[Serusers] dispatcher addition?

[Daniel-Constantin Mierla]

Hello,

On 05/17/05 10:22, Hendrik Scholz wrote:

> Hi!
>
> Andrei Pelinescu-Onciul wrote:
>
>> Balance the REGISTERs after the to uri and the INVITEs after the request
>> uris (ds_select_dst("..", "3"), not documented but present in unstable).
>
>
> I already found those when backporting the dispatcher module to 0.8.14.
>
>> If the uri is an alias (e.g. lookup("aliases") returns true) balance the
>> message again after the request uri/send it back to the load balancer.
>
>
> Let's pretend this:
> I register UA 'a' and it get's balanced to SER backend 'Y'.
> I register UA 'b' and it get's balanced to SER backend 'Z'.
>
> Now 'a' also has an alias (a phone number) of '123456'.
>
> If I call 'a' the load balancer takes care of everything and backend 'Y'
> can process the call.
> Now '123456' get's balanced to 'Z' due to the hash algorithm.
> Since the initial register of 'a' was on 'Y' the 'Z' backend doesn't
> know anything about the alias.
> Or am I getting something wrong here?
>
> My idea was to get the alias from Radius instead of the incomplete
> usrloc DB. The additional hop involved is needed to push the
> request to the backend ('Y') where 'a' initially registered on.

there could be more complex scenarios, for example if you use speed 
dials then you have kind of aliases per users and must take in 
consideration the r-uri and from uri. I  have started working on a 
controller system for dispatcher to be able to do the distribution after 
interaction with some backend. This has to follow the logic of SIP 
routing policy prior to user location lookup.

>
>> An extra round trip might be involved, but if your users don't use
>> aliases very often it might not be an issue.
>
>
> We do have many aliases and all calls from the PSTN have to be
> looked up but I think it's easier to do the lookup on the backend
> rather than having a usrloc DB on the load balancer.

One solution would be the usage of a distributed and replicated database 
system (cluster) to store user profiles. This will allow an increase of 
queries with less performance penalties but will add some overhead for 
maintenance.

Daniel

>
> Hendrik
>