, SCS Request SCS AV stream AV stream Source device L2/L3 tags UDP packets with priority and drop eligibility. Wired connection to AP. Destination makes an SCS request to the AP to inform it that the stream has DEI and the method of tagging. When SCS active, the AP can use the DEI tagging to choose packets to discard if conditions deteriorate. Alex Ashley, NDS Ltd

  24. AP Mixed Wired/Wireless Example,Destination SCS Request SCS AV stream 1 AV stream 1 AV stream 2 AV stream 2 Source device L2/L3 tags UDP packets with priority eligibility. Request SCS Destinations make SCS requests to the AP to select the UP of each AV stream. The UP used by each destination is a management (configuration) decision. When SCS active, the AP can use the UP (and EDCA params) to provide intra-AC prioritization. Alex Ashley, NDS Ltd

  25. AP Another Wireless Example,Source SCS Request SCS AV stream 1 AV stream 2 AV stream 1 AV stream 2 Source device L2/L3 tags UDP packets with priority eligibility. Source makes SCS requests to the AP to select the UP of the AV streams When SCS active, the AP can use the UP (and EDCA params) to provide intra-AC prioritization. Alex Ashley, NDS Ltd

  26. Conclusions This proposal to fulfils two of the PAR objectives of the 11aa task group: • Graceful degradation of audio video streams when there is insufficient channel capacity, by enabling packet discarding without any requirement for deep packet inspection, • Drop Eligibility Indicator • SCS to allow non-AP STA to configure DEI signaling from upper layers • Intra-Access Category prioritization of transport streams by modifying EDCA timing and parameter selection without any requirement for deep packet inspection • Creation of up to 4 extra EDCA parameter sets to facilitate intra-access category prioritization and a method to subdivide AIFS. • AIFSF to provide finer grained medium access probability • SCS to allow selection of UP and EDCA Parameter Set. Alex Ashley, NDS Ltd

  27. Normative Text • All proposed changes • 09-0726r0 But if we don’t want to adopt all features: • Or just want to cause pain to our editor • SCS + DEI • 09-0726r1 • Alternate EDCA • 09-0850r0 • Fractional AIFSN • 09-0853r0 Alex Ashley, NDS Ltd

  28. Motion • Move to incorporate the text changes in 11-09-0726-00-000aa-stream-classification-service.doc into the TGaa draft • Moved: • Seconded: • Result: Alex Ashley, NDS Ltd

  29. References • 11-09-0726r0 “Stream Classification Service” • 11-09/0022r0 “Implementation for Intra-AC Differentiated Services” • 11-08/0764r1 “Using packet drop precedence for graceful degradation” • 11-09/0264r0 “Drop Precedence in wireless, wired-wireless networks” • 11-09/0371r0 “TGaa minutes for Vancouver” Alex Ashley, NDS Ltd

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