WAN serial connections

WAN serial connections
5.2.2 This page will discuss WAN serial connections.


For long distance communication, WANs use serial transmission. This is a process by which bits of data are sent over a single channel. This process provides reliable long distance communication and the use of a specific electromagnetic or optical frequency range.

Frequencies are measured in terms of cycles per second and expressed in Hz. Signals transmitted over voice grade telephone lines use 4 kHz. The size of the frequency range is referred to as bandwidth. In networking, bandwidth is a measure of the bits per second that are transmitted.

For a Cisco router, physical connectivity at the customer site is provided by one of two types of serial connections. The first type is a 60-pin connector. The second is a more compact ‘smart serial’ connector. The provider connector will vary depending on the type of service equipment.

If the connection is made directly to a service provider, or a device that provides signal clocking such as a channel/data service unit (CSU/DSU), the router will be a data terminal equipment (DTE) and use a DTE serial cable. Typically this is the case. However, there are occasions where the local router is required to provide the clocking rate and therefore will use a data communications equipment (DCE) cable. In the curriculum router labs one of the connected routers will need to provide the clocking function. Therefore, the connection will consist of a DCE and a DTE cable.

The next page will discuss routers and serial connections