Computer Science Networking

A computer network is a group of interconnected computers and devices that communicate with each other and share resources, such as files, printers, and internet connections.

• LAN (Local Area Network): A network that is confined to a small geographic area, such as a single building or campus. It is typically used for connecting personal computers and workstations to share resources and information.
• WAN (Wide Area Network): A network that covers a broad area, such as a city, country, or even globally. WANs are used to connect multiple LANs and other types of networks, often via leased telecommunication lines.

An IP address (Internet Protocol address) is a unique identifier assigned to each device connected to a network that uses the Internet Protocol for communication. It allows devices to locate and communicate with each other.

• IPv4: Uses a 32-bit address scheme, allowing for approximately 4.3 billion unique addresses. It is written in decimal format (e.g., 192.168.1.1).
• IPv6: Uses a 128-bit address scheme, allowing for a vastly larger number of addresses. It is written in hexadecimal format (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334).

The OSI (Open Systems Interconnection) model is a conceptual framework used to understand and implement network protocols in seven layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application. It standardizes networking functions to allow interoperability between different systems and protocols.

• Physical Layer: Deals with the physical connection between devices and the transmission of raw binary data over a medium.
• Data Link Layer: Provides error detection and correction, and frames data for the Physical layer.
• Network Layer: Handles routing of data packets between devices across different networks.
• Transport Layer: Ensures reliable data transfer with error recovery and flow control (e.g., TCP).
• Session Layer: Manages sessions or connections between applications.
• Presentation Layer: Translates data formats between the application and the network.
• Application Layer: Provides network services directly to user applications (e.g., HTTP, FTP).

TCP/IP (Transmission Control Protocol/Internet Protocol) is a suite of communication protocols used to interconnect network devices on the internet. It roughly maps to the OSI model but uses four layers: Link, Internet, Transport, and Application.

• TCP (Transmission Control Protocol): A connection-oriented protocol that ensures reliable data transfer with error checking, acknowledgments, and flow control.
• UDP (User Datagram Protocol): A connectionless protocol that sends data without establishing a connection, providing lower latency but no guarantee of delivery, ordering, or error checking.

A subnet mask is used to divide an IP address into a network and host portion. It helps in determining the subnet to which an IP address belongs, facilitating routing and efficient IP address management. For example, a subnet mask of 255.255.255.0 indicates that the first three octets are the network part, and the last octet is for host addresses.

A default gateway is a network node that serves as an access point to other networks, typically used to route traffic from a local network to external networks or the internet. It is usually the IP address of a router on the local network.