1. doc.: IEEE 802.11-04/1436r0 Submission November 2004 Mike Moreton, STMicroelectronicsSlide 1 L2 Domain Indication Mike Moreton, STMicroelectronics 15 th November, 2004

2. doc.: IEEE 802.11-04/1436r0 Submission November 2004 Mike Moreton, STMicroelectronicsSlide 2 Cross Subnet Roaming –When a STA roams from one AP to another, it runs the risk that the new AP may not be connected to the same IP subnet. Its IP address will no longer be valid It will have no connection to the IP router it was previously using. –Changing IP address normally disrupts established sessions –Wouldn’t it be nice if when choosing which AP to roam to, the STA knew whether each AP being considered was definitely on the same subnet as the current one?

3. doc.: IEEE 802.11-04/1436r0 Submission November 2004 Mike Moreton, STMicroelectronicsSlide 3 Solution Requirements Each AP should include an IE in its Beacons and Probe Response Frames that contains the “L2 Domain ID”. APs that advertise the same L2 Domain ID should always be on the same subnet. APs that advertise different L2 Domain IDs should in general be on different subnets. SSID is not suitable –Different ESSes can share the same SSID.

4. doc.: IEEE 802.11-04/1436r0 Submission November 2004 Mike Moreton, STMicroelectronicsSlide 4 A Simple L2 Domain ID Use the Spanning Tree Protocol (STP) Root MAC address as the L2 Domain ID. STP elects a root bridge from the bridges connected to a L2 domain. The MAC address of this bridge is included in STP messages broadcast to the L2 domain. –APs don’t have to implement STP, they just have to understand these messages. –MAC addresses are globally unique so no chance of two root nodes having the same address.

5. doc.: IEEE 802.11-04/1436r0 Submission November 2004 Mike Moreton, STMicroelectronicsSlide 5 What if the Root Node Changes? Happens very rarely in practice. STAs need not assume that different L2 Domain IDs always mean different subnets –Go through current roaming procedure in this case – no disadvantage over current system.

6. doc.: IEEE 802.11-04/1436r0 Submission November 2004 Mike Moreton, STMicroelectronicsSlide 6 FAQ. What if STP is not being used in this L2 domain? –APs will not see STP messages, and will not know the root node, so should not automatically broadcast the L2 domain ID. What if someone wants to hard configure the L2 Domain ID? –Fine – hard configuration should take precedence over STP.