Emergency Calls - Nokia ESERIES E61I User Manual

particular local port. This information is used to set up
UDP communication between two hosts that are both
behind NAT routers.
STUN is a client-server protocol. Nokia E61i includes a
STUN client which will send a request to a STUN server.
The server then reports back to the STUN client the public
IP address of the NAT router, and the port opened by the
NAT to allow incoming traffic back in to the network.
The response also allows the STUN client to determine
what type of NAT is in use, as different types of NATs
handle incoming UDP packets differently.
Protocols like SIP use UDP packets for the transfer of
sound/video/text signaling traffic over the Internet.
As both endpoints are often behind NAT, a connection
cannot be set up in the traditional way. This is where
STUN is useful.
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Emergency calls

Your device attempts emergency calls primarily over
cellular networks. If an emergency call using cellular
networks is not successful, your device attempts an
emergency call through your Internet call provider. Due to
the established nature of cellular telephony, you should
use cellular networks for emergency calls, if possible. If
you have cellular network coverage available, make sure
that your cellular phone is switched on and ready to make
calls before you attempt an emergency call. The capability
for an emergency call using Internet telephony depends on
the availability of a WLAN network and your Internet call
provider's implementation of emergency call capabilities.
Contact your Internet call provider to check the Internet
telephony emergency call capability.