Knowledge centreTelecom glossary
Plain-language definitions for the technologies, measurements and network concepts used throughout the site.
How to use this glossary
These definitions are written for everyday reading. They provide a useful starting point for understanding an offer or discussing a project, while the precise meaning may still depend on the supplier, country and contract.
When comparing services, do not look at one technical term in isolation. Capacity, latency, coverage, equipment, support and price work together, and the best balance depends on the location and intended use.
Terms shown: 39 of 39
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- 5G#
The fifth generation of mobile networks. It can provide higher capacity and lower latency than earlier generations, but performance depends on spectrum, coverage, device and network load.
Put it into practice : Mobile
- Bandwidth#
The theoretical or provisioned capacity of a connection, usually expressed in bits per second. It is not the same as the speed observed by every application.
Put it into practice : Internet
- Latency#
The time required for data to travel to a destination and back. Low latency matters for calls, gaming, remote control and interactive cloud services.
Put it into practice : Internet
- Fibre optic#
A physical medium that transmits data as light. Fibre can deliver high capacity and low latency, subject to local infrastructure and equipment.
Put it into practice : Internet
- eSIM#
A downloadable mobile subscription profile stored in a compatible device, replacing or complementing a removable SIM card.
Put it into practice : Mobile
- Roaming#
Use of a mobile service on a visited network outside the home network. Countries, allowances and charges depend on the agreement and plan.
Put it into practice : Mobile
- Wi-Fi#
A local wireless network connecting devices to a router or access point. Wi-Fi quality is distinct from the quality of the Internet line.
Put it into practice : Network
- SD-WAN#
Software-defined wide-area networking that applies central policies to traffic across one or more access links.
Put it into practice : Business
- VPN#
An encrypted logical tunnel between a device or site and another network. A VPN protects traffic in transit but does not make every endpoint trustworthy.
Put it into practice : Support
- IoT#
The Internet of Things: connected sensors, meters, vehicles and equipment that exchange data with applications.
Put it into practice : Solutions
- SLA#
A service-level agreement defining measurable targets such as availability or response time, together with scope and exclusions.
Put it into practice : Business
- Failover#
Automatic or manual transfer of traffic from a failed or degraded link to another available path.
Put it into practice : Network
- Access point#
A device that provides Wi-Fi service to nearby devices. Its position, radio settings, wired uplink and number of simultaneous users all affect the result.
Put it into practice : Network
- Bandwidth symmetry#
The relationship between download and upload capacity. Symmetric access is especially useful for cloud backups, video meetings, uploads and remote work.
Put it into practice : Internet
- DNS#
The naming service that translates a domain name into an IP address. A connection can be online while a DNS fault still prevents websites or applications from being reached.
Put it into practice : Support
IETF — RFC 1034: Domain Names
Technical reference in English · Source checked on- Ethernet#
A wired local-network standard used to connect routers, switches, access points and devices. It is usually more predictable than Wi-Fi for fixed equipment.
Put it into practice : Network
- FTTH#
Fibre to the Home: optical fibre delivered to a home or premises. Final availability and installation remain dependent on the address and building conditions.
Put it into practice : Internet
- IPv6#
The newer Internet addressing protocol, designed to provide a much larger address space than IPv4. Compatibility depends on the access provider, router and applications.
Put it into practice : Solutions
IETF — RFC 8200: IPv6
Technical reference in English · Source checked on- Jitter#
Variation in packet delay over time. High jitter can affect calls, video meetings and other real-time services even when headline speed looks sufficient.
Put it into practice : Support
IETF — RFC 3393: IP Packet Delay Variation
Technical reference in English · Source checked on- Packet loss#
Packets that do not reach their destination. It can cause stuttering calls, slow transfers and unstable applications; the cause may be local or upstream.
Put it into practice : Support
IETF — RFC 7680: One-Way Loss Metric
Technical reference in English · Source checked on- PoE#
Power over Ethernet: a method that carries electrical power and network data over the same Ethernet cable, often for access points, cameras and phones.
Put it into practice : Network
- QoS#
Quality of Service: traffic rules that prioritise selected flows, such as voice or critical applications, when link capacity is under pressure.
Put it into practice : Network
- Router#
Equipment that directs traffic between networks, commonly between a local network and an Internet access service. It differs from a Wi-Fi access point or a simple switch.
Put it into practice : Network
- SSID#
The visible name of a Wi-Fi network. Separate SSIDs can help distinguish employee, guest and connected-device access when the underlying network is properly segmented.
Put it into practice : Network
- VoIP#
Voice over Internet Protocol: calls carried over IP networks. Call quality relies on capacity, latency, jitter, packet loss, equipment and sensible prioritisation.
Put it into practice : Support
- Zero trust#
A security approach that verifies identity, device posture and permissions for each access request instead of trusting a network simply because it is internal.
Put it into practice : Solutions
NIST SP 800-207: Zero Trust Architecture
Technical reference in English · Source checked on- RTO#
Target time to restore a service after an interruption. Define it for a business service and check it during a recovery exercise.
Put it into practice : Business
NIST SP 800-34 Rev. 1: Contingency Planning
Technical reference in English · Source checked on- RPO#
Maximum acceptable data loss, expressed as time between the last recoverable state and the incident.
Put it into practice : Business
NIST SP 800-34 Rev. 1: Contingency Planning
Technical reference in English · Source checked on- End of support#
Point after which a supplier no longer guarantees some fixes or assistance for a device or version. Check the exact product and contract.
Put it into practice : Solutions
- CGNAT#
Sharing one public IPv4 address among multiple subscribers. Incoming connections may be restricted; check public IP, IPv6 or an appropriate relay for the intended use.
Put it into practice : Internet
- MTU#
Maximum packet size on a link, in bytes. A path or VPN mismatch can prevent some exchanges even when a connection appears active.
Put it into practice : Internet
- DNSSEC#
Signatures used to verify the authenticity of DNS data. It does not encrypt queries and requires correct key and delegation management.
Put it into practice : Support
IETF — RFC 4033: DNS Security
Technical reference in English · Source checked on- VLAN#
Logical separation of networks on Ethernet infrastructure. Routing and filtering rules are also needed to control communication.
Put it into practice : Network
- Latency median#
Middle value of sorted received replies; with an even count, the average of the two central values. Report it with the number of replies and probes without a reply.
Put it into practice : SupportInternet
NIST — Percentiles
Technical reference in English · Source checked on- Latency P95#
95th percentile of received replies. The nearest-rank method selects the value at ceiling(0.95 × count). It describes the upper distribution, without measuring jitter or guaranteeing future results.
Put it into practice : SupportInternet
NIST — Percentiles
Technical reference in English · Source checked on- PMTUD#
Path MTU discovery finds a usable IP packet size along a route. A tunnel can reduce this size. Filtering required ICMP messages can disrupt discovery.
Put it into practice : NetworkSupport
IETF — RFC 8201: Path MTU Discovery for IPv6
Technical reference in English · Source checked on- TCP MSS#
Maximum TCP data size advertised by a receiver, excluding IP and TCP headers. It differs from MTU; options and encapsulation also need to be considered.
Put it into practice : NetworkSupport
IETF — RFC 9293: TCP
Technical reference in English · Source checked on- DNS TTL#
Time in seconds for which a DNS reply may be cached. Lowering it on the server does not change replies already stored. Negative answers also have a cache lifetime.
Put it into practice : BusinessSupport
IETF — RFC 2308: DNS Negative Caching
Technical reference in English · Source checked on- Captive portal#
An authorisation step on a guest network before full Internet access. Joining Wi-Fi does not mean this step is complete or that clients are isolated from one another.
Put it into practice : NetworkMobile
IETF — RFC 8910: Captive-Portal Identification
Technical reference in English · Source checked on
These definitions explain terminology; they do not confirm compatibility or availability of an offer.
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