1. TDLS Setup Date: 2008-03-12 Authors: Mar 2008 September 2007
doc.: IEEE /2376r0
Mar 2008
TDLS Setup
Date:
Authors:
L.Chu Etc.
Steve Emeott, Motorola

2. TDLS Setup in [1] TDLS Setup goes through 3-way handshakes:
Mar 2008
TDLS Setup in [1]
TDLS Setup goes through 3-way handshakes:
TDLS Setup Request (STA1STA2)
TDLS Setup Response (STA2STA1)
TDLS Setup Reply (STA1STA2)
If security is required between STAs using direct path, SMK handshake messages 1, 2, 3 shall be included in TDLS Setup messages. AP
AP Path 2a 1a 2a 1a 1b 1b
Direct Link
STA1
STA2
L.Chu Etc.

3. Problem 1 with TDLS Setup
Mar 2008
Problem 1 with TDLS Setup
The draft does not define the behavior of STAa and STAb try to setup TDLS direct link path at almost the same time.
If the draft allows the continuation of each setup procedure,
Both of the STAs are initiator stations.
If security is required in the DLS path,
there are two set of INonce, PNonce etc. which is difficult to get master key.
Who will start 4-way handshake to get the temporary session key.
The procedure to fix this problem should be provided. AP
AP Path
STAb initiated setup procedure. 2a 1a 2a 1a
STAa initiated setup procedure. 1b 1b
Direct Link
STAa
STAb
L.Chu Etc.

4. Solution to TDLS Setup Problem 1
Mar 2008
Solution to TDLS Setup Problem 1
Solution 1
If STAa and STAb try to setup TDLS direct link path at almost the same time, one TDLS Setup Request can be ignored, for example:
the request from the STA with larger MAC address (or larger AID) is ignored.
The STA with lower MAC address (or lower AID) may send a TDLS Setup Response with status code “collided TDLS Setup”.
Solution 2
If STAa and STAb try to setup TDLS direct link path at almost the same time, both TDLS Setup Request can be ignored. Two STAs can go through a backoff procedure before trying another TDLS Setup procedure with the peer STA.
It seems that solution 1 is a good method.
L.Chu Etc.

5. Problem 2 with TDLS Setup
Mar 2008
Problem 2 with TDLS Setup
In MLME section (section 11), if security is required between STAs using direct path, SMK handshake messages 1, 2, 3 shall be included in TDLS Setup messages.
In security section (section 8), each time a STA receive a SMK handshake message, it will verify the Peer MAC address against existing direct link. If no direct link exists, it silently discards the message.
Apparently, these two places give contradictory descriptions.
L.Chu Etc.

6. Solution to TDLS Setup Problem 2
Mar 2008
Solution to TDLS Setup Problem 2
On receipt of Message 1, the peer STA performs following actions:
a) Verify the initiator MAC address against existing direct link or Message 1 being part of TDLS Setup Request. If no direct link exists or Message 1 is not part of TDLS Setup Request, it silently discards the message.
On receipt of Message 2, the initiator STA performs following actions:
a) Verify the peer MAC address against existing direct link or Message 2 being part of TDLS Setup Response. If no direct link exists or Message 2 is not part of TDLS Setup Response, it silently discards the message.
On receipt of Message 3, the peer STA performs following actions:
a) Verify the initiator MAC address against existing direct link or Message 3 being part of TDLS Setup Confirm. If no direct link exists or Message 3 is not part of TDLS Setup Confirm, it silently discards the message.
L.Chu Etc.

7. September 2007
doc.: IEEE /2376r0
Mar 2008
Reference
[1] IEEE P802.11zTM/D0.2 Draft STANDARD for Information Technology – Telecommunications and information exchange between systems – Local and metropolitan area networks – Part 11 Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications Amendment 7: Direct Link Setup
L.Chu Etc.
Steve Emeott, Motorola