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Networks & Infrastructure
Cable-Tec Expo 2008: Tekelec relieves IP peer pressure
TekPath Route Director bridges TDM to VoIP
by Sean Buckley
If service providers could build their voice networks from scratch today, it’s obvious they would start with an all-IP-based foundation. The reality is that they spent the better half of the last century building out a voice network to support quality voice service based on TDM technology.
While VoIP is gaining momentum, it’s still a relatively nascent market with only 10 percent worldwide penetration.
What has held up a larger proliferation of VoIP services is the provider’s inability to route calls between the IP and TDM worlds—two worlds with different numbering schemes.
One answer to the call routing problem is to use electronic number mapping (ENUM). Otherwise known as E.164 number mapping, ENUM is a Domain Name System (DNS)-based protocol that can perform and expand call completion over VoIP networks.
Leveraging the work it has done with SS7 Signaling Transfer Points (STP) for number portability, Tekelec has created the TekPath Route Director ENUM product.
Acting as a subscriber routing database (SRdB), TekPath collapses both TDM and VoIP address functions into one network element. It can convert both ported and non-ported telephone numbers into a domain name (see Figure 1).
Robby Benedyk, senior product manager for Tekelec's TekPath Route Director product, says that while ENUM certainly was a forward-looking idea when it emerged in 1999-2000, it was a solution looking for a problem.
“There were no takers because there was not enough IP traffic to use the system,” he says. “What has changed is more deployment of IP and more desire to interoperate between operators. The interesting thing is a service provider wants to be able to not only exchange information within [its] network but also be able to exchange routing information directly [among] other carriers.”
All about the apps
No matter how compelling ENUM is, it will be nothing more than a concept if it can’t enable new applications.
As a hybrid private/carrier ENUM subscriber routing database, the TekPath router can convert a telephone number into a domain name. TekPath can then connect a TN to a domain name, which is used to network the operator’s uniform resource identifier (URI) to the TN.
To perform provisioning, TekPath leverages the Tekelec Local Service Management System (LSMS) for downloading number portability subscriber data to one or more systems.
In addition to supporting multiple traditional TDM and IP-based interface protocols such as SS7, ISDN User Part, SIP and ENUM, TekPath can enable a number of applications including VoIP peering, IMS peering and multimedia message services (see Figure 2).
As an early adopter, Tekelec is taking an active role in advancing ENUM in both the cable and traditional telco network domains. For one, Tekelec has been collaborating with Cable Labs to develop and promote the ENUM server provisioning specification (ESPP), which helps cable operators connect their own IP network islands.
ESPP, which has been submitted to the IETF for consideration, enables a cable operator to receive session establishment from a myriad of sources, including its own back office systems, a session peer or a federation registry.
Multi-faceted solution
As ENUM has found its way into carrier lab and field trials, three main methods have emerged:
• Public ENUM. As its name implies, public ENUM requires any subscriber or carrier to opt into a public database. What’s troublesome for service providers is that because it is public, subscriber information could be compromised.
• Private ENUM. Not surprisingly, service providers favor private ENUM, since it gives them control over the subscriber data. With private ENUM a service provider can route services directly to end users by using their final private URIs.
• Operator ENUM: Similar to private ENUM, operator ENUM is designed to help service providers implement peering arrangements. With operator ENUM, one service provider can deliver any kind of content (e.g., VoIP call, video session, etc.) to the next by correlating a TN to a carrier domain.
While acknowledging the three ENUM approaches, Benedyk believes carrier and private ENUM ultimately will prevail.
“I believe public will go away and there will be private and carrier ENUM,” Benedyk says. “When we talk about carrier ENUM, it means I want to know who the carrier of record is for that query and operator A wants to know that B has that number. Once you get inside operator B, he’s going to have that private information he’s not going to share with other operators, but he’s going to want it in the same database.”
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