Help · Jargon buster

PlainEnglish.

Every acronym we throw around, defined in one sentence.

Telecom is built on three-letter acronyms layered on three-letter acronyms. This is the plain-English version — what each term means, why it matters, and which Giant page goes deeper on it. Skip the jargon, get the gist. Specific question? Search the whole site or ring us.

A

ADSLAsymmetric Digital Subscriber Line: Old-style broadband over a full copper pair. Up to 24 Mbps download, 1 Mbps upload. Being phased out — see PSTN switch-off.

B

BBUBattery Back-Up Unit: A small UPS that keeps a digital phone working in a power cut. Free for vulnerable customers under Ofcom GC C5; £4.99/mo add-on otherwise.
BGPBorder Gateway Protocol: The internet's routing protocol — how networks tell each other which IP ranges they're responsible for. Wholesale customers can have us announce their BGP routes.

C

CGNATCarrier-Grade Network Address Translation: When your ISP shares one public IPv4 address across hundreds of customers because they don't have enough to go around. Means inbound ports don't work, port forwarding does nothing, and you can't self-host. L2TP is the usual escape hatch.

D

DDIDirect Dial-In: A unique inbound phone number that rings a specific extension, not the main switchboard. Standard on VoiceCloud.

E

eSIMEmbedded SIM: A SIM that lives in software on the phone — no physical card. Activated by scanning a QR code; live in ~90 seconds.
Ethernet: Either the network protocol used for wired connections, or a 'leased line' product where Giant deploys a dedicated business-grade fibre to the premises (no contention, hard SLA).

F

FTTCFibre To The Cabinet: Fibre runs to the green street cabinet, copper for the final stretch into your home. Up to 80 Mbps down / 20 Mbps up. Being replaced by FTTP as Openreach lights up new postcodes. See also FTTP.
FTTPFibre To The Premises: Full fibre — glass cable all the way into your home. Speeds 100 Mbps to 8 Gbps symmetric depending on the wholesale carrier. Every Giant residential broadband plan is FTTP where available.

G

Giga Boost: Giant-specific — temporarily uncap a residential line for a download-heavy evening (big game patches, OS updates). Self-service via the customer portal, no charge. Available on selected packages.

I

ISDNIntegrated Services Digital Network: Pre-internet business voice technology over copper. Off-sale since 2025, fully switched off January 2027. Migrations land on VoIP.
ISPInternet Service Provider: Companies that sell broadband to end customers. Giant is an independent UK ISP.

L

L2TPLayer 2 Tunnelling Protocol: Standard VPN-style tunnel protocol that lets any router get a different public IP from a different network. Giant's L2TP service uses it to deliver a real static IPv4 + IPv6 /48 to any UK broadband line — useful for escaping CGNAT, self-hosting, or keeping a fixed IP when you switch ISP.

M

Mbps / Gbps: Megabits and Gigabits per second — the bandwidth units used in broadband. 1 Gbps = 1,000 Mbps. Note bits, not bytes — divide by 8 for download speeds in MB/s.
MNO / MVNOMobile Network Operator / Mobile Virtual Network Operator: MNO = owns the masts (EE, O2, Vodafone, Three in the UK). MVNO = rides someone else's masts under a different brand. Giant Mobile is an MVNO.

O

OTSOne Touch Switch: Ofcom rule (12 Sep 2024) requiring the new broadband provider to handle the whole switch — old provider notified, cutover scheduled, no double-billing. We do this automatically.

P

PACPorting Authorisation Code: Text PAC to 65075 from a mobile to get the code that lets you take your number to a new carrier. Free, returned in seconds, valid 30 days.
Port-in / port-out: Moving a phone number between providers. Free for mobile; £12 ex VAT per number for VoIP / landline. Number stays the same.
PSTNPublic Switched Telephone Network: The traditional analogue voice network running over copper. Being switched off nationally by January 2027. Replacement is digital voice (VoIP) over your broadband.

Q

QoSQuality of Service: Network-level traffic prioritisation — giving voice or gaming packets head-of-queue treatment. We don't throttle or QoS residential traffic at the ISP level.

S

SIPSession Initiation Protocol: The protocol VoIP uses to set up calls. Most modern desk-phones, softphones and PBXs speak SIP.
SIP-to-SIM: Giant-specific — attach a VoiceCloud extension to a real mobile SIM. The business DDI rings the mobile over the cellular voice channel (not over data, not via an app).
SoGEASingle Order Generic Ethernet Access: FTTC broadband without the bundled analogue phone line. Used during PSTN migration when a customer needs broadband but doesn't want the legacy voice channel.
STACService Termination Authorisation Code: Like PAC but for cancelling a mobile without porting the number. Text STAC to 75075. Free, instant.
Symmetric: Upload speed equals download speed. Standard on full fibre (FTTP) tiers from CityFibre / Netomnia / LCR Connect. Important for streaming, video calls, file sync. See also FTTP.

U

UPRNUnique Property Reference Number: A national ID for every UK property. Used by Ofcom's coverage data and by Openreach's order systems. We pull coverage by postcode and aggregate per UPRN.

V

VoIPVoice over Internet Protocol: Phone calls carried as data over your broadband. Replaces analogue PSTN. Residential = Giant Home Phone. Business = VoiceCloud.
VoLTEVoice over LTE: Mobile calls carried over 4G instead of the older 2G/3G voice channel. HD-quality, faster call-connect, lower latency. Default on every modern phone.

W

WiFi calling: Your mobile makes / receives calls and texts over your home WiFi when cell signal is weak. Same number, same dial. Works on Giant SIMs across all major networks.

X

XGS-PON10-Gigabit-capable Symmetric Passive Optical Network: The latest generation of full-fibre access technology. Symmetric 10 Gbps per shared fibre. Our fastest full-fibre network runs XGS-PON — that's what delivers our 8 Gbps tier.

Related help

All help topics

Pair withOne Touch Switch·PSTN switch-off·Number porting·Search the site

Missing a term? Tell us.

If we use an acronym anywhere on the site without defining it, that's a bug. Email help@giant.net.uk and we'll add it.

Search the site Suggest an entry