Leased line

Historically, this is the first form of relatively high-speed communication. xDSL is a family of technologies for accessing the Internet through a wired communication line (for example, telephone or cable television networks) through the use of a frequency band separate from the telephone band. xDSL technology involves the use of xDSL modems as the terminal equipment , which in fact allows the signal to pass through a separate frequency band from telephone communications. Advantages of xDSL technology:

• The ability to use the already deployed infrastructure of wired communication networks (most often telephone networks and cable television networks),
• Possibility of simultaneous Internet and telephone / television viewing sessions.

Disadvantages:

• Dependence on the quality of communication lines (eg: the same telephone lines or cable television lines);
• The limited connection speed from the separate frequency band used for organizing, which in turn depends on the one hand on the features of the used communication line and, on the other hand, on the particular xDSL technology.

For example, in the HDSL and SHDSL technologies used to connect corporate users to the Internet, modems were installed on the subscriber side and on the side of the Internet provider, and the connection speed reached 2.3 Mbps with a communication range of not more than 5 km when using a standard telephone cable ( 0.4 mm subscriber and 0.5 mm station). When using a line built on other types of wire, the range can increase depending on its cross section, for example, up to 15-18 km with a cross section of 1.2 mm. (Nowadays, cheap and cheap home-based connections at speeds above 50 Mbps are becoming more and more common, in comparison, the HDSL / SHDSL connection speed is clearly low. This is despite the fact that the HDSL / SHDSL connection is relatively expensive.) It was used as a connection to the Internet, and for the organization of corporate communications. Before the advent of ADSL technology and optical lines, it was the basis for building corporate communication networks and Internet connections for organizations.

Also, such a line could be used as a connecting line from a departmental telephone exchange to a subscriber. The loop resistance in this case should not exceed 900 Ohms for office PBXs of the Panasonic type and can be 3-6 kOhm in stations intended for organization of departmental communications, which is up to about 30 km on a standard cable of city communication lines.

ADSL is the most widely used xDSL technology. The technologically available maximum speed of incoming traffic with ADSL connection is 24 Mb / s. ADSL is currently also the most affordable xDSL technology, which makes it possible to use it to connect home users using the already deployed wired telephone infrastructure.

In many foreign countries, where cable television networks have historically evolved before the mass development of low-cost home high-speed Internet access networks via leased lines (most often via ADSL , twisted pair or GPON ), the technology of connecting home users via cable television via TV is also common cable modems .

There is also VDSL technology. Prior to the massive reduction in the cost of Ethernet access and fiber-optic communications, VDSL was often used to connect corporate users, replacing HDSL / SHDSL technology in this sector of the economy. In particular, the maximum available speed of the VDSL connection was at 40 Mb / s.

A physical wired leased line is a physically isolated wired communication channel. Currently, the most common are two types of physical wired leased lines: Ethernet- twisted pair and GPON . In the first case, a hardware router designed for Ethernet networks is most often installed on the subscriber side. In the case of GPON , a GPON terminal, also often called an optical fiber modem, is installed on the subscriber side. Currently, these are the most massive technologies for connecting corporate and home users. In particular, it is also the cheapest high-speed access technology: the speed of unlimited (without limiting incoming and outgoing traffic) Ethernet / GPON connections at the level of, for example, 100 Mbit with a tariff not exceeding 300 rubles / month is currently a common phenomenon (at least in large and many medium-sized cities of Russia).

A radio relay connection, also known as "radio access", is a connection to the Internet through a radio relay channel between the subscriber and the radio station of the Internet provider. Naturally, in this case, on the side, the subscriber also uses subscriber radio equipment for direct radio relay communication with the selected base radio station of the provider. This technology provides a fairly high speed of Internet connection and, of course, does not depend on wired networks, while some options for microwave Internet connections are only slightly more expensive than connecting to the Internet via Ethernet / GPON , which also makes them available for home users and, often more importantly, small businesses that are spatially remote from wired networks.