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Copyright 2003 www.ciscopress.com
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CCNA 3 Chapter 1
Review: The OSI Reference Model and Routing
Copyright 2003 www.ciscopress.com
Objectives• Describe the overall function of the OSI
reference model and the problems it solves • Describe the characteristics of the:
– OSI physical layer– OSI data link layer– OSI network layer– OSI transport layer
• Describe the function of routing in networks• Understand the different classes of routing
protocols
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Types of Ethernet• Ethernet and IEEE 802.3 — LAN specifications,
which operate at 10 Mbps over coaxial and twisted-pair cable.
• 100-Mbps Ethernet — A single LAN specification, also known as Fast Ethernet, which operates at 100 Mbps over twisted-pair cable.
• 1000 Mbps Ethernet — A single LAN specification, also known as Gigabit Ethernet, which operates at 1000 Mbps (1 Gbps) over fiber and twisted-pair cables.
• 10 Gigabit Ethernet is only supported over fiber optic media.
Copyright 2003 www.ciscopress.com
Three Varieties of 10 Mbps Ethernet
• 10BASE-2
– Known as thin Ethernet or thinnet
– Allows network segments up to 185 meters on coaxial cable
• 10BASE-5
– Known as thick Ethernet or thicknet
– Allows network segments up to 500 meters on coaxial cable
• 10BASE-T
– Carries Ethernet frames on inexpensive twisted-pair wiring
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Path Switching
The network layer (3) address does not change. The data link layer (2) MAC address changes for each segment.
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Static Versus Dynamic Routes
• The purpose of a static route• Why dynamic routing is necessary• Dynamic routing operations• How distances on network paths are
determined by various metrics• Classes of routing protocols• Time for convergence
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Routing Protocols
• A routing protocol defines the set of rules used by a router when it communicates with neighboring routers, including the following: – How to send updates – What knowledge these updates contain– When to send this knowledge – How to locate recipients of the updates
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Distance Vector Routing Basics
• Routing updates explained• The problem of routing loops• The problem of counting to infinity• Link-state routing basics• How link-state protocols exchange routing
information• How topology changes propagate through the
network of routers
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The Transport Layer
• Segmenting upper-layer applications• Establishing a connection• Data transfer• Reliability with windowing• Acknowledgment techniques