Networking Terminology

Networking Fundamentals and Core Terminology

• Network: A collection of interconnected devices that possess the capability to communicate with one another.

• Node: Refers to any single device that is connected to a network, such as a computer, printer, or mobile device.

• IP Address: A unique numerical label assigned to every device participating in a computer network that uses the Internet Protocol for communication.

• MAC Address: A unique physical identifier assigned to a network interface controller (NIC) for use as a network address in communications within a network segment.

• Subnet Mask: A number that defines the range of IP addresses that can be used within a network; it identifies which portion of the IP address belongs to the network and which portion belongs to the host.

• Default Gateway: The specific node on a computer network that serves as an access point or IP router that a networked computer uses to send information to a computer in another network or the internet.

• Domain Name System (DNS): A hierarchical and decentralized naming system for computers, services, or other resources connected to the internet; it translates easily remembered domain names into numerical IP addresses.

• Dynamic Host Configuration Protocol (DHCP): A network management protocol used on Internet Protocol (IP) networks whereby a DHCP server dynamically assigns an IP address and other network configuration parameters to each device on a network.

• Router: A physical or virtual appliance that passes information between two or more packet-switched computer networks.

• Switch: A networking device that connects devices on a computer network by using packet switching to receive and forward data to the destination device within the same network.

• Hub: A basic networking device that connects multiple computers or other network devices together; unlike a switch, it broadcasts data to all ports regardless of the destination.

• Firewall: A security system designed to monitor and control incoming and outgoing network traffic based on predetermined security rules.

• Protocol: A formal set of rules that govern how data is transmitted and received over a network.

• Transmission Control Protocol (TCP): A core protocol of the Internet Protocol Suite that provides reliable, ordered, and error-checked delivery of a stream of packets.

• User Datagram Protocol (UDP): A simple, connectionless transmission model that provides faster transmission but without the reliability or error-checking of TCP.

• Port: A logical construct that serves as a communication endpoint in a computer's operating system, used to identify specific processes or types of network services.

• Local Area Network (LAN): A computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus, or office building.

• Wide Area Network (WAN): A telecommunications network that extends over a large geographical distance, often established with leased telecommunication circuits.

• Virtual Private Network (VPN): A service that creates a safe, encrypted connection over a less secure network, such as the public internet.

• Bandwidth: The maximum rate of data transfer across a given path or network, typically measured in bits per second.

• Latency: The time delay experienced in a system, specifically the time it takes for data to travel from its source to its destination.

• Packet: A small segment of a larger message. Data sent over computer networks, such as the internet, is divided into packets.

• Service Set Identifier (SSID): A sequence of characters that uniquely names a wireless local area network (WLAN).

• Access Point: A device that creates a wireless local area network, or WLAN, usually in an office or large building.

• Topology: The physical or logical arrangement of the elements (links, nodes, etc.) of a communication network.

Address Resolution Protocol (ARP)

• Definition: The Address Resolution Protocol (ARP) is a communication protocol used for discovering the link-layer address, such as a MAC address, associated with a given internet layer address, typically an IPv4 address.

• Function: It connects a logical IP address to a physical MAC address on a Local Area Network (LAN).

Command-Line Networking Tools

Interface and Connectivity Tools

• Ipconfig: Displays current network configuration values.

• ipconfig/all: Provides exhaustive and detailed IP information for all adapters.

• ipconfig/release: Manually drops the current IP address lease from the DHCP server.

• ipconfig/renew: Requests a new IP address lease from the DHCP server.

• ipconfig/flushdns: Purges the DNS resolver cache, which can resolve connection issues.

• Ping [IP]: Sends ICMP Echo Request packets to a specific IP address to verify network connectivity and measure response time.

• Tracert [IP]: Traces the path that a packet takes to reach a destination, detailing every hop along the route.

System and Status Tools

• Nslookup [domain]: Queries the Domain Name System to obtain domain name or IP address mapping or other specific DNS records.

• Netstat -an: Displays all active network connections and the ports on which the computer is listening.

• Arp -a: Displays the current ARP cache tables, showing the mappings of IP addresses to physical MAC addresses.

• Hostname: Displays the name assigned to the local computer system.

• Getmac: Retrieves the MAC addresses of all network adapters in the system.

Network Services and Settings

• Net share: Lists todos shared resources available on the system.

• Net start/stop: Used to manually start or stop specific Windows services.

• Netsh: A command-line utility that allows for the local or remote configuration of the network settings of a computer.

The OSI Model: Layer 7 - Application Layer

This layer interacts directly with software applications. Key protocols and their standard ports include:

• DNS ($53$): Converts human-readable domain names into IP addresses.

• DHCP ($67/68$): Automatically assigns IP addresses and network parameters to hosts.

• HTTP ($80$): Used for transmitting unencrypted web traffic.

• HTTPS ($443$): Used for secure, encrypted web traffic using TLS/SSL.

• SMTP ($25$): Simple Mail Transfer Protocol; used for sending email messages.

• POP3 ($110$): Post Office Protocol version $3$; used for receiving email locally from a server.

• IMAP ($143$): Internet Message Access Protocol; used for email synchronization across multiple devices.

• SNMP ($161/162$): Simple Network Management Protocol; used for monitoring and managing network devices.

• NTP ($123$): Network Time Protocol; used for synchronizing the clocks of computer systems.

• SSH ($22$): Secure Shell; used for secure remote access to a computer.

• FTP ($21$): File Transfer Protocol; used for transferring files between a client and server.

• SFTP ($22$): Secure File Transfer Protocol; utilizes SSH for secure file transfers.

• TFTP ($69$): Trivial File Transfer Protocol; a simplified, lightweight version of FTP.

• SIP ($5060/5061$): Session Initiation Protocol; used for signaling and controlling multimedia communication sessions such as VoIP calls.

• RTP: Real-time Transport Protocol; responsible for the delivery of audio and video media over networks.

The OSI Model: Layer 6 - Presentation Layer

• Role: Functions as a data translator for the network.

• Process: Takes data received from the Application Layer and prepares it for the Session Layer by:

  • Changing the data format to ensure compatibility.

  • Encrypting data for security.

  • Compressing data to optimize transmission.

• Objective: Ensures that information sent from the application layer of one system can be read by the application layer of another system.

The OSI Model: Layer 5 - Session Layer

• Purpose: Establishes, manages, and terminates communication sessions (links) between applications on different devices.

• Coordination: Functions similarly to a phone call coordinator, ensuring the connection remains open for the duration of the transfer, managing the flow of data, and ensuring the session ends correctly.

The OSI Model: Layer 4 - Transport Layer

Focuses on the end-to-end communication between devices. Two primary protocols are used:

• TCP: A reliable, connection-oriented protocol. It uses sequencing to ensure data arrives in the correct order and acknowledgments to ensure guaranteed delivery of all segments.

• UDP: A fast, connectionless protocol with minimal overhead. It is used for applications where speed is the priority over perfect reliability.

The OSI Model: Layer 3 - Network Layer

This layer is responsible for packet forwarding, including routing through intermediate routers. Key protocols include:

• Internet Control Message Protocol (ICMP): Primarily used to send error messages and operational information, such as connectivity tests like ping.

• Open Shortest Path First (OSPF): A link-state routing protocol used to find the most efficient path for data within a single autonomous system or internal network.

• Border Gateway Protocol (BGP): The standardized exterior gateway protocol designed to exchange routing and reachability information among autonomous systems; it is the core routing protocol of the internet.

• Generic Routing Encapsulation (GRE): A tunneling protocol developed by Cisco that can encapsulate a wide variety of network layer protocols inside virtual point-to-point links.

• Internet Protocol Security (IPsec): A suite of protocols used to secure Internet Protocol communications by authenticating and encrypting each IP packet in a data stream; commonly used for VPNs.

• Multiprotocol Label Switching (MPLS): A data-carrying technique that increases speed and controls traffic flow by using short path labels rather than long network addresses.

• Virtual Extensible LAN (VXLAN): An encapsulation protocol used to run Layer $2$ networks over Layer $3$ infrastructure by wrapping Ethernet frames inside UDP packets.

The OSI Model: Layer 2 - Data Link Layer

Handles the movement of data across the physical link in a network. Critical protocols and concepts include:

• ARP: Resolves IP addresses to MAC addresses.

• Ethernet: The standard technology for establishing Local Area Networks.

• Spanning Tree Protocol (STP): A network protocol that ensures a loop-free topology for any bridged Ethernet local area network.

• Link Aggregation Control Protocol (LACP): Provides a method to control the bundling of several physical ports together to form a single logical channel to ensure high availability.

• Virtual Local Area Network (VLAN): Allows for network segmentation, enabling one physical network to be split into multiple logical networks.

The OSI Model: Layer 1 - Physical Layer

• Primary Function: The transmission and reception of raw, unstructured binary data bits across a physical medium.

• Media Types: Includes physical hardware such as copper cables, fiber optic lines, and radio waves.

• Data Conversion: This layer is responsible for converting digital data into physical signals, such as electrical pulses, light flashes, or radio signals, for transmission.