Browse our complete collection of questions and answers.
DNSSEC adds cryptographic signatures to DNS records so a resolver can verify that an answer genuinely came from the domain's owner and was not altered in transit. It addresses a real weakness, and
A WAF inspects the content of web requests and blocks those it judges malicious — operating at the application layer, which is what distinguishes it from an ordinary network firewall. The distinction
HTTP Strict Transport Security is a instruction from a website telling your browser to only ever connect to it over HTTPS — and to refuse to proceed if anything is wrong, without offering you a way
A certificate authority (CA) issues them, and what most certificates prove is narrower than people assume: control of the domain name, and nothing else. What a certificate contains. The domain name
A point of presence (PoP) is a physical location where a network has equipment that other networks or customers can connect to — the places where an abstract "network" actually touches the ground.
Successive specifications for twisted-pair Ethernet cable, differing in how well they resist interference — which is what determines the speed and distance they can support. What all of them share.
Power over Ethernet (PoE) delivers electrical power along the same cable that carries data, so a device needs only one connection rather than a network cable and a mains adapter. Why it is useful.
Continuously and invisibly — your phone is constantly measuring nearby cells and the network moves your connection between them, ideally without you noticing. What a cell actually is. A mast site is
The principle that networks should carry all traffic equally, without favouring or discriminating between sources, destinations or applications on commercial grounds. What it prohibits, specifically:
The final connection from a network's local distribution point to each individual building is disproportionately expensive, and that single fact shapes almost everything about broadband availability,
Cable broadband delivers internet over the coaxial television network, using a standard called DOCSIS — Data Over Cable Service Interface Specification — that defines how data shares that cable with
Fixed wireless access (FWA) delivers broadband to a building over a radio link rather than a wire — typically from a mobile network's 4G or 5G masts to a receiver in your home. Why it exists. Digging
Because latency over satellite is dominated by orbital altitude, and the difference between orbits is a factor of forty. Geostationary orbit (GEO), at roughly 35,786 km. A satellite there orbits at
Through submarine fibre optic cables lying on the seabed — not satellites, which carry a negligible share of intercontinental traffic despite what most people assume. The scale. Well over 95% of
Maximum transmission unit is the largest packet size a link will carry — and a mismatch produces one of the most confusing faults in networking: most things work, but some websites hang after loading
The path your packets take toward a destination, hop by hop — and it is genuinely useful for diagnosis, provided you know which parts of it to ignore. How it works — a clever trick. Every IP packet
Time to live is how long a DNS record may be cached before it must be looked up again — and it is the reason a change you made an hour ago is still not visible to everyone. Why caching exists.
Each record type answers a different question about a domain, which is why a single domain has many records and why editing the wrong one breaks something unrelated. A — maps a name to an IPv4
DNS over HTTPS (DoH) encrypts your DNS queries so that whoever carries your traffic cannot read which sites you are looking up. It closes a genuine privacy gap and shifts trust rather than
A virtual LAN splits one physical network into several logically separate ones, so devices on different VLANs cannot see each other even though they share the same switch and cabling. How it works.
A set of techniques for deciding which traffic gets priority when there is not enough capacity for everything — because the only time prioritisation matters is when a link is full. The problem. A
Because a video call does not need much bandwidth — it needs packets arriving consistently, and these two measures describe whether they do. Latency is how long a packet takes to travel, measured as
Layers of headers wrapped around your data, each added by a different part of the networking stack and each read by a different piece of equipment along the way. Why layers exist. Each layer solves
TCP guarantees delivery; UDP does not — and that single trade-off determines which one every internet application uses. TCP (Transmission Control Protocol). A connection-oriented, reliable protocol:
A physical location where many independent networks connect to one another directly, rather than sending traffic through a chain of intermediaries. The problem it solves. Without exchanges, two
Network Address Translation lets many devices share one public IP address, by rewriting addresses and ports as traffic passes through the router. Why it exists. IPv4 provides around 4.3 billion
Dynamic Host Configuration Protocol hands out network settings automatically, so a device joining a network can configure itself without anyone typing anything. What it supplies. Not just an IP
It tells a device which part of an IP address identifies the network and which part identifies the host — and therefore whether a destination is local or has to go via the router. The decision it
Carrier-grade NAT is a technique ISPs use to share a single public IP address between many customers — a response to IPv4 address exhaustion, and a cause of a specific and confusing set of problems.
How far the fibre actually goes — and that single fact determines almost everything about the speed and reliability you get. FTTC — fibre to the cabinet. Fibre runs from the exchange to the green
Border Gateway Protocol is how independent networks tell each other which addresses they can reach. It is the routing system the entire internet depends on — and it works largely on trust, which is
A content delivery network is a distributed set of servers that store copies of a website's content close to its users — so the data travels a shorter distance and arrives sooner. The physical
The two ways networks connect to each other — and the distinction is essentially who pays whom. The internet is a network of networks. No single organisation runs it. Around a hundred thousand
Access to their network, and through it a share of a shared resource — which is why "up to" appears in every advertisement and why your speed varies by time of day. What the connection is. Your line
Because prompt notification is a condition of almost every policy, and late notification can reduce or defeat a claim that would otherwise have been paid in full. What policies typically require.
An insurance company owned by the organisation it insures, established so that a business can insure its own risks rather than buying cover from a commercial insurer. Why an organisation would do
A broker generally acts as your agent, not the insurer's — which is the distinction determining what they owe you and who is responsible when something goes wrong. What that means. As your agent, a
The schedule contains what is specific to you; the wording contains the terms that apply generally — and the two must be read together, because neither is the policy on its own. The policy schedule.
Two distinct problems created by information being unequally held between insurer and insured — and almost every feature of how insurance is designed and priced is a response to one or the other.
A heightened duty of honesty and disclosure between insurer and insured — historically far stricter than in ordinary contracts, and substantially reformed in the UK because the old rule produced
A legally recognised relationship between the insured and the subject of the insurance, such that they would suffer a loss if the insured event occurred — and without it, a policy is not insurance
Three ways of setting an amount the insured bears — and although the first two are used almost interchangeably, the third behaves entirely differently. Excess. The amount deducted from every claim
Whether the limit applies to each claim separately or to everything in the policy period combined — and the difference determines whether a second claim leaves you with any cover at all. Per-claim
Which policy responds — the one in force when the incident happened, or the one in force when the claim is made. It is the single most consequential distinction in liability insurance, and it
An allowance included in a price for work that cannot yet be defined — and understanding it is the key to knowing which parts of a builder's quote are firm and which are not. What it is. Where an
A barrier built into a cavity wall to collect water that has crossed the outer leaf and direct it back outside — and missing or badly installed cavity trays are among the most common causes of
A screed is a levelling layer laid over a structural floor to provide a flat surface for the finish; a damp proof membrane (DPM) is a barrier preventing moisture rising from the ground through the
There is no general rule — not the left-hand side, not the side with the posts — and every widely repeated shortcut is a myth. Ownership is determined by the title documents, and frequently by
An insurance policy that stands behind a contractor's own guarantee, so that the guarantee remains usable if the contractor ceases to trade — which is precisely when a guarantee is otherwise
The Construction (Design and Management) Regulations, governing health and safety in construction — and yes, they apply to domestic projects, which surprises almost every homeowner having work done.