[OpenSIPS-Users] TCP AORs and db_mode 1/2/3

[Bogdan-Andrei Iancu]

Hi Brian,

opensipslist at encambio.com wrote:
> Hello Bogdan,
>
> An lun., févr 08, 2010, Bogdan-Andrei Iancu schrieb:
>   
>> opensipslist at encambio.com wrote:
>>     
>>> Thinking today about why my messages are sometimes routed to
>>> nonexistent TCP endpoints, I came upon the following idea:
>>>
>>>   It seems that if the usrloc db_mode is anything but 0,
>>>   then TCP AORs could be read from the database after a
>>>   crash. This can't work because once OpenSIPS stops,
>>>   the TCP connections are destroyed. They aren't reusable
>>>   again, because routers and firewalls would block the
>>>   connections that OpenSIPS tries to reestablish.
>>>
>>> First of all, is that right?
>>>
>>>       
>> That is correct.
>>
>>     
>>> If so, then for what reason are the db_modes 1, 2, and 3
>>> even useful at all? For UDP-only systems, right?
>>>
>>>       
>> not really. Even if the TCP conn is lost while the registration
>> still valid, the conn can be re-established from the client side
>> (like the client placing a call).
>>
>>     
> I tested this and at least with my routers when a TCP connection
> to OpenSIPS is lost the NAT binding is destroyed. Should the UAC
> place a call once OpenSIPS is started again, a new TCP connection
> is created with a new NAT binding and a different outgoing TCP port.
>   
yes, it may depend on the policy of the NAT device - but it is true, it 
may work or not
> That means that should OpenSIPS reuse the old TCP port from the
> registration in usrloc, then it could send for example a NOTIFY
> to the wrong place, right?
>   
not really - the TCP conn reusage is done based on destination - when 
opensips needs to send via TCP to IP:port, it looks through all existing 
connections if there is one pointing to IP:port -> if found, it will use 
that one. Otherwise, it will try to open a new one.
> By the way, I set db_mode to 0 to avoid this problem. The location
> table in db_text is still being populated when save() is called.
> Doesn't the db_mode '0' parameter of usrloc mean that nothing will
> be written to the database when save() is called?
>   
in mode 0 there is not interaction with the DB (neither read, not write)..

Regards,
Bogdan
> Regards,
> Brian
>
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>   


-- 
Bogdan-Andrei Iancu
www.voice-system.ro