Articles

A byte (B) contains eight bits (b). Internet connection rates are commonly shown in bits per second, whereas file and memory sizes are shown in bytes. The prefixes matter: decimal kB, MB and GB are not the same as binary KiB, MiB and GiB.

A computer virus is malicious code that attaches to another file or program and can spread when that host is run. Not all malware is a virus: worms, trojans and ransomware may spread or operate differently. The distinction matters when choosing a response to suspicious behaviour.

DNS over HTTPS (DoH) and DNS over TLS (DoT) encrypt DNS exchanges between a client and its chosen resolver. Both protect this part of the path against casual inspection and modification on the network. Neither makes website visits wholly invisible or anonymous.

DNS resource records store information needed by a domain: addresses, mail servers, delegation and other service settings. Each record has a name, type, value and time to live (TTL) for caching. Different types answer different questions, so one domain can have several records for separate purposes.

A domain name is registered for a limited period. If its registration is not renewed, the website and mail may stop working, and the name may later become available to somebody else. The exact recovery stages depend on the top-level domain and registrar.

IP geolocation approximately associates a network address with a country, region, city or provider. Its accuracy depends on the database and the connection type. A location result is neither a person’s coordinates nor proof of their physical whereabouts.

On Unix-like systems, chmod changes access permissions on files and directories. Read, write and execute permissions are set separately for the owner, the group and other users. Directory permissions have their own meaning: they affect listing names, creating or removing entries, and accessing a known path.

A browser’s “DNS error” describes a symptom, not a single root cause. A name might be mistyped, an authoritative server unreachable, a resolver might hold an older answer, or DNSSEC validation might fail. Identify the failing stage before changing a configuration.

A DNS cache keeps recent answers so every request does not need a complete lookup through the naming hierarchy. Caches may exist in an application, the operating system and the recursive resolver. Removing an answer from one of them does not immediately replace copies elsewhere.

Nslookup is a command-line tool for asking a DNS server about a domain or an IP address. It helps distinguish a name-resolution issue from a problem with a website or mail service. Its answer depends on the chosen resolver and its cache; it is not necessarily the authoritative source.

HTTP defines requests and responses between a client and a web server. HTTPS uses the same web semantics over a protected connection: data is encrypted, and the client checks that the server is authorised for the name in the address bar. This protects the exchange in transit, not the honesty of the site owner.

HTTP/3 is a version of HTTP that uses QUIC instead of the familiar HTTP/2, TLS and TCP combination. QUIC runs over UDP but adds reliable streams, congestion control and secure connection establishment. Supporting HTTP/3 alone does not make every page fast.

An internet speed test measures throughput between your device and a particular test server at a particular time. Most tests show download, upload and latency separately. The result depends on the server, route, local network and current load; one measurement cannot describe the performance of every website or application.

IPv4 and IPv6 are two versions of Internet Protocol that both operate on today’s Internet. IPv4 addresses are 32 bits long; IPv6 addresses are 128 bits long. The larger IPv6 address space does not automatically make a connection faster or safer. Performance and exposure depend on the route, network and configuration.

A temporary IPv6 address is an additional device address used for outgoing connections. It changes over time so that one fixed device identifier is harder to correlate across visits. The mechanism does not make a person anonymous or necessarily change the address prefix assigned to their network.

A fast download result does not guarantee a smooth call or game. Interactive traffic also depends on latency, changes in latency known as jitter, and packet loss. Each describes a different aspect of the connection, so measure them separately before changing equipment or blaming a server.

Internet access rates are usually advertised in megabits per second, written Mbps or Mb/s. File sizes and download programs often use megabytes and MB/s. A byte contains eight bits, so the numbers differ by a factor of about eight even before protocol overhead is considered.

A port check reports how one connection attempt appeared from one network location. “Open”, “closed” and “filtered” are useful diagnostic labels, but a single result cannot identify every device involved or determine whether an application is secure.

Ping checks whether a destination responds to network probes and measures the time until each answer returns. It is a useful first diagnostic step, but it does not measure download bandwidth and cannot by itself establish that an application or website is healthy.

Provider-independent (PI) address space is registered independently of any single upstream Internet provider. A holder can normally retain it when changing providers, subject to registry policy and routing arrangements. PI does not automatically make a service reachable worldwide: network operators must accept and carry the route to the prefix.

A public IP address is used for communication across the Internet and must be unique within the public routing space. A private IPv4 address is intended for a local network: the same address, such as 192.168.1.10, can be used in different homes at the same time. To understand an address shown in settings, distinguish the device, router and provider.

Punycode is an encoding used to represent Unicode characters in an ASCII-compatible form for internationalised domain names. A domain written with national characters may therefore appear in technical data as a label beginning xn--. The encoding changes representation; it does not establish that a website is genuine.

A static IP address is deliberately kept fixed for an interface or service. A dynamic address is assigned automatically and may change, but it need not change every time a device reconnects. These terms describe how an address is assigned, not whether it is public or private: either scope can use either assignment method.

TCP and UDP carry application data over IP, but provide different services. TCP gives applications an ordered byte stream with acknowledgements and retransmission. UDP sends individual datagrams without those transport-level guarantees. Neither choice is automatically better: the application’s requirements decide.

A temporary email service provides an address that receives messages for a limited period or until its mailbox is removed. It can keep a one-off registration separate from your main inbox. The address does not make you anonymous, and losing access to it can also mean losing access to the account created with it.

A TLS certificate warning means the browser could not validate a protected connection to the site in the address bar under its security rules. The causes differ: a wrong name, invalid dates, an untrusted chain or something unusual on the network. Read the exact error before acting.

Traceroute is a diagnostic view of the possible path packets take towards a destination. It lists responding hops and the time taken for probe responses. A trace is a snapshot under particular network conditions, not a permanent map of the Internet or proof of where every application packet travels.

Nameservers host a DNS zone and provide authoritative answers for it. Delegation tells the DNS hierarchy where to direct queries for a domain. The nameserver setting at a registrar and the NS records inside the zone are related but not identical control points.

RIPE NCC is the Regional Internet Registry serving Europe, the Middle East and parts of Central Asia. It distributes and registers Internet number resources, including IP address space and autonomous system numbers (ASNs), under the policies applicable to its region. It also maintains a database of registration and contact information used by network operators.

A domain name is a human-readable name in the DNS hierarchy, such as example.org. It can be used for websites, email and other services, but buying a domain does not automatically create any of them. The name is registered under a top-level domain according to that registry’s rules and then configured through DNS.

A firewall allows or blocks network traffic according to rules. It can run on a computer, a home router or at a cloud network boundary. Rules control access to connections; they do not automatically make an allowed application secure.

A hosting provider supplies computing resources and network connectivity for a website, application or related service. Depending on the plan, it may also manage the operating system, databases, email, backups and technical support. A domain registration is a separate service, even when the same company sells both. The right plan depends on traffic, control needs and maintenance capacity.

A MAC address is an identifier used by a network interface at the link layer. Ethernet and Wi-Fi commonly use 48-bit addresses, usually displayed as six pairs of hexadecimal digits. The address helps devices exchange frames on a local network. It is different from an IP address, which supports communication across networks.

A network port is a number used by transport protocols such as TCP and UDP to direct traffic to the right service. Together, a protocol, IP address and port form a practical endpoint for a connection. A port is a logical identifier, not a physical socket on a router.

A proxy server receives a request from one party and passes it toward another server. A forward proxy acts on behalf of a client, while a reverse proxy stands in front of one or more application servers. Proxies can filter requests, cache responses, manage access or distribute load. Their benefits depend on configuration and the trust placed in the operator.

A subdomain is a name within a wider domain hierarchy. In blog.example.org, blog sits under example.org. Subdomains can separate a website, mail, an API and other services, but the name alone creates no web page. You still need DNS records and a server configured to accept it.

A userbar is a small graphic placed in a forum or community profile signature. These narrow banners were especially popular in the 2000s for showing interests, affiliations or a link to a site. Today they are mainly a historical web format, although some communities still allow them.

A web service is an interface through which applications exchange data or invoke functions over a network. A website is designed primarily for people to read and use; a web service exposes a contract intended for software clients. The same product can provide both. Many services use HTTP and JSON, but the term includes other protocols and data formats.

A website is a collection of web resources presented under one or more addresses, usually with related pages and a common purpose. A domain name, a hosting server and a web page are related parts, but they are not interchangeable. Understanding the difference helps when publishing or troubleshooting a site.

An autonomous system, or AS, is a group of IP networks operated under a coherent external routing policy. It is identified by an autonomous system number, or ASN. Network operators use BGP to announce reachable IP prefixes and exchange routing information with other networks. An ASN identifies a routing participant, not a person or a physical server.

An email address identifies a mailbox or routing destination, usually in the form local-part@domain. The part before the at sign is interpreted by the mail provider; the domain after it is resolved through DNS. An address can be valid in form yet fail to receive mail if its domain or mailbox is not configured.

An IP address identifies an interface on an IP network so packets can be delivered to a destination. It is a network address, not a permanent identity for a person or even a particular device. A computer can have several addresses at once, and an address can change when the connection changes.

Antivirus software helps detect, block and remove malicious programs. Modern security products often combine file scanning, behaviour monitoring, web protection and operating-system safeguards. They reduce risk but cannot guarantee that every new or targeted attack will be stopped. Protection also depends on timely updates and the choices made by the device owner.

Carrier-grade NAT (CGNAT) is IPv4 address translation performed inside an Internet provider’s network. It lets multiple subscribers share one public IPv4 address. Outgoing connections often work normally, but incoming access to a server at home may be unavailable without a provider-supported arrangement.

DNS propagation is the informal name for the interval when resolvers still return different answers after a record changes. DNS does not broadcast a new value to every server at once. Recursive resolvers fetch answers when needed and may retain them in a cache for the permitted lifetime.

DNS, the Domain Name System, is a distributed naming system that helps applications locate network resources. A website name can resolve to IPv4 or IPv6 addresses, while other records direct email or identify authoritative name servers. A domain name does not have to point to just one server.

DNSSEC adds digital signatures to DNS data. A validating resolver can detect a forged response or a broken chain of trust. It protects the origin and integrity of records, but does not encrypt DNS queries or automatically make a website trustworthy.

Encryption transforms readable information into ciphertext that can be recovered with the right key. Its purpose is to keep data confidential during transfer or storage. Hashing and checksums solve different problems: their output is not decrypted to recover the original message. Confusing these operations can lead to a false sense of security.

Internet Protocol (IP) carries packets between networks using IP addresses. Today, IPv4 uses 32-bit addresses and IPv6 uses 128-bit addresses. IP provides addressing and routing, but does not by itself promise that every packet arrives, arrives in order or has protected contents. Other protocols and applications add the services they need.

localhost normally refers to the machine from which a request is made. Its familiar addresses are IPv4 127.0.0.1 and IPv6 ::1. Traffic to them is handled inside that machine’s network stack rather than travelling through the home router to the Internet. A localhost test therefore answers a narrow question: does the service work locally?

MTU is the largest network packet size an interface or link can carry without splitting it at that layer. A common Ethernet MTU is 1500 bytes, but tunnels and other links may allow less. A connection must work within the limits of the path it actually takes.

NAT, or Network Address Translation, changes packet addresses at a network boundary. In a home network, a router commonly lets several privately addressed IPv4 devices use one external IPv4 address. It often changes port numbers as well so that it can distinguish multiple simultaneous connections.

A normal DNS lookup obtains an address from a name. Reverse DNS asks a different question: given an IP address, which name is recorded in its dedicated reverse zone? The answer comes from a PTR record. It is useful in network and mail operations, but it does not establish a person’s identity or site ownership.

Spam is unwanted bulk communication, most commonly email but also messages through social networks, messengers and comments. It can be advertising, fraud or a delivery channel for malware. The fact that a message is unsolicited does not prove that it is dangerous, but its links, attachments and requests deserve careful handling.

WHOIS is the traditional way to look up registration information for a domain or an Internet number resource. For generic top-level domains, RDAP is now the primary modern source of registration data. A result may show a registrar, dates, status codes and nameservers, while personal details about the registrant are often withheld.