NAT Issues |
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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. |
Note: If you experience problems with NAT your best friend(s) is your ITSP (Internet Telephony Service Provider) or/and network administrator. Always consult them when in doubt.
Most likely you are behind a NAT if you use an Internet gateway connecting your local network to a broadband network via a DSL or cable modem, use Internet Connection Sharing in Windows XP or Windows, or are on a private network (your computer has an IP address started with 10.0.x.x, 192.168.x.x, 172.x.x.x).
If your service profile allows you to do this, you may check if SJphone is behind NAT. Switch to Advanced Mode.
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
A main reason to use NAT is the fact that IP addresses rapidly become scarce. In addition, NAT provides an extra layer for network security by obscuring a private network from an outsider. Please note, that NAT is not the same thing as a firewall or proxy server.
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
Below are NAT traversal methods that SJphone supports. Which is to be used, depends on your ITSP (Internet Telephony Service Provider), on your network configuration, etc. Always consult your ITSP (Internet Telephony Service Provider) or/and network administrator when in doubt.
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
Attention! You must completely understand what you are doing while changing these settings. Always consult your ITSP (Internet Telephony Service Provider) or/and network administrator when in doubt.
Consult your ITSP or SIP Proxy administrator on which method to use:
1. A second proxy is used for NAT traversal:
Enter the proxy's DNS name or IP address to the Proxy for NAT field on the SIP Proxy tab. Enter the port number if it is not a default value (5060) and there is no this information in the NAPTR/SRV DNS records.
Note: If a second proxy for NAT is used, SIP messages do not include the STUN information.
2. One proxy supports NAT traversal or rport.
Disable STUN usage by clearing the Use discovered address in SIP option on the STUN tab.
3. One proxy does not support NAT traversal
Select the Use discovered address in SIP option on the STUN tab. STUN settings are on the STUN tab. For the most cases the default settings are correct.
This is the worst case and you may experience problems with calls. Consult your ITSP (Internet Telephony Service Provider) or/and network administrator in this case.