The VoIP Peering Puzzle�Part 54: Buyer’s Guide, Part 1

For the last year or so, we have been examining a number of challenges associated with VoIP peering. Along the way, we looked at the work of the Internet Engineering Task Force’s SPEERMINT working group, Electronic Numbering, or ENUM, which correlates Internet Protocol addresses with telephone numbers, providers of these ENUM translation services; concepts of PBX trunking and the SIPconnect standards; the architecture and functions of session border controllers; and overviews of more than 25 vendors’ session border controller products .

To wrap up this series, we’ll look at some of the business issues that enterprise managers should consider when looking into a peering architecture for their network.

To peer or not to peer?
VoIP peering brings with it a whole new set of challenges that are much like running your own telco—including address conversions and billing issues—in addition to the more basic functions of just providing end user connectivity.

So the first question that you need to ask is whether or not this is a business that you really want to get into. If you cannot make a business case for the peering project based upon projected cost savings or other strategic advantages, then perhaps a move into this area of technology, with its many facets of complexity, should be kept on the back burner for a while. For starters, check out the on-line Enterprise Savings/ROI Estimator provided by the Voice Peering Fabric (see

Choose your partners carefully
It is likely that you will be entering into agreements with several third parties when you jump into the VoIP peering arena, including peering exchanges, Electronic Numbers (ENUM) registries, and application service providers (ASPs) of 411 and 911 services, as well as switching system and session border controller manufacturers. As the saying goes “you have to kiss a lot of frogs to find your prince”, and from my experience examining products and services in this area, there are a few frogs lurking out there in the pond. Make sure that your business due diligence uncovers those amphibians before you begin signing contracts.

Where does the PBX fit in?
Keep in mind that peering is just one part of your overall VoIP and converged networking architecture, and that one of the fundamental building blocks of your enterprise architecture remains the premises switching system, or PBX. If your PBX system has not been upgraded to an IP-based system, then that research should be close to the top of your priority list. If it has, then see if the IP-PBX is compatible with the SIPconnect specification—an industry effort to provide peering interoperability between IP-IBXs and VoIP service providers (see

Addressing is a big deal.
ENUM providers boasting of a database capacity of 500 million telephone numbers in their registries sound like a huge number, but if those are not the numbers you need, that benefit diminishes pretty quickly. Some of the registries come with extensive telephone and Internet experience, which is also a plus. The ENUM Forum is a good place to start your research in this area (see

What’s protecting your border?
A session border controller (SBC) is your first line of defense against unauthorized access into your network. But as you might expect, not all systems are created equal, and some products that might better be described as border routers claim to be full-blown SBCs. Fortunately, the IETF has done some of the homework for you in this area, and defined some clear functional criteria that should be considered.

Stay tuned—our concluding tutorial will review the SBC technical capabilities that one of the IETF working groups has developed.

Copyright Acknowledgement: © 2007 DigiNet Corporation ®, All Rights Reserved

Author’s Biography
Mark A. Miller, P.E., is President of DigiNet Corporation®, a Denver-based consulting engineering firm. He is the author of many books on networking technologies, including Voice over IP Technologies, and Internet Technologies Handbook, both published by John Wiley & Sons.

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