AIN anyone? - advanced intelligent networking - Technology Information

Communications News, Nov, 1999 by Ripley Hotch

The advanced intelligent network brings some smarts to IP.

NaviNet is a wholesale dial-up provider for ISPs, but it's not burdened by rack upon rack of modems, each requiring a port and line. Instead, it uses a gateway that talks to the Signaling System 7 (SS7) network. "That lets us terminate modem calls from the PSTN directly to the modem boxes, so it doesn't have to go through a PBX," says CTO Jim Winkleman.

The result is that NaviNet doesn't have to buy dial tone and can control the capacity of the trunks it uses. The cost savings and control are a direct result of using the SS7 network in coordination with IP.

SS7 is the intelligence in the advanced intelligent network (AIN) that the telephone companies have been deploying for the better part of a decade. A separate data network, it handles all the information about a particular call enabling familiar value-added features like caller ID and a host of others.

"SS7 technology is the key enabler of convergence services," says Dan Bantukul, senior product manager at Tekelec. "The provisioning of intelligent network services across PSTN and IP networks requires the interworking of SS7 and PSTN signaling and next-generation IP telephony protocols. Without SS7, IP telephony cannot take advantage of services consumers enjoy within the PSTN network, such as calling-card services, toll-free number service, local number portability, and more. Also, convergence services must include PCS services, as well as landline services, for which SS7 already provides the support and infrastructure."

"Most people who are going to put SS7 signaling over IP will be using private networks, but it still will be cheaper," says Paul Nevill, director of STP (signal transfer point) marketing for Alcatel North America.

SS7 over IP has become a serious contender for bringing about the convergence of voice and data networks that, so far, has been piecemeal at best. A number of companies, including Tekelec, telecom technologies, Ascend (Lucent), Cisco, 3Com Corp., Ericsson, ECI Telecom, Nokia/Vienna Systems, Netrix, Hypercom, Nortel Networks, VocalTec, RADVision, Siemens, and others, are offering SS7-to-IP gateways to bring PSTN-type services to IP networks.

Lucent's AG Communications, for example, announced in late summer its Centrex Feature Gateway product that extends office Centrex features over packet networks. As with other gateways, the product is taking advantage of the end-to-end signaling capabilities of SS7 to come closer to giving users the same quality that the public telephone network now provides but with the cost savings of an IP network.

"One of the features we have in our current gateways sets service bits in the IP header to indicate to the backbone network that it is a voice packet," says Jose Garcia, managing director of the Ascend MultiVoice IP product line. "If you have a core Ascend ATM or Frame Relay switch, a software feature allows it to look at that type of service bit, and it maps to the appropriate ATM class of service." This implementation is not standard but points the way for some of the signaling to work.

HOW IT WORKS

One of the problems for convergence on the IPnetwork using SS7 is that the standards are still being worked on by the various standards bodies; many should be settled by early next year. The outlines are reasonably clear, though.

Between the PSTN and the IPnetwork is a gateway; in the past, this has been one device running various proprietary protocols. Now, however, gateways are being "decomposed," according to Trillium CEO Jeff Lawrence whose company writes software for all the major protocols. The reason for that is to match the IPnetwork to the way the PSTN works with the media stream separated from the signaling (SS7) network.

That means there is a signaling gateway and a media gateway, each of which is coordinated by the media gateway controller. The protocol is media gateway control protocol (MGCP).

The devices mediate the signaling and media for the H.323 protocol in the IP network and the various SS7 protocols on the PSTN side. The media gateway controller also maps the directory number to the appropriate IP address of the gatekeeper in the IPnetwork.

"The MGCP paradigm is very much in line with how the service providers do business," says Rob Veschi, CEO of eNet. "It's a device at the far end that gets its command set from a central set."

IMAGINATION IN APPLICATIONS

One obvious application of SS7 over IP is voice over IP (VoIP) connecting to the PSTN. But there are other applications that are intriguing, some already in use, like the NaviNet one.

"You could give one number in the whole country and let the network handle the most efficient connection," says Dave Curley, vice president for global marketing for Bridgewater Systems, a supplier of gateways. "It starts taking advantage of the intelligent network on the voice side that SS7 was intended to do. This allows the telcos to stop paying all that reciprocal compensation stuff because they would terminate the call and provide a data pipe to the ISP so the ISP wouldn't have the modems. And that allows them to charge for ISP-based services."