What is Ethernet?
Ethernet (the name commonly used for IEEE 802.3 CSMA/CD) is the dominant cabling and low level data delivery technology used in local area networks (LANs). First developed in the 1970s, it was published as an open standard by DEC, Intel, and Xerox (or DIX), and later described as a formal standard by the IEEE. Following are some Ethernet features:
- Ethernet transmits data at up to ten million bits per second (10Mbps). Fast Ethernet supports up to 100Mbps and Gigabit Ethernet supports up to 1000Mbps. Many buildings on the Indiana University campus are wired with Fast Ethernet and the campus backbone is Gigabit Ethernet.
- Ethernet supports networks built with twisted-pair (10BaseT), thin and thick coaxial (10Base2 and 10Base5, respectively), and fiber-optic (10BaseF) cabling. Fast Ethernets can be built with twisted-pair (100BaseT) and fiber-optic (100BaseF) cabling. Currently, 10BaseT Ethernets are the most common.
- Data is transmitted over the network in discrete packets (frames) which are between 64 and 1518 bytes in length (46 to 1500 bytes of data, plus a mandatory 18 bytes of header and CRC information).
- Each device on an Ethernet network operates independently and equally, precluding the need for a central controlling device.
- Ethernet supports a wide array of data types, including TCP/IP, AppleTalk, and IPX.
- To prevent the loss of data, when two or more devices attempt to send packets at the same time, Ethernet detects collisions. All devices immediately stop transmitting and wait a randomly determined period of time before they attempt to transmit again.
What is DSL Internet service?
DSL (digital subscriber line) technologies, often grouped under the term DSL, connect a computer to the Internet. DSL uses existing copper pair phone line wiring in conjunction with special hardware on the switch and user ends of the line. This special hardware allows for a continuous digital connection over the phone lines.
Since the connection is digital, DSL technology doesn't have a digital-to-analog conversion like traditional modems. It eludes voice audio spectrum frequency boundaries because it can use frequencies above the voice audio spectrum. This means you can use your phone while maintaining your Internet connection.
These different frequencies allow DSL to encode more data, and allow Internet connection speeds of up to 50 times faster than standard modems, and up to 12 times faster than an ISDN connection. Additionally, since DSL is not a bus technology, it offers more consistent bandwidth than cable modems in which multiple users share very high bandwidth media. However, distance limitations can affect the transmission rates or can be too great, rendering DSL infeasible. Also, the condition of your existing wiring can affect transmission rates.
The most commonly available DSL technology is ADSL, or asymmetric DSL. It is asymmetric in that it is designed to accommodate typical consumer Internet use, with much more data flowing toward the user (multimedia and text) than from the user (mostly keystrokes and mouse behavior). The downstream rate (receiving rate) varies from 1.5 to 9Mbps; the upstream rate (sending rate) varies from 16 to 640Kbps. These speeds depend greatly on the distance to the telephone company's central office.
