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Chapter 10 The VoIP Account Screens
Outbound Proxy
Your VoIP service provider may host a SIP outbound proxy server to handle all of
the WiMAX Device's VoIP traffic. This allows the WiMAX Device to work with any
type of NAT router and eliminates the need for STUN or a SIP ALG. Turn off a SIP
ALG on a NAT router in front of the WiMAX Device to keep it from retranslating the
IP address (since this is already handled by the outbound proxy server).
NAT and SIP
The WiMAX Device must register its public IP address with a SIP register server. If
there is a NAT router between the WiMAX Device and the SIP register server, the
WiMAX Device probably has a private IP address. The WiMAX Device lists its IP
address in the SIP message that it sends to the SIP register server. NAT does not
translate this IP address in the SIP message. The SIP register server gets the
WiMAX Device's IP address from inside the SIP message and maps it to your SIP
identity. If the WiMAX Device has a private IP address listed in the SIP message,
the SIP server cannot map it to your SIP identity.
Use a SIP ALG (Application Layer Gateway), STUN, or outbound proxy to allow the
WiMAX Device to list its public IP address in the SIP messages.
Speed Dial and Peer-to-Peer Calling
Speed dial provides shortcuts for dialing frequently used phone numbers. You can
map a phone number to an alphanumeric keypad key (1 to 9) and then use that
keypad key to call the phone number (press and hold the key for one second or
longer). Use this screen to add, edit, or remove speed-dial numbers for outgoing
calls.
You also have to create speed-dial entries if you want to make peer-to-peer calls
or call SIP numbers that use letters.
In peer-to-peer calls, you call another VoIP device directly without going through a
SIP server. Enter the callee's IP address or domain name. The WiMAX Device
sends SIP INVITE requests to the peer VoIP device when you use the speed dial
entry.
You do not need to configure a SIP account in order to make a peer-to-peer VoIP
call.
DTMF
Dual-Tone Multi-Frequency (DTMF) telephone call signaling uses pairs of
frequencies (one lower frequency and one higher frequency) to set up calls. It is
also known as Touch Tone. Each of the keys on a DTMF telephone corresponds to a
different pair of frequencies.
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MAX318M2W User's Guide
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