growing the network © 2004 cisco systems, inc. all rights reserved. understanding the challenges of...

Growing the Network

© 2004 Cisco Systems, Inc. All rights reserved.

Understanding the Challenges of Shared LANs

INTRO v2.0—3-1

© 2004 Cisco Systems, Inc. All rights reserved. INTRO v2.0—3-2

Outline

• Overview

• Early Local Area Networks

• Ethernet LAN Segments

• Extending a LAN Segment

• Collisions

• Collision Domains

• Summary

• Lab Exercise 3-1: Creating an Ethernet Hub-Connected Network


Early Local Area Networks


• Signals degrade with transmission distance.

• Each Ethernet type has a maximum segment length.

LAN Segment Limitations


Extending LAN Segments

• Bandwidth is shared

• Extends cable distances

• Repeats or amplifies signal


Collisions


Multiple Collision Domains


Summary

• The early version of Ethernet was called thick Ethernet and was large, expensive, difficult to install, limited to 500 meters before a repeater was required, limited in the number and placement of stations, relatively difficult in adding new users, and provided 10 Mbps of bandwidth.

• The later version of Ethernet, thin Ethernet, was smaller, limited to 185 meters before a repeater was required, limited in the number and placement of stations, easier in adding new users, and provided 10 Mbps of bandwidth.


Summary (Cont.)

• A segment is a network connection made by a single unbroken network cable. Ethernet cables and segments can only span a limited physical distance after which transmissions will become degraded.

• A hub extends network segments by receiving incoming bits, amplifying the electrical signal, and transmitting these bits through all of its ports to the other devices on the network.

• If two or more stations on a segment transmit at the same time, a collision results.


Summary (Cont.)

• The network segments that share the same bandwidth are called collision domains because when two or more devices communicate at the same time, collisions may occur within that segment.

• It is possible to use other network devices operating at Layer 2 (or above) of the OSI model to divide network segments to reduce the number of devices that are competing for bandwidth on a given segment and to provide more bandwidth to the devices in the segment.

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