Steps to Integrate SIP Trunks into the Enterprise
Communications Transformations - Part 2
By Cisco Systems
Published August 2007; Posted December 2007


IP-based unified communications is widely deployed in enterprise networks, both for internal calling in the campus and between branch offices of the sites comprising the network. Such enterprise networks increasingly use IP-capable user endpoints (IP phones or softphones), and although interconnections of older time-division multiplexing (TDM) private branch exchanges (PBXs) and key systems through voice-over-IP (VoIP) gateways still exist in many networks, adoption of IP user endpoints in the typical enterprise network is increasing rapidly.

Access to the public switched telephone network (PSTN) from the enterprise network is, however, still predominantly TDM-based. Typically located at each network site, VoIP gateways provide connectivity from IP user endpoints to the traditional PSTN.

The next stage in advancing business communications, which is beginning to occur in enterprise networks, takes unified communications traffic destined beyond the enterprise also to IP. Similar to enterprise networks, service provider networks have widely deployed VoIP inside their own networks and although the enterprise’s PSTN interconnection points are still almost exclusively TDM-based, the PSTN backbone has in many cases already deployed VoIP traffic. This situation makes it technically possible to use VoIP also as the method of voice interconnection between enterprise and service provider networks. As unified communications Session Initiation Protocol (SIP) trunk offerings from service providers mature over the next several years, IP interconnection for unified communications presents a new business opportunity for an increasing number of enterprises.


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