This MIB is intended to be implemented on all those devices operating as Central controllers, that terminate the Light Weight Access Point Protocol tunnel from Cisco Light-weight LWAPP Access Points. Information provided by this MIB is used to study the RRM on the WLAN. The relationship between CC and the LWAPP APs can be depicted as follows: +......+ +......+ +......+ + + + + + + + CC + + CC + + CC + + + + + + + +......+ +......+ +......+ .. . . .. . . . . . . . . . . . . . . . . . . +......+ +......+ +......+ +......+ + + + + + + + + + AP + + AP + + AP + + AP + + + + + + + + + +......+ +......+ +......+ +......+ . . . . . . . . . . . . . . . . . . . +......+ +......+ +......+ +......+ + + + + + + + + + MN + + MN + + MN + + MN + + + + + + + + + +......+ +......+ +......+ +......+ The LWAPP tunnel exists between the controller and the APs. The MNs communicate with the APs through the protocol defined by the 802.11 standard. LWAPP APs, upon bootup, discover and join one of the controllers and the controller pushes the configuration, that includes the WLAN parameters, to the LWAPP APs. The APs then encapsulate all the 802.11 frames from wireless clients inside LWAPP frames and forward the LWAPP frames to the controller. GLOSSARY Access Point ( AP ) An entity that contains an 802.11 medium access control ( MAC ) and physical layer ( PHY ) interface and provides access to the distribution services via the wireless medium for associated clients. LWAPP APs encapsulate all the 802.11 frames in LWAPP frames and sends them to the controller to which it is logically connected. Light Weight Access Point Protocol ( LWAPP ) This is a generic protocol that defines the communication between the Access Points and the Central Controller. Central Controller ( CC ) The central entity that terminates the LWAPP protocol tunnel from the LWAPP APs. Throughout this MIB, this entity is also referred to as 'controller'. Mobile Node ( MN ) A roaming 802.11 wireless device in a wireless network associated with an access point. Mobile Node and client are used interchangeably. Radio Resource Management ( RRM ) RRM is the system level control of co-channel interference and other radio transmission characteristics in wireless communication systems. Received Signal Strength Indicator ( RSSI ) A measure of the strength of the signal as observed by the entity that received it, expressed in 'dbm'. Coverage Hole Detection ( CHD ) If clients on an Access Point are detected at low RSSI levels, it is considered a coverage hole by the Access Points. This indicates the existence of an area where clients are continually getting poor signal coverage, without having a viable location to roam to. Dynamic Channel Assignment (DCA) Dynamic channel assignment (DCA) is used by the controller to minimize adjacent channel interference between access points. Dynamic Frequency Selection (DFS) Dynamic frequency selection (DFS) is used by the controller to detect radar signals and avoid interfering with them. RRM RF Grouping Radio Resource Management (RRM) allows the Cisco WLAN controllers to continuously analyze the existing RF environments, and automatically adjust the AP power and channel configurations in order to help alleviate overlapping channel interference, signal coverage problems, and so forth. An RF group is a cluster of Cisco wireless controllers that coordinates its RRM calculations on a per 802.11-network basis. An RF group exists for each 802.11 network type. Clustering controllers into RF groups enables the RRM algorithms to scale beyond a single controller. +....+ Auto-leader +....+ Auto-member + + < + + (802.11a network) +....+ + C1 + + + + + Static-member +....+ Static-leader + + < +....+ (802.11b network) +....+ With the help of above diagram, different aspects of RRM RF Grouping can be explained. Grouping can be configured for 3 modes. 1) Automatic 2) Static 3) Off If the mode is 'Automatic', the controllers automatically form groups and elect leaders to perform better dynamic parameter optimization. If the mode is 'Static', user can select one controller as the group leader and configure the group members manually. If the mode is 'Off', no dynamic grouping occurs. Each controller optimizes only its own APs' parameters. In the above diagram, controller C1 forms a RF group with controller C2 in 802.11a network. And with controller C3, it forms a different group in 802.11b network. For the 802.11a network, the gorup mode is selected as 'Automatic'. So between C1 and C2 controllers, one would be selected as group leader and the other controller as member automatically by the algorithm. In the above case C1 is the group leader and C2 is the group member. Now for 802.11b network, group mode is selected as 'Static'. Also the user has manually configured C3 as the leader in this group and C1 was added to this group as member. REFERENCE [1] Wireless LAN Medium Access Control ( MAC ) and Physical Layer ( PHY ) Specifications [2] Draft-obara-capwap-lwapp-00.txt, IETF Light Weight Access Point Protocol