OSPF: LSA Throttling

OSPF uses the same idea behind LSA throttling as it does for SPF throttling.  Its intended purpose is to rate limit the amount of times a specific LSA is re-advertised to a network.  The functionality behind LSA throttling also relies on three timers:

start-interval
hold-interval
max-interval

Once an LSA has not been updated for more than max-interval and it needs to be updated it will be created and flooded after the start-interval, when the next wait interval is set to the value of the hold-interval.

If the same LSA needs to be updated within the wait interval since it was last originated, the true origination and flooding will be postponed until the current wait interval expires and after creating and flooding the updated LSA.

The hold interval is doubled and used as the next wait interval, and will do so each time the LSA has to be updated within the hold interval until it’s capped by the max interval. Making the LSA throttling behavior exactly the same as the SPF throttling behavior.

By default Cisco routers update the LSA immediately and does not progressively increase the interface for subsequent origination’s which is set to 5 seconds by default.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s