Use of Timing Advertisement, VSIE & Vendor Action Frame Mar 2009

1. Use of Timing Advertisement,VSIE & Vendor Action FrameMar 2009 Alastair Malarky MARK IV IVHS amalarky@ivhs.com http://www.ivhs.com 905-624-3020 x 1203

2. Background • I raised a comment to 1609.3 v1.0 stating we should be able to send Timing Advertisement without WSAs – John suggested I clarify this. • I stated at last meeting we should use VSIE to authenticate any 802.11 management frame • I believe we will want other 1609 management messages as time goes on and we may not want to tie these to the Timing Advertisement frame.

3. Timing Advertisement Frame (802.11pD6.0) Information is provisional – Only provided for use in discussion of frame use in 1609

4. Timing information element (802.11pD6.0) Information is provisional – Only provided for use in discussion of frame use in 1609

5. Why Timing Advertisement without WSA • We originally discussed the possibility of STAs which are not providers but which provide only timing information. • A STA may want to obtain a more accurate update of UTC • Doesn’t want to wait until it gets into coverage of a provider. • If there are other STAs around that have UTC it can get it from them • It may be operating only on an SCH. • The 802.11 information in the Timing Advertisement frame, including the Timing information element, is not necessarily needed at the frequency of WSAs. • There may be cases, e.g. 1609.1, of devices which don’t want WSA but may want UTC to a coarser accuracy than that required for sync • other local functions • security functions

6. Need for 1609 Management messages • 1609.1 needs to pass management messages between devices • 1609.2 may want this for certificate distribution etc. • May in the future want management messages like: • Mesh/multi-hop tables • Transfer “situation picture” for populating local dynamic map • Download of regulatory table (as per European concept) • Request for Timing Advertisement message reqd. • Getting UTC even if no provider around • Getting UTC if always on service channel

7. 802.11 frames from 1609 perspective • A 802.11 Timing Advertisement management frame that can contain: • A Timestamp • A Timing information element that allows us to determine UTC from TSF timer • Some high level 802.11 fields like Country and Capability • Multiple Vendor Specific information elements (VSIEs) • Standard 802.11 management (incl. action) frames including 802.11k radio measurement frames, each of which can contain: • Multiple VSIEs • 802.11 Vendor Specific Action frame that can contain: • a vendor specific data element up to the maximum MMPDU length

8. VSIE & Vendor Specific Action frame (802.11pD6.0) • Organization Identifier is 5 octets for 1609 • Contains IAB • VSIE (255-i octets max): • Vendor Specific Action frame: • Will know in few days if frame changes are generally accepted (ballot closes 31 Mar) Information is provisional – Only provided for use in discussion of frame use in 1609

9. Organization Identifier • Written to cover any IEEE-RA assigned public unique identifier : • 24 bits : OUI • 36 bits : IAB and OUI-36 • Any future growth • Number of octets used depends on assigned identifier • 5 bits for 1609 = 0x0050C24A4<y> • Last 4 bits can be used as sub-identifier by 1609: • Security mechanism ? • Protocol extension (1609.1, CALM …) ? • 1609 IAB is sufficient; No need to apply for OUI-36. Information is provisional – Only provided for use in discussion of frame use in 1609

10. VSIE & Vendor Specific Action Frame • Vendor Specific information element (VSIE) • Only as part of 802.11 management frames • Limited to 255 octets but multiple can be used per frame • Each enough for authentication plus limited data • One not enough for WSA • Waste 8/255 octets with overhead & segmenting just in VSIEs • Waste in repetitive transmission of other 802.11 elements if not required • Vendor Specific Action (VSA) frame • Stand-alone management frame • Doesn’t contain Timestamp • Doesn’t have other overhead elements • No segmentation required (unless exceed maximum MMPDU)

11. Recommendation 1 We use VSIE to provide 1609 authentication of 802.11 frames • includes the Timing Advertisement frame and 802.11k frames. • Note the Vendor Specific Action frame can contain 1609 authentication and doesn’t need a VSIE • We can optionally use VSIEs for 1609 management messages, but for long items such as WSA, I would recommend the Vendor Specific Action frame.

12. Adding Authentication to 802.11 frames • Data being signed does not have to be encapsulated in signature • Both transmitter and receiver must know what portion of the non-encapsulated data is included in signature calculation process • Security process SAPs only need to know 2 data blobs in, one blob out.

13. VSIE Authentication & 1609 • 1609.3 (since no 1609.5) is place to specify how/when we add authentication to VSA and VSIE • SAP call to Security (1609.2) • 1609.3 defines blobs • 1609.3 is place to specify we use VSIE to add authentication to 802.11 management frames. • 1609.3 must also define for 802.11 frames what the non-encapsulated data blob contains. • For example can’t include Timestamp – added at physical layer on transmission • If 1609 supports different authentication mechanisms, then we could use the last 4 bits of Organization Identifier to indicate mechanism used • Alternatively the signing could include that. • Last 4 bits might be better to indicate protocol extension, like 1609.1

14. Recommendation 2 We use the Vendor Specific Action frame to carry all 1609 management messages • WSA is just one 1609 management message • 1609.1 can use this frame instead of WSMs (current draft) for management functions • We can in the future add 1609 management messages at any time without needing to go back to 802.11 • The Vendor Specific Action frame can contain 1609 authentication itself – doesn’t need VSIE

15. Impact on Providers • All providers transmit both: • Vendor Action Frames containing WSA • Timing Advertisement frame containing Timing information element • The Timing Advertisement frames can go out at much less frequent intervals if required. • They can also go out on service channels • 1609.3 should define which of the “optional” elements in the 802.11 frame are mandatory for provider transmitting with WSAs

16. Recommendation 3 • We create a 1609.3 management message for “Request for Timing Advertisement”. • Any STA can transmit this on any channel • I suggest the frame contains a ‘time error” indicator. • Any 1609 STA, even a user STA can transmit Timing Advertisement frame in response to request • if it’s estimate of UTC is below the error value in the request. • 1609.3 should define which of the “optional” elements in the 802.11 frame are mandatory for such responses. • Response is returned in same channel