Networking Glossary: Plain-English Definitions
Plain-English definitions for the words used in StashGrid lessons. Each word has two levels: In plain words (what it is, with an everyday comparison) and The technical version (what you would say in an exam or to a colleague). Where an official standard exists, the Official spec line links to it. In lessons, hover over (or tap) a dotted word for a popup of both levels.
Jump to: 169.254.x.x address · Band and channel · Batch · Bit and byte · Broadcast address · Command prompt · Command switch · curl · dBm · Default gateway · DHCP · DNS · DNS record types · DNS resolver · DNSSEC · Domain name · DORA · Dual-stack · Email header · Hop · ICMP · IP address · ipconfig · IPv4 · IPv6 · Latency · Lease · NAT · Network classes · nslookup · Octet · Packet · Packet loss · Phishing · ping · Powers of 2 · Private IP address · Public IP address · RDAP · Registrar · RFC · Router · Slash notation · SPF, DKIM and DMARC · SSID · Subnet · Subnet mask · tracert · TTL · VLAN · whois · Wireshark
169.254.x.x address
In plain words: The “I could not get a real address, so I made one up” address. You are connected but cannot get online.
The technical version: APIPA / link-local address. Windows assigns itself one in 169.254.0.0/16 when DHCP does not answer.
Official spec: RFC 3927 (link-local)
Band and channel
In plain words: Wi-Fi uses lanes of radio. If your neighbour is in the same lane, you slow each other down.
The technical version: 2.4 GHz and 5 GHz are bands, split into channels. On 2.4 GHz only 1, 6 and 11 do not overlap.
Batch (.bat) file
In plain words: A saved to-do list for the computer. Double-click it and it does the steps in order.
The technical version: A plain-text script of command prompt commands, run in sequence. It can run anything, so only run ones you wrote or have read.
Bit and byte
In plain words: A bit is one on-or-off switch. Eight of them make a byte.
The technical version: The smallest unit of data: 0 or 1. An IPv4 address is 32 bits, grouped as four 8-bit octets.
Broadcast address
In plain words: The last address in a neighbourhood, used to shout to everyone at once.
The technical version: The highest address in a subnet. A packet sent to it goes to every device in the subnet, so it cannot be assigned to one device.
Command prompt (cmd)
In plain words: A window where you type instructions instead of clicking. The shortcut name is cmd.
The technical version: Windows’ text-mode shell (cmd.exe). PowerShell is a newer one. On a Mac the equivalent is Terminal.
Command switch (option)
In plain words: A little extra word after a command that changes how it works, like setting the oven to “fan.”
The technical version: An argument starting with - or / that modifies a command, for example the -d in tracert -d. Each command has its own list.
curl
In plain words: A small tool that fetches a web address for you from the command prompt and prints what comes back, like a browser with no window.
The technical version: A command-line program for transferring data over HTTP and other protocols. Built into current Windows (as curl.exe), macOS and Linux.
dBm (signal strength)
In plain words: How strong the Wi-Fi signal is. The number is negative, and closer to zero is stronger.
The technical version: Decibels relative to a milliwatt. Around −50 is excellent, −67 is good for video, −80 is weak, −90 is unusable.
Default gateway
In plain words: The door out of your network. It is your router.
The technical version: The router address your device sends traffic to when the destination is not on its own subnet. At home, often 192.168.1.1.
DHCP (Dynamic Host Configuration Protocol)
In plain words: The front desk of your network. When a phone or laptop joins, DHCP hands it an address, like a hotel handing you a room key, so nobody types it in by hand.
The technical version: Dynamic Host Configuration Protocol. A service, normally on your router, that leases each device an IP address, subnet mask, gateway and DNS server automatically.
Official spec: RFC 2131 (DHCP), RFC 2132 (options), RFC 8415 (DHCPv6)
DNS (Domain Name System)
In plain words: The internet’s phone book. You type an easy name like stashgrid.ai, and DNS looks up the number address that computers really use, the way a street address tells the mail carrier where to go.
The technical version: Domain Name System. A worldwide set of servers that turns names into IP addresses. Your device asks a DNS server (usually your router or your provider) every time you visit a site.
Official spec: RFC 1034 (concepts), RFC 1035 (implementation)
DNS record types (A, AAAA, MX, NS, TXT)
In plain words: The different kinds of answer DNS can give: an address, a mail server, who is in charge, or a note.
The technical version: A maps a name to an IPv4 address, AAAA to an IPv6 address, CNAME to another name, MX to mail servers, NS to the zone’s name servers, TXT to free text such as SPF policies.
DNS resolver
In plain words: The helper that looks up names for you, like a receptionist who knows who to ask. Your router or internet provider normally runs it.
The technical version: A server that answers DNS questions for clients, asking other DNS servers if it does not already know and remembering answers for a while (caching).
DNSSEC
In plain words: A tamper-proof seal on DNS answers. It lets your computer check that a website’s address answer was not faked on the way. It does not hide or encrypt anything.
The technical version: DNS Security Extensions. Adds digital signatures (RRSIG, DNSKEY, DS records) forming a chain of trust from the root zone down. A validating resolver rejects answers whose signatures do not check out.
Official spec: RFC 4033 (overview), RFC 4034 (records), RFC 4035 (protocol), RFC 9364 (summary)
Domain name
In plain words: The easy-to-read name of a website or email sender, like example.com. In an email from sam@example.com, the domain is the part after the @.
The technical version: A name registered in the global naming system, made of labels separated by dots, and resolved to addresses by DNS.
DORA
In plain words: The four-step chat a device has to get an address: it asks, an offer comes back, it says yes, and the server confirms.
The technical version: Discover, Offer, Request, Acknowledge: the four DHCP messages, sent over UDP ports 68 (device) and 67 (server).
Dual-stack
In plain words: Using the old and new kinds of address at the same time, like a shop with a front door and a new side door.
The technical version: A host or network running IPv4 and IPv6 together. It is how the transition is done, because IPv6 is not backward compatible with IPv4.
Official spec: RFC 4213 (transition)
Email header
In plain words: The hidden “envelope” of an email that shows where it really came from. The name you see on top can be faked; the envelope is much harder to fake.
The technical version: Metadata lines (From, Reply-To, Return-Path, Received, Authentication-Results) added by the sender and each mail server along the way.
Hop
In plain words: One stop along the road between you and a website, like one town on a road trip.
The technical version: One router-to-router jump. A path of 12 hops passes through 12 routers or gateways.
ICMP (Internet Control Message Protocol)
In plain words: The internet’s way of sending tiny “are you there?” and “that did not arrive” notes between devices.
The technical version: Internet Control Message Protocol. Carries status and error messages. ping and tracert both use it. Some routers and firewalls ignore it on purpose, so silence is not always a fault.
Official spec: RFC 792 (ICMP)
IP address
In plain words: A device’s street address on a network: four numbers separated by dots, like 192.168.1.37.
The technical version: A 32-bit number (IPv4), written as four octets. It combines which network the device is on and which device it is on that network.
Official spec: RFC 791 (IPv4)
ipconfig
In plain words: Shows your computer’s network settings, including its address.
The technical version: A Windows command that displays IP configuration; /all adds details like DHCP server and lease times, /release and /renew control the DHCP lease.
IPv4
In plain words: The original kind of internet address: four numbers with dots, like 192.168.1.37. There are only about 4.3 billion of them, and they ran out.
The technical version: 32-bit addresses (about 4.3 billion). The free pools of the regional registries ran out between 2011 and 2015, which is why NAT is everywhere.
IPv6
In plain words: The newer kind of internet address, long enough that we will never run out. It looks like 2001:db8::1, with letters and colons. Windows has it switched on already.
The technical version: 128-bit addresses written as eight groups of hex, defined in RFC 8200 and RFC 4291. Devices usually run IPv4 and IPv6 side by side (dual-stack).
Official spec: RFC 8200 (IPv6), RFC 4291 (addressing)
Latency (ping time)
In plain words: How long a message takes to get there and back. Lower is better.
The technical version: Round-trip time in milliseconds. Under about 50 ms feels instant for most use; games and calls notice high or jumpy latency.
Lease
In plain words: An address that is lent to you for a while, like a library book you have to renew.
The technical version: The time a DHCP server lets a device keep an address before it must renew. Home routers often use hours to a day.
NAT (Network Address Translation)
In plain words: What your router does to let every device in the house share one internet address, like a receptionist forwarding calls to the right desk.
The technical version: The router rewrites private source addresses to its public address and remembers each conversation so replies return to the right device.
Official spec: RFC 3022 (NAT)
Network classes (A, B, C)
In plain words: The original small, medium and large address sizes: A is huge, B is big, C is small.
The technical version: Class A starts 1 to 126 (default /8), B starts 128 to 191 (/16), C starts 192 to 223 (/24). Modern networks use any slash, but exams and defaults still use classes.
nslookup
In plain words: A tool that asks DNS “what is the address for this name?” and shows you the answer.
The technical version: A command-line DNS query tool built into Windows (and available on Mac and Linux). Can request specific record types and choose which server to ask.
Octet
In plain words: One of the four numbers in an address. It is eight switches, so it can count from 0 to 255.
The technical version: An 8-bit group. 2 to the power of 8 gives 256 values, 0 to 255.
Packet
In plain words: A small parcel of data with an address on it. Everything you do online is sent as lots of tiny parcels.
The technical version: A unit of data with a header (addresses, TTL, protocol) and a payload. Large data is split into packets and reassembled at the destination.
Packet loss
In plain words: Messages that were sent but never answered, like letters that get lost in the mail.
The technical version: The percentage of packets that get no reply. Steady loss to the final destination causes stutter, freezes and slow pages.
Phishing
In plain words: A fake email, text or website that pretends to be someone you trust, like your bank, to trick you into giving up a password or money.
The technical version: Social engineering by message. Typical signs are urgency, a mismatched sender domain, a link that does not go where it says, and a request for credentials or payment.
ping
In plain words: A quick “are you there?” knock on another device’s door that times how fast the answer comes back.
The technical version: Sends ICMP echo requests and reports replies and round-trip time. Windows sends 4 by default; macOS and Linux keep going until you stop them.
Powers of 2
In plain words: Numbers that double each time: 1, 2, 4, 8, 16, 32, 64, 128. Each switch in an octet is worth one of them.
The technical version: Each bit position is worth twice the one to its right. Add the values of the bits that are on to get the octet value.
Private IP address
In plain words: An address used inside your home or office only, like an apartment number: many buildings reuse the same ones.
The technical version: Reserved ranges: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. Not routable across the internet.
Official spec: RFC 1918 (private addresses)
Public IP address
In plain words: Your home’s address as the rest of the internet sees it, like the street address of the whole building.
The technical version: The routable address your provider gives your router. Every device inside shares it through NAT.
RDAP (Registration Data Access Protocol)
In plain words: A modern lookup for “who registered this website name, and when?” The most useful part is the date, because brand-new names are a warning sign.
The technical version: A standard, web-based (HTTPS and JSON) replacement for whois. Gives registration dates, registrar, name servers and status in a consistent format.
Official spec: RFC 9082 (query format), RFC 9083 (responses)
Registrar
In plain words: The shop a website name was bought from.
The technical version: An accredited company that registers domain names for customers, such as GoDaddy or Namecheap. It is not necessarily where the website is hosted.
RFC (Request for Comments)
In plain words: The official instruction manual for an internet technology, written and published by the engineers who designed it. Free for anyone to read.
The technical version: Numbered documents from the IETF and RFC Editor that define internet standards. Examples: RFC 1035 (DNS), RFC 2131 (DHCP), RFC 8200 (IPv6).
Official spec: RFC 2026 (how standards are made)
Router
In plain words: The box that connects your home to the internet and passes data between networks.
The technical version: Forwards packets between networks. At home it is usually also the Wi-Fi access point and the DHCP server.
Slash notation (CIDR)
In plain words: A short way to write the mask: /24 means the first 24 switches are the network.
The technical version: Classless Inter-Domain Routing notation. The number after the slash is the count of network bits, so /24 equals 255.255.255.0.
Official spec: RFC 4632 (CIDR)
SPF, DKIM and DMARC
In plain words: Three checks that ask: did this email really come from the company it says it did? A “fail” is a warning sign.
The technical version: SPF lists servers allowed to send for a domain, DKIM is a digital signature on the message, and DMARC says what to do if either fails. Shown as pass or fail in the header.
SSID
In plain words: The name of a Wi-Fi network, the one you pick from the list.
The technical version: Service Set Identifier: the network name broadcast by an access point.
Subnet
In plain words: A smaller neighbourhood carved out of a bigger network.
The technical version: A range of addresses sharing the same network prefix. Subnetting divides a network to organise traffic and control who can talk to whom.
Subnet mask
In plain words: A number that tells a device which part of an address is the street (the network) and which part is the house number (the device).
The technical version: A 32-bit pattern of ones then zeros, written like 255.255.255.0. Ones mark the network part, zeros the device part.
tracert
In plain words: Shows the road your data takes to a website, one stop at a time.
The technical version: The Windows traceroute command. Sends ICMP echo requests with rising TTL values so each router on the path reports back. Macs and Linux use traceroute.
TTL (Time To Live)
In plain words: A countdown stamped on every packet so it cannot wander the internet forever.
The technical version: A counter that drops by one at every router. At zero the router discards the packet and replies with an ICMP time-exceeded message. Traceroute uses this to make each router identify itself. (DNS records have a different TTL: how long an answer may be remembered.)
Official spec: RFC 791 (IPv4 header)
VLAN
In plain words: A way for one network switch to act like several separate ones, so groups of devices cannot see each other.
The technical version: Virtual LAN. Splits a switch into separate broadcast domains using tags. Usually paired with one subnet per VLAN.
whois
In plain words: An old lookup that tells you who registered a website name and when.
The technical version: A text protocol (port 43) for domain and IP registration data. Much personal detail is now hidden for privacy. RDAP is its modern replacement.
Official spec: RFC 3912 (whois)
Wireshark
In plain words: A free tool that lets you watch the actual messages travelling over your network, like a window onto the mail room.
The technical version: A packet analyser that captures traffic on an interface and decodes it by protocol.
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