Data Center Infrastructure & Design: Operation & Maintenance

Incident response is the prepared, practised process by which an organisation detects a security incident, contains it, removes the cause, recovers, and learns from what happened.

Threat modelling is the structured practice of asking what could go wrong with a system, who would make it go wrong and how, while the design can still be changed cheaply.

Phishing is an attack that deceives a person into revealing credentials, approving a payment or running malicious content, usually through a message that impersonates someone they trust.

Routing is how packets move between networks: each router holds a table of known destinations and the next hop toward each, learned by configuration or by a protocol, and forwards each packet to the most specific match.

Switching is the forwarding of frames within a single network segment by a device that learns which hardware address sits on which port and sends each frame only where it needs to go.

A VLAN divides one physical switched network into several logical segments, each with its own broadcast domain, by tagging frames with a VLAN identifier so that ports and devices in different VLANs cannot reach each other without a router.

Uptime is the proportion of time a service answers requests, quoted in nines, and a service level agreement is the contract clause setting out how that proportion is counted and what the provider owes when it falls short.

Shared hosting puts your website on a machine that is simultaneously running hundreds of other people's, pooling its processor, memory and disk between all of you, which is both why it costs so little and why your speed partly depends on strangers.

A VPS is a software-defined slice of one physical machine that behaves as a server in its own right, with its own operating system, reserved CPU, memory and disk, and administrative access down to the kernel.