[asterisk-users] SIP Qualify

[Eric "ManxPower" Wieling]

Jason Parker wrote:
> I think you misunderstand what qualify is/does.  It appears that you believe that qualify=1000 means that it'll send out a qualify packet every 1000ms.  This isn't an unreasonable assumption, but it is wrong.  The qualify=1000 means that Asterisk will wait 1000ms for the device to respond to the qualify packet.  If after 1000ms there is no "yes, I'm here" packet, then it will be considered UNREACHABLE.  Qualify packets are sent out at a set interval, which, as you can see, is 60 seconds.  If the device was previously determined to be UNREACHABLE, the qualify packets will then be sent out every 10 seconds instead.

One thing to remember, a qualify packet is a SIP OPTIONS packet, not a 
ping packet.  Many phones are very slow in responding to an OPTIONS 
packet.  If the phone got busy doing something like downloading a 
rinetone or saving a directory entry, the phone may take a while to 
respond to the options packet.  As you can see, you cannot use the 
"qualify option" to measure network latency between the server and the 
SIP device.

My main issue with the "qualify option" is that if even one OPTIONS 
packet is lost or if the phone is busy doing something and so takes 
longer then the qualify= is set to, the phone will become UNREACHABLE.

In 1.2, chan_IAX2 has a smoother to do some sort of averaging on qualify 
response times.  chan_sip does not have this.

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