[asterisk-users] Purpose of qualify=yes

[Sebastian]

Hi,

On 09/16/2010 05:28 PM, Gareth Blades wrote:
> 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.

In have some experience with IAX qualify. Might not be of direct benefit 
though to this particular thread. I have the following IAX peer as the 
outgoing IAX trunk at one of my sites:

[outgoing_trunk]
type=peer
host=iax-out.our_iax_host.net
username=my_username
auth=plaintext
secret=my_password
qualify=no

To start with, I used qualify=yes. Which worked well for about 6 months. 
But after that, the peer would become unavailable every few days - and 
nobody could do outgoing calls. I would login remotely, and check that I 
can ping ok the IAX provider. However, Asterisk kept on showing the peer 
as unreachable even though it was clearly online. It looks to me like, 
from time to time, the IAX provider would become unavailable for a 
period of time (maybe maintenance at night) and Asterisk would just give 
up after some retries, and mark it as unreachable. The problem is that 
Asterisk wouldn't change its mind unless I did a full Asterisk restart.

After I turned off the qualify, no more problems. It looks like Asterisk 
is searching now for the IAX provider every time a call is attempted - 
so it doesn't matter if they are unavailable for a period of time.

At least this is the conclusions I have reached. So it seems that 
sometimes qualify is not a good idea.

Sebastian


>
> 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
>>
>>
>>
>
>