Table of Contents

Introduction 2-4
Reasons 4-5
Advantages 5
Disadvantages 5
Summary 6
Reference 7

Introduction

The Ethernet is a system used in the connection between a number of computers to form a Local Area Network(LAN), which consist of the physical and data link layer. During the 1980s, one of the first widely deployed Ethernet supported a theoretical data rate of 10Megabit per second(Mbps). Over the years through the advancement of technology, the maximum data rates were increased to 100Mbps to todays peak performing a whopping 1Terabit per second(Tbps), but only active in area of research.
As workplaces slowly become a more computerised and network based, with the rise of emails and the internet, Ethernet has become more prevalent. Every computer that requires a connection to another or link to systems uses the Ethernet. The computers you use at home, in your office at work, in school that accesses the internet through the use of the Ethernet.

Ethernet LANs consist of network nodes and interconnecting media. The network nodes fall into two major classes:
Data terminal equipment (DTE) - Devices that are either the source or the destination of data frames. DTEs are typically devices such as PCs, workstations, file servers, or print servers that, as a group, are all often referred to as end stations.
Data communication equipment (DCE) - intermediate network devices that receive and forward frames across the network. DCEs may be either standalone devices such as repeaters, network switches, and routers, or communications interface units such as interface cards and modems.

LANs take on many topological configurations, but regardless of their size or complexity, all will be a combination of only three basic interconnection structures or network building blocks. The simplest structure is the point-to-point interconnection, shown in Figure: Example Point-to-Point Interconnection. Only two network units are involved, and the connection may be DTE-to-DTE, DTE-to-DCE, or DCE-to-DCE. The cable in point-to-point interconnections is known as a network link. The maximum allowable length of the link depends on the type of cable and the transmission method that is used.

Figure: Example Point-to-Point Interconnection

The original Ethernet networks were implemented with a coaxial bus structure, as shown in Figure: Example Coaxial Bus Topology. Segment lengths were limited to 500 meters, and up to 100 stations could be connected to a single segment. Individual segments could be interconnected with repeaters, as long as multiple paths did not exist between any two stations on the network and the number of DTEs did not exceed 1024. The total path distance between the most-distant pair of stations was also not allowed to exceed a maximum prescribed value.

Figure: Example Coaxial Bus Topology

Because Ethernet devices implement only the bottom two layers of the OSI protocol stack, they are typically implemented as network interface cards (NICs) that plug into the host device's motherboard. The different NICs are identified by a three-part product name that is based on the physical layer attributes.

All higher-speed Ethernet specifications include definitions for managed objects and control agents that are compatible with Simple Network Management Protocol (SNMP) and that can be used to gather statistics about the operation of the network nodes and to assist in network management. Because user information is anecdotal at best and usually comes long after the fact, all larger networks should at least be configured with managed switches and network servers to ensure that potential problems and bottlenecks can be identified before they cause serious network deterioration.

By now, it should be apparent that upgrading existing networks typically does not require wholesale equipment or media changes, but it does require knowledge of the current network configuration and the network location of potential problems. This means that a network management system should be in place and that a cable plant database should be both available and accurate. It is time-consuming and often difficult to determine link type and availability after the cables have been pulled through conduit, buried in walls, and layered in cable trays.

Links are often the limiting factors in network upgrades. Existing Category 5 links should support all current Ethernet rates from 10 Mbps to 1000 Mbps, although they should be tested to ensure their capability to support gigabit rates. If the network is equipped with only Category 3 cable, some links will have to be replaced before upgrading to 1000 Mbps. A similar situation exists with single- and multimode fiber. Multimode fiber cannot be used for all backbone installations. Single-mode fiber, on the other hand, not only can support all backbone lengths up to 10,000 meters at 1000 Mbps, but it also will be capable of supporting backbone use at 10-gigabit data rates in the future. Switch replacement can begin as soon as the necessary links are available. Existing switches at the campus and building distributor levels can often be reused at the building or floor distributor level. NICs can generally be replaced to extend the useful life of end stations. And so on. Reasons Other technologies and protocols have been touted as likely replacements, but the market has spoken. Ethernet has survived as the major LAN technology (it is currently used for approximately 85 percent of the world's LAN-connected PCs and workstations) because its protocol has the following characteristics:
Is easy to understand, implement, manage, and maintain
Allows low-cost network implementations
Provides extensive topological flexibility for network installation
Guarantees successful interconnection and operation of standards-compliant products, regardless of manufacturer

Due to Ethernet being easy to understanded, implemented, managed, and maintained, the migration of lower end performing Ethernet to a higher performing one is possible. Gigabit Ethernet follows the same form, fit and function as its 10 Mbps and 100 Mbps Ethernet precursors, allowing a straightforward, incremental migration to higher-speed networking. Cost of ownership is an important factor in evaluating any new networking technology. The overall cost of ownership includes not only the purchase price of equipment, but also the cost of training, maintenance and troubleshooting. Competition and economies of scale have driven the purchase price of Ethernet connections down significantly. Gigabit Ethernet requires only incremental training of personnel and incremental purchase of maintenance and troubleshooting tools. In addition, deployment of Gigabit Ethernet is faster than alternative technologies. Network administrators today face a myriad of internetworking choices and network design options. They are combining routed and switched networks, and building intranets of increasing scale. Ethernet networks are shared and switched based on bandwidth and cost requirements. Gigabit Ethernet can be switched, routed and shared.. All of today’s internetworking technologies, as well as such technologies such as IP-specific switching and Layer 3 switching, are fully compatible with Gigabit Ethernet, Just as they are with Ethernet and Fast Ethernet. Desktop CPUs are increasing in speed at a rapid rate. The Peripheral Connection Interface (PCI) bus is becoming increasingly popular for implementing desktop computing platforms. This high-performance bus enables desktop CPUs to fully utilize the bandwidth of Fast Ethernet connections. Cisco anticipates that manufacturers of high-end desktop systems will offer 100-Mbps Ethernet connections on their motherboards. Workstation and server technology is advancing to enable CPUs to flood multiple Fast Ethernet links with network traffic. Each of these technology trends points to the need for gigabit networking technology that can be deployed for backbone, server, and eventually desktop connections. The simple migration and support offered by Ethernet, Combined with scalability and flexibility to handle new applications and data types, makes Gigabit Ethernet the strategic choice for high-speed, high-bandwidth networking. Gigabit Ethernet is an extension to the highly successful 10 Mbps and 100 Mbps IEEE 802.3 Ethernet standards. Offering a raw data bandwidth of 1Gbps, Gigabit Ethernet maintains full compatibility with the huge installed base of Ethernet nodes.

Advantages

Gigabit Ethernet is backward-compatible, with legacy Ethernet hardware standards that already are well understood by most network managers and users. Gigabit Ethernet technology is driving down the cost of Ethernet and Fast Ethernet and soon will rival Fast Ethernet in price per port. Due to the simplicity inherent in the design of Ethernet, it can be an inexpensive technology to implement. The coaxial cable used in a Ethernet network is very well shielded, and has a very high immunity from electrical noise caused by outside sources.

Disadvantages The Ethernet system suffers from a few drawbacks, as nothing is perfect. The system applies only for short distance networks - can only reach around 350 feet without daisy-chaining switches together. The Ethernet is not fault tolerant . For example, if any device or cable section attached to the network fails, it will most likely make the entire network go down. Ethernet networks are very difficult to troubleshoot. There is no easy way to determine what node or cable section is causing a problem, and the network must be troubleshot by a "process of elimination." This can be very time consuming.

Summary The impressive bandwidth that Gigabit Ethernet offers, ten times that of Fast Ethernet, makes it a natural choice for network backbones. Savvy industrial integrators are keeping their networks up to date by using Gigabit Ethernet switches for any new or replacement network installation. In addition, Gigabit Ethernet has enabled integrators to implement large scale video streaming applications, such as IP video surveillance and audio/video conferencing. With traffic continuing to grow rapidly in networks around the world, Gigabit Ethernet is set to take over as the preferred high-speed network solution.
Reference
http://compnetworking.about.com/cs/ethernet1/g/bldef_ethernet.htm http://compnetworking.about.com/od/ethernet/l/aa102900c.htm http://www.cisco.com/en/US/tech/tk389/tk214/tk277/tsd_technology_support_sub-protocol_home.html http://www.hardwaresecrets.com/article/231 http://www.siemon.com/us/white_papers/06-01-10_10G-horizontal-cabling-choices.asp http://www.teach-ict.com/technology_explained/ethernet/ethernet.html http://www.tomshardware.com/reviews/gigabit-ethernet-bandwidth,2321.html