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.[42] 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.[43]
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)[44] or MPLS over OTN.[45][46] Dedicated internet access (DIA) services for businesses can be delivered using PON networks.[47]
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[48][49] or mesh[50] network topology in their core network.[51][52] The networks run by access providers can be considered wide area networks.[53] 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.[54]
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,[61] 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.[62]
Hosting ISPs
Internet hosting services provide email, web-hosting, or online storage services. Other services include virtual server, cloud services, or physical server operation.[63]
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.[64]
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)[65][66] 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.[64] Transit ISPs provide large amounts of bandwidth for connecting hosting ISPs and access ISPs.[67]
Virtual ISPs
A virtual ISP (VISP) is an operation that purchases services from another ISP, sometimes called a wholesale ISP in this context,[89] 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.
Wireless ISP
A wireless Internet service provider (WISP) is an Internet service provider with a network based on wireless networking. Technology may include commonplace Wi-Fi wireless mesh networking, or proprietary equipment designed to operate over open 900 MHz, 2.4 GHz, 4.9, 5.2, 5.4, 5.7, and 5.8 GHz bands or licensed frequencies such as 2.5 GHz (EBS/BRS), 3.65 GHz (NN) and in the UHF band (including the MMDS frequency band) and LMDS.[90]
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.[91] 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.[92] 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
