Networking Reviewer

Data Communication

is the exchange of data between two or more devices via a transmission medium such as cable or air. It involves transmitting digital or analog data over a communication channel. Goal: To ensure that data is delivered accurately, timely, and efficiently.

Data Communication

is the exchange of data between two or more devices via a transmission medium such as cable or air. It involves transmitting digital or analog data over a communication channel. Goal: To ensure that data is delivered accurately, timely, and efficiently.

Delivery, Accuracy, Timeliness, and Jitter

Key characteristics of data communication

Delivery

Data must be delivered to the correct destination.

Accuracy

Data must be delivered without errors.

Timeliness

Data must be delivered in a timely manner.

Jitter

Variations in packet arrival times should be minimal.

Message, Sender, Receiver, Transmission Medium, and Protocol

Components of Data Communication

Message

The actual data (text, audio, video, etc.)

Sender

The device that initiates the transmission.

Receiver

The device that receives the data.

Transmission Medium

Physical path (e.g., cable, fiber, air).

Protocol

Set of rules for communication.

Connectivity, Efficiency, Productivity, Scalability, and Foundation of IT

Importance of Data Communication

Connectivity

Enables communication between distant devices.

Efficiency

Reduces costs by enabling data sharing.

Productivity

Supports real time collaboration and services.

Scalability

Allows for flexible and scalable networks.

Foundation of IT

Core of modern digital systems and internet services.

Transmission Media

Physical pathways for information travel.

Two Main Categories of Transmission Media

Guided Media: Physical links that guide signals; Unguided Media: Signals transmit through air or space.

Guided Media

Aso known as wired media, refers to transmission pathways where data signals are physically directed along a solid medium. The signals are contained within a cable or fiber, which guides them from the source to the destination.

Twisted Pair Cable

Insulated copper wires twisted to reduce interference.

Unshielded Twisted Pair (UTP)

Common, inexpensive (e.g., Cat5e, Cat6).

Shielded Twisted Pair (STP)

Added metallic shield for better protection, more expensive.

Coaxial Cable

Central copper conductor, insulator, metallic shield, outer jacket. Better shielding than twisted pair. Cable TV, older Ethernet (10Base2, 10Base5), broadband internet.

Fiber Optic Cable

Transmits data using light pulses through glass or plastic strands. High bandwidth, long distance, no EMI.

Single Mode Fiber (SMF)

Thin core, single light path for long distance and high bandwidth.

Multi Mode Fiber (MMF)

Wider core, multiple light paths for shorter distances.

Unguided Media

Often referred to as wireless media, represents a category of transmission pathways where data signals propagate through the air or free space without the need for a physical conductor. Allows signals to spread out and be received by any device within their range.

Radio Waves

Electromagnetic waves, long distances, penetrate walls. AM/FM radio, Wi Fi, Bluetooth, cellular networks.

Microwaves

High frequency radio waves, line of sight, susceptible to weather. Satellite communication, terrestrial microwave links.

Infrared

Infrared light, short range, requires line of sight, cannot penetrate objects. Remote controls, short range PANs.

Network Devices

Devices used to connect, manage, and control communication between devices in a network.

NICs (Network Interface Cards)

Hardware component allowing a computer to connect to a network. Essential for any device to communicate on a network. Physical Connection (e.g., RJ 45 port); Data Conversion (parallel to serial and vice versa); Unique MAC Address.

Routers

Forwards data packets between computer networks; "traffic director.". Crucial for connecting local networks to the internet. Inter network Communication (e.g., home network to internet); Packet Forwarding (uses IP addresses to find best path); Routing Tables (stores network path info); Network Address Translation (NAT) (shares public IP in home networks).

Switches

Connects multiple devices within a Local Area Network (LAN). Operates at Data Link Layer (Layer 2). Forms the backbone of most modern LANs for efficient communication. Intelligent Forwarding (learns MAC addresses, sends data only to destination port); Collision Domains (each port is a separate collision domain, reduces congestion); Full Duplex Communication (send or receive data simultaneously).

Network Topology

The arrangement of different elements (links (communication path), nodes (devices), etc.) in a computer network. It defines how devices are connected and how data is transmitted.

Bus Topology

Single central cable (backbone) connects all devices. Data is transmitted in both directions. Simple and cost effective but difficult to troubleshoot. Coaxial cable.

Star Topology

All devices are connected to a central hub or switch. Easy to install and manage. Failure of the hub or switch brings down the entire network. Twisted pair cable.

Ring Topology

Devices are connected in a circular path. Data travels in one direction or both in dual ring. Failure in one device can affect the whole network, unless dual ring.

Mesh Topology

Every device is connected to every other device. Provides high redundancy and reliability. Very expensive and complex to implement.

Tree Topology

Combination of star and bus topologies. Hierarchical structure with a root node. Scalable but dependent on the backbone cable.

Hybrid Topology

Mix of two or more topologies. Flexible and scalable. Can be costly and complex.

Circuit Switching

A method of implementing a telecommunications network in which two network nodes establish a dedicated communications channel before they may communicate. Provides the full bandwidth of the channel and remains exclusively connected for the duration of the communication session.

History and Development of Circuit Switching

Was used in traditional telephone networks. In January 1878, the first telephone switch went into operation in New Haven, Connecticut, and telephone switching was used to interconnect users by creating circuits between them.

How Circuit Switching Works

The sender establishes a connection, network switches reserve a dedicated route and resources, data flows through the established path, and the resources are released when the communication ends.

Packet Switching

A data transmission method where information is divided into smaller units called packets. These packets are sent through different network nodes or switches and are later combined again at the destination.

History of Packet Switching

Paul Baran proposed dividing data into smaller packets between 1960 and 1962, while Donald Davies independently developed a similar concept and used the term packets. In 1967, Lawrence Roberts adopted packet switching for ARPANET, which had its first successful test in October 1969.

Packet Switching

Data is divided into packets containing a sequence number, destination address, and a portion of the total data. The packets move between routers, which determine the path at each hop and can use different routes when a path is busy or unavailable.

Message Switching

A connectionless network switching approach in which the complete message is routed from the sender node to the receiver node one hop at a time. The message is stored at intermediary nodes before being forwarded to the next node using the store and forward method.

History of Message Switching

Was used before packet switching and served as a replacement for circuit switching. Its early applications included telex networks and paper tape relay systems, while Western Union used a message switching system called Plan 55 A in the 1950s to process telegrams.

How Message Switching Works

The sender adds the destination address to the complete message, which is sent to an intermediary node. The node stores the entire message, determines the next route, and forwards it when the route is available until the message reaches its destination.

Router

A device that links separate networks together, commonly used across LANs, WANs, and MANs, and operates at Layer 3 of the OSI model by moving data packets from one network to another.

Network Switch

A device that connects multiple devices within a single LAN so they can exchange data packets and share a network while avoiding interference with one another.

Differences Between a Router and a Switch

Most network switches operate at Layer 2, although Layer 3 switches are also available, while routers operate at Layer 3. Routers process packets and use routing tables to determine IP addresses, while switches handle packets and frames and use CAM tables to identify MAC addresses.

Static Routing

A method of manually configuring routes in a router’s routing table to control the path that data packets take to reach their destination. Static routes remain unchanged unless the network administrator manually modifies them.

Dynamic Routing

A method where routers automatically choose and update routes based on the current state of the network. It allows data to use different paths when there are changes, such as a connection or node failure, as long as other routing paths are available.

Direct Routing

Occurs when the sender and destination host are connected to the same physical network. The sender can send an IP packet to the destination without passing through another machine or router.

Default Routing

Uses a route, also called the gateway of last resort, when a router does not have a specific route for a data packet. The packet is then forwarded to a predefined next hop.