Leased line

A leased line is a permanent (steady standing the so-called " dedicated " ) connecting two communication partner via a telecommunications network. In contrast, in a dial-up connection is temporarily established and terminated by a select operation.

About the connection to any type of data to be transmitted, for example, analog (eg phone call) or digital (eg, direct data connection). The connection itself can be physically carried out, eg as a pair of copper wires from terminal to terminal, or virtual, as part of an overall infrastructure such as SDH or ATM Virtual Circuit. The connection of a dedicated data line is bit transparent.

The connection can not be established from the party via a selection process, such as tone dialing, but must be produced by the network operator. Leased lines therefore have no phone number.

The term dedicated line is sometimes also used to refer to a long-lasting connection of any kind, and quality. The simplest form of such a (not connected on the supply side ) leased line is a permanent dial-up line made ​​over the telephone network. Here the modems of the participants are programmed so that they select each other.

The technical term for leased lines according to the product designations Deutsche Telekom as direct data connection ( DDV) or standard fixed line (SFV ) are referred to. The analog leased lines of Deutsche Telekom could be used until 30 September 2009. The German Telekom coined the term Direktrufnetz for phone lines, a dedicated line was designated as a major port for direct call (HFD ). Other names are: Mietleitungsverbindung (MLV ) or leased line.

Media

Initially a dedicated line are actually realized as a wire connection, which has been connected between the two endpoints. Meanwhile, however intelligent multiplex systems are used for this purpose, which can be switched flexibly from a central network management system from the network operator.

Copper lines

Most of Germany's installed dedicated lines to the copper cables have data transfer rates up to 2 Mbit / s For these compounds, the copper wires of the fixed network are usually sufficient. For higher bandwidth coaxial cables were used frequently in the past, today they are increasingly replaced by optical fibers.

Fiber Optic

Leased lines to fiber optics are only offered with limited bandwidth by some network operators, thus providing, for example, the German Telekom under the name DDV -M Ethernet100 a step of 10 Mbit / s scalable dedicated line with data transfer rates up to 100 Mbit / s.

Since about 2004 are increasingly alternative network operators in the German market that offer optical waveguide ( or a WDM band of a fiber ) without bandwidth limitation or restriction on use. This port is referred to as dark fiber, since the customer must provide themselves for the ' light ' on the line.

Data transfer rate

Leased lines are with data transfer rates of 50 bit / s to hire up to 16 Gbit / s. (2006 )

The most common types are E1 (up to 2 Mbit / s) and E3 (up to 34 Mbit / s).

Costs

In general, the leased line is rented. The price is dependent inter alia on the length of the line, the gross data rate made ​​available and the line medium. This may come cost of data volume for bundled offerings.

Availability

The technical characteristics of leased lines, particularly the demands on the quality as reliability and bit error rate are, (formerly Regulatory Authority for Telecommunications and Post) established in Germany by the appropriate federal agency, the Federal Network Agency. If leased lines realized on optical fiber connections, you can start from a very low error rate in the physical layer. Important leased lines can also be protected (see Protection) through the preparation of alternative channels. Typical are 98.5 % availability over the year for copper lines, 99.5 % to fiberglass. However, this availability arise primarily through the recovery time for complete failure of a compound and less by sporadic bit errors.

Interfaces

For leased lines different interfaces are used. The data transmission device for connection to a 2-Mbit/s-Standleitung often has an X.21 or G.703 interface. Then put on these interfaces at the two ends of a leased line, the respective router networks connected to.

Dedicated line to the Internet

A dedicated line often used - is to connect to the Internet - especially of companies. The leased line then leads an Internet service provider to the Point of Presence ( PoP). When connected in this manner over a dedicated line a network to the Internet, it usually contains the allocation of at least without a fixed public IP address. These leased lines are then particularly suitable to operate servers on the Internet. Frequently leased lines are used for the connection of two private ( sub) networks, here then no public IP addresses are assigned. Also, in leased lines of the second type only the provision by the provider charges, while leased line to the Internet in addition to providing also the volume of data transferred is paid.

Permanent DSL connection

The connection via a DSL modem to the Internet is sometimes referred to as a leased line, such as real (S ) DSL ​​-based leased lines, such as those offered or QSC has offered till April 2, 2009 for residential customers, for example, Arcor. Quasi-permanent lines with regular forced separation and changing IP address as they offer such as the German Telekom and Telekom Austria are no dedicated lines.