1. Use of BSSID in WAVE Date: 2007-11-15 Authors: November 2007
doc.: IEEE /2901r0
November 2007
Use of BSSID in WAVE
Date:
Authors:
Doug Kavner, Raytheon
Doug Kavner, Raytheon

2. November 2007
doc.: IEEE /2901r0
November 2007
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
Doug Kavner, Raytheon

3. Desired Functionality
November 2007
doc.: IEEE /2901r0
November 2007
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
Doug Kavner, Raytheon

4. November 2007
doc.: IEEE /2901r0
November 2007
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 , clause
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
Doug Kavner, Raytheon

5. November 2007
doc.: IEEE /2901r0
November 2007
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 , p. 78 first sentence
Doug Kavner, Raytheon
Doug Kavner, Raytheon

6. Proposed Solution Transmit all data frames with a wildcard BSSID
November 2007
doc.: IEEE /2901r0
November 2007
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
Doug Kavner, Raytheon

7. Option to retain MAC filtering
November 2007
doc.: IEEE /2901r0
November 2007
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
Doug Kavner, Raytheon

8. Implications to use of the Distribution System
November 2007
Implications to use of the Distribution System
Can’t use wildcard BSSID in RA of “To DS” data frame
Would need to footnote Table 7-7 in IEEE Std
For “From DS” frame in WAVE mode, TA ≠ BSSID
For “To DS” frame in WAVE mode, RA ≠ BSSID
Distribution system clauses in the base document may need changes
Distribution to STA not based on BSSID
BSSID ≠ WAVE BSS Initiator MAC address
WAVE permits distribution without association
Doug Kavner, Raytheon

9. Alternative Solution Retain current non-wildcard BSSID for a WAVE BSS
November 2007
doc.: IEEE /2901r0
November 2007
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
May be difficult to implement
All data frames currently have a single value, the BSSID
Fewer issues to the distribution system
Raises question of why we have a BSSID at all
More straightforward to just use proposed solution without the filtering option
Doug Kavner, Raytheon
Doug Kavner, Raytheon