Ethernet And Atm: Which Will Prevail?

Ethernet and ATM: Which Will Prevail?

Author: Ingrid Giraud

Abstract

Sending data through the internet efficiently has always posed many problems. The two major technologies used, Ethernet and Asynchronous Transfer Mode (ATM), have done an admirable job of porting data, voice and video from one point to another. However, they both fall short in differing areas; neither has been able to present the "complete" package to become the single, dominant player in the internet market. They both have dominant areas they cover. Ethernet has dominated the LAN side, while ATM covers the WAN (backbone). This paper will compare the two technologies and determine which has a hand-up in the data trafficking world.

Network Technology Overview

The Ethernet has been around for several decades and is a mature data transfer mechanism based on packets and internet protocol (IP). Its main focus has always been the LANs and transfer of data. ATM is a recent technology that many thought would replace Ethernet as the technology of choice. It can transfer data, voice and video at a much higher rate of speed than Ethernet. So why hasn't ATM replaced Ethernet? In a world where everyone wants everything faster and more efficient, ATM should be the hands-down choice for a networking service. However, it's not as simple as that. Reviewing the advantages and disadvantages of each should be very revealing as to who has the upper hand in network technologies.

ATM Characteristics

ATM is geared toward high speed voice and video transmission, much like a telephone network. It uses a cell-switching and multiplexing technology. The data (this refers to data, voice and video) is transferred between two points on a dedicated circuit in 53 byte cells. Each cell is the exact same size, no matter what data is being sent. The cells consist of 5 bits of header information and 48 bits of actual data. Using a smaller, consistent cell size means there's less delay between when each cell processes at the other end. Using dedicated circuits via virtual circuits ensures there is no interruption in the data transfer. This is extremely important to voice and video transmissions, because they are highly intolerant to data delays. This improves the Quality of Service (QoS) and speed of transfer, which can be between 25 Mbps to 622 Mbps.

On the downside of ATM is the cost. This is costs concerning the setup (equipment and time), configuration and maintenance. ATM cannot use the existing equipment used with Ethernets and setup and configuration is time consuming and not easy. Most companies are hard pressed to pay these costs.

Ethernet Characteristics

Ethernet is ingrained in LANs worldwide. It is the technology of choice amongst most businesses. This is because it's cheap, easy to maintain and install and it is fairly fast. It ranges in speeds from 10 Mbps to 100Mbps (Gigabyte Ethernet technology is right around the corner offering 1000Mbps). Ethernet does not use dedicated circuits; rather it broadcasts its data packets to the network and lets the intended recipient claim them as they find them. The packet or frame sizes are not standard, but the headers are. This poses more efficient use of bandwidth. The packet sizes can be anywhere from 72 to 1526 bytes and 26 bytes of that is dedicated to the header, no matter what size the packet.

Since Ethernet transmissions are not dedicated, each packet fights for space within the bandwidth.

On the downside of Ethernet, is data collisions and/or traffic jams. Data collisions are caused by the sending and receiving ends transmitting at the same time, which is a hazard of not having dedicated circuits. The traffic jams are caused