Glossary
Plain-English definitions of the phone-system and networking terms used in these docs. Anywhere you see a dotted-underlined word, hover or tap it for the same quick definition.
- ACD
- Automatic Call Distribution — the system that lines callers up in a queue and hands each one to the next available agent.
- codec
- The method used to compress and decompress voice audio for a call — e.g. G.711 (standard quality) or G.722 (HD/wideband).
- DHCP
- Dynamic Host Configuration Protocol — the service that automatically gives each device on your network its settings (like its address) when it connects.
- DID
- Direct Inward Dial — a phone number that reaches your system from the outside world. You point each DID (number) at where its calls should go.
- digest auth
- A password check where the secret is never sent in the clear — the two sides prove they know it using a one-time challenge.
- DTMF
- The touch-tones a phone makes when you press its keypad — how a caller 'presses 1 for sales'.
- extension
- A short internal number (like 101) that identifies one phone or person on your system.
- HMAC
- A cryptographic signature that lets the receiver verify a message really came from you and wasn't tampered with in transit.
- IAX2
- Inter-Asterisk eXchange v2 — an alternative calling protocol that sends everything over a single connection, which makes it simpler to get through routers than SIP.
- IVR
- Interactive Voice Response — the automated menu that answers a call and says 'press 1 for sales, 2 for support'. Also called an auto attendant.
- MAC address
- A permanent hardware ID printed on every network device (like a phone). Your system uses it to recognise which phone is which.
- NAT
- Network Address Translation — the feature in your internet router that lets all the devices in your office share one public internet address. Great for the internet, occasionally fiddly for phone calls.
- PIN
- Personal Identification Number — a short numeric code used to authorise something, like joining a conference or checking voicemail.
- REGISTER
- The message a phone or trunk sends to say 'I'm here, send my calls to this address'. Phones re-register periodically to stay reachable.
- RTP
- Real-time Transport Protocol — the internet standard that carries the actual voice audio during a call (SIP sets the call up; RTP carries the talking).
- SDP
- Session Description Protocol — the little bit of text phones exchange to agree on how to send audio (which addresses, ports and codecs to use).
- SIP
- Session Initiation Protocol — the most common internet standard for setting up phone calls. It's how phones and providers say 'ring this number', 'answer', and 'hang up'.
- T.38
- The international standard for sending faxes reliably over the internet instead of a traditional phone line.
- TFTP
- Trivial File Transfer Protocol — a very simple, old method some phones use to download their configuration file when they start up.
- trunk
- The connection between your phone system and a phone-service provider — the pipe that carries calls to and from the outside world.
- VLAN
- Virtual LAN — a way to split one physical office network into separate logical networks, e.g. keeping phones on their own network away from computers.
- webhook
- A way for your system to notify another program instantly when something happens, by sending it an HTTP message — the reverse of that program having to keep asking.
- WebRTC
- The technology built into modern web browsers that lets them make real phone/video calls with no plugin or app to install.