One Comment on “Which two Cisco Unified Wireless Network capabilities use information that is provided by Radio Resource Manag”

1. raghu says:

   January 9, 2015 at 12:09 am

   First we should learn how the RRM works:

   1) Controllers (whose APs need to have RF configuration computed as a single group) are provisioned with the same RF Group Name. An RF Group Name is an ASCII string

   each AP will use to determine if the other APs they hear are a part of the same system.

   (RF groups are groups of controllers that share the same RF group name and whose APs can hear the neighbor messages of each other)

   2) APs periodically send out Neighbor Messages, sharing information about themselves, their controllers, and their RF Group Name. These neighbor messages can then be

   authenticated by other APs sharing the same RF Group Name.

   3) APs that can hear these Neighbor Messages and authenticate them based on the shared RF Group Name, pass this information (consisting primarily of controller IP

   address and information on the AP transmitting the neighbor message) up to the controllers to which they are connected.

   4) The controllers, now understanding which other controllers are to be a part of the RF Group, then form a logical group to share this RF information and subsequently

   elect a group leader.

   5) Equipped with information detailing the RF environment for every AP in the RF Group, a series of RRM algorithms are used to optimize AP configurations.

   Information from Radio Resource Management (RRM) monitors the radio resources, performs dynamic channel assignments, provides detection and avoidance of interference,

   and provides the dynamic transmit power control (TPC).

   The RRM neighbor message contains the following information:

   * Radio Identifier: If the AP had multiple radios, this field identifies the radio used to transmit the message.
   * Group ID: The 16-bit value and controller MAC address. This information is used to detect rogue access points. The access points will then check the beacon/probe-

   response frames in neighboring access point messages to see if they contain an authentication information element (IE) that matches that of the RF group. If the check

   is successful, the frames are authenticated. Otherwise, the authorized access point reports the neighboring access point as a rogue, records its BSSID in a rogue

   table, and sends the table to the controller.

   * WLC IP Address: RF group leader’s management IP address. This address is discovered through Over-the-Air Provisioning (OTAP)
   * AP Channel: The native channel that the AP uses to service clients.
   * Neighbor Message Channel: The channel the message is sent on.
   * Power: The power level at which the message is transmitted.
   * Antenna Pattern: The antenna pattern currently in use

   Note:

   Dynamic channel assignment is used to dynamically allocate access point channel assignments to avoid conflict and to increase capacity and performance. For example,

   two overlapping channels in the 802.11g band, such as 1 and 2, cannot both simultaneously use 54 Mbps. By effectively reassigning channels, the controller keeps

   adjacent channels separated, thereby avoiding this problem.

   Over-the-Air Provisioning (OTAP) is a method for APs to discover the management IP of a controller over the air.

   A rogue AP is an AP that is unknown to the controller.

   
   
   
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