Yealink SIP-T54S Administrator's Manual page 130

Administrator's Guide for SIP-T2 Series/T19(P) E2/T4 Series/T5 Series/CP860/CP920 IP Phones
short media path in the same network would be chosen, which will probably have better quality
than the long one.
ICE is a complex solution to the problem of NAT traversal. Due to its complexity there is very
limited client support for ICE today.
SIP and TLS Source Ports for NAT Traversal
You can configure the SIP and TLS source ports on the IP Phone. Previously, the IP phone used
default values (5060 for UDP/TCP and 5061 for TLS). In the configuration files, you can use the
following parameters to configure the SIP and TLS source ports:
Local SIP Port

TLS SIP Port

If NAT is disabled, the port number shows in the Via and Contact SIP headers of SIP messages.
If NAT is enabled, the phone uses the NAT port number (and NAT IP address) in the Via and
Contact SIP headers of SIP messages, but still use the configured source port.
Procedure
NAT traversal can be configured using the following methods.
Central Provisioning
(Configuration File)
104
Configure STUN feature and STUN server
on a phone basis.
Parameters:
sip.nat_stun.enable
sip.nat_stun.server
sip.nat_stun.port
Configure manual NAT feature on a
phone basis.
Parameters:
network.static_nat.enable
<y0000000000xx>.c
network.static_nat.addr
fg
Configure ICE feature.
Parameter:
ice.enable
Configure TURN feature and TURN
server.
Parameters:
sip.nat_turn.enable
sip.nat_turn.server
sip.nat_turn.port