Cisco Cisco 5520 Wireless Controller Referencia técnica
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Radio Resource Management–Radio Frequency Grouping Algorithm
RF Grouping
Under Monitor Intervals (Wireless > 802.11a/b > RRM > General), the default value of Channel Scan
Frequency is 180 seconds. This means that all channel dwells must be completed within 180 seconds.
So depending on the number of channels defined by the selection in the Monitor list, the interval between
dwells will increase or decrease.
Frequency is 180 seconds. This means that all channel dwells must be completed within 180 seconds.
So depending on the number of channels defined by the selection in the Monitor list, the interval between
dwells will increase or decrease.
For instance:
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Channel List = DCA, slot = 0 (2.4 GHz)–DCA defines channels 1, 6, 11 for a total of 3 channels.
So 180 (seconds)/3(channels) = 60, the AP will go off channel every 60 seconds to listen.
So 180 (seconds)/3(channels) = 60, the AP will go off channel every 60 seconds to listen.
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Channel List = Country, slot = 1 (5 GHz)–In the -A regulatory domain (US) there are 21 channels
defined. So, 180(seconds)/21(channels) = 8.57, the AP will go off channel every 8-9 seconds or so
to listen for 50 ms.
defined. So, 180(seconds)/21(channels) = 8.57, the AP will go off channel every 8-9 seconds or so
to listen for 50 ms.
Neighbor Packet Frequency is also defined on the same page; the default value is 60 seconds. This
means that the radio must go off channel and send a single NDP packet for every channel defined by the
channel monitoring list within 60 seconds. Using the same example from above where Channel List =
Country and slot=1 (5 GHz), this translates to 60 (seconds)/21 (channels) = 3 seconds. So, every 3
seconds the radio is sending an NDP packet.
means that the radio must go off channel and send a single NDP packet for every channel defined by the
channel monitoring list within 60 seconds. Using the same example from above where Channel List =
Country and slot=1 (5 GHz), this translates to 60 (seconds)/21 (channels) = 3 seconds. So, every 3
seconds the radio is sending an NDP packet.
Both the Channel Scan Interval and Neighbor Packet Frequency should be left at the default values. By
default, the Monitoring Channels list is set to use country channels and this is best for wIPS
configurations. However, if wIPS is not a primary concern, you can select DCA channels and reduce off
channel activity to just the channels that you are using.
default, the Monitoring Channels list is set to use country channels and this is best for wIPS
configurations. However, if wIPS is not a primary concern, you can select DCA channels and reduce off
channel activity to just the channels that you are using.
RF Grouping
RRM RF Grouping is a central function for RRM. RF Grouping forms the basis for two management
domains within the RF Network–the administrative and the physical domain.
domains within the RF Network–the administrative and the physical domain.
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Administrative domain–For RRM to work properly it must know which APs and controllers are
under administrative control. The RF Group name is an ASCII string that all controllers and APs
within the group will share.
under administrative control. The RF Group name is an ASCII string that all controllers and APs
within the group will share.
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Physical RF Domain – For RRM to calculate channel plans and power settings it is essential that
RRM is aware of the RF Location of the APs and their relation to one another. Neighbor messaging
uses the RF Group Name in a special broadcast message that allows the APs in the RF group to
identify one another and to measure their RF Proximity. This information is then used to form RF
Neighborhoods within the RF Group.
RRM is aware of the RF Location of the APs and their relation to one another. Neighbor messaging
uses the RF Group Name in a special broadcast message that allows the APs in the RF group to
identify one another and to measure their RF Proximity. This information is then used to form RF
Neighborhoods within the RF Group.
Each RF Group must have at least one RF Group Leader per band. The RF Group Leader is the physical
device responsible for:
device responsible for:
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Configuration
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Running active algorithms
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Collection and storage of RF Group Data and metrics
There will be a minimum of two RF Group Leaders, one for each band–802.11b and 802.11a (2.4 and 5
GHz), respectively. While RF Group Leaders for different bands can coexist on the same physical WLC,
they often do not. It is also not uncommon for there to be more than one group leader per band in larger
systems that have geographic diversity.
GHz), respectively. While RF Group Leaders for different bands can coexist on the same physical WLC,
they often do not. It is also not uncommon for there to be more than one group leader per band in larger
systems that have geographic diversity.
Two modes of the RF grouping algorithm exist in the system today. RF Group Leaders can be selected
automatically (legacy mode) or assigned statically. Both methods of assignment were overhauled with
the addition of static RF Grouping in version 7.0 of the Cisco Unified Wireless Networking (CUWN)
code.
automatically (legacy mode) or assigned statically. Both methods of assignment were overhauled with
the addition of static RF Grouping in version 7.0 of the Cisco Unified Wireless Networking (CUWN)
code.