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EDCF Access Categories

EDCF Access Categories. Menzo Wentink, Intersil; Sunghyun Choi, Javier del Prado, Sai Shankar Philips Research USA; Atul Garg, Philips Semiconductors mwentink@intersil.com and sunghyun.choi@philips.com. Introduction.

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EDCF Access Categories

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  1. EDCF Access Categories Menzo Wentink, Intersil; Sunghyun Choi, Javier del Prado, Sai Shankar Philips Research USA; Atul Garg, Philips Semiconductors mwentink@intersil.com and sunghyun.choi@philips.com M.M. Wentink, Intersil & S. Choi, Philips

  2. Introduction Priority, Priority Parameter, Delivery Priority, TCs, Queues and EDCF Parameters M.M. Wentink, Intersil & S. Choi, Philips

  3. Status as of 802.11e/D1.3 (1) • Priority parameter = TC (from 0 to 15) • provided in the MA-UNIDATA.request • Priority (from 0 to 7) • extracted from the Priority Parameter • indirectly in the Delivery Priority of the TSPEC • Delivery Priority (from 0 to 7) • mapped from Priority using dot11PriorityMapping M.M. Wentink, Intersil & S. Choi, Philips

  4. Status as of 802.11e/D1.3 (2) 16 Priority Parameters or TCs 8 Priorities 8 Delivery Priorities <= 8 Physical Queues EDCF Parameters (AIFS, CWmin,…) M1 M2 M3 M.M. Wentink, Intersil & S. Choi, Philips

  5. Status as of 802.11e/D1.3 (2) • Mapping M1 using table dot11PriorityMapping • Mapping M2 not specified • Mapping M3 between access parameters (i.e., AIFS[i], Cwmin[i], PF[i]) and queues is currently problematic • this was noted earlier by Sunghyun Choi • see next slides! • more details about the problems can be found in submissions by Choi, et al. (01/534) and Wentink (01/541) • the solution outlined in this proposal supersedes the solutions in the above mentioned documents M.M. Wentink, Intersil & S. Choi, Philips

  6. Problematic Descriptions in D1.3 • 9.1.3.1: • “An ESTA or EAP may implement fewer than 8 physical queues and shall provide a mapping from traffic categories and delivery priorities to the available queues by means of the dot11PriorityMapping table in the MAC MIB.” • 9.2.3.4: • “An ESTA that provides fewer than 8 output queues shall use the TxAIFS [TC] slot boundary for queue [i] where TC is the highest priority TC assigned to queue [i]. • What happens if an ESTA has only one queue? • All frames will be served using TC=7 AIFS !!! • This does not sound reasonable at all !!! M.M. Wentink, Intersil & S. Choi, Philips

  7. Problematic Descriptions in D1.3 • 9.2.4: • The enumeration of implemented queues determines which access parameters should be used: “queue i uses CWmin[i]" • 9.2.3.4: • “An ESTA that provides fewer than 8 output queues shall use the TxAIFS [TC] slot boundary for queue [i] where TC is the highest priority TC assigned to queue [i]. • So which access parameters should be used for queue i when there are <8 queues? M.M. Wentink, Intersil & S. Choi, Philips

  8. Proposed Solution M.M. Wentink, Intersil & S. Choi, Philips

  9. Proposed Solution (1) • Delete the concept of Delivery Priority • confusing with Priority • doesn’t appear to have any use in the draft • Introduce the concept of Access Category (AC) • an Access Category represents a single virtual DCF • Let 4 ACs be normative, for EAP and ESTA • in absence of certain types of traffic, the corresponding queue does not have to be implemented • i.e. no burden on dedicated application terminals, like phones • Note 4 ACs does not limit the number of queues to 4. M.M. Wentink, Intersil & S. Choi, Philips

  10. Proposed Solution (2) • Simplify M1 and M2 into one unique mapping M0: • see tables on next slides Priority Access Category M0 • Let the QoS Parameter Set element contain 4 sets of access parameters • M3is now a trivial one-to-one mapping between access parameters and ACs M.M. Wentink, Intersil & S. Choi, Philips

  11. Proposed Solution (3) 16 Priority Parameters or TCs 8 Priorities M0 4 ACs (↔ 4x EDCF parameters) M.M. Wentink, Intersil & S. Choi, Philips

  12. Proposed Solution – M0 (I) • Priority to Access Category mapping, alt. I • according to 802.1D tables H.15, H.16 • introduces a ‘lower-than-best-effort’ AC bk = background sp = spare be = best effort ee = excellent effort vi = video cl = controlled load vo = voice nc = network control M.M. Wentink, Intersil & S. Choi, Philips

  13. Proposed Solution – M0 (II) • Priority to Access Category mapping, alt. II • dedicated AC for voice, video • no ‘lower-than-beest-effort’ AC, but this does not exclude a ‘lower-than-best-effort’ priority. bk = background sp = spare be = best effort ee = excellent effort vi = video cl = controlled load vo = voice nc = network control M.M. Wentink, Intersil & S. Choi, Philips

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