Re[4]: [Serhelp] third part session control

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Re[4]: [Serhelp] third part session control

Jiri Kuthan-3
[cc: changed to serusers, which is publicly archived]

There is no B2BUA support in SER. You can try to use some
existing B2BUA implementation. You can use SER along with
B2BUA too -- they interact using SIP. You just need to set
SIP routing accordingly to your scenario.

You should be perhaps warned of some side-effect of use
of the B2BUA technology. The root reason is B2BUAs break
the end-to-end model, in which intelligence lives in
end-devices. With B2BUA, you put a fair amount of work
on a network entity. That breaks e2e security, degrades
scalability and robustness -- B2BUA's failure affect
all existing calls.

-Jiri

At 01:18 PM 12/4/2002, Igor Vasiliev wrote:

>Hello,
>
> I've tryed to read B2BUA's doc that I could find.
>But I did't properly understand how it should works with SER.
>Should SER redirect any INVITE(e.t.c) request to B2BUA,
>and after B2BUA'll try to establish connection with a calee
>on behalf of B2BUA?
> Or B2BUA should be stand alone programm working without
>any SIP proxy server?
> Then how could it find out callee location.
>
>Could anybody describe me shortly a interaction model
>between caller B2BUA SER and callee.
>Just general example.
>
>Thanks
>Igor Vasiliev
>
>
>
>
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>
>
>
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>
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>
>
>_______________________________________________
>Serhelp mailing list
>serhelp at lists.iptel.org
>http://lists.iptel.org/mailman/listinfo/serhelp 

--
Jiri Kuthan            http://iptel.org/~jiri/ 



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Re[5]: [Serhelp] third part session control

Igor Vasiliev
>
> There is no B2BUA support in SER.
Yes, I know.
> You can try to use some
> existing B2BUA implementation. You can use SER along with
> B2BUA too -- they interact using SIP. You just need to set
> SIP routing accordingly to your scenario.
Problem of my understanding is here.
How should I redirect requests?

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Re[5]: [Serhelp] third part session control

serhelp (Jiri)
At 02:21 PM 12/4/2002, Igor Vasiliev wrote:
>> You can try to use some
>> existing B2BUA implementation. You can use SER along with
>> B2BUA too -- they interact using SIP. You just need to set
>> SIP routing accordingly to your scenario.
>Problem of my understanding is here.
>How should I redirect requests?

Requests are redirected in SER using sl_send_reply with
a 3xx code in it. That has nothing to do with B2BUAs, though.

You can proxy requests too -- again, how you route them
depends on what you want to accomplish. For example, you
can look at URIs and route all requests with nummerical
usernames to a B2BUA, whereas everything else will be
routed using a user location database. There are really
no limits on what your routing policy may be.

>>From SER to B2BUA?
>Please give me an example of their interaction.

http://www.iptel.org/ietf/callprocessing/apps/draft-rosenberg-sipping-app-interaction-framework-00.txt
and
http://www.iptel.org/ietf/callprocessing/apps/draft-rosenberg-sip-app-components-01.txt
give examples of server interactions.

>Could I use B2BUA without SER(and without any SIP proxy)?

Yes. There is BTW many other things which you can do without
any SIP proxy -- skiing, playing chess, having phone conversation,
and many more.

-Jiri



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Re[5]: [Serhelp] third part session control

Igor Vasiliev
> At 02:21 PM 12/4/2002, Igor Vasiliev wrote:
> >> You can try to use some
> >> existing B2BUA implementation. You can use SER along with
> >> B2BUA too -- they interact using SIP. You just need to set
> >> SIP routing accordingly to your scenario.
> >Problem of my understanding is here.
> >How should I redirect requests?
>
> Requests are redirected in SER using sl_send_reply with
> a 3xx code in it. That has nothing to do with B2BUAs, though.
>
> You can proxy requests too -- again, how you route them
> depends on what you want to accomplish. For example, you
> can look at URIs and route all requests with nummerical
> usernames to a B2BUA, whereas everything else will be
> routed using a user location database. There are really
> no limits on what your routing policy may be.
Does it mean that some request(e.g. depends on caller name)
I can redirect to B2BUA?

Is such scenario correct?
caller --->SER --->B2BUA ----> callee

> >Could I use B2BUA without SER(and without any SIP proxy)?
> Yes. There is BTW many other things which you can do without
> any SIP proxy -- skiing, playing chess
:)
I just mean, could caller send INVITE directly to B2BUA?

Regards
Igor Vasiliev





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Re[5]: [Serhelp] third part session control

serhelp (Jiri)
At 03:57 PM 12/4/2002, Igor Vasiliev wrote:
>Does it mean that some request(e.g. depends on caller name)
>I can redirect to B2BUA?

Yes. You can proxy SIP servers in long chains, in which each
element adds some value. A proxy server in the middle of
a chain can decide what the next hop for a request would be.
For example, you can make such a SIP-routing decison with SER:

# prefix for germany -- route over b2bua.germany.bar
if (uri="^sip:+49[0-9]*@foo.bar) t_relay_to("b2bua.germany.bar", "5060");
# anything else is routed using userloc database
else {
  if (!lookup("location")) {
        sl_send_reply("404", "Not Fond");
   } else {
       # forward to the destination in UsrLoc database
        t_relay();
   }
}

SER is then acting as a "switch", switching by request URI.

>Is such scenario correct?
>caller --->SER --->B2BUA ----> callee

Such a scenario can be correct to. How you construct the chains
depends mainly on how you want to concatenate values added
by each element in the path. One element can add authentication,
another one user location, yet another firewall control, etc...
Alternative, all the functionality can be merged in a single
server. That is the freedom of choice when building SIP
networks.


>> >Could I use B2BUA without SER(and without any SIP proxy)?
>> Yes. There is BTW many other things which you can do without
>> any SIP proxy -- skiing, playing chess
>:)
>I just mean, could caller send INVITE directly to B2BUA?

:)

Yes -- a B2BUA could be certainly built in such a way, which
delivers all features a proxy server does.

-Jiri



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