Ethernet

Table of Contents

Chapter Goals




Ethernet Technologies


Background
Ethernet—A Brief History
Ethernet Network Elements
Ethernet Network Topologies and Structures
The IEEE 802.3 Logical Relationship to the ISO Reference Model
The Ethernet MAC Sublayer


The Basic Ethernet Frame Format
Frame TransmissionHalf-Duplex Transmission—The CSMA/CD Access Method
Full-Duplex Transmission—An Optional Approach to Higher Network Efficiency
Flow Control


Frame Reception
The VLAN Tagging Option


The Ethernet Physical Layers


Encoding for Signal Transmission
The 802.3 Physical Layer Relationship to the ISOReference Model
10-Mbps Ethernet—10Base-T
100 Mbps—Fast Ethernet


100Base-X
100Base-T4
100Base-T2


1000 Mbps—Gigabit Ethernet


1000Base-T
1000Base-X


Network Cabling—Link Crossover Requirements


System ConsiderationsChoosing UTP-Based Components and Media Category
Auto-negotiation—An Optional Method for Automatically Configuring Link Operational Modes
Network Switches Provide a Second, and Often Better, Alternative to Higher Link Speeds in CSMA/CD Network Upgrades
Multispeed NICs
Choosing 1000Base-X Components and Media
Multiple-Rate Ethernet NetworksLink Aggregation—Establishing Higher-Speed Network Trunks
Network Management
Migrating to Higher-Speed Networks


Summary
Review Questions



Chapter Goals

• Understand the required and optional MAC frame formats, their purposes, and their compatibility requirements.
• List the various Ethernet physical layers, signaling procedures,and link media requirements/limitations.
• Describe the trade-offs associated with implementing or upgrading Ethernet LANs—choosing data rates, operational modes, and network equipment.


Ethernet Technologies


Background

The term Ethernet refers to the family of local-area network (LAN) products covered by the IEEE 802.3 standard that defines what is commonly known as the CSMA/CDprotocol. Three data rates are currently defined for operation over optical fiber and twisted-pair cables:
• 10 Mbps—10Base-T Ethernet
• 100 Mbps—Fast Ethernet
• 1000 Mbps—Gigabit Ethernet
10-Gigabit Ethernet is under development and will likely be published as the IEEE 802.3ae supplement to the IEEE 802.3 base standard in late 2001 or early 2002.
Other technologies and protocolshave 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
• Providesextensive topological flexibility for network installation
• Guarantees successful interconnection and operation of standards-compliant products, regardless of manufacturer

Ethernet—A Brief History

The original Ethernet was developed as an experimental coaxial cable network in the 1970s by Xerox Corporation to operate with a data rate of 3 Mbps using a carrier sense multiple accesscollision detect (CSMA/CD) protocol for LANs with sporadic but occasionally heavy traffic requirements. Success with that project attracted early attention and led to the 1980 joint development of the 10-Mbps Ethernet Version 1.0 specification by the three-company consortium: Digital Equipment Corporation, Intel Corporation, and Xerox Corporation.
The original IEEE 802.3 standard was based on, and...