it is just bypass to enable call transfers for users connected to sipx,
when uplink ITSP doesn't support REFER.
sipxbridge works as SBC in b2bua mode, it stays in path of all calls to
and from Your uplink ITSP and when it receives REFER i just makes new
call (using INVITE) to Your ITSP, and then bridges new call with proper
leg of previous call and disconects other one.
so inside sipx 'domain' you can use call transers using refer, and from
Your ITSP side there are only invites byes and cancels.
in ex. in case when someone from outside calls you inside sipx, and you
forward it back outside - from ITSP point of view there will be 2 calls,
one to and one from your sipx, and he would have no idea that those
calls are related.
drawback is of course that rtp streams are going back and forth through
your internet uplink and AFAIR deaf silence at some point of transfer,
but at least it works with all lousy ITSP's.
You should check sipx documentation or sipx mailing list, this thread is
getting off-topic.
and REFER is not only for blind transfers ;-)
Grzegorz Stanislawski
W dniu 2011-02-27 20:35, Youngjin Park pisze:
Hi,
Can you tell me what advantage on INVITE has against REFER?
REFER is a kind of blind transfer and INVITE in sipXbridge is 3PCC?
Thanks in advance.
Youngjin
On Sun, Feb 27, 2011 at 6:40 AM, Grzegorz Stanislawski
<stangrze(a)netitel.pl <mailto:stangrze@netitel.pl>> wrote:
Hi.
We have proverb for this, i don't know english version but it
goes like this:
"When it isn't known what it's all about, it's about
money"
Your ITSP had troubles with proper handling second transfer for
billing purposes so decided to disable it.
Proxy doesnt participate in call transfer, but ITSP it must
charge users properly: Alice should pay just for call to Bob,
Bob for "his" call to Charlie and so on.
If You are using sipX You should use sipXbridge, it replaces
REFER with INVITE and bridges calls.
Grzegorz Stanislawski
W dniu 2011-02-25 11:40, niklas rehnberg pisze:
Hi,
Thank for the quick response.
The issue occur only when the Alice is a PSTN client.
My ITSP says that they only supporting one call transfer
(very strange).
They can not explain why etc...
PSTN client: Alice
MGW/MGC(ITSP): Cisco/SER
Our sip server: SIPX
BR Niklas
2011/2/25 Iñaki Baz Castillo <ibc(a)aliax.net
<mailto:ibc@aliax.net> <mailto:ibc@aliax.net
<mailto:ibc@aliax.net>>>
2011/2/25 niklas rehnberg <niklas.rehnberg(a)gmail.com
<mailto:niklas.rehnberg@gmail.com>
<mailto:niklas.rehnberg@gmail.com
<mailto:niklas.rehnberg@gmail.com>>>:
Hi,
Have following issue:
Alice calling Bob.
Bob make call transfer to Charlie (works fine)
Charlie transfer Alice to David. (the call break)
Why is not possible to transfer the call more than one time?
Is it any parameters?
My ITSP use SER together with Cisco MGW.
Niklas, nothing in SIP protocol neither in SER/Kamailio
makes your
scenario to fail. It must be a problem in your custom
setup. Try
identifying the problem capturing SIP traces.
Also take into account that a proxy doesn't participate
at all in the
process of a "call transfer". It's just a transparent
mechanism for a
proxy.
--
Iñaki Baz Castillo
<ibc(a)aliax.net <mailto:ibc@aliax.net> <mailto:ibc@aliax.net
<mailto:ibc@aliax.net>>>
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