Access providers Access provider ISPs provide Internet access directly to end customers such as businesses and consumers, employing a range of technologies to connect users to their network. Available technologies have ranged from computer modems with
acoustic couplers to telephone lines, to television cable (CATV),
Wi-Fi, and fiber optics. For users and small businesses, traditional options include copper wires to provide
dial-up, DSL, typically
asymmetric digital subscriber line (ADSL), cable modem or
Integrated Services Digital Network (ISDN) (typically
basic rate interface). Using
fiber-optics to end users is called
Fiber To The Home or similar names. Customers with more demanding requirements (such as medium-to-large businesses, or other ISPs) can use higher-speed DSL (such as
single-pair high-speed digital subscriber line),
Ethernet,
metropolitan Ethernet,
gigabit Ethernet,
Frame Relay, ISDN
Primary Rate Interface,
Asynchronous Transfer Mode (ATM),
synchronous optical networking (SONET) or MPLS over OTN. Dedicated internet access (DIA) services for businesses can be delivered using PON networks.
Wireless access is another option, including
cellular and
satellite Internet access. Access providers may have an MPLS (
Multiprotocol label switching) or formerly a SONET
backbone network, and have a ring or mesh network topology in their core network. The networks run by access providers can be considered
wide area networks. ISPs can have
access networks, aggregation networks/aggregation layers/distribution layers/edge routers/metro networks and a
core network/backbone network; each subsequent network handles more traffic than the last. Mobile service providers also have similar networks. These providers often buy capacity on submarine cables to connect to Internet exchanges and engage in private peering with other carriers and networks including Tier 1 carriers at data centers, for example by connecting to the
NAP of the Americas, a data center which connects many Latin American ISPs with networks in the US.
Mailbox providers A
mailbox provider is an organization that provides services for hosting electronic mail domains with access to storage for mail boxes. It provides
email servers to send, receive, accept, and store email for
end users or other organizations. Many mailbox providers are also access providers, but some are not (e.g.,
Gmail,
Yahoo! Mail,
Outlook.com,
AOL Mail,
Po box). The definition given in RFC 6650 covers
email hosting services, as well as the relevant department of companies, universities, organizations, groups, and individuals that manage their mail servers themselves. The task is typically accomplished by implementing
Simple Mail Transfer Protocol (SMTP) and possibly providing access to messages through
Internet Message Access Protocol (IMAP), the
Post Office Protocol,
Webmail, or a proprietary protocol.
Hosting ISPs Internet hosting services provide email, web-hosting, or online storage services. Other services include
virtual server, cloud services, or physical server operation.
Transit ISPs Just as their customers pay them for Internet access, ISPs themselves pay upstream ISPs for Internet access. An upstream ISP such as a tier 2 or tier 1 ISP usually has a larger network than the contracting ISP or is able to provide the contracting ISP with access to parts of the Internet the contracting ISP by itself has no access to. In the simplest case, a single connection is established to an upstream ISP and is used to transmit data to or from areas of the Internet beyond the home network; this mode of interconnection is often cascaded multiple times until reaching a
tier 1 carrier. In reality, the situation is often more complex. ISPs with more than one
point of presence (PoP) may have separate connections to an upstream ISP at multiple PoPs, or they may be customers of multiple upstream ISPs and may have connections to each one of them at one or more point of presence.
Border Gateway Protocol is used by routers to connect to other networks, which are identified by their
autonomous system number.
Tier 2 ISPs depend on Tier 1 ISPs and often have their own networks, but must pay for transit or Internet access to Tier 1 ISPs, but may peer or send transit without paying, to other Tier 2 and/or some Tier 1 ISPs. Tier 3 ISPs do not engage in peering and only purchase transit from Tier 2 and Tier 1 ISPs, and often specialize in offering Internet service to end customers such as businesses and individuals. Some organizations act as their own ISPs and purchase transit directly from a Tier 1 ISP. Transit ISPs may use OTN (
Optical transport network) or SDH/SONET (Synchronous Digital Hierarchy/Synchronous Optical Networking) for transmitting data through optical fiber over long distances such as across a city or between cities. For transmissions in a metro area such as a city and for large customers such as data centers, special pluggable modules in routers, conforming to standards such as
CFP, QSFP-DD, OSFP, 400ZR or OpenZR+ may be used alongside DWDM and many vendors have proprietary offerings. Long-haul networks transport data across longer distances than metro networks, such as through
submarine cables, or connecting several metropolitan networks. Optical line systems and packet optical transport systems can also be used for data transmission in metro areas, long haul connections and data center interconnect. Ultra long haul transmission transports data over distances of over 1500 kilometers. ISPs connect to each other and to customers via
data centers hosting meet-me rooms. which allow the VISP's customers to access the Internet using services and infrastructure owned and operated by the wholesale ISP. VISPs resemble
mobile virtual network operators and
competitive local exchange carriers for voice communications.
Free ISPs Free ISPs are Internet service providers that provide service free of charge. Many free ISPs display advertisements while the user is connected; like commercial
television, in a sense they are selling the user's attention to the advertiser. Other free ISPs, sometimes called
freenets, are run on a nonprofit basis, usually with volunteer staff.
ISPs in rural regions It is hypothesized that the vast divide between broadband connection in rural and urban areas is partially caused by a lack of competition between
ISPs in rural areas, where there exists a market typically controlled by just one provider. A lack of competition problematically causes subscription rates to rise disproportionately with the quality of service in rural areas, causing broadband connection to be unaffordable for some, even when the infrastructure supports service in a given area. In contrast, consumers in urban areas typically benefit from lower rates and higher quality of broadband services, not only due to more advanced infrastructure but also the healthy economic competition caused by having several ISPs in a given area. How the difference in competition levels has potentially negatively affected the innovation and development of infrastructure in specific rural areas remains a question. The exploration and answers developed to the question could provide guidance for possible interventions and solutions meant to remedy the digital divide between rural and urban connectivity.
Satellite Internet services == Altnets ==