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How Cisco is Using SIP Trunks to Reduce Calling Costs

Like many large enterprises, Cisco makes a lot of phone calls.  Cisco previously used a lot of TDM trunks from multiple carriers to carry thousands of voice calls from our North American Cisco offices to the PSTN. The problem is, we had over 100 TDM trunks we were paying for every month, to carry our voice calls for these sites.  Four years ago we started looking around for a more cost-effective and manageable way to support all these calls.  After a good deal of searching, screening vendors and testing, we finally found it, using Session Initiation Protocol (SIP) trunking technology.

For the Cisco campuses in San Jose and Research Triangle Park (RTP), we will replace over a hundred PRI (23 channel) TDM trunks, used for long-distance voice calls for all of our North American sites, with SIP trunks.  The new San Jose link is a 250 Mbps SIP trunk carved out of a 10 Gigabit Ethernet WAN access line, while the RTP link is a 20 Mbps SIP trunk carved out of a 45 Mbps DS3 WAN access line. Together, these SIP trunks give us the capacity to carry over 2400 concurrent calls and a total voice call volume of 2 million minutes per month.
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