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Use of BSSID in WAVE

Use of BSSID in WAVE. Authors:. Date: 2007-11-15. Abstract. It is proposed to set the BSSID in all data frames transmitted in WAVE mode to the wildcard BSSID. This is to permit simultaneous reception of WAVE BSS data frames and non-BSS data frames on the same channel. Desired Functionality.

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Use of BSSID in WAVE

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  1. Use of BSSID in WAVE Authors: Date: 2007-11-15 Doug Kavner, Raytheon

  2. Abstract It is proposed to set the BSSID in all data frames transmitted in WAVE mode to the wildcard BSSID. This is to permit simultaneous reception of WAVE BSS data frames and non-BSS data frames on the same channel. Doug Kavner, Raytheon

  3. Desired Functionality • WAVE mode permits transmission of data frames without an established WAVE BSS • Normally with a wildcard BSSID • It may be desirable now or in the future to permit this in conjunction with WAVE BSS data frames from the same STA • 802.11p does not explicitly exclude this operation currently • Note: BSSID for a WAVE BSS is the MAC address of the WAVE BSS Initiator Doug Kavner, Raytheon

  4. The Problem (1) • BSSID in transmitted data frames is the currently joined BSSID • BSSID is not specified on a frame-by-frame basis from higher layers • See IEEE Std 802.11-2007, clause 6.2.1.1.2 • Adding a frame specific BSSID would require changing MA-UNITDATA.request and may not be supportable on current implementations • Resetting the MAC to change the BSSID is not feasible • Loss of MAC state and queued packets • Latency Doug Kavner, Raytheon

  5. The Problem (2) • Using a non-wildcard WAVE BSSID for non-BSS data frames is problematic • Assume two nearby WAVE BSSs with BSSID=3 and BSSID=4 • STAs on BSSID 3 will filter data frames from BSSID 4 • Non-BSS data frames sent from a STA on BSSID 4 will also be filtered by STAs on BSSID 3 • Running in promiscuous mode would circumvent the primary purpose of multiple BSSIDs, which is to permit filtering of broadcast/multicast data frames • IEEE Std 802.11-2007, p. 78 first sentence Doug Kavner, Raytheon

  6. Proposed Solution • Transmit all data frames with a wildcard BSSID • Implications to WAVE BSS Data Frames • Unicast Data Frames: None • Filtering is already based on the RA alone • RA will remain the MAC address of the WAVE BSS Initiator • Broadcast Data Frames: Will be processed by all STAs, including those not in the WAVE BSS • Do not use if filtering is desired (see next side) Doug Kavner, Raytheon

  7. Option to retain MAC filtering • To broadcast to the WAVE BSS only: • Use a locally administered multicast MAC address for the RA • Multicast MAC would be unique to a specific WAVE BSS • Embedded in WIE • Need to add a new WAVE BSS specific filtering requirement when a local group address is detected in the RA • Ugly, but defendable (perhaps) • May be difficult to support for some implementations • Backwards compatibility? Doug Kavner, Raytheon

  8. Alternative Solution • Retain current non-wildcard BSSID for a WAVE BSS • Specify that no BSSID filtering is performed for data frames in WAVE mode • Less breakage to 1609 • Raises question of why we have a BSSID at all • More straightforward to just use proposed solution without the filtering option Doug Kavner, Raytheon

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