Re: [OpenSIPS-Users] Media Proxy: Strange behaviour...

Thu, 24 Sep 2009 02:32:56 -0700

Hi Dan,

I saw,

Dan Pascu ha scritto: 
On 21 Sep 2009, at 13:17, Mauro Davì wrote:

  
Thanks Dan.

The problem was that Fastweb released a public not assigned IP  
Addresses to its customers
For example an UA connected with Fastweb (Italian operator) received a public IP (according to rfc1918)
23.238.97.105 that isn't assigned by IANA (http://www.iana.org/assignments/ipv4-address-space/). It's unallocated.
The UA received this IP Address and contacts the SIP Proxy obviusly the UA is behind a NAT, the real pubblic IP address
used to connect to Internet was another a Public Assigned IP in my case: 93.41.132.110.

The who is lookup say:

IP Address 93.41.132.110
Host 93-41-132-110.ip81.fastwebnet.it
Location IT IT, Italy
City Terni, 18 -
Organization Fastweb
ISP Fastweb
AS Number AS12874 Fastweb Autonomous System
Latitude 42°56'67" North
Longitude 12°61'67" East
Distance 874.92 km (543.65 miles) 

The solution could be to change not only the owner connection  
information present in the SDP (to ensure that the connection goes  
from the UA to the Media Proxy) but also the owner information (in  
this way opensips substitute the faked Fastweb ip address with the  
Media Proxy public IP address).

Do you agree??
So... In the SDP part of the INVITE I received:

v=0
o=- 3462098794 3462098794 IN IP4 23.238.97.105
s=SJphone
c=IN IP4 23.238.97.105
t=0 0
m=audio 49156 RTP/AVP 8 0 3 98 97 101
c=IN IP4 23.238.97.105
a=rtpmap:8 PCMA/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:3 GSM/8000
a=rtpmap:98 iLBC/8000
a=fmtp:98 mode=20
a=rtpmap:97 iLBC/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=setup:active
a=sendrecv

In wich, the owner information (o=) and the connection information (c=) contains the IP address assigned to the UA (23.238.97.105).

When the opensips server received the INVITE it changed the connection information and forwarded the INVITE to the destination.
The SDP information contained in the forwarded INVITE was:

v=0
o=- 3462098794 3462098794 IN IP4 23.238.97.105
s=SJphone
c=IN IP4 <MEDIA PROXY PUBLIC IP ADDRESS>
t=0 0
m=audio 30690 RTP/AVP 8 0 3 98 97 101
c=IN IP4 <MEDIA PROXY PUBLIC IP ADDRESS>
a=rtpmap:8 PCMA/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:3 GSM/8000
a=rtpmap:98 iLBC/8000
a=fmtp:98 mode=20
a=rtpmap:97 iLBC/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=setup:active
a=sendrecv

To be honest, I haven't the slightest idea of what you are talking  
about...

--
Dan

Now... to resolve "my problem", the opensips server need to modify not only the SDP connection information (c=), but also the
SDP owner information (o=). In this way the Media Proxy won't send the RTP packet to the 23.238.97.105 not assigned IP Address
(that was my problem).

Is this correct?

Thanks a lot and Regards,

    MD

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