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The European version of the T1 is the E1, which operates at 2.048 Mbps.


Real World Scenario




The T3 Connection


A T3 line works similarly to a T1 connection, but carries a whopping 44.736Mbps. This is equivalent to 28 T1 channels (or a total of 672 DS0 channels). Currently this service requires fiber-optic cable or microwave technology. Many local ISPs have T3 connections to the major ISPs, including SprintNet, AT&T, and MCI. Also, very large, multinational companies use T3 connections to send voice and data between their major regional offices.


As with the T1, the T3 has a European counterpart, the E3, which operates at 34.368Mbps.


Asynchronous Transfer Mode (ATM)


ATM (asynchronous transfer mode, not to be confused with automated teller machines) first emerged in the early 1990s. If networking has an equivalent to rocket science, then ATM is it. ATM was designed to be a high-speed communications protocol that does not depend on any specific LAN topology. It uses a high-speed cell-switching technology that can handle data as well as real-time voice and video. The ATM protocol breaks up transmitted data into 53-byte cells. A cell is analogous to a packet or frame, except that an ATM cell does not always contain source or destination addressing information; also, the ATM cell contains neither higher-level addressing nor packet control information.

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