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Enterprise VoIP Solutions: Page 3 of 8

Of course, you should still talk to salespeople and lay the groundwork for a VoIP pilot. Determine whether you have the skills in-house to manage the new technology and deal with new security problems. One note: The 10 percent of readers with security concerns should check out a free, 99-page report by the National Institute of Standards and Technology (NIST) titled "Security Considerations for Voice Over IP Systems," available at csrc.nist.gov/ publications/ nistpubs/ 800-58/SP800-58-final.pdf.

Before building a purchasing proposal, evaluate your infrastructure to ensure that your network can handle VoIP (see "Prepare Your Network for VoIP,"). If you lack QoS and high availability, it could be tough going. In that case, a phased approach may be in order.

Determine the optimum mix of TDM and VoIP for your network. For example, VoIP could be used to trunk together legacy PBXs. It's also possible to have one PBX support a mix of VoIP and TDM phones. Some vendors, notably Cisco, will push you toward pure IP simply because that's what they sell, while legacy PBX vendors like Avaya take a different approach, placing no real limitations on the number of TDM phones in the mix. In fact, if you own an Avaya PBX, you may be able to add VoIP functionality and start reaping the benefits without a forklift upgrade. Many legacy vendors also offer pure IP systems backed by a long track record of providing solid voice services.

Prime VoIP candidates are companies with many, geographically dispersed offices. VoIP can trunk locations together over existing data WAN circuits, saving on long-distance while making more efficient use of bandwidth and improving intracompany communications. It also provides some flexibility in PBXs locations. For example, some locations could have only VoIP phones, accessing a PBX at another location. Keep in mind that in some cases, VoIP calls can take up more bandwidth than corresponding circuit-switched calls, depending on the type of codec used (for more on codecs, see the "VoIP Codecs" sidebar). In our reader poll, about three-fourths of those installing VoIP weren't sure which codec they were using! Another benefit that VoIP provides for those with physically dispersed locations is the opportunity to easily consolidate multiple vendors' PBX systems, cutting maintenance costs.

Redmond's SIP Stake