New subject: [Serusers] Multihomed SER & NAT

21 Aug 2006

Hi all,

finally I figured out how to change the sdp - part of the message by using
force_rtpproxy.

All works fine, I can make calls in both directions, but i still got two problems:

1. If someone from outside(VoIP - Provider) calls my UA, i have a ~10 sec. delay before i
hear audio.
- i checked my dumpfile, and saw that the delay is between the last 180 Ringing and the
200 OK.
(- However RTP - Packets are sent before the 200 OK, after a 183-Message. Dont understand
why but I dont think it matters that much.)

2. If the call is terminated from outside(VoIP - Provider) the BYE message is not handled
correctly by SER.
- the previous messages from the Voip provider have all a via HF with the private IP of my
UA. The BYE message doesnt have such a Via. All other Via and RR fields are present.
- also the BYE uri is somewaht strange. Instead of sip:123456@privateIPofUA it contains
sip:123456@publicIPofSER.

Thanks in advance for any help Smile

Best regards
Sebastian.

...
  -----Ursprüngliche Nachricht-----
 Von: "Greger V. Teigre" &lt;greger(a)teigre.com&gt;
 Gesendet: 10.08.06 15:41:31
 An: Sebastian Gabris &lt;Sebastian.Gabris(a)web.de&gt;
 CC: serusers(a)lists.iptel.org
 Betreff: Re: [Serusers] Multihomed SER & NAT 
fix_nated_contact() is meant for changing the IP address of the Contact
...
  header when SER has a public address and the UA has a
private (i.e.
 behind NAT). This means that it will rewrite Contact to contain the
 source ip address:port found in the UDP/TCP header.
 This is probably correct, because I assume the UA cannot be reached
 from the outside anyway. If you record-route, subsequent requests
 should go through your ser.

 If you have problems with responses not being returned, have a look at
 Via headers as they control how answers to i.e an INVITE are routed
 back to the UA.  You may want to have a look at the rr module double
 record route parameter to make sure that SER creates one record-route
 for the internal and one for the external interface.
 g-)

 Sebastian Gabris wrote:
  After reading a bit more mails, I came to two possible problems:
 1. fix_nated_contact() needs a registrar to work properly
  I dont use a registrar, since i register at the VoIP - Provider.
 or
 2. fix_nated_contact() is not ment to be used on this scenario
 Any ideas on this?
 Sebastian

  Hi everybody,
 need some help on nattraversal.
 i use a multihomed SER, one private IP & one public IP.
 MyUA(privateIP) <-> (privateIP)SER(publicIP) <-> UA-(VoIP - Provider,
pubicIP)
 If i try to make a call from private net to public net, SER doesnt change the contact
address. He changes the sdp - connection field but he, puts in the wrong IP - address.
 Instead o writing down his public IP, SER writes his private IP.
 Then SER forwards the call on his public interface to the provider, which will get wrong
Contact & SDP information.
 After reviewing my logs i saw that SER does the nat_uac_test, but the fix_nat_contact
& fix_sdp dont work dont do what they should do :)
  Here are the important bits of my config:
  fork=yes
 log_stderror=no mhomed=1
 listen=10.x.x.x
 listen=193.x.x.x
 loadmodule "/usr/lib/ser/modules/nathelper.so"
 modparam("usrloc", "db_mode", 0)
 modparam("registrar", "nat_flag", 6)
 modparam("nathelper", "natping_interval", 30) # Ping interval 30 s
 modparam("nathelper", "ping_nated_only", 1) # Ping only clients
behind NAT
  if (nat_uac_test("3")) {
  if (method == "REGISTER" || ! search("^Record-Route:")) {
  log(2,"LOG: Someone trying to register from private IP, rewriting\n");
fix_nated_contact(); # Rewrite contact with source IP of signalling
  if (method == "INVITE") {
  fix_nated_sdp("1"); # Add direction=active to SDP
  };
  force_rport(); # Add rport parameter to topmost Via
  setflag(6); # Mark as NATed
  };
  };
 ... and so on.
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