AASTRA 6700i series, 9143, 9480i, 9480i CT SIP Administrator Guide EN - Manual (Page 203)

4-40 41-001343-01 Rev 03, Release 3.2.2
Interactive Connectivity Establishment (ICE) Support
The phones now support the Interactive Connectivity Establishment (ICE) Protocol. ICE makes
use of the Session Traversal Utilities for NAT (STUN) protocol and its extension, Traversal
Using Relay NAT (TURN).
In an ICE environment, two agent endpoints (or two phones communicating at different
locations) are able to communicate via the SIP Protocol by exchanging Session Description
Protocol (SDP) messages. At the beginning of the ICE process, the agents are ignorant of their
own topologies. In particular, they might or might not be behind a NAT (or multiple tiers of
NATs).
ICE allows the agents to discover enough information about their topologies to potentially find
one or more paths by which they can communicate.
The ICE Protocol is automatically enabled if both STUN and TUNR servers are configured in
the network. The following occurs when ICE is used on the phone:
• The TURN address/port is always used as the preferred media address in initial INVITES.
• Media is sent through the TURN server prior to the completion of the ICE connectivity
check.
• A Re-INVITE is used to adjust media (if required) after the ICE connectivity check is
complete.
• When ICE is enabled, call hold is performed via the sendonly attribute instead of changing
the media address to 0.0.0.0.
• The ICE Protocol supports the RTCP SDP attribute (RFC 3605)
STUN and TURN can be enabled using the Aastra Web UI or the configuration files. This
automatically enables ICE.
Reference
To configure STUN and TURN (which automatically enables ICE), see “Configuring STUN and
TURN Servers Using the Configuration Files” on page 4-37 and “Configuring STUN and
TURN Servers Using the Aastra Web UI” on page 4-38 .