The purpose of SIP NOTIFY

Hello everyone. Sorry for not an asterisk specific question.

I’m seeing that Linksys ATAs send a “NOTIFY” packet every 30 secs. And asterisk replies with “OK”. This happens even when an ATA is not registered. I was just curios about the purpose of the “NOTIFY”. Why are they sending it? What are they notifying asterisk about (there isn’t any specific info in the packet, just regular sip headers)?

I guess it is being used the same way as Asterisk (and other systems) use OPTIONS, to test the connection. However, you really need to ask Linksys.

Asterisk uses it for Presence, Message Waiting, and to signal the progress of attended transfers.