Optional Voip Trunk Configurations - Nortel BCM50 Configuration Manual

Optional VoIP trunk configurations

A number of VoIP trunk features are optional to setting VoIP trunk functions. The following
briefly describes these features:
• Port settings (firewall): In some installations, you may need to adjust the port settings before
the BCM can work with other devices.
Firewalls can interfere with communications between the BCM and another device. The port
settings must be properly configured for VoIP communications to function properly. Using the
instructions provided with your firewall, ensure that communications using the ports specified
for VoIP are allowed.
A Nortel IP telephone uses ports between 51000 and 51200 to communicate with the system.
The system, by default, uses ports 28000 to 28255 to transmit VoIP packets.
BCM uses UDP port ranges to provide high priority to VoIP packets in existing legacy IP
networks. You must reserve these same port ranges and set them to high priority on all routers
that an administrator expects to have QoS support. You do not need to reserve port ranges on
DiffServ networks.
You can select any port ranges that are not used by well-known protocols or applications.
Each H.323 or VoIP Realtime Transfer Protocol (RTP) flow uses two ports, one for each
direction. The total number of UDP port numbers to be reserved depends on how many
concurrent RTP flows are expected to cross a router interface. In general:
— Include port number UDP 5000 in the reserved port ranges, for the QoS monitor.
— The port ranges reserved in a BCM system are also reserved by the remote router.
— You must reserve two ports for each voice call you expect to carry over the IP
network.
— You can reserve multiple discontinuous ranges. BCM requires that each range meet
the following conditions: Each range must start with an even number; each range must
end with an odd number; no more than 256 ports can be reserved.
Note: By default SIP uses port 5060.
• Gatekeepers: The BCM supports the use of an ITU-H323 gatekeeper. A gatekeeper is a
third-party software application residing somewhere on the network, which provides services
such as:
— address translation
— call control
— admission control
— bandwidth control
— zone management
— IP registration
Chapter 43 VoIP trunk gateways
Networking Configuration Guide
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