SIP is an Internet standard for establishing and managing voice and video connections and is commonly used within organizations that have implemented voice over Internet protocol (VoIP) telephony. With SIP trunking, it also becomes the means of placing calls over carrier networks, allowing enterprises to consolidate their carrier trunk connections from many offices to a smaller number of data centers or communications hubs. They can then avoid long distance tolls by routing more calls over their wide-area networks.
"A lot of people are trying to save costs -- that's a major factor," said Courtney A. Mobley, an information systems coordinator from George Washington University who is working on a SIP trunking project. The preliminary engineering work has already been done, and the university is testing an initial implementation. "I think it's going to happen in the next year," he said.
Mobley said he was at the conference looking for practical tips, both in terms of understanding what users are looking for from Unified Communications and the kind of troubleshooting he will need to do to keep them happy. The university is already starting to deal with some of these challenges as more staff members rely on the IP network for voice. "If you can prove where the problem is and get the right people who need to solve the problem, that's really important," he said.
Mobley was among a hardy group of conference goers who got up early on Thursday, the last day of the conference, for a "coffee talk" discussion of the practicalities of SIP trunking. Sorrell Slaymaker, VP of communications architecture at Unified IT Systems, led a question and answer session on building the business case, getting the implementation right, and putting the right support in place.
SIP trunking is not an initiative to be taken on lightly, Slaymaker said. "Voice is one of those critical applications where if it doesn't work, everyone is unhappy." Although vendors make very expansive claims for return on investment, Slaymaker said the biggest savings he has ever seen from the transition is 70% -- with 45% to 50% being more common. Some of the savings are diminished by the "cleanup" aspects of the transition, such as chasing down and eliminating all the individual phone connections a big organization has established over the decades.
The business case is most compelling for large organizations with thousands of telephone trunks to replace. That also means it tends to be a multi-year process, since it's impractical to convert more than a handful of sites per week, Slaymaker said.
Among the questions raised by IT and network managers were how to handle fax lines, how to troubleshoot problems, and how much of the work can be delegated to a carrier, rather than implemented internally.
Slaymaker said many business processes and many older workers still depend on the departmental fax machine, so converting them to IP has to be part of the project. Some organizations run into trouble trying to implement voice compression on their VoIP systems, which tends to interfere with fax transmission. He doesn't recommend voice compression anyway because "it doesn't buy you much" and risks degrading voice quality.
For troubleshooting, his top recommendation is to include border session controller appliances as part of the network architecture. These are often included to improve security, but also offer monitoring functions that make it easier to trace problems with dropped or low-quality sessions. Acme Packet and Sonus Networks are two of the best specialty vendors in that niche, he said.
SIP trunking requires a "rock solid" wide-area network between branch offices and the data centers that will be routing calls, Slaymaker said. If your WAN is not up to the task, consider having a carrier provide it as a managed service, he said. "You don't necessarily have to have a private MPLS [multiprotocol label switching] network -- the carriers will give you very good SLAs [service-level agreements] if you are using their Internet [connectivity] on both sides," he said.