| The Cisco proprietary BOD is triggered by outgoing traffic levels only. When the traffic level reaches a configured level, the access router assigns the other B channel to share the traffic.
If you have an access server that is
connected to an ISDN BRI (2B+D) with BOD configured, only one B
channel is usually used for communications. If you transfer a large
file, the BOD feature senses the additional traffic and allocates a
second B channel. The router load balances the traffic between the
two B channels. When you finish transferring the file, the second B
channel will time out and go idle, saving you connect time.
The dialer initiates another call to the destination if a packet is transmitted on a dialer interface and the transmission load on the interface exceeds the specified load threshold. The dialer then makes additional calls, as needed, to expand the bandwidth.
The
dialer load-threshold
command is used to configure
(Cisco proprietary) BOD by setting the maximum load before the
dialer places another call to a destination. The following is an
example of BOD configuration:
Router(config)#int bri 0
Router(config-if)#dialer load-threshold load
The load value is a number from 1 to 255 that is directly related to the bandwidth of the link, which can be specified by the
bandwidth
command. The lowest value, 1, brings up the second link instantaneously. Any value greater than 1 specifies how much bandwidth on the first B channel must be used before the second B channel is used for BOD. The bandwidth is defined as a ratio of 255, where 128 is 50 percent and 255 is 100 percent of the available bandwidth.
Load Average Calculation
Although the load-interval interface configuration command is often used for dial backup purposes to increase or decrease the likelihood of a backup interface being implemented, it can be used on any interface. The
load-interval command allows you to change the default interval of
5 minutes to a shorter or longer period of time. If you change it to a shorter period of time, the input and output statistics that display when you use the show interface command will be more current and based on more instantaneous data, instead of reflecting a more average load over a longer period of time. The default is 300 seconds
(5 minutes). The new value has to be a multiple of 30, between 30 and 600 seconds.
Using BOD, the load calculation takes into
consideration the outbound traffic exclusively. If you wish both inbound and outbound traffic to be used in the load calculation, use
MLP.
|