[asterisk-dev] RFC: Refactor qualify and res_pjsip/endpt_send_request

[Olle E. Johansson]

On 30 Mar 2015, at 16:54, Mark Michelson <mmichelson at digium.com> wrote:

> On 03/28/2015 08:06 PM, Joshua Colp wrote:
>> George Joseph wrote:
>>>> The fact that it goes to unavailable would be a bug. Why does it do so?
>>> 
>>> Mark should probably chime in here but I think it's because the
>>> earliest you could get a response from pjsip when a contact isn't
>>> reachable is the unconfigurable 32 seconds.   As I said that's a long
>>> time to leave a contact available when it really isn't. Without
>>> implementing our own timer setting the contact to unavailable was
>>> probably the lesser of 2 evils.
>> 
>> No matter what there's going to be a period where you are potentially wrong. I don't think making it unavailable was done on purpose.
>> 
> Actually, I believe the timer may be configurable. In the type=system settings, there are timer_t1 and timer_b settings. timer_t1 is the base used for determining the retransmission interval, and timer_b is the maximum time we will wait before giving up sending the request. The defaults for these values are 500 ms and 32000 ms respectively. If you were to change timer_b to be a smaller value, then presumably you would have a shorter time before the transaction times out.
> 
> A couple of caveats about these settings
> 1) Since they're in the "type=system" settings, any change you make requires an Asterisk restart in order to take effect.
Are you serious? That's a very strange design. Without knowing anything about PJSIP, I think that is something that
needs to be fixed. There are several SIP phones based on PJSIP where I can set timers without restarting. Wonder
how they did it. 

> 2) PJSIP applies these timers globally. They will affect ALL SIP transactions, not just the OPTIONS transactions from the qualify checks.
That seems very strange, but I have to trust you here. It makes the channel driver rather unusable in gateway situations where
it's a requirement that I have one set of timers for my internal systems and one for external clients.

/O