DS-3 which stands for Digital Signal Level 3, equates to 28 T-1 lines or 44.736 million bits per second (roughly 43-45 Mbps upstream/downstream speeds). DS-3s have enough bandwidth to allow very large database transferring over busy wide area networks and the capability of handling 672 simultaneous voice conversations. DS-3s typically run long haul over fiber optics and coax in the last mile, however there are many exceptions to this. Also, because fiber is only available in limited parts of the US (vs. copper), expensive build-outs are sometimes required for full DS-3 access.
In North America, DS-3 translates into T-3, which is the equivalent of 28 T-1 channels, each operating at a total signaling rate of 1.544 Mbps. The 28 T-1s are multiplexed through an M13 ('Multiplex 1-to-3' multiplexer), and 188 additional signaling and control bits are added to each T-3 frame. As each frame is transmitted 8,000 times a second, the total T-3 signaling rate is 44.736 Mbps. In a channelized application, T-3 supports 672 channels, each of 64 Kbps. In the European hierarchy, a DS-3 is in the form of a E-3, which runs at a total signaling rate of 34.368 Mbps, supports 480 channels, and is the equivalent of 16 E-1s.
If you're moving a DS-3 (or any other DS signal) across continents, the standards of the target country rule. Channels get muxed and demuxed, with signaling conventions translated as well. For example: On the US side T-1s are in multiples of 24 x 64 Kbps circuits (total 1.5 Mbps) and in the UK, it's 30 x 64 Kbps (total 2 Mbps). If you were to interconnect to the US at a DS-3 level, you would not receive 28 T-1s with 6 spare channels- You would get multiples of 30 E/T-1s. As they arrived in the UK, they would be muxed and demuxed, along with translated signaling conventions.
Who uses DS-3s? Companies who host high traffic web sites, support web hosting, and need high capacity bandwidth on an as-needed basis. Also universities/colleges, government offices, and high volume call centers. A full DS3 can accommodate many simultaneous users depending on the requirements of the business. Generally a DS3 line is installed as a major networking channel for large corporations or universities with high volume network traffic. This is an always-on, high-speed connection that provides a dedicated, stable and reliable link to the Internet, and can support up to 500 or more computer users.
