Roaming Requirements Discussion

1. Roaming Requirements Discussion Michael Montemurro, Chantry Networks Darwin Engwer, Nortel Networks Michael Montemurro, Chantry Networks

2. Introduction • Doc 04/084 – Demonstrates why Fast Roaming is needed • Doc 04/086 – Presents a definition for Roaming and a test topology • To put further scope into the definition of fast roaming • Propose breaking down the problem into elements that could be used to evaluate of different solutions Michael Montemurro, Chantry Networks

3. Roaming in the context of 802.11 • Recall the worst case scenario (doc 04/086): • AP’s on different channels, single ESS • AP’s connected via a switch • Downlink traffic only • Both AP’s remain powered up during roam • How is this differentiated from 802.21? • 802.21 solves different MAC’s, different ESS, Michael Montemurro, Chantry Networks

4. What is the roaming problem? Network Switch Switch AP AP ESS AP and MU Share State MAC, DS, Security, QoS MU Roaming Determination Link Quality, Scan Results, Service Availability, Velocity Michael Montemurro, Chantry Networks

5. The Elements of Roaming • How to determine when/where to roam? • How to minimize the time it takes to move state from one AP to another or establish state at the new? Michael Montemurro, Chantry Networks

6. When/Where to Roam? • IEEE 802.11 standards • States that the STA/MU can be only connected to one BSS/AP at any point in time • MU has to decide when and where to roam • Cellular standards • Roaming is network driven • MU moves within the network • The Network hands off the connection from cell to cell Michael Montemurro, Chantry Networks

7. STA Considerations for Roaming • TGk provides metrics for a roaming decision • Depends on roaming time versus velocity of the client • When is roaming calculated versus when does it roam? • Depends on service availability on new AP? • Is there bandwidth available? • Will the connection be secure? Michael Montemurro, Chantry Networks

8. Minimizing Roaming Time • What can a STA or AP do to minimize re-connection time? • Need to moving connection state for the STA from the current AP to the new AP • Need to update the DS with the new link state Michael Montemurro, Chantry Networks

9. State Transitions for Roaming Two options: • Transition connection state from one AP to another ( requires AP to AP communications) • Derive a new connection state between one MU and the AP (MU to AP communications only) • State transition could occur before or during the roaming event Michael Montemurro, Chantry Networks

10. MU/AP Connection State • MAC/PHY – link state, radio parameters, rate, etc. • Security – PMK, PTK, etc. • QoS – TSPEC • DS – physical port map (MAC – Port Number) Michael Montemurro, Chantry Networks

11. State Transition Considerations • Needs to be secure • Do AP’s need to communicate? • Over the air? Over the wired network? • Could we leverage IAPP? CAPWAP? • AP-AP communications needs to be secure • Should the AP’s share state information? Michael Montemurro, Chantry Networks

12. Other considerations • Does the process start before the MU roams? (i.e. like Pre-authentication) • Should the MU reserve resources before it moves? • Should the DS reserve resources before the MU moves? Michael Montemurro, Chantry Networks

13. Conclusions • The two elements to fast roaming are: • Determination of when/where to roam • Need to consider service availability • Minimize the time it takes to establish a new connection state at the new • Needs to be secure • Minimize roaming time Michael Montemurro, Chantry Networks