In Italy, leased lines are available at speeds of 64 kbps (finished by the DCE2 or DCE2 modem) or a multiple of 64 kbps ranging from 128 kbps to framed or unframed E1 (DCE3 modem) in digital form (PDH service, known as CDN, Circuito Diretto Numerico). Local telephone companies can also supply CDA (Circuito Diretto Analogico) which are simple pairs of dry copper between two buildings, without any line access: in the past (before 2002) a full analog base band has been provided, which is a way for the customer to implement xDSL technology between sites: today, everything is limited to 4 kHz of carrier channel, so the service is only a POTS connection without a setup chain connection. In the Uk, leased lines are available at speeds ranging from 64 kbps in increments of 64 kbps to 2048 Mbps via a channelled E1 rear circuit and at speeds between 2,048 Mbps and 34,368 Mbps via E3 channelled tail circuits. The NTE terminates the circuit and provides the desired presentation most often X.21, but higher-speed interfaces such as G.703 or 10baseT are available. However, some ISPs use the term more flexibly and define a leased line as “any bandwidth service provided by a leased fibre optic connection.” With the transition from the Basic Bell network to digital circuits in the 1970s, leased line services (or private lines) were digital. This has enabled ES AT-T to offer digital data services (later renowned digital data services) that have begun to provide RNIS and T1 lines on customer premises to establish a connection.  In the 1990s, with advances in the internet, leased lines were also used to connect customer sites to the PSI point of presence, while over the next decade there was a convergence of the aforementioned services (Relay Frame, ATM, Internet for Business) with integrated MPLS offerings. As demand for data networks increased, telecommunications companies began to build more advanced networks using package changes in addition to their infrastructure. For example, a number of telecommunications companies have included ATM, Frame-Relay or RNIS offerings in their service portfolios. The leased lines were used to connect the customer`s position to the access point of the telecommunications network.
When providing services to businesses, you most often come across service level agreements. This can range from office services to accounting, but it is mostly found in IT services such as leased lines and Internet connections.