Specifications

Engineering Guidelines
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• Network address translation (NAT) and firewall: Although there are emerging standards
to allow VoIP through firewalls and NAT devices, these are still in early development. To
allow voice through a firewall, a number of ports need to be opened because one controller
may use a range of ports that are dynamically assigned. Opening all possible ports negates
the usefulness of the firewall. NAT needs to change addresses, but may have difficulty
mapping a single controller device to multiple internet addresses, or translating IP address-
es that are buried in control messages. Generally, these issues are resolved by using VPNs.
• Virtual Private Network (VPN): VPNs are simply a pipe or tunnel across an ISP network,
which allows a remote device to react as though it is still connected to the enterprise network.
Be aware that the VPN may be across an unknown network or across the Internet. It may
be necessary to get certain Service Level Agreements (SLA) to ensure timely delivery of
data. Where encryption is used, additional delay may also be added to the data.
• Teleworker: The Mitel Teleworker Solution is for remote workers who need to connect to
the Internet and send traffic through a business firewall and NAT combination.