IT Glossary · Networking
ILL stands for Internet Leased Line — a dedicated internet connection reserved exclusively for one business, with identical upload and download speeds and a contractual uptime guarantee. Unlike broadband, the bandwidth is not shared with anyone else.
In networking terms, an Internet Leased Line is a private point-to-point circuit running from your office to your service provider's nearest exchange or point of presence, then onto their internet backbone. The word "leased" is literal: you are renting a fixed slice of capacity on that fibre for the term of your contract, and it stays yours whether you use it or not. This is what engineers mean by a 1:1 or "uncontended" line — a 100 Mbps ILL delivers 100 Mbps at 4pm on a weekday exactly as it does at 3am, because no other subscriber shares that capacity. Consumer broadband works on the opposite principle: a single fibre feed is divided among many subscribers at contention ratios of anywhere from 1:8 to 1:50, so your real throughput depends on what your neighbours are doing. An ILL also runs symmetrically — 100 Mbps up as well as down — whereas broadband is deliberately lopsided, often giving you a tenth of your download speed for uploads. That asymmetry is invisible when you are browsing and painful the moment you host a video call, push a cloud backup, run a VPN, or operate any server your customers reach from outside. In India the acronym appears in three places you are likely to have seen it: ISP tariff sheets (where "ILL" distinguishes the business product from FTTH), enterprise RFPs, and TRAI/DoT licensing documents, where leased circuits are regulated separately from retail broadband.
Indian businesses moved to cloud-delivered software faster than they upgraded the pipe underneath it. A 40-person office running Zoho or Microsoft 365, taking customer calls over VoIP, joining Zoom or Google Meet calls, and backing up to AWS is placing continuous demand in both directions — precisely the pattern shared broadband handles worst. The failure mode is rarely a dead connection; it is a video call that degrades every afternoon, an ERP screen that takes eleven seconds to load, and a nightly backup that never finishes. Those are contention symptoms, and no amount of speed-test megabits fixes them. There is a compliance dimension too: CERT-In directions require Indian organisations to retain accurate logs and report incidents within six hours, which is materially easier when you hold static IPs and a provider-managed router than when your public IP rotates. The practical threshold most Indian SMEs hit is around 20-25 concurrent users on cloud applications, or the first day someone runs a customer-facing service from the office.
Related terms: Broadband, SD-WAN, MPLS, Last-Mile Connectivity, Static IP, Contention Ratio, SLA, Dark Fibre, FTTH, CPE
ILL is the abbreviation for Internet Leased Line. In telecom and networking documents it is sometimes written as "Internet Leased Circuit" or just "leased line", and all three refer to the same product: a dedicated, symmetric, SLA-backed internet connection sold to businesses. It is not related to the medical word "ill".
In a network diagram, ILL denotes the dedicated WAN link between a site and its internet service provider — a point-to-point circuit terminating on a managed router at your edge. Because the capacity is uncontended and the public IPs are static, an ILL is normally the link that carries VPN tunnels, VoIP trunks, and any inbound traffic to services you host. In multi-site designs it commonly serves as the primary underlay beneath SD-WAN, with a broadband or 4G/5G link as the secondary path.
In tier-1 commercial fibre zones on a 12-month contract: roughly ₹6,000-7,000/month for 10 Mbps, ₹12,000-20,000 for 30-50 Mbps, ₹25,000-38,000 for 100 Mbps, ₹40,000-45,000 for 200 Mbps, and ₹1,50,000 or more for 1 Gbps. Add 18% GST. Addresses outside an existing fibre footprint carry a one-time installation charge of ₹15,000-50,000 and take considerably longer to provision. Prices vary by city — Hyderabad and Chennai are usually the cheapest of the metros, Mumbai the most expensive.
Four differences that matter. Contention: an ILL is 1:1 and yours alone, broadband is shared at 1:8 to 1:50. Symmetry: an ILL uploads as fast as it downloads, broadband does not. SLA: an ILL carries a contractual uptime guarantee with compensation, broadband is best-effort. IP addressing: an ILL includes static public IPs, broadband is normally dynamic. An ILL costs roughly three to ten times more, which is why the sensible rule is to buy broadband until cloud applications, VoIP or hosted services make the shared line unreliable, then move.
Tata Communications, Airtel Business, Jio Business, BSNL and Vodafone Idea Business operate nationally. ACT Fibernet, Hathway and a range of regional operators compete in specific cities, often at lower prices where their fibre already reaches your building. There is no single best provider — the right answer is address-specific, because whoever already has fibre in or near your building will quote a shorter timeline and a lower install cost.
Two to four weeks if your building already sits in a live commercial fibre zone. Six to twelve weeks when fibre has to be extended to reach you. The engineering is rarely the delay — building permissions, society or landlord approvals, and municipal right-of-way clearances are what stretch the timeline, so start those conversations the day you sign.
99.5% on a standard single-link plan, which still permits about 3.6 hours of downtime a month. Premium plans reach 99.9% (roughly 43 minutes) or 99.99% (about 4 minutes), typically by adding a diverse second path. Read the mean-time-to-repair clause as carefully as the uptime figure: a four-hour MTTR with a same-day engineer is worth more in practice than a headline percentage backed by a two-day response window.
One is enough for most offices. Take two — from different providers, on physically diverse last-mile routes, with BGP failover on your edge router — when an hour offline costs you real money: contact centres, trading and payments, hospitals, and any business whose customers reach a service you host. Dual 100 Mbps lines run about ₹50,000-60,000/month combined and get you past 99.99% in practice.
Yes, and it is the most common enterprise design in India. The ILL becomes the high-quality underlay carrying latency-sensitive traffic such as voice, video and ERP, while cheaper broadband or 4G/5G links carry bulk internet and act as failover. SD-WAN steers each application to the right path automatically, which lets multi-branch businesses keep leased-line quality where it counts without buying leased lines everywhere.
Yes — 18% GST on the monthly rental and on the one-time installation charge. Registered businesses can normally claim it as input tax credit, so compare vendors on the pre-GST figure. Ask for the HSN/SAC code on the invoice; telecom services fall under SAC 9984 and your accounts team will need it.
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