Ccna 1 Ch 2 Cli Modified by Tn

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Communicating over theNetwork

© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 1Version 4.0

Network Fundamentals – Chapter 2



Objectives

Describe the structure of a network, including the devicesand media that are necessary for successful

communications.Explain the function of protocols in networkcommunications.

Explain the advantages of using a layered model todescribe network functionality.

Describe the role of each layer in two recognized network

models: The TCP/IP model and the OSI model.Describe the importance of addressing and namingschemes in network communications.

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The Elements of Communication

3 common elements of communication• message source• the channel

• message destination

network – Data or information networks capable of carrying many different

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Segmentation and Multiplexing

Messages are not sent as a single stream of bits, insteadthey are segmented and multiplexed

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Message Labeling

Segmentation and multiplexing introduce more complexityto data transmission

Each message must be labeled for ordering and assembling

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Network Hardware and SoftwareHardware- devices (hosts, switches, routers…)- media (copper, fiber, wireless…)

Software- services, processes, programs

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End devices (hosts)

End devices (hosts ) form interface with human network &communications network- computers

- network printers- VoIP phones- cameras- mobile devices

- …

Role of end devices:

- client- server- both client and server

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Intermediary DevicesNetwork Access Devices ( Hubs , switches , and wireless access points )Internetworking Devices ( routers )Communication Servers and Modems

Security Devices ( firewalls )

Role of an intermediary device- - Manages the data as it flows through the network

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Network Media

The signal encoding that must occur for the message to be transmitted isdifferent for each media type ( electrical impulses , pulses of light ,patterns of electromagnetic waves )

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Local Area Networks (LANs)

• A network serving a home, building or campus isconsidered a Local Area Network (LAN)

• A LAN is usually administered by a single organization

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Wide Area Networks (WANs)

LANs separated by geographic distance are connected by anetwork known as a Wide Area Network (WAN)

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The Internet

The Internet is defined as a global mesh of interconnectednetworks

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Network Symbols

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Protocols and Layered Communication

A protocol is a set of predetermined rules- proprietary- industry standard

Logical layers are introduced to describe a communication

2.3.2

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Protocols interaction – protocol stack

Main protocols used in communication between web serverand web browser

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Different Implementation of Protocols

Many diverse types of devices can communicate using thesame sets of protocols

This is because protocols specify network functionality, notthe underlying technology to support this functionality- different browsers- different web servers

- erent ost ng operat ng systems

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Layered model of Networking

benefits of using a layered model• Assists in protocol design• Fosters competition

• Changes in one layer do not affect other layers• Provides a common language

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Protocol and Reference Models

reference model protocol model

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TCP/IP Model (Internet Model)

open standard

uses Requests for Comments (RFCs) produced by theInternet Engineering Task Force (IETF)

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Logical Communication Process

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Protocol Data Units (PDUs) and Encapsulation

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Sending and Receiving Process

2.4.6 2.4.7

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The ISO/OSI Reference Model

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Comparing the OSI and TCP/IP model

PT

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Addressing in the Network

The addressing in the network occurs at 3 distinct layers:

- datalink layer

- network layer- transport layer

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Datalink Layer Addressing

the host physical address , contained in the header of the Layer 2 PDU,called a frame

used in the delivery of messages on a single local network

Layer 2 address is unique on the local network

in a LAN using Ethernet, this address is called the Media Access Control(MAC) address

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Network Layer Addressingthe host logical address , contained in the header of the Layer 3 PDU,called a packet (or sometimes a datagram )

used in the delivery of messages from one local network to another localnetwork , therefore include identifiers that enable intermediary networkdevices to locate hosts on different networks

Layer 3 address is usually unique on the global scale (excluding privateaddressing)

routers use the network identifier portion of this address to determinewhich path to use to reach the destination host .

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Transport Layer Addressing

does not identify a destination host or a destination network

identifies a specific process or service running on the destination hostdevice that will act on the data being delivered

each application or service is represented at Layer 4 by a port number,contained in a segment (TCP) or datagram (UDP)

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