[OpenSIPS-Users] [RFC] OpenSIPS 2.0 - changes on the SIP messages

[Bogdan-Andrei Iancu]

Hi Brett,

Thanks for the feedback - one of the goals of my email was to see how 
"serious" and "spreading" is the issue with changes being applied at the 
end. If the users do actually see here no problem, fine with me :)

Best regards,
Bogdan

Brett Nemeroff wrote:
> >From a user's perspective...
> I can clearly see the need to pull information from the original 
> message as well as the "processed, unsent message". I'm aware of this 
> issue, but I've never ran into an issue where it's really been a 
> problem. Typically, these issues are resolved by instead of using 
> something like message headers, using previously set AVPs in the 
> script. Maybe my assumption is from my lack of running into the 
> problem, but I *think* it can be resolved by smart scriptwriting...
>
> I don't know a whole lot about how the message is processed under the 
> hood, but.. from a user perspective, I'd rather change my 
> scriptwriting to handle these issues (assuming there is a way to 
> mitigate the issue) than make an architectural change that would 
> overall impair performance and scalability.
>
> -Brett
>
>
> On Wed, Apr 28, 2010 at 5:40 AM, Bogdan-Andrei Iancu 
> <bogdan at voice-system.ro <mailto:bogdan at voice-system.ro>> wrote:
>
>     Hi,
>
>     sorry for crossposting, but I thing this topic is interesting both for
>     users (as experience) and for developers (as solution).
>
>     So, right now the code for 2.0 got to a stage were we need to "apply"
>     changes on the received messages (like adding VIA headers, changing
>     headers, etc). And before starting the work on this area, I would like
>     to get some opinions on the available options:
>
>        1) keep the current mechanism for changing the SIP messages by
>     using
>     lumps that are applied only when the message is sent out :
>           Advantages: code is there and works; the mechanism is very
>     fast ;
>     no need to re-parse the message after the parsing
>           Disadvantages : from script or code, you are not able to see the
>     previous changes you did on the message, like:
>                     if you remove a hdr, it will be marked to be removed,
>     but you will still see it there after the removed
>                     if you add a new hdr, you will not be able to see it
>     (it will be actually added only when the message will be sent out)
>                     if you replace the contact hdr (like after
>     fix_nated_contact() ) will not see the new contact, but the old one
>                     trying to apply 2 changes in the same area (like
>     changing twice the contact) will result in bogus result.
>
>        2) find a new approach that will allow to push in realtime the
>     changes on messages
>           Advantages: the change will take affect instantly, so all the
>     disadvantages from 1) (as user experience in operating opensips) will
>     disappear .
>           Disadvantages : the code will probably be slower (the changes
>     part), but will speed up other parts of the code (where you need to
>     manually identify the prev changes);
>                 changed parts of the SIP message will require re-parsing
>     (so the code will have to check the state of a header (if parsed
>     or not)
>     before each usage)
>                 you will not be able to undo changes on the SIP
>     messages in
>     an easy way (for example during the parallel and serial forking on
>     per-branch changes)
>
>     So this is the dilemma: if the current mechanism (with applying
>     changes
>     at the end) such a bad user experience (scripting) in order to try for
>     2.0 a different approach ?
>
>     I would like to hear some opinions from both people writing
>     scripts and
>     people writing code.
>
>     Thanks and regards,
>     Bogdan
>
>     --
>     Bogdan-Andrei Iancu
>     www.voice-system.ro <http://www.voice-system.ro>
>
>
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-- 
Bogdan-Andrei Iancu
www.voice-system.ro