All-fiber network expands LANs into WANs

Dec. 1, 1996

All-fiber network expands LANs into WANs


A data-transport provider, Cox Fibernet, Atlanta, GA, and Racal-Datacom Inc., Sunrise, FL, are improving Cox Communications` existing fiber-optic network with high-speed, multiprotocol, multimedia modules to handle transmissions between LAN (local area network) and WAN (wide area network) business customers. Cox Fibernet has purchased Racal PremNet 5000 systems for use in Hampton Roads, VA; New Orleans, LA; and Oklahoma City, OK. These fiber systems enable the simultaneous transport of Ethernet, token ring, T1, analog voice, Asynchronous Transfer Mode (ATM) and full-motion video signals over the same singlemode fiber pairs.

Cox Communications, with about 3.2 million cable subscribers nationwide, has long-term plans to extend the LAN-to-WAN service to all its markets. The expansion of its service results from the company`s fiber-rich network. Louis Kerner, industry analyst at Merrill Lynch, forecasts that 72% of Cox Communications systems will be upgraded to either 550- or 750-MH¥capabilities by the end of 1997. He ranks the company`s networks as the most technologically advanced in the country and gives high ratings to its management team.

A wholly-owned operating unit of Cox Communications, "Fibernet has been a local networking company since 1994, providing DS-1 and DS-3 services [at 1.544 and 44.736 Mbits/sec, respectively] to local and national telecommunications companies," explains Mark Dickherber, director of national operations for Cox Fibernet. "It was the availability of incremental fiber strands from Cox Communications` installed plant that convinced Fibernet to sell native LAN services."

Dickherber says Fibernet`s mandate is to find and exploit new markets and services for fiber-based transport. Each network is nearing 700 deployed route-miles and 25,000 fiber-miles. Some fiber runs have been built by Fibernet independently of Cox; however, 98% of the fiber plant is shared.

"Transparent bandwidth is PremNet`s big advantage," says Abdul Noury, product manager with Racal-Datacom. "With applications used today in commercial environments such as client/servers, CAD/CAM [computer-aided design/computer-aided manufacturing] traffic and Internet access, inter-LAN communication requires more bandwidth than in the past." Companies buying networking solutions complain that even T1 speeds at 1.554 Mbits/sec are not sufficient for LANs and that T1 lines are expensive.

Two architecture hierarchies

In Hampton Roads, Cox Communications has deployed its network in a ring-in-ring topology, with singlemode fiber used as the backbone between nodes in the network. This topology was researched, developed and pioneered by two Cox engineers, Mark Davis and Albert Young. The topology brings the company`s network to the 99.9% availability required for today`s telecommunications services. According to Cox engineers, only when service enters residential areas is coaxial cable deployed. Two types of hardware hierarchies are used in this network, depending on the client`s location and the transport requirements.

The simplest hierarchy employs PremNet systems at strategic customer locations that are interconnected over Cox Communications` 100-Mbit/sec fiber network. The second design, owned and operated by Cox Fibernet, uses a tiered approach, with the systems acting as access nodes to an OC-12 Sonet backbone at speeds of 622 Mbits/sec.

The foundation network in Hampton Roads, New Orleans and Oklahoma City is an all-fiber-based Sonet ring backbone that runs on Fujitsu Sonet electronics and distributes service to Sonet, DS-1 and DS-3 customers. Sonet equipment is also employed to deliver those services to the premises.

The network in Hampton Roads and New Orleans is a combination of ring-in-ring and star-bus (which is being replaced by ring-in-ring) architectures. Oklahoma City is already converted to ring-in-ring. The basic topology in all three networks is a metropolitan distribution ring, and on top of that, a Sonet ring. Another distribution architecture layered on that ring is a native LAN using Racal`s fiber solution.

Fibernet is operating a strictly telephony network. "There is no HFC [hybrid fiber/coaxial-cable] plant; it`s an all-fiber solution," says Dickherber. Sonet levels range from OC-3 to OC-48 speeds (155 Mbits/sec to 2.5 Gbits/sec, respect ively), and connections exist to virtually all the long-distance carriers in the market. In addition, as many as three Internet service providers use Fibernet.

Off the backbone ring, two distribution rings also use Fujitsu`s Sonet electronics. From one of the distribution rings, 64-kbit/sec DS-0 or DS-1 traffic is multiplexed up to DS-1 or DS-3. Cox Fibernet`s engineers maintain that Fibernet`s network is different from other high-end telecommunications providers because it is 100% Sonet-based.

The second set of distribution rings is where the Racal-Datacom solution applies. Many customers within Cox Communications` cable clusters use native LAN services. For example, if a commercial customer already has a 16-Mbit/sec LAN operating in several buildings, these separate networks are being connected through PremNet electronics to create a 16-Mbit/sec WAN. The electronics solution accepts all the 4-, 10- and 16-Mbit/sec traffic and routes it through distribution rings to multiple locations.

Each system includes an OC-3 connection, which provides connectivity to Cox Communications` higher-speed Sonet networks. The ability to connect multiple stand-alone LANs together into one complete WAN can provide for huge savings for users.q

Paul Palumbo writes from Seaside, CA.

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