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
+    +  <------------->  + C2 +
+    + (802.11a network) +....+   
+ C1 +   
+    +           
+    +  Static-member    +....+ Static-leader
+    +  <------------->  + C3 +
+....+ (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