The search for higher speed networks is on! If your school is demanding large scale Internet access, updated “suite” applications, CD-ROM servers and other demanding network applications, your current network infrastructure may not be up to the challenge. As the current generation of hardware and software becomes more robust, an up to date network infrastructure becomes ever more critical. One of the hottest topics today in networking is switched Ethernet. A new generation of network electronics has evolved with a full product line of switched Ethernet products. These products deliver higher speed networks, increased reliability of data, greater bandwidth to the desktop, and upgrades to future technologies.

To understand the significance of switching, one must consider the inherent design of older Ethernet networks. Earlier Ethernet networks ran on coaxial cable and typically connected together on a single piece of cable with “T” connectors at every workstation. If one computer failed along the line, it had potential to bring down the rest of the chain and all computers on the line shared the entire Ethernet segment.

In addition, these networks were highly susceptible to “collisions”. One of the main principals of an Ethernet network is the Carrier Sense Multiple Access (CSMA) design. CSMA is a way the computers can get onto the network. For example, if a computer wants to transmit, it must send out a data packet. Before starting to transmit, it listens to make sure no other PC is transmitting. Once the computer senses that the line is clear, it sends a packet and then frees the line for other PC's to transmit. This design had several flaws. First, when two computers send out data packets at the same time, a data “collision” occurs. The electrical signals, which carry the information they are sending bump into each other. This ruins both signals and both will have to transmit their information again. This causes the overall network speed to slow, and the computers must then re-send the data. Second, when several computers are sending and receiving data on the network, they could easily dominate the network, causing problems for other computers that want to send data packets. Third, many of the computers tend to share a single Ethernet segment, limiting the amount of data flow to every computer.

The next generation of Ethernet networks, called 10Base-T, used hubs to control network access. Computers on a network were cabled directly to the network hub using twisted pair cable instead of coaxial cable. Some hubs were “intelligent”, containing sophisticated management software that worked to avoid and/or manage data collisions (SNMP/RMON). Two alternative versions of collision detection were evoked (CSMA/CA and CSMA/CD) that attempted to reduce both the number of collisions and the severity of their impact. However sophisticated these networks were, the computers were still sharing Ethernet segments and were limited in scalibility.

The latest generation of Ethernet networks uses switches instead of hubs. The major difference between a switch and a hub is how it handles data packets. Each data packet contains two media access control (MAC) layer addresses: the sender's and the receiver's. The switch maintains a table of MAC addresses and their matching connections. It uses the table to determine where to send a packet. In addition every port on the switch is assigned its own Ethernet segment. This separates the computers into distinct segments or zones, avoiding data collisions. Moreover, switches can deliver a full 10mb. segment to every port, insuring greater bandwith to each workstation. Network switches come in a variety of configurations including twisted pair and fiber interfaces, and offer additional high-speed ports to other technologies such as 100BaseT, 100BaseVG, full-duplex Ethernet, FDDI, and ATM. The price per port is substantiality lower than it was one year ago. Management software is available to remotely manage and control every port on a switch as well.

Today’s networks are asked to transmit more data than ever before. Older networks are becoming increasingly stressed with todays demanding applications. Even with state of the art computers, software, and peripherals, a sub-standard network infrastructure will compromise the entire system. Switches should definitely be in your plans for all but the smallest networks. An upgrade to your existing network may be as simple as replacing network equipment with switches, allowing you to reap the benefits of the newest technology available. Copyright ©1997 Steven Moskowitz All Rights Reserved