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.
BSS Color Optimization (BCO)
BCO is used by the controller to minimize BSS color collisions
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 group 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
ication is generated when the AP receives at least
'packet count' packets, represented by clrRrmParametersVoicePktCount
for voice or clrRrmParametersDataPktCount for data, from a client
in any given 5 second interval and 'packet percent' of the packets,
represented by clrRrmParametersVoicePktCount for voice and
clrRrmParametersDataPktCount for data, from the client are below
the 'RSSI threshold' represented by
clrRrmParametersVoiceRssiThreshold for voice and
clrRrmParametersDataRssiThreshold for data.
ciscoLwappRrmRfGroupLeaderChange
.1.3.6.1.4.1.9.9.615.0.2
ication would be generated,
from the controller that is elected as the
new leader, when RF Grouping is done.
It has MAC address and details of the new Group Leader.
ciscoLwappRrmRfGroupMemberAdded
.1.3.6.1.4.1.9.9.615.0.3
ication is generated from the group leader
when a new member is added to the RF group.
This notification has MAC address and details of
new group member.
ciscoLwappRrmRfGroupMemberRemoved
.1.3.6.1.4.1.9.9.615.0.4
cation is generated from the group leader,
when a member is removed from the RF group.
This notification has MAC address and details of
removed group member.
ciscoLwappDot11ClientCoverageHolePreAlarmRev
.1.3.6.1.4.1.9.9.615.0.5
generates this notification when the
RRM coverage hole detection algorithm detects areas of radio
coverage in a wireless LAN that are below the level needed for
robust radio performance.
If clients on a access point are detected at
threshold levels (RSSI, percentage of failed
packets, and number of failed packets) specified in RRM
configuration, the access point sends a 'coverage hole'
alert to the controller.
This notification is generated in any of the following
conditions
1)When the failed packet count
is more than failed packet count threshold represented by
clrRrmParametersVoicePktCountThreshold for voice and
clrRrmParametersDataPktCountThreshold for data.
2)When the percentage of failed packet count is more than
the failed packet count threshold represented by
clrRrmParametersVoicePktPercentThreshold for voice and
clrRrmParametersDataPktPercentThreshold for data.
3)When RSSI value is lower than the RSSI threshold represented
by clrRrmParametersVoiceRssiThreshold for voice and
clrRrmParametersDataRssiThreshold for data.
ciscoLwappRrmRfGroupLeaderChangeRev
.1.3.6.1.4.1.9.9.615.0.6
ication would be generated,
from the controller that is elected as the
new leader, when RF Grouping is done.
It has MAC address and details of the new Group Leader.
ciscoLwappRrmRfGroupMemberAddedRev
.1.3.6.1.4.1.9.9.615.0.7
ication is generated from the group leader
when a new member is added to the RF group.
This notification has MAC address and details of
new group member.
ciscoLwappRrmRfGroupMemberRemovedRev
.1.3.6.1.4.1.9.9.615.0.8
cation is generated from the group leader,
when a member is removed from the RF group.
This notification has MAC address and details of
removed group member.