[asterisk-users] Purpose of qualify=yes

[Gareth Blades]

One of the main benefits of qualify=yes is to detect network problems 
with peers.
We send a lot of calls via a service provider using SIP but we have 
qualify-yes set so that if it becomes unreachable the dial fails 
immediatly without having to wait for a timeout which enables us to 
seamlessly failover to an ISDN connection.

Chris Owen wrote:
> 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
> 
> 
>