Allied Telesis AT-9800 BGP Enhancements, BGP Backoff Lower Threshold, Upper and Lower Thresholds

102 BGP Enhancements Release Note

BGP Enhancements

In Software Release 2.8.1, the following enhancements have been added to

Border Gateway Protocol functionality:

■BGP Backoff Lower Threshold

■BGP Peer and Peer Template Enhancements

■Displaying Routes Learned from a Specific BGP Peer

This section describes the enhancements. The new and modified commands to implement them are described in Command Reference Updates.

How to configure BGP backoff

BGP Backoff Lower Threshold

The BGP backoff utility allows other processes access to the memory resources they need, without actually shutting BGP down unless it determines that BGP has backed off for a prolonged period of time.

BGP backoff is disabled by default, however it automatically enables the first time a peer is added.

Upper and Lower Thresholds

This Software Version adds a lower threshold for BGP backoff, which allows BGP to remain backed off until the system memory is much less utilised. To set this threshold, use the new low parameter in the command:

set bgp backoff[=20..100] [basetime=0..100] [consecutive=0..1000] [low=15..99] [multiplier=1..1000] [step=1..1000] [totallimit=0..1000]

Thresholds Together, the backoff and low parameters create upper and lower thresholds which trigger and maintain BGP backoff. When memory usage exceeds the upper threshold, BGP backoff is triggered. BGP continues to back off until memory usage falls below the lower threshold. At this stage BGP begins processing again, unless the total or consecutive backoff limits were reached.

Both threshold values represent a percentage of total system memory use. The upper threshold is set using the backoff parameter, and must be a higher percentage than the lower threshold. The lower threshold is set using the low parameter, and must be a lower percentage than the upper threshold. The backoff and low parameters cannot be set to the same value.

The default value for the backoff parameter is 95%, while the default value for the low parameter is 90%.

As the router or switch will not allow the backoff parameter value to be set below the low parameter, we recommend that you always adjust these parameters in the same command. For example:

Consecutive backoffs

set bgp backoff=88 low=84

If BGP gets to the end of the backoff period and system memory is still above the lower memory use threshold, BGP backs off immediately without performing any processing. Such backoffs are called consecutive backoffs. The consecutive backoffs default limit is now 5.

Software Version 2.8.1 C613-10477-00 REV B