NAT Traversal and SIP |
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Symptoms that you have problems with NAT:
• | Audio goes only one way (either inbound or outbound). |
• | Incoming calls cannot reach you. |
You are NOT behind NAT if you see the following:
• | NAT/Firewall: Open Internet |
You are behind NAT if you see the following:
• | NAT/Firewall: Full Cone NAT |
• | NAT/Firewall: Restricted Cone NAT |
• | NAT/Firewall: Port Restricted Cone NAT |
• | NAT/Firewall: Symmetric NAT |
• | NAT/Firewall: NAT of Unknown Type |
It is unclear if you are or are not behind NAT if you see the following:
• | NAT/Firewall: Unknown |
• | NAT/Firewall: Symmetric Firewall |
• | NAT/Firewall: Blocked |
SJphone and NAT
Unfortunately, NAT makes communications for SJphone and other Internet phones much more difficult. The situation is even worsened by the fact that there are several types of NAT, each imposing different restrictions, and different methods are required to traverse a NAT. SJphone provides most of them.
NAT traversal methods
1. Symmetric media streams: SJphone is pre-configured to use it. No additional configuring is required.
2. STUN protocol
3. rport SIP extension
4. OPTIONS request registration refresh
5. outgoing INVITE transaction refresh
Settings in the Call through SIP Proxy profile type for the NAT traversal
1. A second proxy is used for NAT traversal:
2. One proxy supports NAT traversal or rport.
3. One proxy does not support NAT traversal