Recommended Settings - Cisco BPX 8620 Installation And Configuration Manual

Chapter 19 Configuring Circuit Lines and Ports
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Recommended Settings

You should be aware of the dynamic relation between the two timer parameters:
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A connection that is derouted at a period of time between 0 and N will send out Abit = 0 at a time between
X and X + N, if the connection continues to be in a derouted state. In cases where there are many Abit
status changes to report to CPE, the last Abit updates can be delayed much longer because Abit updates
process about 47 connections per second.
To make a compromise between performance and the granularity of timers, N is configured to be from
3 to 255 seconds; the greater the value of N, the better the system performance.
It is recommended that X (value of Abit Timer Multiplier M * the value of the Abit Timer Granularity
N) is set so when a trunk fails, the connections are given sufficient time to reroute successfully, avoiding
the need to send out Abit = 0.
If the value of X (value of Abit Timer Multiplier M * value of Abit Timer Granularity N) is set to be
smaller than the normal time to reroute connections when a trunk fails, the time it takes to finish
rerouting them can take longer. This can happen for line cards and feeder trunks that have the LMI/ILMI
protocol running on those cards, such as BXM on BPX and Frame Relay cards on IGX.
It takes time for those cards to process the Abit status information for each connection coming from
Note
the controller card.
The change in the Abit behavior is completely local to the node and is applicable to the master and slave
ends of connections when the connections are derouted. When only one of the nodes connected by a
connection has this feature turned on, the timing in sending the Abit notification at one end of the
connection can be drastically different from the other end.
Therefore, it is recommended that the Early Abit Notification on ILMI/LMI Using Configurable Timer
feature be configured the same on all nodes.
Also, because timers on nodes are not in sync, there is a slight time difference (3 seconds maximum) in
sending Abit from the two ends of a connection, even if the cnfnodeparm parameter settings on the
nodes are the same.
Release 9.3.30, Part Number 78-12907-01 Rev. E0, May 2005
If the cnfnodeparm parameter Abit Timer Multiplier M is set to 0, switch software behaves the same
way as in Release 9.1.07, which supported the Send Abit on Deroute feature.
To follow the general Release 9.2 interoperability guideline, it is not recommended that the Early
Abit Notification on ILMI/LMI Using Configurable Timer feature be used when the standby control
processor is in a locked state.
Abit Timer Granularity N—Defines the granularity of the timers where the time period is referred
to as N. You specify N by the value of the
default value for N is 3 sec.
Parameter X—Determines the time to wait before Abit = 0 is sent out if the connection is in a
derouted state. Parameter X is set to be M*N.
Abit Timer Multiplier M—Configures M to be from 0 to 100. The default value for M (Abit Timer
Multiplier M parameter) is 0, which means Abit = 0 is sent out on deroute.
Local Management Interface and Integrated Local Management Interface
Abit Timer Granularity N parameter. The
cnfnodeparm
Cisco BPX 8600 Series Installation and Configuration
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