WAN, Switching, and DSL Technologies: Understanding Network Connections

Understanding Wide Area Networks (WANs)

A WAN (Wide Area Network) spans a large geographic area, sometimes a country or continent. It contains a collection of machines dedicated to running user programs. These machines are called Hosts. The hosts are connected by a communication subnet. The subnet's job is to conduct messages from one host to another. The separation of the unique aspects of the communication network (subnet) and areas of application (hosts) greatly simplifies the overall design of the network.

Key Components of a WAN

• Switching Computers (ECD): Each ECD uses a protocol responsible for routing the data correctly and providing support to computers and end-user terminals connected to it.
• Computer User (DTE): The DTE support function is called a packet assembler/disassembler.
• Network Control Center (NCC): The NCC is responsible for the efficiency and reliability of network operations.

Types of Network Switching

• Circuit-switched: In these networks, a call must be made to establish communication. Once the connection is established, users have a direct link through the various network segments.
• Message-switched: In this type of network, the switch is usually a computer that accepts traffic from computers and terminals connected to it.
• Packet-switched: In this type of network, user data is broken down into smaller pieces called packets.

Connection-Oriented vs. Connectionless Networks

• Connection-Oriented Networks: These networks require a connection to be established before data transfer can occur.
• Connectionless Networks: Also known as datagram networks, these networks transition directly from the idle state to the data transfer mode.
• Public Switched Telephone Network (PSTN): This network was originally designed for voice use and analog systems.

Types of Switching Lines

• Switched Lines: These lines require dialing a code to communicate with the other end of the connection.
• Dedicated Lines: These lines maintain a permanent connection between two or more points. They may be two-wire or four-wire.
• Point-to-Point Lines: These lines bind two data terminal equipment (DTE).
• Multipoint Lines: These lines connect three or more DTE.
• Digital Lines: In this type of line, bits are transmitted as digital signals. Each bit is represented by a voltage variation using digital encoding.

DSL Technology

DSL (Digital Subscriber Line) is a technology that enables high-speed connections using phone lines and allows continuous online access 24 hours a day. With DSL, there is no need to call the ISP each time you want to access the network; your PC will be connected continuously.

ADSL, ADSL2, and ADSL2+

ADSL (Asymmetric Digital Subscriber Line) transforms ordinary phone lines into high-speed lines. It is a technology for transmitting digital information at high bandwidth over existing copper lines to homes and businesses.

ADSL2 and ADSL2+ technologies offer significantly higher transfer rates than conventional ADSL, using the same telephone infrastructure based on copper wires.