Different Types of DSL
Here's Some Very Useful Information on Each Type of DSL:ADSL
- Asymmetric Digital Subscriber Line (ADSL) is the form of DSL that is most familiar to home and small business users. ADSL is called "asymmetric" because most of its two-way bandwidth is devoted to the downstream direction, which sends data to the user. Only a small portion of bandwidth is available for upstreaming (for sending user-interaction messages). Most Internet users, and especially those who use graphics- or multi-media intensive Web data, need lots of downstream bandwidth. For these applications, user requests and responses are small and require little upstream bandwidth. Using ADSL, up to 8 Mbps of data can be sent downstream and up to 640 Kbps are available for upstreaming. The high downstream bandwidth means that your telephone line will be able to bring motion video, audio, and 3-D images to your computer or hooked-in TV set. And, more good news, a small portion of the downstream bandwidth can be devoted to voice, rather than data, so you can make phone calls without having to use another separate line.
- Delivers simultaneously high-speed data and POTS voice service over the same telephone line. Supports a range of speeds from 1.5 Mbps to 8 Mbps downstream and 64 Kbps to 640 Kbps upstream.
- Consumer DSL (CDSL) is somewhat slower than ADSL (1 Mbps downstream), but has the advantage that a "splitter" does not need to be installed.G.Lite or DSL Lite
- G.Lite (also known as DSL Lite, splitterless ADSL, and Universal ADSL) is a slower ADSL that does not require splitting of the line at the user end. G.Lite provides a data rate from 1.544 Mbps to 6 Mpbs downstream, and from 128 Kbps to 384 Kbps upstream. In other words, it's faster than CDSL. G.Lite is expected to become the most widely installed form of DSL and the most sought after by home consumers.
- Supports POTS. A variant of ADSL based on the G.Lite standard for 1.5 Mbps downstream and 384 Kbps upstream. Intended for the mass market, including consumers, small businesses and remote offices.
- High bit-rate DSL (HDSL) is used for wideband digital transmission within a corporate site and between the telephone company and a customer. The main thing about HDSL is that it is symmetrical (upstreaming and downstreaming). For this reason, the maximum data rate is lower than for ADSL. HDSL can carry huge amounts of data, as is the case for T1 lines in North America. For this reason, it is the DSL service used for T1 lines.
- Supports symmetric service at 1.54 Mbps, but does not support POTS. HDSL is the DSL service already widely used for T1 lines. HDSL uses four wires (two pairs) instead of the new standard two wires used for other DSL flavors. A new version, HSDL-2, provides the same speed capabilities as HDSL, but uses only a single wire pair.
- IDSL (ISDN DSL) is actually closer to Integrated Services Digital Network (ISDN) (with data rates and service at 128 Kbps) than it is to the much higher rates of ADSL. It offers an "always-on" alternative to ISDN service and a data rate capacity of up to 144 Kbps.
- Offers an always-on alternative to dial-up ISDN service with a capacity up to144 Kbps.
- Rate-Adaptive DSL (RADSL) uses software to determine the rate at which signals can be transmitted on a given customer phone line. It adjusts the delivery rate accordingly. RADSL delivers from 640 Kbps to 2.2 Mbps downstream and from 272 Kbps to 1.088 Mbps upstream over an existing line.SDSL
- Single-Line DSL (SDSL) supports symmetric service. It is the same as HDSL with a single line carrying 1.544 Mbps each direction.
- Supports symmetric (downstream and upstream) services at 160 Kbps to 2.3 Mbps. SDSL does not support POTS connections.
- Unidirectional DSL (UDSL) is in the proposal stage. It's a unidirectional version of HDSL.VDSL
- Very High Data Rate DSL (VDSL) is a developing technology that promises huge data delivery rates at very high speeds (between 51- 55 Mbps) at very short distances (up to 1000 feet in length).
- Supports up to 51 Mbps at very short distances. VDSL is the high-end member of the DSL family.
- x2/DSL is a planned modem that will support 56 Kbps modem communication. It is upgradeable, through new software installation, to ADSL when it becomes available in the user's area.