The SIP-Based System Used in Connection with a Firewall Peter Koski, Jorma Ylinen, Pekka Loula Tampere University of Technology, Pori Pohjoisranta 11 A, P.O.Box 300, FIN Pori,Finland speaker ： Wenping Zhang date ：

2 Outline Introduction Types of NAT Technology Example Conclusion References

3 Introduction Different methods, such as ALG, STUN, TURN and FCP have been proposed for using SIP together with firewalls and NAT. The most suitable solution has to be determined in every situation. In this paper a system which makes it possible to offer SIP service to customers behind NAT is presented.

4 Types of NAT Full Cone Restricted Cone Port Restricted Cone Symmetric

5 Full Cone

6 Restricted Cone

7 Port Restricted Cone

8 Symmetric

9 Technology 1/2 Simple Traversal of UDP through NATs (STUN)

10 Technology 2/2 Traversal Using Relay NAT (TURN)

11 Example 1/3 INVITE SIP/2.0 Via: SIP/2.0/UDP :5060 ;branch=z9hG4bK58659f1f From: " " ;tag=00115c40752 To: Call-ID: CSeq: 101 INVITE Contact: Content-Type: application/sdp Content-Length: 247 v=0 o=Cisco-SIPUA IN IP s=SIP Call c=IN IP m=audio RTP/AVP a=rtpmap:0 PCMU/8000 INVITE SIP/2.0 Record-Route: Via: SIP/2.0/UDP Via: SIP/2.0/UDP :5060; rport=1162 ; received= From: " " ;tag=00115c40752 To: Call-ID: CSeq: 101 INVITE Contact: Content-Type: application/sdp Content-Length: 286 v=0 o=Cisco-SIPUA IN IP s=SIP Call c=IN IP m=audio RTP/AVP a=rtpmap:0 PCMU/8000

12 Example 2/3 Use STUN for SIP Registration

13 Example 3/3 Use STUN for RTP

14 Conclusion STUN and TURN require client support and this may be a problem in some cases. TURN can be used with a symmetric NAT, but few clients support TURN.

15 References The SIP-Based System Used in Connection with a Firewall NAT Traversal for VoIP