Sonet links local area networks
stephen hardy
Emphasizing fiber`s evolution beyond long-haul backbone applications, Cabletron Systems, Rochester, NH, has introduced a suite of Fast Ethernet products that will link dispersed high-speed local area networks (lans) using Synchronous Optical Network (Sonet) rings. While some question the current need for Sonet bandwidths in such applications, company officials believe users will welcome Sonet-based solutions if they are priced aggressively and packaged as part of an overall bandwidth-management strategy.
Cabletron`s new Fast Ethernet Port Interface Modules will provide direct Sonet access for the company`s family of SecureFast SmartSwitches (see figure on page 23). These switches provide lan-based services, including secure-port and media-access-control-based virtual networks, security policies, capacity planning, trend analysis, call accounting, and load sharing meshed topologies.
The time is right for Sonet in such wide area network (wan) applications, says Michael Leland, director of telecommunications marketing at Cabletron. Sonet elements such as add/drop multiplexers are now widely available in metropolitan areas, he says. This makes the technology a good foundation for an offering the company hopes will reach a wide spectrum of users.
Sonet also offers significant cost advantages over such traditional wan strategies as DS-3 routers (operating at 44.736 Mbits/sec) and Asynchronous Transfer Mode (atm) connections, Leland says. For example, the company estimates that a router-based approach to point-to-point connectivity would cost $30,000 to $40,000 at each end of the connection. This price range includes the purchase of a router, a DS-3 interface within the router, a DS-3 channel service unit/digital service unit, and, perhaps, a D-3 multiplexer. Placing an atm switch or other access device at each end of the point-to-point network would cost a comparable $30,000 to $35,000, he estimates.
The price for Cabletron`s Sonet approach varies slightly with a user`s requirements, according to Leland. The module is available in three configurations: multimode, singlemode short-haul (2 km), and singlemode long-haul. The list prices for the first two are $4500 and $7900, respectively; while a price for the singlemode long-haul module has not been determined, Leland expects its price tag will approximate that of the other singlemode device.
Regardless of which option the user selects, Leland says, the startup costs for Sonet represent a significant savings over DS-3 router and atm alternatives. These savings continue for the life of the network, according to Leland, because the per-month charge for OC-3c (155-Mbit/sec) Sonet lines tends to be nearly $3000 less than for DS-3 and atm links. Taking into account the fact that the Sonet approach is protocol-independent and doesn`t suffer the performance losses associated with having to go through a router processor or atm segmentation and reassembly, Leland believes his company has come up with a winner.
The trick, of course, is that one must already have Cabletron equipment on site to use the modules. Cabletron hopes to approach users outside its current customer base in partnership with service providers. "The most attractive [approach], from our standpoint, is offering it as part of a lan extension service offered by a carrier," Leland says. In this strategy, the switch and its accompanying interface module would be offered as customer premises equipment, at a package price somewhere around $7000 or $8000.
Will Sonet fit?
In spite of its cost savings, the current Cabletron offering has some shortcomings, according to Fred McClimans, an analyst at Current Analysis Inc., Ashburn, VA. The Cabletron solution works best in point-to-point applications, he says; multipoint applications remain a bit problematic. According to McClimans, multipoint application of the Sonet modules would require intercession at the central office level and the installation of a two-port Fast Ethernet hub for carrier access only. Alternatively, users could emulate a point-to-multipoint connection by bringing in multiple Sonet/Fast Ethernet connections to a single location. Both approaches are unwieldy, particularly when compared to current DS-3 router and atm alternatives.
Another concern is the wan/lan market`s willingness to accept Sonet. "While the market for transparent lan services is continuing to grow, there has not been much of a market for services above 16 Mbits/sec--although DS-3 services have been available for a while via HSSI [high-speed serial interface] and `grouped` Ethernet and there are some `limited` atm services available," McClimans says. "It is unclear if the market will readily respond to a full 100-Mbit/sec service this year--long-term yes, but near-term is questionable. Users are also not that familiar with Sonet, and may shy away from a Sonet solution at this time. Limited provider availability could also be a problem."
While Leland admits that "if you look at the sales right now of DS-3 and higher interfaces, they account for probably less than 10% of all the sales of data transmission services for wan use," he is much more bullish on Sonet`s chances in the marketplace.
"From our analysis, what we`re seeing is that more and more customers--if a higher-speed wan access technology were made available at a cost-effective price--would definitely consider moving to a higher-bandwidth platform," Leland explains. "We find that the burden is being placed on organizations to deliver high-speed access based on cost. So if we can change this business model and make it more cost- effective for either the service provider to provide this high-speed transport or for customers to go out and actually obtain OC-3c access to a carrier-supplied add/drop multiplexer, then I think we might help to curb that price barrier."
A further key to breaking the "cost barrier" is to provide users with a way of managing those costs, says Leland. That`s why he feels offering the Sonet connectivity as a package with the resource management functions supplied by the company`s other products will make Sonet appear an even better bet for wan use.
"The concern that I have as I watch some of the industry trends is people assume that they can grow more bandwidth just to satisfy their bandwidth requirements. I think the bigger answer to the question is more of a managed bandwidth, some way of actually obtaining some statistical accounting about where your bandwidth is going," he explains.
"I think that once companies get a handle on exactly where their bandwidth is being used and, in turn, where their revenue is being spent to facilitate these services, it will either be more cost-justified to deliver these services, or companies can start finding ways that their information technology department can become either a mock profit center or at least allocate appropriately the amount of money they need to spend for future wan deployment," Leland concludes. q