June 2000

BY TRACEY VENTERS

While surfing the Web recently, I ran across an explanation of a new model for providing telephony services. The model, I read, involved distributing service intelligence throughout the network and allowing service providers to develop features without depending on switch vendors, thus enabling rapid introduction of highly customized features. Sounds like the typical mantra for the new, converged voice and data network, right? Actually it was a somewhat dated white paper expounding the benefits of AIN.

So here we are, years later, still searching for the Holy Grail that will really allow us to create our own voice services. How can we expect IP to succeed where IN has failed? Simply put, because IP is the Great Equalizer. No one can argue against the ubiquity and pervasiveness of HTTP and HTML. Although standards such as AIN were based on a robust, well-defined call model, such standards were complex and not extensible. The result was that to provide true differentiation, AIN vendors had to develop extensions to the protocols that made them non-standard and proprietary.

To be fair, HTML has its limitations. Specialists from disciplines as diverse as musical composition, chemical engineering, and financial services have been frustrated by its inability to express content specific to their field. To address this, eXtensible Markup Language (XML) was created. XML is not a single markup language, but rather a meta-language that allows extensions to be created for specific domains without breaking the overall compatibility of net-centric content. Unlike HTML, however, XML is suitable for running applications as well as browsing documents.

In the telephony industry, several XML-based languages are being created, debated, and deployed. Among these are Call Processing Language (CPL), Call Processing Markup Language (CPML), VoiceXML, Telephony Markup Language (TML), and Extensible Telephony Markup Language (XTML). It remains to be seen which of these will be the real winners.

In the meantime, savvy network operators will leverage their existing SS7 infrastructures, including IN elements, while transitioning to the new network. Media gateways take care of encoding and decoding between TDM and IP traffic, and softswitches can provide full SS7 connectivity, as well as support of IP-centric protocols such as SIP or H.323. Softswitch vendors are also recognizing the powerful potential of XML, and either integrating or providing access to XML-based application servers. It seems that with XML, we may finally get what we were looking for in AIN.

Tracy Venters is director of product marketing for telecom technologies, inc., which supplies softswitch-based solutions for network and service providers offering end-to-end solutions. For more information, visit telecomtechnologies.com.

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BY REG CABLE

As IP telephony networks continue to be deployed and interconnected with the PSTN, we confront a growing thicket of complications. Contributing to this inconvenient growth are two particular problems: 1) The scarcity of SS7 point codes. 2) The profusion of international SS7 variants. It is possible to penetrate this thicket, however, with the appropriate commitment to standardization efforts (in the case of point codes), and with the deployment of SS7 signaling gateways and converters (in the case of international variants).

CODE POINT SCARCITY
Point codes are used in the PSTN to identify intelligent network (IN) entities, such as switches, databases, or signal transfer points. They function similarly as IP addresses in the IP world. In creating their SS7 standard, however, the ITU set aside only 16 bits to define each point code, limiting the number of unique point codes to 16,384. Since then, each country using ITU point codes has issued its own point codes for its own devices. Some have even chosen to deviate from the ITU standard to provide a greater number.

Convergence of circuit-switched and packet-based networks is creating still greater demand for point codes as more small IP telephony devices are added. While the signaling incompatibilities can be addressed with SS7 protocol conversion, constraints in the number of available point codes remain fundamentally limiting.

Long-term, this problem must be addressed in an appropriate standards forum. In the meantime, one approach to using existing point codes as efficiently as possible is to rely on utilizing distributed signaling gateways that support multiple IP telephony devices while sharing a single SS7 point code.

VARIANT VAGARIES
A critical complication of the IP migration, often misunderstood or underestimated, is that not all SS7 protocols are equal. As public-switched networks were developed globally, SS7 evolved into islands of national and international variants. While IP telephony is based on internationally agreed upon standards, nations developed their own SS7 flavors that did not necessarily cross borders.

Based on American National Standards Institute (ANSI) standards, the North American signaling architecture has become the most complex, radically different from elsewhere. Those in most of the rest of the world are defined by the ITU. Meantime, European countries, Japan, and China each have adopted major variant changes within the ITU standard. The globalization of e-business and the era of 24-hour markets will not tolerate this tangled mass.

Although SS7 was not included in first-generation media gateways and media gateway controllers, subsequent generations incorporated limited SS7 but without concern for overall network optimization. Networks are evolving, however, toward an architecture that includes stand-alone, full-function SS7/IP signaling gateways that drive multiple IP telephony devices (that is, media gateways, media gateway controllers, and database servers) and seamlessly interact with the PSTN.

If they incorporate SS7-to-SS7 converters, vendors of first-generation public switches (e.g., Nortel, Lucent, Ericsson, Alcatel) need not retrofit their products aimed at systems being deployed in countries with different national SS7 standards. Similarly, IP switch and media-gateway controller makers can create call-control software and SS7-to-IP interworkings, then use SS7 gateways with protocol conversion built in. Then they can drop their devices into differently flavored SS7 networks around the world without modification.

Reg Cable is vice president, Signaling Systems Group, Performance Technologies, which is a global supplier of high-performance telecommunications and networking products for wireless and next-generation networks. For more information, visit www.pt.com.

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Q: How might PSTN and IP networks complement each other?

A: In the converged network scenario, SS7 becomes the language through which the packet network signals the PSTN. The signaling is accomplished by means of signaling gateways that sit next to a media gateway controller (MGC or Softswitch). Going forward, the same methodology applies, at least until we have only one network -- but that could take a while!

Q: Could you distinguish between immediate, near-term, and long-term opportunities?

A: Immediate opportunities are centered around enhanced services for the PSTN and wireless HLR/VLR. In the near-term, such opportunities expand to the deployment of signaling gateways, that is, gateways that signal the SS7 network. The signaling functionality could reside in its own separate box, or it could be embedded into other gear. Longer term, we should expect the introduction of SS7 over IP (SIGTRAN or something like it). Once SS7 over IP is implemented, then we can think of the gateways expanding functionality to do this as well.

Q: Will IP networks become so prevalent (and capable) that they might eventually obviate SS7?

A: PSTN enhanced applications are here today. As are the wireless applications. As for the IP network, the deployment of signaling gateways is just starting. Long-term, we think SS7 will assume even greater importance, since eliminating SS7 would require a "homogeneous" IP network -- not a practical reality. We are sure that IP networks will become much more prevalent, but we don't expect phone lines will disappear. That is farfetched, and will be for some time!

We thank Venkataraman Prasannan for his responses to our questions. Prasannan is director of marketing for RadiSys Corporation, which designs and manufactures embedded subsystems that are used in a wide variety of telecommunications equipment. For more information, visit www.radisys.com.

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BY JEAN-RENE BOUVIERr

Today's business world is marked by the emergence of new, innovative voice services running over converged voice and data networks. Businesses are moving from traditional infrastructure to converged networks to handle voice, data, and multimedia traffic. As these different networks and traffic types merge, we see huge potential in cost savings, increased competition, and richer communication services for businesses.

Many "new" solutions, designed to bring voice over data networks, are being proposed. However, while these solutions may well intrigue us, they are not exactly tried and true, nor do they offer the best QoS when used by themselves. It is understood that most of the new converged networks will be based on IP; however, converged networks will also incorporate a wide range of technologies, with the SS7 network acting as the "glue" that holds together many of the pieces. The SS7 network is one of the most critical components of today's telecommunications infrastructures. It provides for call setup on circuit-switched networks via high speed, out-of-band connections, as well as for transaction capabilities that harness remote database interaction.

As the trend for convergence gathers pace, we can expect to see SS7 networks play an increasingly crucial role in the development and deployment of so-called converged services. Mobile, PSTN, and IP networks will continue to exist side by side, but SS7 networks will provide the bridge that connects these heterogeneous networks. With this signaling layer in place, the opportunities for creating innovative applications that span voice, data, and multimedia are immense. SS7 technology will ensure that reliability and quality levels users take for granted on everyday voice services, will be achieved via converged services, which we are only just beginning to imagine.

Jean-Rene Bouvier is general manager of Hewlett-Packard's Telecom Infrastructure Division. For more information, visit www.hp.com/communications/products/tid/index.html.

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BY VENKATARAMAN PRASANNAN

Nothing is so engaging to developers as virgin territory -- new frontiers. So, when developers consider SS7, they may well ask themselves if it represents a frontier, or something more, well, mature. Superficially, SS7 would seem very mature indeed. SS7 goes back to the 1960s, and by now SS7 coverage is quite broad. (In North America, over 160 million telephone lines access CO-based switches, over 98 percent of which have SS7 connectivity. And, for wireless services, most infrastructures provide 100 percent SS7 coverage.)

But another issue needs to be considered. Capacity. As the demand for call forwarding, call return, and other intelligent services increases, so will the need for SS7.

Four years ago, landline ISUP traffic (call setup) was 7 times that of TCAP (database lookups). The end of 1999 predicted ISUP traffic predicted to be only 2 times TCAP traffic. These figures show an increase in the number of service control points (SCPs) and intelligent peripheral platforms needed to address the increase in database accesses via intelligent telephony applications. This increase, paired with local number portability requirements, clearly indicates demand for more capacity for SS7 networks. And this demand is what makes SS7 a frontier for developers. And what might developers accomplish in this frontier? Let's look at a few possibilities.

SS7 AND IP TELEPHONY
SS7 links large-scale IP telephony media gateways and the PSTN. Although IP may be used to carry the actual voice data across the long haul, if one or both parties use a standard telephone (attached to the PSTN), the IP telephony gateway must interoperate with the PSTN switch.

For large installations, this interoperability relies on SS7 in a signaling gateway, and provides features such as call setup and tear down and database lookups. Interoperability with the existing SS7 network is absolutely required to raise the level of service offered by IP telephony.

ENTERPRISE APPLICATIONS
Most SS7 signaling points are found within IN/AIN networks. But a few large customers (call centers) enjoy SS7 access also. Such access improves efficiency, adds new functionality, and lowers costs through faster call setup, automatic number identification (ANI), and savings related to the ability to purchase high-capacity trunks.

In addition to the demand for IP signaling gateways, there is significant potential for customer premise-based SS7 access for smaller-scale CTI installations. Recently, the number of smaller call centers and IVR applications has grown rapidly. SS7 access to these installations improves the efficiencies of inbound calls through intelligent routing.

WIRELESS APPLICATIONS
Service providers may use SS7 to connect to Home Location Register (HLR) and Visitor Location Register (VLR) databases. The HLR stores subscriber information within the wireless providers' home service area. This information is not shared between networks. When a phone is purchased and activated, a record is created in the HLR. And, when the customer roams, the VLR is used to store information about the customer. The roaming information is stored in the VLR so the customer can continue to make and receive calls and be billed properly. This information is shared between networks.

Venkataraman Prasannan is director of marketing for RadiSys Corporation, which provides embedded subsystems. For more information, visit www.radisys.com.

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