[asterisk-users] Purpose of qualify=yes

[Chris Owen]

We have a tenant who has been having issues with a congested connection and in trouble shooting it we've noticed that there seems to be a lot of SIP traffic even when none of the phones are doing anything.

We've determined that this traffic is mostly INFO packets generated by setting qualify=2000.   I understand that 2000 ms is the default value for the qualification parameter but what I'm unclear on is exactly what the purpose of having asterisk qualify the phones is.

I know that in a NAT situation, qualifications can help keep UDP sessions open in the firewall but in our case most phones are not behind NAT.

I realize qualifying phones is also how asterisk keeps track of who is available for things like BLF but surely it doesn't need to do that every 2 seconds to keep the BLFs reasonably current.

So I guess my question is what is the real purpose of the qualify setting in a non-NAT situation and can one safely set the qualification as something higher.   I'd think something like 15 seconds would be more than enough for BLFs and the like.

Chris