Behavior With Previous Releases - Cisco BPX-BXM-155-8DX Installation And Configuration Manual

Chapter 21 Configuring ATM Connections
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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 may 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 can be configured to be
from 3 to 255 seconds; the bigger the value of N, the better the system performance will be.
It is recommended that X (value of Abit Timer Multiplier M * the value of the Abit Timer Granularity
N) be set such that 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 may 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. Note
that it takes time for those cards to process the Abit status information for each connection coming from
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 may 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
nodes are the same.

Behavior with Previous Releases

A pre-Release 9.1.07 node or Release 9.1.07 node with the Send Abit on Deroute feature (
Send Abit immediately parameter) turned off behaves the same way as a Release 9.2 node with the Early
Abit Notification on ILMI/LMI Using Configurable Timer feature disabled.
A Release 9.1.07 node with the
same way as a Release 9.2 node with the Send Abit Early parameter set to yes and the Abit Timer
Multiplier M set to 0.
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.
There is no impact on control processor switchover or trunk card redundancy switchover because
connections are not rerouted.
Release 9.3.0, Part Number 78-10674-01 Rev. D0, July 2001
Parameter X
The time to wait before Abit = 0 is sent out if the connection is in a derouted state.
X, is set to be M*N
Abit Timer Multiplier M
M can be configured to be from 0 to 100. Default value for M (Abit Timer Multiplier M parameter)
is 0, meaning Abit = 0 is sent out on deroute.
Local Management Interface and Integrated Local Management Interface Parameters
Send Abit immediately parameter set to yes behaves the
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Cisco BPX 8600 Series Installation and Configuration
parameter settings on the
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