SIP trunking (VoIP based on the Session Initiation Protocol, which has become the industry standard for enterprise VoIP) has been in development for years. It's now becoming mainstream as enterprises focus on cutting costs. But before kissing TDM voice goodbye, you need to make sure that the sellers keep their pricing and performance promises, and that you don't put your network or its economics at risk. Here's how.
Part I: The SIP Trunking RFP
Understand How Different Offerings Meet Your Needs (or Don't)
After you've developed a business case and strategy, it should come as no surprise that using a Request For Proposals--or whatever term you use--and evaluating responses from several vendors is the best way to compare SIP trunking offers and the vendors' ability and willingness to meet your needs. Those needs differ across organizations, but here are a few that appear on most lists.
Service Availability
SIP trunking provides a connection from a company's MPLS network to the PSTN that is designed to replace all or most off-net TDM local and long distance voice services.
In the same way that it is rarely possible to purchase all of your local services from a single Local Exchange Carrier (LEC)--because different LECs offer services in different areas--SIP trunking with local calling capability is not available everywhere from every vendor. Level 3 brags about covering "85 percent of all U.S. households." Other vendors aren't explicit about their geographic coverage, although coverage is rapidly becoming fairly ubiquitous. Most advertise SIP trunking availability in the U.S. Mainland, but where the holes are is not easy to figure out.
AT&T says that its SIP trunking service--Business VoIP--with local calling capabilities is "only available where the necessary local service facilities and required 911 or E911 capability is available," but that turns out to be most places, and certainly most urban areas. Verizon's local calling capability is available only "[a]t Customer locations that are served by a MCI Legacy Company local switch...as determined by" Verizon--which, again, is most places. Sprint is silent.
If the SIP trunking provider's service footprint aligns with most of your footprint, replacing your local services with SIP trunking can consolidate billing, administration and operational management from many LEC relationships.
The RFP is your chance to pin the vendors down. Give them a list of your U.S. locations and have them identify anywhere their SIP trunking product is not currently available, and when they anticipate it will be available in those locations.
Technical Considerations and Interoperability
SIP is an industry protocol that continues to evolve, resulting in a range of equipment compatibility and interoperability problems. In order to work, your IP PBXs, SIP trunk service and edge devices must be compatible. If they aren't, you can't complete voice calls.
Vendors will list the equipment compatibility/certification tests their SIP trunking services have passed, but that's not enough. When you move beyond basic features, SIP trunking may not operate consistently across equipment. Interoperability issues also arise from tweaks to the standard SIP implementation by OEMs, IP PBXs that are not fully patched, and special gateway devices.
In addition, not all codecs that you may want to employ may be supported. For example, a SIP provider may only support G.729a for voice calls, but toll-quality voice requires support for G.711.
To illustrate, Verizon's SIP trunking services are advertised as interoperable with certain Avaya, Cisco and Nortel IP PBXs, but "[a]ny SIP phone, firewall and/or gateway used by Customer must be certified for use with VoIP as determined by" Verizon. Similarly, AT&T states that its IP Flexible Reach BVoIP service is interoperable with certain Cisco, Polycom, Avaya, Toshiba, and CosmoCom gear, but requires that the customer's SIP equipment be "AT&T certified". The list of IP PBXs certified by vendors as compatible with their SIP trunking services is updated frequently. Give the vendors a list of the IP PBXs you have already installed or are looking to install, and ask them to identify any that have not been certified as interoperable with their SIP trunk service. For these, ask the vendors if interoperability testing is planned or, if a listed IP PBX in question was found not interoperable, what steps are being taken to correct this. You should also ask for the details of how each vendor's service supports the SIPconnect specification as well as inbound toll-free features and call center capabilities if your enterprise expects to use them.
Even if a vendor has certified your IP PBXs as interoperable, says its service supports fax, in-bound toll-free features, and call center capabilities, and has listed all the local calling features you need, you will want to test these features and the quality of the service before signing up for a multi-year term. Pilot tests allow just that, so make sure you get a meaningful pilot. In the RFP, ask each vendor to commit to provide a pilot test of its SIP trunking service (at little or no cost) at one or two of your major locations for 60-90 days, and try to get a pilot that allows termination of domestic and international on-net and off-net calls. If you are not satisfied with the service, you should be allowed to terminate it and any related services (e.g., access lines and larger ports you contracted for to accommodate SIP trunking) without liability.
Vendor Service Pricing: Are You Comparing Apples and Orangutans?
The vendors' SIP trunking pricing models are as clear as mud. Many (including Verizon and AT&T) charge on a per-concurrent-call basis, which basically means you are paying for the capacity to place a certain number of calls simultaneously; others (such as Level 3) charge on a bandwidth and concurrent call basis; and still others, like Sprint, allow an organization to send as many concurrent calls as possible over the bandwidth in an "integrated" access line. All SIP trunking vendors include unlimited on-net calls regardless of concurrent call capacity but subject to access bandwidth constraints.
Adding complexity, some vendors allow you to burst above the number of concurrent calls at a particular site so long as the total number of calls at all locations do not exceed the aggregate number of concurrent calls across all locations. This allows enterprises to save money by sizing their overall "concurrent call" requirement based on aggregate peak calls; not peak calls at individual locations. Verizon’s program is called Burstable Enterprise Shared Trunks ("BEST"), (but is limited to 50 concurrent calls above the base number of concurrent calls subscribed to at any particular location, regardless of the aggregate number of concurrent calls to which the customer subscribed). In contrast, Level 3's offer for "pooled concurrent call paths" does not appear to have a location-specific cap.
Once you've figured out the line costs, off-net pricing confusion kicks in. Off-net calls come in three flavors--local, domestic long distance and international. There is usually no charge for SIP trunked local usage--the cost is bundled into the concurrent call charge so the pricing is like flat rate business lines rather than metered lines. But look out for different definitions of "local"--is a local call one that is local to the centralized SIP Trunk at the data center to which all off-net calls are sent for "distribution" to the PSTN, or local to the original calling party--which could be on the other side of the country? How each vendor defines local calling in the SIP trunk world can have a material impact on which calls incur usage charges and which don't. None of the vendors price international and domestic off-net calls the way this was done in the classic TDM model. TDM interstate rates and intrastate rates differ, and intrastate TDM rates typically vary by state, but SIP vendor off-net domestic LD rates don't vary by jurisdiction. That's helpful, but it means that you can't simply compare current TDM rates to SIP rates on a per-minute basis. You need to understand your current usage profile and price your usage using the TDM and SIP rates to compare total usage costs--it's a spread sheet, not four numbers. In a further wrinkle, vendors (notably AT&T) also offer bundled usage pricing where a customer buys bundles of minutes at a fixed price or where each concurrent call charge provides a bundle of included minutes. And in addition to all of the above, a range of additional fees and charges apply to SIP Trunking--one-time charges, set-up fees, change fees, DID telephone number charges, toll-free feature charges, and charges for service features such as Voicemail, remote office, attendant console, and auto attendant.
If you haven't already thrown this article aside and reached for the Excedrin, use the RFP to solicit comprehensive pricing proposals from vendors in a consistent format, so that you can understand and compare the total cost of each vendor's product. It can be done--really.
SIP Trunking and 911 Access to Emergency Services
SIP trunking claims to offer benefits over TDM in terms of cost reductions and flexibility. Even if that is true--and it is--poorly implemented SIP trunking could significantly increase your company’s "911" emergency services risks. You need to decide whether these benefits outweigh the additional risks. Use the RFP to gather the information you need for that analysis. Basic 911 access and routing is "built into" local TDM service. More advanced E911 capabilities--notably specific information on the location of a caller--are now deployed in much of the US.
When a caller dials 911 in the TDM world, the call is routed directly by a site-based PBX over the PSTN to the public safety access point (PSAP) nearest the caller. The PSAP receives location information and call-back information. SIP trunking turns this on its head. A SIP provider's ability to support E911 compliance in a specific location depends on factors like SIP provider service interoperability with the LEC, PSAP capability, an enterprise's E911 server equipment, and whether the enterprise is updating E911 server database information. In your RFP, ask vendors about their E911 capabilities at each of your company locations. Also ask how they deliver E911 with a centralized architecture where all voice traffic is routed over the internal data network to centralized SIP Trunks at a small number of data center locations for egress to the SIP trunking provider (and then the PSTN).
A SIP trunking provider's E911 capabilities may provide only the main address and the main billing telephone number for a location, and not additional detail such as floor location. Without "E911 level" location details, the PSAP would send help to the location without knowing the floor number, which in high-rise environments can be a significant problem.
The solution to managing and minimizing E911 risks is likely to involve a combination of steps, including retaining some TDM PSTN trunks at large locations as a backup for delivering 911 calls from those locations; making arrangements with the PSAP to provide correct, specific end user location information (and updating that information on a timely basis); designing and implementing a 911 policy and calling plan for worker health/safety; and training employees on any new limitations on 911 calling. It's a good idea to put appropriate 911 warning labels on phones as a "reminder" of these limitations.
SIP Trunking Privacy and Security
The emergency services risk with SIP Trunking is the inability to access information on the location of a caller. The privacy risk is the opposite; if a SIP call passes through or interconnects to the public Internet, it's the potential risk that information can be accessed through eavesdropping and hacking. In the SIP trunking world, voice is an application on the data network, and the impact of a security breach, even if it originates within the company, needs to be taken into account in a way that is specific to voice. Existing data network defenses don't necessarily work and may not work with a vendor's SIP services. Be prepared.
Eavesdropping is a particular concern. In TDM networks, eavesdropping requires intrusion into the PBX or physical access to the telephone wire. TDM PBXs have fewer access points than their VoIP counterparts, largely because SIP trunking routes voice calls over an IP packet network with numerous nodes, and more access points means more opportunity for eavesdropping. For example, if a call is made from a soft phone in a hotel room over the public Internet, deployment of appropriate VPN IPSec security controls needs to be integrated with the enterprise's UC infrastructure and/or the SIP provider's solution to provide any necessary security.
Appropriate physical and logical security for all network devices is a must, but it's not enough for SIP trunking. The enterprise has to know if it will depend on the SIP provider to support Secure Real Time Transport Protocol (encryption of the voice stream) and Transport Layer Security (encryption of the SIP protocol). In addition, the enterprise must ensure its infrastructure provides a secure foundation for SIP trunking implementation, including separate VLANs and potentially separate VPNs in the wide area network, session border controllers and SIP-specific intrusion detection/protection appliances.
But you cannot look at these without knowing whether a particular vendor's SIP trunking services are compatible with them. Use the RFP to ask the vendors whether their services are compatible with VoIP encryption, the level of encryption with which they are compatible, and the session border controllers with which their services are compatible.
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We could say a lot more about how to use an RFP for SIP trunking, but service availability, interoperability, pricing structure differences, emergency services and security risk are the top priorities. We hope that we've given you enough to think about until our next article--which will discuss incorporating SIP Trunking into, or on top of, your telecom service contracts.
Deb Boehling ([email protected]) and Hank Levine ([email protected]) are partners at Levine, Blaszak, Block & Boothby ("LB3"), the premier law firm representing enterprise customers in connection with telecom and IT agreements. Ben Fox ([email protected]) and David Lee ([email protected]David Lee) are consultants with TechCaliber Consulting, LLC ("TC2"), a global technology and telecom consultancy that advises enterprises seeking to reduce their telecom and technology costs as they upgrade their services.
