At 05:17 AM 3/18/2004, zeusng wrote:
Hi,
Is that a way to check the Top most Via rport with the sender's port?
I have a UA capable of detecting its symmetric NAT's public address and advertise it in the SIP message. Below is an example of the message. The device has private address 192.168.x.x and is set to listen SIP message at port 5070, the NAT's public address is y.y.y.y, the register is listening at public address z.z.z.z port 5060.
UA1 192.168.5.5:5070 --> NAT (y.y.y.y:60500) --> Proxy z.z.z.z:5060
SEND >> z.z.z.z:5060 REGISTER sip:xyz.org SIP/2.0 Via: SIP/2.0/UDP y.y.y.y:5070;rport;branch=z9hG4bKA38B122163B34FA9B039C915AA2ACB43 From: UA1 sip:ua1@xyz.org To: UA1 sip:ua1@xyz.org Contact: "UA1" sip:ua1@y.y.y.y:5070 Call-ID: F75DAF8081B44B62905C14B20CC7421C@xyz.org CSeq: 7900 REGISTER Expires: 1800 Max-Forwards: 70 User-Agent: Some SIP User Agent Content-Length: 0
RECEIVE << z.z.z.z:5060 SIP/2.0 200 OK Via: SIP/2.0/UDP y.y.y.y:5070;rport=60500;branch=z9hG4bK381E2433E71D4FE995B208FFD8AF8F15 From: UA1 sip:ua1@xyz.org To: UA1 sip:ua1@xyz.org;tag=794fe65c16edfdf45da4fc39a5d2867c.8eac Contact: "UA1" sip:ua1@y.y.y.y:5070 Call-ID: F75DAF8081B44B62905C14B20CC7421C@xyz.org CSeq: 7900 REGISTER Contact: sip:ua1@y.y.y.y:5070;q=0.00;expires=1800 Server: Sip EXpress router (0.8.12-tcp_nonb (i386/linux)) Content-Length: 0 Warning: 392 z.z.z.z:5060 "Noisy feedback tells: pid=18470 req_src_ip=y.y.y.y req_src_port=60500 in_uri=sip:xyz.org out_uri=sip:xyz.org via_cnt==1"
Here, the client 192.168.5.5 (not show in the message) send a message with source address 192.168.5.5 source port 5070 to proxy z.z.z.z port 5060. Because of some intellegence in the UA (STUN in this case), it determines that the public address of the NAT is y.y.y.y.
When contructing the Register request, it use the public IP y.y.y.y in the Via and Contact header. The message, upon reaching the NAT, be translated to have source address y.y.y.y and port 60500. None of the nat_uac_test() function can detect that the UA is behide NAT and thus save the contact as sip:y.y.y.y:5070. The reply of the register is fine as it follow the rport.
If however, someone invite this client, SER will return sip:y.y.y.y:5070. Due to the nature of symmetric NAT, port 5070 is block and cannot reach UA1.
Then "Some SIP User Agent" is broken. STUN can't be used with symmetric NATs. y.y.y.y is of zero value.
-jiri
I know I can setup PAT to have all incoming traffic with port 5070 to forward to 192.168.5.5 and make is looks like restricted cone NAT but the NAT device is own by the customer and I have no control.
Is there a way in SER that I can check the rport with the source port, if different, rewrite the contact as sip:[source address]:[rport]?
Regards,
Zeus Ng, CISSP, CCSA Principal Consultant iSquare Technology Tel: +61 2 9419 3887 Fax: +61 2 9410 2629 Mob: 0416 135 794 Email: zeus.ng@isquare.com.au
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