[Serusers] NAT

Wed Aug 25 21:36:06 CEST 2004

On Wed, 25 Aug 2004, Michael Shuler wrote:

Hello,

> In the nat helper module it says:
>
> 1.5.1. fix_nated_sdp(mode)
> Rewrites Contact HF to contain request's source address:port.
>
> Meaning of the parameters is as follows:
>
> mode - 0x01 (add direction=active), 0x02 (rewrite media IP address with
> source address of the message).
>
> I understand what 0x02 is doing, can someone explain what 0x01 is actually
> doing?

It's explained here:

http://www.ietf.org/internet-drafts/draft-ietf-mmusic-sdp-comedia-08.txt

The natted UA needs to send some rtp traffic to the remote UA (or
rtpproxy) to open the nat translation in the local router before it's able
to receive media from the remote.

Regards.

> > -----Original Message-----
> > From: Richard [mailto:richard at o-matrix.org]
> > Sent: Wednesday, August 25, 2004 12:51 PM
> > To: 'Michael Shuler'; serusers at lists.iptel.org
> > Subject: RE: [Serusers] NAT
> >
> >
> > You can either use nathelper or mediaproxy. Check the
> > documentation on these
> > two modules. There are good explanation on why/how.
> >
> > -----Original Message-----
> > From: serusers-bounces at lists.iptel.org
> > [mailto:serusers-bounces at lists.iptel.org] On
> > Behalf Of Michael Shuler
> > Sent: Wednesday, August 25, 2004 7:44 AM
> > To: 'Michael Shuler'; serusers at lists.iptel.org
> > Subject: RE: [Serusers] NAT
> >
> > Anyone have an explanation or did this email miss the list?
> >
> > ----------------------------------------
> >
> > Michael Shuler, C.E.O.
> > BitWise Systems, Inc.
> > 682 High Point Lane
> > East Peoria, IL 61611
> > Office: (217) 585-0357
> > Cell: (309) 657-6365
> > Fax: (309) 213-3500
> > E-Mail: mike at bwsys.net
> > Customer Service: (877) 976-0711
> >
> > > -----Original Message-----
> > > From: serusers-bounces at lists.iptel.org
> > > [mailto:serusers-bounces at lists.iptel.org] On Behalf Of Michael Shuler
> > > Sent: Tuesday, August 24, 2004 5:50 PM
> > > To: serusers at lists.iptel.org
> > > Subject: [Serusers] NAT
> > >
> > >
> > > I'm trying to understand the NAT process, can someone tell me
> > > if this is
> > > correct
> > >
> > > Here is my original INVITE from client IP 123.123.123.123
> > > which is received
> > > from port 5002 (because its behind a NAT router):
> > >
> > > INVITE sip:2175850357 at sip2.bwsys.net;user=phone SIP/2.0
> > > Via: SIP/2.0/UDP
> > 192.168.100.2:5060;branch=z9hG4bK-4qxhdyvuyz6t;rport
> > > From: "Mike's Springfield snom 1"
> > > <sip:MikeSnom1 at sip2.bwsys.net>;tag=k91lt5ydem
> > > To: <sip:2175850357 at sip2.bwsys.net;user=phone>
> > > Call-ID: 3c275253ad55-krb7eduyhd2m at 192-168-100-2
> > > CSeq: 1 INVITE
> > > Max-Forwards: 70
> > > Contact: <sip:MikeSnom1 at 192.168.100.2:5060;line=rygvn8mw>
> > > P-Key-Flags: keys="3"
> > > User-Agent: snom200-3.42
> > > Accept-Language: en
> > > Accept: application/sdp
> > > Allow: INVITE, ACK, CANCEL, BYE, REFER, OPTIONS, NOTIFY,
> > > SUBSCRIBE, PRACK,
> > > MESSAGE, INFO
> > > Allow-Events: talk, hold, refer
> > > Supported: timer, 100rel, replaces
> > > Session-Expires: 3600
> > > Content-Type: application/sdp
> > > Content-Length: 256
> > >
> > > v=0
> > > o=root 20147217 20147217 IN IP4 192.168.100.2
> > > s=call
> > > c=IN IP4 192.168.100.2
> > > t=0 0
> > > m=audio 10048 RTP/AVP 18 0 8 101
> > > a=rtpmap:18 g729/8000
> > > a=rtpmap:0 pcmu/8000
> > > a=rtpmap:8 pcma/8000
> > > a=rtpmap:101 telephone-event/8000
> > > a=fmtp:101 0-15
> > > a=sendrecv
> > >
> > >
> > >
> > > Now this invite is going to get forwarded to my TNT (with a
> > > public IP) which
> > > has SIP capabilities and hands of PRI to a phone switch.  So
> > > to make NAT
> > > support work what would this message look like after being
> > > proxied and NAT
> > > "adjusted" and what function in SER would be needed to make
> > > the changes
> > > happen?
> > >
> > > Now I know the proxy should be able to learn the port that
> > > the INVITE comes
> > > in on and can send SIP messages back via the learned port,
> > > but I do not
> > > understand how the RTP stream works when NAT is involved.  My
> > > guess is that
> > > anything what says 192.168.100.2 (the NAT'ed IP) needs to get
> > > changed to the
> > > proxy's public IP of 198.88.216.87:5060.  This would include
> > > the Via and
> > > Contact.  Now the SDP "c" line has to be changed because it says
> > > 192.168.100.2 but it should be changed to 123.123.123.123
> > (the clients
> > > learned IP).  Now that leaves us to the problem of the RTP
> > > port.  The client
> > > says it wants to receive on 10048, but how does the generic
> > > NAT router know
> > > that the snom wants this port opened?
> > >
> > >
> > > ----------------------------------------
> > >
> > > Michael Shuler, C.E.O.
> > > BitWise Systems, Inc.
> > > 682 High Point Lane
> > > East Peoria, IL 61611
> > > Office: (217) 585-0357
> > > Cell: (309) 657-6365
> > > Fax: (309) 213-3500
> > > E-Mail: mike at bwsys.net
> > > Customer Service: (877) 976-0711
> > >
> > > _______________________________________________
> > > Serusers mailing list
> > > serusers at lists.iptel.org
> > > http://lists.iptel.org/mailman/listinfo/serusers
> > >
> >
> > _______________________________________________
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> > serusers at lists.iptel.org
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> >
>
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>
>

Saludos
JesusR.

-------------------------------
Jesus Rodriguez
VozTelecom Sistemas, S.L.
jesusr at voztele.com
http://www.voztele.com
Tel. 902360305
-------------------------------