Meeting the connection requirements in an enterprise WAN takes careful planning, and is an ongoing process. To successfully deploy and manage your WAN environment, you must be comfortable with the technology involved. WAN connections fall into three major categories: dedicated, packet switched, and circuit switched.
DedicatedDedicated WAN connections, also sometimes referred to as point-to-point or leased lines, are the pinnacles of the WAN hierarchy. A dedicated WAN connection, in a nutshell, is a private line, dedicated to your private use, from one point to another. It is the WAN equivalent of an Ethernet cable from the central site to the branch office. Table 2.1 lists some of the pros and cons of the dedicated connection.
Circuit SwitchedA circuit-switched WAN connection uses a dedicated circuit through the underlying network, typically the phone company, for the duration of the session. Circuit-switched technologies include asynchronous modem connections and ISDN. As Table 2.2 shows, circuit-switched connections have some distinct advantages as well as some major disadvantages.
The single biggest advantage to a circuit-switched WAN connection is that they are typically available wherever there is a phone line. The speed limitation on the circuit-switched connection, which is a result of their wide availability and the underlying technology, is its biggest drawback.
Packet SwitchedPacket-switched network connections share a lot of the benefits of both dedicated and circuit-switched networks while minimizing the drawbacks. Like a circuit-switched network, the packet-switched network uses a public, readily available backbone, usually the phone company, for network connectivity. Unlike the circuit-switched network, each packet is switched independently of the others. If the network encounters a problem, resulting in the loss of one or more packets, it can route the rest of the transmission around the problem. As with a dedicated circuit, a packet-switched circuit makes greater speeds available to you, typically T1 or better. Packet-switched connections have one major advantage over dedicated circuits, however, and that is cost. Because you are sharing the "backbone" connection with other subscribers, the cost is usually a fraction of what a dedicated connection would be. |