Hi Alex, thanks for the answer. My customer is on the SIP side. So my customer sees a prefix of my PSTN gateway in the contact header. Sequential requests are being sent to <prefix><number>@<gateway_ip>. However I think when I remove the prefix from the contact, the gateway would have no problem in responding to this seq. request (Isn't the call defined by to_tag, from_tag, call_id?). So I want to hide the contact prefix from the UA. Efelin 2012/2/17 Alex Balashov &lt;abalashov(a)evaristesys.com&gt;om>: > Efelin, > > There is probably some confusion here.  The 200 OK message is from your gateway (in your call flow), and it can put whatever it wants in the Contact URI; you have no control over that on the Kamailio side.  You might be able to influence it with configuration settings on the GW side, but most likely not. > > However, much more importantly: the contact URI in the replies from the gateway only serves to target your UA's sequential requests.  It has nothing to do with the other side of your GW.  If it's a SIP -> TDM or analog GW, then SIP details are totally irrelevant.  If it's a SIP-to-SIP media gateway, it's a back-to-back user agent, meaning it generates a whole new logical call leg on the other side and bridges it to the incoming one from the UA.  The parameters in that new leg are completely independent of any attributes of the old one. > > Regardless, the contact URI is something sent back to the UA to tell it how to communicate with the GW.  In the overall scheme of your call flow,  no matter the media, it is a "purely internal" attribute. > > -- > This message was painstakingly thumbed out on my mobile, so apologies for brevity and errors. > > Alex Balashov - Principal > Evariste Systems LLC > 260 Peachtree Street NW > Suite 2200 > Atlanta, GA 30303 > Tel: +1-678-954-0670 > Fax: +1-404-961-1892 > Web: http://www.evaristesys.com/, http://www.alexbalashov.com > > On Feb 17, 2012, at 9:20 AM, Efelin Novak &lt;efelin.novak(a)gmail.com&gt; wrote: > >> Hi folks, >> >> I have a topology like this: >> >> UA -> kamailio -> PSTN GW. >> >> When I'm placing calls to a PSTN I have to append prefixes so the PSTN >> GW knows how to route the call. So the request-uri is >> <prefix><number>@<gateway_ip> e.g. 999123456(a)192.168.1.1. When the UA >> calls to the GW a "200 OK" message contains a contact header with >> 999123456(a)192.168.1.1. This is a problem because I don't want my >> customers to see gateway prefixes. >> >> The Topoh module only hides IP addresses or the  domain part. Is there >> any way to remove prefixes. This document >> (http://www.kamailio.org/events/2011-Cluecon/DCM-kamailio-security.pdf) >> stated "encoding IP and prefixes can be set via parameters". Can I >> remove prefixes from the contact in any other way than some contact >> header substitutions? >> >> Thanks >> >> Efelin >> >> _______________________________________________ >> SIP Express Router (SER) and Kamailio (OpenSER) - sr-users mailing list >> sr-users(a)lists.sip-router.org >> http://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-users > > _______________________________________________ > SIP Express Router (SER) and Kamailio (OpenSER) - sr-users mailing list > sr-users(a)lists.sip-router.org > http://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-users

On 02/17/2012 10:33 AM, Efelin Novak wrote: Not sure I follow.  The initiating UA is obligated to use whatever contact is provided by the UAS for sequential requests. -- Alex Balashov - Principal Evariste Systems LLC 260 Peachtree Street NW Suite 2200 Atlanta, GA 30303 Tel: +1-678-954-0670 Fax: +1-404-961-1892 Web: http://www.evaristesys.com/, http://www.alexbalashov.com/ _______________________________________________ SIP Express Router (SER) and Kamailio (OpenSER) - sr-users mailing list sr-users(a)lists.sip-router.org http://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-users

On 02/17/2012 11:30 AM, Efelin Novak wrote: I am unable to understand this statement. However, the client does not receive ACKs. -- Alex Balashov - Principal Evariste Systems LLC 260 Peachtree Street NW Suite 2200 Atlanta, GA 30303 Tel: +1-678-954-0670 Fax: +1-404-961-1892 Web: http://www.evaristesys.com/, http://www.alexbalashov.com/ _______________________________________________ SIP Express Router (SER) and Kamailio (OpenSER) - sr-users mailing list sr-users(a)lists.sip-router.org http://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-users

Hi Alex, thanks for the answer. My customer is on the SIP side. So my customer sees a prefix of my PSTN gateway in the contact header.

Sequential requests are being sent to<prefix><number>@<gateway_ip>. However I think when I remove the prefix from the contact, the gateway would have no problem in responding to this seq. request (Isn't the call defined by to_tag, from_tag, call_id?).