After checking the version number and doing any other preliminary checks, processing will depend upon the value in the command field . Output processing Let describe the processing used to create response messages that contain all or part of the routing table. In this case, the resulting message is sent to only one destination. Every 30 seconds, a response containing the whole routing table is sent to every neighboring gateway . - by triggered updates. Whenever the metric for a route is changed, an update is triggered.
Triggered updates require special handling for two reasons.
First, experience shows that triggered updates can cause excessive loads on networks with limited capacity or with many gateway s on them. Thus the protocol requires that implementors include provisions to limit the frequency of triggered updates. After a triggered update is sent, a timer should be set for a random time between 1 and 5 seconds. If other changes that would trigger updates occur before the timer expires, a single update is triggered when the timer expires, and the timer is then set to another random value between 1 and 5 seconds. Triggered updates may be suppressed if a regular update is due by the time the triggered update would be sent.