Ruankao Network Planning Designer (Senior) key terms

The central processing unit is the main processor in a computer. It fetches instructions, decodes them, and carries out arithmetic, logic, and control operations while coordinating other components.

Temporary, volatile computer memory that holds programs and data currently in use. Its contents disappear when power is lost, but it allows fast reading and writing.

A small, fast memory area close to the processor that stores frequently used instructions and data. It reduces average access time by keeping likely-needed information nearby.

The quantity identified by one memory address, such as a byte or a word. A bus-width calculation requires this convention before converting address counts into byte capacity.

A seven-layer framework describing how network functions are divided, from physical transmission up to application services, used as a common vocabulary for comparing protocols and equipment across vendors.

The process in which each protocol layer adds its own header (and sometimes trailer) to data received from the layer above, so that peer layers on the receiving host can interpret and strip that information.

Protocol Data Unit: the named chunk of data at a given layer, such as frame at the data link layer, packet at the network layer, and segment at the transport layer. Naming makes troubleshooting discussions precise.

The specified maximum protocol data size for a link or path model. Encapsulation reduces available payload, and exceeding a limit may require source adaptation, suitable fragmentation or an error response depending on protocol and flags.

Circuit switching reserves a dedicated path for the whole session, while packet switching forwards independently addressed packets over shared links. The contrast explains latency, efficiency, and why data networks use statistical multiplexing.

A forwarding behaviour in which a device receives an entire frame or packet, checks it (for example via FCS or header validation), and only then transmits it onward, trading a little latency for error filtering.

Copper cabling graded by bandwidth performance, such as Cat5e, Cat6, and Cat6A, with different supported frequencies and distances. Category choice determines whether gigabit or 10-gigabit Ethernet can run over the installed link.

A transmission medium carrying data as light pulses through glass or plastic core, immune to electromagnetic interference and supporting long distances. Single-mode suits campus and carrier links; multimode suits building backbones and data centres.

The weakening of a signal as it travels along a medium, measured in decibels. It sets the maximum usable distance for copper and fiber links and drives the need for repeaters or optical amplifiers.

Rules for representing binary data as signal changes: line coding shapes voltage or light levels on a link, while modulation varies a carrier's amplitude, frequency, or phase to carry bits over analogue or wireless channels.

Combining multiple independent signals onto one medium, for example by dividing time (TDM), frequency (FDM), wavelength (WDM), or code space. It underpins carrier trunks and optical backbone capacity planning.

Cyclic redundancy check is an error-detecting code computed over frame bits; the resulting frame check sequence is appended by the sender and recomputed by the receiver, which discards frames that fail the check.

The standard link-layer structure containing destination and source MAC addresses, a type or length field, payload, and a frame check sequence, with preamble and inter-frame gap handling at the physical boundary.

A link-layer identifier commonly48bits for Ethernet, which may be globally assigned, locally assigned or randomized. Switches learn source-address locations within the relevant VLAN and forward under the actual filtering policy.

A logical Layer 2 partition of a switch into separate broadcast domains, identified by a tag such as 802.1Q. VLANs isolate traffic and simplify moves, but require routing or a Layer 3 switch to communicate between them.

A link carrying traffic for several VLANs at once, normally by inserting an 802.1Q tag into each frame. Both ends must agree on tagging and allowed VLAN lists or traffic silently disappears.

Spanning Tree Protocol prevents Layer 2 loops by electing a root bridge and blocking redundant ports, leaving a loop-free tree. Rapid variants converge faster; without it, broadcast storms can saturate a campus network.

The set of devices that receive a frame sent to the broadcast address. Routers and VLAN boundaries delimit broadcast domains, which matters because excessive broadcast traffic degrades every host in the domain.

Wireless LAN standards define radio access in the 2.4, 5, and 6 GHz bands; because stations cannot reliably detect collisions, they use carrier sense multiple access with collision avoidance, including acknowledgements and backoff.

An SSID names a wireless network; clients associate with an access point broadcasting it. Roaming hands a client between access points, ideally with fast key exchange so the session survives without re-authentication delay.

Dotted-decimal 32-bit addresses split into network and host parts by a prefix length or mask. Subnetting borrows host bits to create smaller networks, and correct mask and gateway planning is fundamental to routing design.

Classless Inter-Domain Routing expresses prefixes as address plus length, such as 192.168.10.0/24, and allows route aggregation. It replaced fixed address classes and is the notation used throughout routing configuration.

The router address a host uses when the destination is outside its own subnet. A wrong or missing gateway, or one on a different subnet, is a common cause of partial connectivity.

Address Resolution Protocol maps a known IPv4 address to a link-layer MAC address by broadcasting a request and caching the reply. Stale or spoofed ARP entries cause intermittent loss or man-in-the-middle attacks.

Internet Control Message Protocol carries error and diagnostic messages between IP nodes, powering ping and traceroute. Many networks filter selected ICMP types, so blocked replies do not always mean a host is down.

A diagnostic technique that sends packets with increasing time-to-live values and collects ICMP time-exceeded replies, revealing each router hop. It helps locate where paths diverge or where filtering begins.