An Internet Service Provider (ISP) is a company that connects homes and organizations to the internet. It provides the access line to your location (or arranges one), carries your traffic across its own network and hands it to the rest of the internet, usually along with IP addresses, support and, for business services, a service level agreement. ISPs range from local fiber and wireless operators to national cable and telephone companies and global backbone carriers.
At a glance
- An ISP sells internet connectivity: the access connection, capacity on its network and reachability to the rest of the internet.
- Services range from best-effort broadband to dedicated internet access with committed rates and SLAs.
- Some ISPs own the line to your building; others lease it from another carrier.
- ISPs reach the rest of the internet through peering with other networks, paid transit, or both.
- Which ISPs can serve a site depends on the address, so availability is the first question for any new location.
What problem it solves
Almost every business application now depends on reliable internet access: cloud software, phones, video meetings, payments, remote access and backups. No organization builds its own network to every destination on the internet. An ISP solves that by connecting your site to its network and, through its relationships with other networks, to everywhere else.
For a buyer, the practical problem is choosing the right ISP and service for each site. Providers differ in what they can deliver at a given address, how they price it, how fast they repair faults and how well their network reaches the services you use. A poor choice shows up as slow installs, unreliable service or long outages with nobody accountable.
How it works
Access. The ISP connects your site using fiber, cable, copper, fixed wireless, cellular or satellite. This last mile segment is often the main factor in cost, lead time and reliability. If the ISP’s network does not reach your building, it may build to it or lease access from another carrier.
The ISP’s network. Your traffic is carried to the ISP’s routers and across its regional and backbone network. Business services often include static IP addresses and the option to run routing protocols with the provider.
Reaching the rest of the internet. No single ISP connects directly to every network. ISPs exchange traffic with each other through peering, often at an internet exchange point, and buy IP transit from larger networks to reach destinations they do not peer with. How well an ISP is connected affects the latency and reliability of the routes to the services you use.
Service and support. Business ISPs usually commit to availability and repair-time targets in an SLA and provide a support line or portal for faults. Residential-grade services generally offer fewer commitments.
For help comparing providers at your addresses, see our internet access solution page.
When it matters for buyers
- Opening or moving an office. Check which ISPs serve the building and their lead times before signing the lease.
- Adding redundancy. A backup connection is most useful when it comes from a different ISP on a different physical path.
- Moving to cloud or UCaaS. These services depend on the quality of your ISP’s connection, not just its speed.
- At renewal. Competition may have changed since the contract was signed; new providers may now serve the building.
- Managing many sites. Dealing with dozens of local ISPs adds billing and support overhead, which some businesses solve through an aggregator or managed service.
Questions to ask vendors
- Is our address on your own network, or will you use another carrier for the last mile? If so, which one?
- What is the realistic installation lead time, and are construction or building permissions needed?
- Is the bandwidth committed or best-effort, and is it symmetrical?
- What availability and repair commitments are in the SLA, and how are credits claimed?
- How many static IP addresses are included, and is IPv6 supported?
- How is your network connected to the cloud and SaaS providers we rely on?
- Who do we call when the service is down, and what hours is that support available?
How it differs from an IP transit provider
Every ISP sells internet access, but the term usually refers to providers serving end users: homes and business locations. An IP transit provider sells internet reachability to other networks, such as smaller ISPs, hosting companies and enterprises that run their own routing, usually as a port in a data center. Many large carriers do both. A business site buys internet access from an ISP; an organization with its own address space and routing may buy transit instead, often from the same companies.