gst and Nortel team to build converged network
By ROBERT V. PEASE
Gst Telecom Inc. (Vancouver, WA), a subsidiary of gst Telecommunications Inc., has begun construction of a virtual integrated transport and access (vita) network using Passport and Concorde Asynchronous Transfer Mode (atm) switches from Nortel (Brampton, ON, Canada). The fiber-optic network will transport voice, data, and video traffic using a combination of packet, frame, and cell transmission.
gst, a competitive local exchange carrier with an extensive presence in the western United States, had been seeking the technology to put all of its telecommunications services onto a single, cost-effective network to offer customers a more efficient bundle. At the same time, Nortel was hard at work to develop equipment that would sort between data, voice, and video before and after transmission over atm. An agreement was eventually forged that put both companies on the road to jointly build the vita network.
"We spent numerous months with Nortel engineers in testing and evaluating their solution," says Joseph A. Basile, Jr., president and chief operating officer at gst. "We eventually determined that their solution did, indeed, work."
The solution
The Passport switch, Nortel`s atm adaptation vehicle, is key to enabling one network to handle all types of traffic over atm infrastructure. Termed an intelligent switch, it is designed to accept various types and classes of traffic; transport them as frames, cells, and/or packets; and send them along the atm network.
In the case of gst, the Passport switches will be deployed at the edge of the network, with larger, less sophisticated switches at the network core (see Fig. 1). The incoming traffic is aggregated and classified by cell type or atm adaptation layer (aal) and transmitted along the network. In the case of atm, aal-1, which is merely circuit emulation, can be used for delay-intolerant traffic, such as voice, but fails to leverage the statistical gains afforded with packet switching. aal-2, the standard for voice-over-atm, leverages support for variable-bit-rate quality of service to enable true bandwidth sharing across wide-area network links. The remaining aal-5 is used to move less time-critical data and allow the aggregation of other types of transmissions. For traffic exiting the network, the Passport switch can again sort out the classes of traffic for transmission over specific networks.
gst`s objective in creating one large multifaceted network is to offer its services to customers anywhere on its fiber backbone. The company is expanding its infrastructure by leasing facilities and swapping fiber capacity (see Fig. 2). The first expansion phase is a north-south corridor that begins in the Seattle-Portland area and will extend south to Los Angeles and San Diego. Additionally, Hawaii will be added to the west and Phoenix-Tucson to the east.
"We have a number of cities, like Spokane, that we currently have voice switches in," says Kevin Wright, gst`s chief technology officer. "Once we get our major core backbone installed, it will be a simple, market-driven process to decide which of the other sites will be added next."
The delay
The creation of such converged networks has awaited the maturation of atm technology to the point of handling voice without detrimental effects. Equipment developers have worked on this problem for the last five or six years. Meanwhile, Internet providers and the manufacturers of Internet protocol- (IP-) based equipment have exploited this delay by touting voice-over-Internet capabilities.
However, according to Wright, some of their claims may be overstated. "The problem is that when you look closely at their actual networks," says Wright, "you discover they`re really not designed for heavy, robust use of IP services, especially voice-over-Internet. The systems have a multitude of problems."
Most of those problems derive from the time-critical nature of voice transmission, he says. Sending voice signals via the Internet often causes delays incompatible with voice transmission. The result is distortion at the receiving end that can seldom be avoided without microsecond precision. Nortel and gst claim their vita network is the "next generation network" the industry has been waiting for--a network capable of handling several million voice calls and data without any degradation in quality.
"The old motto used to be that data can ride for free on top of voice," says Ted Gagnon, wide area networks marketing manager for carrier data networks at Nortel. "Now, it`s becoming voice can ride for free on top of data. Data is really driving bandwidth requirements as the demand for more and more Internet connections continues to rise. That being the case, data is essentially driving the need for this type of network."
According to Gagnon, a lot of discussion is taking place regarding frame relay-to-atm interworking, given the large-scale deployment of frame relay networks. For the most part, building an atm network inside of a frame relay network is fairly straightforward. Yet, the conversion of old time-division multiplexing networks to frame relay may not be as easy, says Gagnon.
"The whole focus for the future," says Gagnon, "is on seamlessly bringing your traditional voice traffic onto your atm network. We`re moving to an era of network convergence, where voice and data share network resources. I believe the vita network will be able to address this requirement. Voice, data, Internet traffic--whatever--will ride over an atm circuit, from the customer site out to the central office, and then be switched over a common backbone."
The vita advantage
gst expects its new network capabilities will prove attractive to potential customers.
"We literally will extend the atm cloud to our customer`s premises," says Basile. "Whether the customer has voice, data, or Internet requirements--not just voice-over-Internet, but any Internet requirements--we`ll bundle all those services and transport them to our atm switch for sorting."
Basile says gst is satisfied that this network will offer middle to high-end customers an entire suite of services from a single source on a more cost-effective basis. The regional Bell operating companies (rbocs), he says, currently dominate the local market. Without converged networks, rbocs will have to continue using multiple circuits going to numerous customers, along with countless pieces of equipment, to achieve the same result as the vita network.
Local exchange carriers could also potentially experience some savings in operating expenses, say the Nortel sources. "Local exchange carriers have a lot of money tied up in access charges," says Gagnon. "If they can begin to reduce the number of access costs they`re paying by consolidating multiple services on a common circuit, it`s going to dramatically change their cost structures. I think many are really looking towards that evolution."
gst`s vita network is scheduled to begin phase one of operations in the third quarter of 1998. gst believes that bringing voice, data, and video together on one network architecture is the next logical phase in the development of national and global fiber-optic networks.
"Everything we`re doing has been done before," says Basile. "The thing that`s unique about this is that, to the best of our knowledge, nobody has commercially put all the pieces together and rolled it out as a complete network package." q