Data Communications and the World Wide Web

Data Communications

• The transmission, reception, and processing of digital information
• Data refers to information stored in a digital form
• Information encompasses knowledge or intelligence
• A network is a set of devices, called nodes or stations, interconnected by media links.
• Data communications networks are systems of interrelated computers and equipment.
• Intranets are private networks.
• Firewalls convert intranet addresses to public internet addresses.

World Wide Web (WWW)

• A server-based application allowing subscribers to access its services.

History

• 1844: First telegram transmission between Baltimore and Washington D.C.
• 1874: Baudot invented a telegraph multiplexer.
• 1875: Alexander Graham Bell invented the telephone.
• February 14, 1946: Eckert and Mauchley developed ENIAC, an early computing device.
• 1950: The first computers could only perform one task using batch processing.
• 1951: The UNIVAC was the first mass-produced electronic computer.
• 1980: The development of personal computers.

Network Architecture

• Outlines the products and services necessary for the operation of all components in a data communications network.

Network and Network Protocols

• Outline the current, legacy, and legendary network protocols.
• Modern networks are sophisticated.
• Legacy networks are not actively used.
• Legendary networks are antiquated protocols that have been replaced.

Computer Network Classification

• Networks are categorized based on their communication channel setup and message delivery methods.

Broadcast Network

• All devices on the network share a single channel.
• Messages are intended for all subscribers.
• Data is transmitted in short segments called frames, blocks, or packets.

Point-to-Point

• Only two devices are connected, without the need for addresses.

Data Communication Protocols

• A set of rules that governs the orderly exchange of data.

Network Architecture

• A set of layers and protocols that defines the operation of a network.

Protocol Stack

• Lists the protocols used by a system.

Layered Network Architecture

• Consists of multiple independent levels, each with specific responsibilities and functions.

Connection-Oriented Protocol

• Requires establishing a connection between endpoints before data transmission can begin.

OSI Layer

• The Open Systems Interconnection model defines a layered network architecture.

Local Area Network (LAN)

• A network spanning a single building, typically under a single administrative system.

Network LAN Technologies

• Ethernet (IEEE 802.3): High-speed network technology that uses carrier sense multiple access / collision detection (CSMA/CD) technology for collision detection.
• Fast-Ethernet (IEEE 803.2): A faster version of Ethernet.
• Serial-by-Bit: Transmits data one bit at a time, used for long-distance communications.

Communication Infrastructure

• The facilities used to connect computers within a network, like twisted-pair wire, coaxial cable, or optical fiber cable.

Types of Computer Networks

• The scale of the Network determines the network type.
• Personal Area Network (PAN): Connectivity limited to a small area, often used for devices like smartphones and computers.
• Local Area Network (LAN) - Network spanning a single building under a single administrative system.

Computer Network Topologies

• Topologies describe the physical arrangement of devices in a network.

Point-to-Point

• Network containing exactly two hosts.

Bus Topology

• All stations and devices on the network share a single communication channel.

Star Topology

• All devices connect to a central device (like a hub) via point-to-point connections.

Ring Topology

• Devices on the network are connected in a circular formation.

Mesh Topology

• Each host connects to one or multiple other hosts.
• Full Mesh: All hosts have a point-to-point connection to all other hosts in the network.
• Partially Mesh: Not all hosts are directly connected to every other host.

Tree Topology

• A hierarchical network structure with a root node at the top, branching out to other devices.

Daisy Chain Topology

• Devices are linearly connected in a chain.

Hybrid Topology

• A combination of multiple different network topologies in a single network.

Network Components, Functions, and Features

• Server: Computers that share files, programs, and the network operating system.
• Clients: Devices that access and use shared network resources.
• Shared Data: Data provided by servers to clients such as files, printer programs, and email.
• Shared Printers and Peripherals: Hardware resources provided by servers to clients.
• Network Interface Card (NIC): A special expansion card responsible for preparing data and controlling data flow between the computer and the network.
• Local Operating System: Operating system that allows PCs to access shared files.
• Network Operating System (NOS): Program that enables computers to communicate over a network.

Network Interface Card Characteristics

• The NIC prepares, transmits, receives, and processes data between the PC and the network.
• Each computer requires a NIC.
• The NIC is installed as a daughterboard within the computer.
• Each card has a unique MAC address (also known as the physical, hardware, node, Ethernet, or LAN address).
• The MAC address is necessary for the NIC to function properly and be compatible with the network.

Popular NOS include:

• Unix
• Novell Net Ware
• AppleShare
• Macintosh System 7
• IBM LAN Server
• Compaq OpenVMS