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Simplified Direct Link Setup Frame Transmission

This document discusses a simplified method for transmitting Direct Link Setup (DLS) frames, solving the issues with frame reordering. It proposes a solution that does not violate the IEEE 802 architecture and reduces overhead on the MAC layer entity.

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Simplified Direct Link Setup Frame Transmission

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  1. Simplified DLS Action Frame Transmission in 11Z Date: 2007-12-07 Authors: L.Chu Etc.

  2. Simplified direct link setup frame transmission • Solution to frame reordering • Backup Slides L.Chu Etc.

  3. TDLS action frames are encapsulated in data frames as data frame payload. Encapsulated TDLS action frames go through an AP path from STA1 to STA2 An AP transparently forwards encapsulated TDLS management action frames. An AP is unaware of TDLS management frames that it forwards! Tunneled Direct Link Setup (TDLS) in [1] 6 Variable 4 Octets: 24/26 1 1 TDLS Packet Type MAC Data Header Remote Frame Type TDLS Information LLC/SNAP FCS Data Frame Payload AP AP Path 1b 1a 2a 2b Direct Link STA2 STA1 L.Chu Etc.

  4. MAC layer entity in a STA has to analyze the ethertype octet at the link layer in each data frame that it accepts. It violates IEEE 802 architecture. It puts much overhead on the MAC layer entity. Some overhead is put in AP. An AP has to forward TDLS action frames. Problems with TDLS AP AP Path 1b 1a 2a 2b STA2 STA1 Direct Link L.Chu Etc.

  5. New DLS action frames are defined with new action type. New DLS action frames are sent between two STAs directly New DLS action frames are not encapsulated in MAC data frames. An AP does not forward the proposed DLS action frames. Simplified Direct Link Setup Frame Transmission Variable Octets: 24 1 1 4 TDLS Information Management Frame Header Action Value Category FCS Management Frame Payload AP New DLS action frame path. AP Path 1 STA2 STA1 Direct Link Path 2 L.Chu Etc.

  6. PROs This method does not violate the 802 architecture. This method does not need a new ethertype octet. The MAC entity does not need to analyze ethertype in each data frame! An AP does not forward the proposed DLS action frames. PROs of Simplified DLS Frame Transmission AP SDLS action frame path. AP Path 1 STA2 STA1 Direct Link Path 2 L.Chu Etc.

  7. Simplified direct link setup frame transmission • Solution to frame reordering • Backup Slides L.Chu Etc.

  8. When STA1 sends a Tx Path Switch Request with the direct path indication, it shall stop transmitting frames to STA2 through the AP. STA1 shall buffer the frames to STA2. When STA1 receives a Tx Path Switch Response with the direct path indication, it starts a delay timer. When the delay timer times out, STA1 starts to transmit frames to STA2 through direct link path. Solution to Frame Reorder AP AP Path STA2 STA1 Direct Link Path L.Chu Etc.

  9. [1] 11-07/2515r8, Tunneled Direct Link Setup (TDLS), Menzo Wentink etc. Reference L.Chu Etc.

  10. Simplified direct link setup frame transmission • Solution to frame reordering • Backup Slides L.Chu Etc.

  11. Comments And Replies • [Comment] A station normally receives only frames from the AP, but in your case it also needs to receive frames from any other TA. This does not seem right. It appears like you assume that a direct link is already in place before setting one up?  • [Answer] This is a very good point. Actually I asked this question to myself many times when I prepared this presentation. You are right, a station normally receives only frames from the AP in a infrastructure BSS. My assumption is that  if a station implements 11z DLS, it will receive only new DLS management frames from another non-AP station directly before DLS connection is set up. No data frames are allowed being transmitted between two non-AP stations before the DLS is set up. So this does not means that a direct link is already in place before setting one up. This is what will be defined in 11z standard.  This is similar to the security association between two stations. Unprotected data frames are not allowed between two stations before security association is set up. But security management frames are allowed before this security association is set up.   • [Comment] How do you know whether the intended peer station is in power save or not?  • [Answer] The initiator does not need to know if the intended peer is in power save or not. If the intended peer station is in power save state, the initiator can not set up a direct link any way. So in this case, the initiator will fail to set up a direct link with the destination after being timing out. It can try again later if it wants.  • [Comment] How do you propose to setup a secure direct link without the secure connection via the AP?  • [Answer] To my understanding, it is the master session key that authenticates the peer station. If peer stations have master session key of another station, they can authenticate each other and set up DLS security association. The master session key may be got through the pre-installed key or the security connection with AP to the AAA server.  L.Chu Etc.

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