Avaya 555-245-600 manual IP-based trunks, Fax, Modem, and TTYoIP options

IP-based trunks

Table 16: Fax, Modem, and TTYoIP options (continued)

TTY	US	Default, 45.45 Baudot, interoperates with previous releases
	UK	50 Baudot
	pass-thru	similar to Fax pass-thru
	off	system ignores TTY tones, call remains in administered
		codec
		2 of 2

IP-based trunks

In circuit switched networks, trunks provide the means to interconnect PBXs with each other and to the PSTN. Connection to the public network allows PBX station users to call and be called by terminals that are not part of the PBX private network. An analogous arrangement exists in packet-switched IP networks.

H.323 trunks connect H.323 systems or gateways over IP networks, similar to circuit-switched tie trunks. Similarly, SIP trunks connect SIP systems or gateways over IP networks.

A set of Communication Manager switches can each be attached to an IP network, and voice and fax calls can flow between them in the usual manner except that the call signaling and audio/fax streams are carried over the IP network. The signaling is carried through the C-LAN circuit packs, and the audio and fax streams are carried between switches through the Media Processor circuit packs.

The benefits of using IP trunks include:

●Reducing long distance voice and fax expenses

●Facilitating global communications

●Providing a fully functional network with data and voice

●Converging and optimizing networks by using the available network resources

IP trunk calls can be compressed to save network bandwidth. Repeated compression and decompression (transcoding) results in a loss of data at each stage and degrades the final quality of the signal. The maximum recommended number of compression cycles on a call is three. Normal corporate voice calls or fax calls typically go through fewer than three compression cycles.

IP (H.323 and SIP) trunks can also connect to other vendors' compliant PBXs.

Issue 6 January 2008 133