WAN Technology Description

The LAN (Local Area Network) typically include Nearby devices but when we talk about WAN (Wide Area Network), we are literally talking about devices that can be Far apart. The main priority for WAN is to move data between LAN's. The device which is used to connect the WAN with LAN is called a Router.
To connect our LAN with WAN, we order a Leased Line which is provided to us by an ISP (Internet Service Provider). Leased Line is available in variety of speed. The Leased Line is known by many names like Leased Circuit, Serial Line/Link, P2P Line/Link, T1, WAN Line/Link and Private Line. For connecting a Leased Line on a site, The site requires a CPE (Customer Premises Equipment) which consist of :

• A Router
• Serial Interface Card
• CSU/DSU (Channel Service Unit/Data Service Unit)                                       

The Serial cables that are used between a router and an external CSU/DSU are DTE (Data Terminal Equipment) and DCE (Data Communication Equipment). DTE has a male connector while DCE has a female connector which helps to connect both cables directly. The DCE cable works like a crossover cable because it swaps the transmitting and recieving pairs.
The DCE cables help the CSU/DSU to perform one primary Function which is called CLOCKING.
The Clocking Function tells the router when to exactly send the bits through signaling over the cable.
When we connect the DCE cable in the serial port, the router automatically senses it and supplies Clocking.
Leased Line provides a Layer 1 service which is the reason Leased Line doesn't provide standard Data Link Protocol which is a Layer 2 service.
On the next post we will explain to you the two most popular Data lank protocol which are

HDLC (High-Level Data Link Protocol)
PPP (Point-To-Point Protocol)