382 Chapter 44 Configuring VoIP trunk gatewaysNN40020-603NN40020-603— If your network uses a gatekeeper (H.323 trunks only), there are also specific settingsthat must be set on the your system to recognize the gatekeeper, and also within thegatekeeper application, so that VoIP lines are recognized. Refer to “VoIPinteroperability: Gatekeeper configuration” on page 389. If there is a gatekeeper onthe network, you do not have to configure remote gateway settings.— If you plan to use H.323 trunking and you have a firewall set up, ensure that the portsyou intend to use have been allowed.• SIP network applications consideration:— If you plan to use SIP trunking, and you have a firewall set up, ensure that the portsyou intend to use have been allowed.“Using VoIP to tandem systems” on page 327, and “Configuring fallback over a VoIP MCDNnetwork” in the Device Configuration Guide (NN40020-300).Configuring VoIP trunk media parametersThe VoIP trunk media parameters allow you to specify the order in which the trunk will select IPtelephony system controls for codecs, jitter buffers, silence suppression and payload size.The following path indicates where to access the VoIP trunk media parameters in ElementManager:• Element Manager: Configuration > Resources > Telephony Resources > IP TrunksFor details about the fields on this panel, refer to “H323 Media Parameters” on page 122 and “SIPMedia Parameters” on page 126.1 On the Modules panel, in the Module type column, select the IP Trunks line.2 In the bottom panel, select the H323 or SIP Media Parameters tab.3 Enter the information that supports your system. Ensure that these settings are consistent withthe other systems on the network:• Preferred Codecs: Choose codecs in the same order for all remote equipment.• Settings:— Enable Voice Activity Detection: Disable or enable this feature, based on networkrequirements. Also refer to “Silence suppression” on page 529.— Jitter buffer - Voice: Either choose auto to let the system determine resourceavailability, or choose a buffer size.— Payload Size: Change the defaults to coordinate with other systems on the network.Operations note: Fax tones that broadcast through a telephone speaker may disrupt calls at othertelephones using VoIP trunks in the vicinity of the fax machine. Here are some suggestions tominimize the possibility of your VoIP calls being dropped because of fax tone interference:— Locate fax machine away from other telephones.— Turn the speaker volume on the fax machine to the lowest level, or off, if that option isavailable.
