Digital Infrastructure Glossary

Definitions of common terms used in networking, cloud, data centres, resilience and infrastructure operations.

Anycast: A routing method in which the same network address is announced from multiple locations and traffic is directed according to routing conditions.
Autonomous system: A network or group of networks operated under a common routing policy and identified by an autonomous system number.
Availability: The proportion of a defined period during which a service is usable according to stated measurement rules.
Availability zone: A cloud-provider failure boundary within a region, usually designed with separate facility infrastructure.
Backup: A recoverable historical copy of data or system state kept for restoration.
BGP: Border Gateway Protocol, the routing protocol used by autonomous systems to exchange internet reachability information.
Blast radius: The scope of services, users or components affected by a failure or change.
Capacity headroom: Unused capacity reserved for demand growth, bursts, maintenance and failure states.
Cloud region: A geographic area in which a cloud provider operates one or more availability zones and related services.
Colocation: A model in which customer-controlled equipment is installed in a provider-operated data centre.
Common-mode failure: One event or dependency that affects components believed to be redundant.
Content delivery network: A distributed system that serves cached or optimized content from locations closer to users.
Data centre: A facility designed to house computing, storage and network equipment with supporting power, cooling and security.
Disaster recovery: The people, procedures, infrastructure and data capabilities used to restore services after a serious disruption.
Edge computing: Processing placed closer to users, equipment or data sources rather than only in a central facility or cloud region.
Failover: The movement of service from a failed or unavailable component to an alternate component or location.
Failure domain: A set of resources that can be affected by the same failure event.
Fault tolerance: The ability to continue operating through a defined fault with little or no visible interruption.
High availability: An architecture and operating approach intended to limit service interruption through redundancy, monitoring, failover and testing.
Hypervisor: Software or firmware that creates and manages virtual machines on physical hardware.
Internet exchange point: A shared facility or switching platform where networks exchange traffic.
Latency: The time required for data or a request to travel through a system and produce a response.
Observability: The ability to understand a system’s internal behavior from the evidence it produces, such as metrics, logs and traces.
Peering: A direct traffic-exchange relationship between networks.
Replication: The process of maintaining copies of data in more than one location or system.
Recovery point objective: The maximum acceptable amount of recent data exposure, expressed as a time interval.
Recovery time objective: The target time to restore a service after disruption.
Route diversity: The use of network paths that avoid relevant common physical and upstream failure points.
Service level objective: An internal target for a measurable service outcome such as availability or latency.
Technical debt: Future cost or risk created by short-term technical choices, deferred maintenance or unsupported systems.
Transit: A paid service through which one network obtains reachability to the broader internet through another network.
UPS: An uninterruptible power supply that conditions power and bridges interruptions while longer-duration power is established.
Virtual machine: A software-defined computer environment that runs on a physical host through a hypervisor.