Behavior With Previous Releases; Performance Considerations - Cisco BPX 8620 Installation And Configuration Manual

Local Management Interface and Integrated Local Management Interface

Behavior with Previous Releases

Early Abit Notification on ILMI/LMI Using Configurable Timer is supported on both the BPX and IGX
platforms. A Release 9.2 IGX or BPX node using this feature is compatible with Release 8.4 and Release
8.5 nodes or Release 9.1 IGX and BPX nodes so that all existing connection related functions will
continue to work. However, the timing in sending out the Abit notifications at both ends of connections
may behave differently, depending on how this feature is configured.
A preRelease 9.1.07 node or Release 9.1.07 node with the Send Abit on Deroute feature (cnfnodeparm
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 cnfnodeparm Send Abit immediately parameter set to yes behaves 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.
In releases previous to Release 9.1.07, when connections are derouted, the CPE does not receive Abit
notifications. In Release 9.1.07 on BPX, the Send Abit on Deroute feature was developed, which allowed
the Abit = 0 to be sent immediately when a connection is derouted. This was specified by the
cnfnodeparm Send Abit immediately parameter.
To further enhance the Send Abit on Deroute feature in Release 9.1.07, the Early Abit Notification on
ILMI/LMI Using Configurable Timer feature was implemented in Release 9.2 to allow the network
administrator to configure the node as to when Abit = 0 is sent out if a connection is derouted and not
rerouted quickly. This feature allows you to specify when Abit notifications are sent at Frame Relay and
ATM ports, and at feeder trunks in a tiered network architecture that supports the ILMI/LMI interface.
In a tiered network, the Abit information is used by the feeder nodes such as MGX 8220 (AXIS), which
relays the Abit information to the CPE.

Performance Considerations

The status update messages are throttled at the rate of one message per second. Each message specifies
the conditioning information on a maximum of 47 connections. It can take on the order of minutes for
the ILMI/LMI manager to process the Abit status when there is a large number of connections.
The following are the two factors in performance:
•
•
Cisco BPX 8600 Series Installation and Configuration
19-8
System performance—Determines the value of the time interval that is affected by system
performance. In a network where connections are normally derouted and rerouted quickly before the
bucket timer expires, the performance impact is very small. Only when the timer expires, then
looping through all LCONs and sending update messages will take up some CPU time which is
estimated to be smaller than 1 percent.
Reroute time—Specifies that the reroute time is not affected if LMI/ILMI is running on the
controller card. When the protocol is implemented on the line cards and feeder trunk cards, some
additional Abit status communication between them and controller card may delay the reroute
process.
Chapter 19 Configuring Circuit Lines and Ports
Release 9.3.30, Part Number 78-12907-01 Rev. E0, May 2005