For many years now, telephony voice services for businesses and enterprises have been provided by using legacy PBX systems connected to the Public Switched Telephone Network (PSTN) using TDM connections (T1/E1 ISDN PRI lines or BRI or analog lines). This is shown on the figure below:
Newer telephony systems adopted the IP technology on the internal LAN, but they still used TDM connectivity (ISDN PRI/BRI and analog lines) to connect to the legacy PSTN network as shown below:
The newest trend is to go all-IP using SIP TRUNKING to connect your business office to the Telephony Service Provider network. A SIP Trunk allows the company to replace the traditional TDM fixed lines (PRI, BRI etc) with just a normal IP connection towards the service provider. This solution offers significant cost savings to the enterprise as you avoid costly BRI/PRI lines. Also, voice/data traffic can be converged on a single IP connection. This scenario is shown below:
The Cisco Call Manager Express product can be used as the telephony SIP trunk gateway between the local IP telephony network and the IP Telephony Service Provider. Calls from and to PSTN will be handled by a SIP PROXY server located in the Service Provider network.
A sample Call Manager Express configuration for SIP trunking is shown below (a snippet of the complete configuration is shown):
| voice service voip allow-connections sip to sip sip registrar server expires max 3600 min 3600 localhost dns:mycompany.test.com voice class codec 1 !— Inbound Translation Rule voice translation-profile AutoAttendant !— SIP Trunk Configuration — dial-peer voice 2 voip dial-peer voice 3 voip !— SIP UA Configuration — |
Source from: http://www.cisco-tips.com/sip-trunking-with-call-manager-express/
