Network testing terms in plain words

A burst of frames at line rate with minimum gaps. The test finds the longest burst the device absorbs without loss.

Link speed times RTT, the amount of data in flight on a path. A TCP window smaller than the BDP caps throughput.

A fast hello that notices a dead link or neighbour within tens of milliseconds and tells routing to switch over

Routing protocol between networks and providers. A full IPv4 internet table is close to a million routes.

The heartbeat MEPs exchange in Ethernet OAM. When several in a row go missing, a fault is raised.

The bandwidth a provider guarantees for a service. Traffic within it must pass with the agreed delay and loss.

The time a network needs to find and use a new path after a link or node fails. Traffic lost in that time is what users notice.

How many new sessions a firewall or load balancer sets up each second

The Y.1731 frame that measures two-way delay between MEPs

The unit whose behaviour the test measures. Everything else on the bench is the measuring side.

Traffic spread over several paths of the same cost by a hash of packet headers. A poor hash loads one path and leaves the others idle.

A switch marks packets instead of dropping them, and the sender slows down

Bandwidth above the CIR that the network carries when it has room, with no delay or loss guarantee

A BGP control plane for layer 2 and layer 3 VPNs. In data centers it usually runs with VXLAN.

Extra bits that let the receiver rebuild lost or damaged data without asking for it again

The share of frames the generator sent that never came out of the device

Two units in a cluster, one takes over when the other fails. The test measures how much traffic is lost during the switch.

Checks traffic inline against signatures and blocks what matches

Link-state routing protocol common in operator cores. Close to OSPF in idea, it runs directly over layer 2.

Variation in delay from one packet to the next. Voice and video suffer from it long before the average delay looks bad.

A number agreed before the test that decides pass or fail, for example zero loss at 40 Gbit/s or failover under 50 ms

The full speed of a port. At 10GbE that is about 14.88 million 64-byte frames per second.

The edge of an Ethernet OAM domain that sends and answers checks and measurements

Voice or video quality on a scale from 1 to 5, estimated from loss, delay and jitter

Packets are forwarded by short labels instead of full IP lookups. Operators run VPNs and traffic engineering on it.

The largest packet a link carries without fragmentation. A mismatch along the path often shows up as slow or stuck sessions.

A firewall that sees applications and users and adds IPS, URL filtering and TLS inspection. Throughput falls as each feature is switched on.

The software of a switch or router, for example SONiC on white-box hardware

Tools built into a protocol to check and measure a live link

Link-state routing inside one network. Each router knows the whole topology and computes the shortest paths itself.

Pauses one traffic class on a link so lossless traffic such as RoCEv2 is not dropped under load

IETF methodology for benchmarking routers and switches: throughput without loss, latency, frame loss rate and back-to-back bursts, for each frame size

IETF methodology for benchmarking LAN switches: full-mesh forwarding, behaviour under congestion, MAC table size and address learning rate

The earlier IETF methodology for firewall performance: connection setup rate, concurrent connections and HTTP throughput. RFC 9411 replaced it for modern devices.

The RFC 2544 benchmarks redone for IPv6, with IPv6 frame sizes and extension headers

Framework for TCP throughput testing: shows what an application really gets over a path, given the RTT, the bottleneck and the TCP window

IETF methodology for benchmarking next-generation firewalls and other security devices with real application traffic and the security features switched on

Servers read and write each other's memory over UDP with microsecond latency. AI clusters and storage fabrics run on it.

How long a packet takes to reach the far end plus the time the reply takes to come back

Branch WAN run by policy: the edge picks MPLS, internet or LTE for each application, based on the quality it measures on each link

The figures a provider commits to, such as availability, delay and loss, and what happens when they are missed

Splits one physical network card into several virtual ones, so virtual machines skip the software switch

The encryption under HTTPS and most application traffic. Decrypting it for inspection is the heaviest job a firewall does.

Broadband Forum test plan for Wi-Fi access points: throughput, range, many clients at once, roaming and coexistence with neighbouring networks

What the generator sends: the mix of applications, packet sizes and session rates. We build it from your network data where we can.

The 5G core node that carries subscriber traffic between the radio network and the internet

Carries layer 2 frames inside UDP across an IP network, so one segment can stretch over racks and sites

A real link recreated on the bench: delay, jitter, loss and a bandwidth cap set for each direction. The device meets a long or poor link without leaving the lab.

ITU-T test for turning up Ethernet services: each service is checked against its CIR, EIR, delay, jitter and loss, first step by step, then all together in a long run

ITU-T OAM for Ethernet: continuity checks plus delay, delay variation and frame loss measured between MEPs on a live link