Network Solutions - At the LeXSS

Posted 03/2001

Network Solutions

At the LeXSS
VoDSL Meets the Local Exchange Softswitch
By Stefan Knight

Market supremacy will go to those that develop solutions for uniting the various technology camps under one accord and ensure that local services can be delivered to all subscribers.

It's 2001, and the armies of convergence are meeting at the edge. What will happen next? Will VoIP triumph and be deployed end-to-end? Will VoDSL gateways cease to add value and be consumed by media gateways? Will softswitches actually replace the big iron switches at the edge of the traditional network?

Before pondering answers to these questions, one cannot gloss over the crucial element in the end-to-end equation necessary to provide basic telephony services--the Class 5 CO switch. This last switch in the network does the lion's share of the work. It provides the features that subscribers have become accustomed to paying for--emergency services, billing records, trunk-to-local call switching and conversion--and connects to a host of CPE with unique interfaces and signaling. Has anyone "broken the code" to providing a true Class 5 office replacement on a convergence platform? VoDSL gateways do not inherently provide dial tone, local calling features or digit routing. In essence, they appear to the network like a digital loop carrier, and connect to a Class 5 switch via a remote digital terminal (RDT) interface such as GR-303, TR-008, or V5. Softswitches and media gateways, the state of the art in convergence, still only support Class 4 applications.

In fact, the vast majority of softswitch architectures by and large still only support a subset of Class 4 functionality--primary rate interface (PRI) and Internet offload. Having evolved from Internet technologies and from companies focused in this arena, they are locked into providing dial-up concentration to modem banks and remote access services (RAS). In order for a vision of the packet network to triumph and for protocol lines to be drawn, the provision of dial tone and local calling service intelligence needs to be present between the access and core networks. What is needed is a softswitch that accommodates Class 5 functionality as well as Class 4 features. Enter the local exchange softswitch system (LeXSS).

A LeXSS is a complete edge, access and core solution. There are seven essential elements that need to be addressed in order to "break the code" and unify the access, edge and core as well as replace the Class 5 office:

* The solution needs to interoperate with the wide array of legacy telephony signaling protocols and network interfaces including centralized automating message accounting (CAMA) for E-911, SS7 ISUP and TCAP, T1 CAS, IMT and others.

* The solution needs to deliver the "must have" calling features that a Class 5 switch offers today and that generate margins of 70 percent or higher. There are hundreds of CLASS, custom calling and business group features. The majority of today's softswitches are struggling to implement up to a dozen of them. To effectively replace the legacy local exchange, the list of "must have" features totals just over sixty.

* The solution needs to offer a personal service creation environment. Personal service creation involves two parts: the service provider creating new service offerings consisting of old and new features in new combinations, and a subscriber interface that breaks through the barrier subscribers face when trying to customize feature behavior through a handset keypad. In both cases, web portals and development tools enable rapid feature creation, prototyping, and extensibility of the LeXSS--driven by the unique ingenuity of the service provider.

* The solution needs to integrate seamlessly with packet broadband technologies as well as traditional TDM access technologies. A complete solution supports the installed base by offering connectivity to VoDSL gateways through GR-303 interfaces, as well as by bringing VoDSL AAL2 termination directly into the system.

* The solution needs to offer a way to integrate VoDSL and VoIP technologies. VoDSL is the standard in the access network, while VoATM and VoIP are being deployed in the core network. The complete solution will recognize the tradeoffs between different packet technologies in different parts of the network and efficiently harmonize the conversion from TDM to ATM, TDM to IP, and ATM to IP. It will achieve this without requiring packetized voice to be converted back to TDM in order to translate calls from ATM to IP.

* The solution needs to connect all customers to the network--essential to supplanting legacy solutions. This means that the system is capable of interfacing to PBXs, phones, digital loop carriers and channel banks as well as IADs and next- generation phones with direct packet telephony interfaces. In addition, it means delivering services that are offered in the softswitch over any access or core connection. The crux of this issue is not whether IP or ATM will win out in an end-to-end bid for network supremacy, it is delivering the services created on this new platform to subscribers connected over TDM, ATM or IP.

* The solution needs service management integration. The only way that the packet access network will succeed in uniting with the packet core network through a LeXSS at the edge of the network is through such integration. Service management integration comes in two parts: connectivity to network management, and OSS and billing systems, as well as providing flow through provisioning for services over TDM, ATM or IP.

Market supremacy will go to those that develop solutions for uniting the various technology camps under one accord and ensure that local services can be delivered to all subscribers. VoDSL gateways will continue to have a prominent place in the network by connecting legacy switches to packet access networks. Some VoDSL gateways, those designed around packet switching buses, will make the leap to true media gateways, and thus mature and evolve to take advantage of soft-switch technology.

The softswitch will be the intelligent centerpiece of the network. It will support legacy and next-generation applications over a variety of access and core network interfaces. This model will allow the service provider to leverage its investment in service intelligence separately from its investment in switching hardware. The net result will be a next-generation switching fabric--growing at the rate of Moore's law and controlled by softswitches evolving at Internet speeds.

So what about VoDSL technology? The next chapter of VoDSL standards work is already being written. The new telephony signaling protocol being embraced for service delivery to the IAD is Media gateway control (MEGACO).

MEGACO is rapidly emerging as the protocol of choice in next-generation networks because it allows softswitches to provide services over TDM, ATM and IP networks. It is rapidly replacing media gateway control protocol (MGCP), designed for IP-only implementations. The ITU-T (ITU Telecommunication Standardization Sector) and IETF (Internet Engineering Task Force), the Bell heads and the net heads all have embraced MEGACO. VoDSL gateways will help to evolve packet trunking interfaces and MEGACO support so they can leverage softswitches. Softswitches will incorporate call control for TDM, ATM and IP networks.

Only the strong will survive. The brass ring is certainly local services. Replacing the functionality of a Class 5 switch is the task at hand, and integration will be the key. A tremendous amount of consolidation is sweeping the convergence market space. The year 1999 was punctuated by the rapid acquisition of upstart, convergence hardware vendors by the established players for PRI and Internet offload applications. The state of the art for softswitches was SS7 to PRI signaling. The year 2000 saw the rapid acquisition and merger of softswitch companies--a trend beginning with the merger of CopperCom (www.coppercom.com) and DTI Networks (www.internetfinance.com/dti.htm) in March 2000.

The marketplace is coming to the realization that the "sum of the parts" is required to deliver a true, end-to-end solution. In the race to the Class 5 office, the integrated vendor platforms are clearly in the lead.

Stefan Knight is director of product marketing for CopperCom (www.coppercom.com). He can be reached at sknight@coppercom.com.