Serial - Data Communication Equipment (DCE)

DCE stands for Data Circuit-terminating Equipment or Data Communication Equipment. It is a term used to describe the equipment that provides the clocking signal and manages the data flow over the serial link. Here’s a detailed explanation:

1. Role of DCE:

   • The DCE is responsible for generating the clock signal that synchronizes the communication between devices on a serial link. This is crucial because, in serial communication, both ends must agree on the timing to correctly interpret the transmitted data.

2. Typical DCE Devices:

   • In a network setup, devices like modems, CSU/DSUs and certain types of routers can act as DCE. In a lab or testing environment, a Cisco router can also be configured to act as DCE.

3. Serial Link Configuration:

   • In a serial connection, there are typically two devices involved: the DCE and the DTE. The DTE is usually a terminal, computer, or a router, and the DCE is the device that provides the clocking.
   • When setting up a serial link between two routers, one router will be configured as the DCE and the other as the DTE. The DCE side will provide the clock rate.

4. Setting Clock Rate on Cisco Routers:

   • To configure a Cisco router as a DCE, you connect the serial interface using a special DCE cable. Then, you set the clock rate on the DCE router using the clock rate command in the interface configuration mode. For example:

     Router(config)# interface serial 0/0
     Router(config-if)# clock rate 64000
     

   • This command sets the clock rate to 64 Kbps, which synchronizes the data transmission rate on the serial link.

5. Identifying DCE and DTE Cables:

   • The type of cable used in the connection often determines whether the device will act as a DCE or DTE. Typically, the DCE cable will have a female connector, and the DTE cable will have a male connector.

Understanding the role of DCE in a serial link setup is crucial for network engineers when configuring and troubleshooting serial connections on Cisco routers. Proper clocking ensures reliable data transmission and communication between network devices.