📚 Network Glossary

An Autonomous System Number (ASN) is a unique identifier assigned to a group of one or more IP prefixes managed by a single network operator (like an ISP or large tech company).

The maximum rate of data transfer across a network path, typically measured in bits per second (bps). It represents the capacity of the connection.

Border Gateway Protocol (BGP) is the standardized routing protocol used to exchange routing and reachability information among autonomous systems on the internet.

A Content Delivery Network (CDN) is a geographically distributed group of servers that work together to provide fast delivery of internet content like images, videos, and scripts.

Classless Inter-Domain Routing (CIDR) is a method for allocating IP addresses and IP routing. it replaced the older system based on Class A, B, and C networks.

Distributed Denial of Service (DDoS) is a malicious attempt to disrupt the normal traffic of a targeted server, service or network by overwhelming it with a flood of internet traffic.

Dynamic Host Configuration Protocol (DHCP) is a network management protocol that automatically assigns IP addresses and other configuration parameters to devices on a network, replacing manual static configuration.

The Domain Name System (DNS) is often called the "phonebook of the internet." It translates human-readable domain names (like google.com) into IP addresses (like 142.250.185.46) that computers use to identify each other.

The timeframe it takes for DNS changes to be updated across the entire internet. This process can take anywhere from a few hours up to 48 hours.

Dynamic DNS (DDNS) is a service that keeps a domain name linked to a changing IP address, which is common for residential internet connections.

A firewall is a network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules, creating a barrier between trusted and untrusted networks.

A gateway is a network node that serves as an access point to another network. The default gateway is typically the router that forwards local traffic to the internet.

Internet Control Message Protocol (ICMP) is used by network devices to send error messages and operational information (e.g., used by the Ping command).

An Internet Protocol (IP) address is a unique numerical identifier assigned to every device connected to a network. It serves two main purposes: identifying the host or network interface and providing the location of the device in the network. IP addresses come in two versions: IPv4 (e.g., 192.168.1.1) using 32-bit addresses, and IPv6 (e.g., 2001:0db8:85a3::8a2e:0370:7334) using 128-bit addresses.

A list of IP addresses that are suspected of sending spam, malware, or being part of a botnet. Being on a blacklist prevents you from sending emails.

The process of determining the physical location of a device based on its IP address. Accuracy is high at country level but lower at city level.

Occurs when your true IP address is revealed despite using a VPN or proxy, often due to browser technologies like WebRTC or DNS flaws.

A technique used by attackers to send packets with a false "Source" IP address to impersonate another computer system or hide their identity.

Internet Protocol version 4 (IPv4) is the fourth version of the Internet Protocol and the most widely used protocol for routing internet traffic. It uses 32-bit addresses, allowing for approximately 4.3 billion unique addresses. IPv4 addresses are typically written in dot-decimal notation (e.g., 192.168.0.1).

Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol, designed to replace IPv4. It uses 128-bit addresses, providing approximately 340 undecillion unique addresses. IPv6 addresses are written in hexadecimal notation (e.g., 2001:0db8:85a3::8a2e:0370:7334).

An Internet Service Provider (ISP) is a company or organization that provides internet access to customers. ISPs connect users to the internet through various technologies including DSL, cable, fiber optic, or satellite connections. Your ISP assigns your public IP address.

The variation in latency (delay) over time. High jitter can cause buffering in streaming video and lag in online gaming, even if the average latency is low.

A Local Area Network (LAN) is a network that covers a small geographic area, like a home, office, or group of buildings.

The time delay between sending a request and receiving a response, measured in milliseconds (ms). High latency causes "lag" in real-time applications.

A Media Access Control (MAC) address is a unique hardware identifier assigned to network interface controllers (NICs). Unlike IP addresses, MAC addresses are permanent to the hardware.

A lightweight markup language with plain text formatting syntax. It is designed so that it can be converted to HTML and many other formats using a tool by the same name.

Maximum Transmission Unit (MTU) is the size of the largest protocol data unit (packet) that can be communicated in a single network layer transaction.

Network Address Translation (NAT) is a method of remapping one IP address space into another. It allows multiple devices on a private network to share a single public IP address for internet access, conserving IPv4 addresses.

An Organizationally Unique Identifier (OUI) is the first portion of a MAC address that identifies the manufacturer of the network device.

A small segment of a larger message. Data sent over computer networks is divided into packets to improve efficiency and reliability.

Occurs when one or more packets of data travelling across a computer network fail to reach their destination, causing lag or broken connections.

A network tool used to test the reachability of a host and measure the round-trip time for packets to travel from source to destination.

A port is a virtual point where network connections start and end. ports allow a single IP address to handle multiple services (e.g., port 80 for HTTP, port 443 for HTTPS, port 22 for SSH).

Port scanning is a technique used to identify open ports and services on a target system. It is used for security auditing to find vulnerabilities or verify firewall configurations.

The IP address assigned by your router to devices on your local network. These are not directly reachable from the public internet.

A proxy server acts as an intermediary between your device and the internet. It forwards your requests and hides your IP address, but unlike a VPN, it typically does not encrypt all device traffic.

The IP address assigned by your ISP that identifies your home or business network to the rest of the world on the internet.

Quality of Service (QoS) is a set of technologies that work on a network to guarantee its ability to dependably run high-priority applications and traffic.

A device that forwards data packets between computer networks. It directs traffic on the internet and connects your local network devices to your ISP.

An XML file that lists the URLs for a site along with additional metadata about each URL (when it was last updated, how often it changes, etc.) so that search engines can more intelligently crawl the site.

Secure Shell (SSH) is a cryptographic network protocol for operating network services securely over an unsecured network, typically used for remote logins.

Secure Sockets Layer (SSL) and its successor Transport Layer Security (TLS) are protocols for establishing encrypted links between computers.

A subnet (subnetwork) is a logical subdivision of an IP network. Subnetting improves network performance and security by dividing a large network into smaller segments.

A 32-bit number that divides an IP address into network and host portions. It determines which part of the IP address refers to the network and which part refers to the host device.

The conceptual model and set of communications protocols used on the internet and similar computer networks.

A diagnostic tool for displaying the route (path) and measuring transit delays of packets across an Internet Protocol (IP) network.

Time to Live (TTL) is a value in an IP packet that tells a network router whether or not the packet has been in the network too long and should be discarded.

User Datagram Protocol (UDP) is a communications protocol that is used across the internet for especially time-sensitive transmissions such as video or gaming.

A Virtual Private Network (VPN) creates an encrypted tunnel between your device and a VPN server, hiding your real IP address and encrypting your traffic to prevent interception and bypass geo-restrictions.

A Wide Area Network (WAN) is a large network of information that is not tied to a single location. The internet is the largest WAN in the world.

Web Real-Time Communication (WebRTC) is a free, open-source project that provides web browsers and mobile applications with real-time communication via APIs.

A query and response protocol that is widely used for querying databases that store the registered users or assignees of an internet resource.

Extensible Markup Language (XML) is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. Commonly used for sitemaps.