SONET Ring and Distributed Voice
Trunking Support Business Continuity Mission
by Barb Renner
On a typical day, an average of sixty-eight thousand local telephone calls are placed to and received from the University of Cincinnati's campus telephone system. The local calls are carried to and from the UC campus on twenty Primary Rate Interface (PRI) ISDN trunks, equivalent to 460 single telephone lines, that connect the campus telephone system to the public telephone network. In December 2003, UCit moved the local calling service from Cincinnati Bell Telephone (CBT) to Time Warner Telecommunications (TWTC). This change involved moving the 556 and 558 exchanges from CBT to TWTC, and required nationwide coordination with every long distance service provider. The seamless move from CBT to TWTC resulted in substantial savings that helped the organization maintain services despite budget reductions.
In addition to changing local service provider vendors, UCit changed the location configuration of the local PRI trunks. Previously, all twenty PRI trunks terminated in the main east campus node room. If there was a telephone system outage on east campus, west campus users could only make and receive on-campus calls because there were no outbound or inbound trunks installed on west campus. UCit, along with TWTC, moved ten PRI trunks, equivalent to 230 single telephone lines, to a west campus node room for distributed trunking on the UC campus. Each side of campus is now equipped with its own dedicated telephone trunks.
TWTC provides a second level of diversity to the UC campus via a Synchronous Optical NETwork (SONET) fiber optic ring that terminates in two locations: one on east campus and another on west. The SONET ring equips the UC campus with two separate physical paths to carry calling traffic to and from UC. During normal operations, calling traffic is only carried on the side of the ring which serves as primary. If service is disrupted on the primary side of the ring, the ring's intelligence detects the problem and automatically diverts calling traffic to the alternate, or protected, path of the ring, with minimal service disruption.
Both the SONET ring and distributed trunking provide the UC campus with a backup route for timely recovery from a service interruption.
You may send email to the author at Barb.Renner@UC.Edu.
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