Chapter 1 Internet Working

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CCNA Bootcamp

Chapter 1: Internetworking


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Chapter 1 Objectives

The CCNA Topics Covered in this chapter include:

Internetworking Basics

Layered Models

The OSI Model

Ethernet Networking Data Encapsulation

Ciscos Three-Layer Model

Chapter 1 Written Labs and Review Questions


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How would you say the PC named Bobcommunicates with the PC named Sally?


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Switches can replace the hub, breaking up collision domains.

Keep in mind that the hub used in the figure just extended the onecollision domain from the switch port.


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Heres a list of some of the things that commonly causeLAN traffic congestion:

Too many hosts in a broadcast domain Broadcast storms Multicasting

Low bandwidth Adding hubs for connectivity to the network A bunch of ARP or IPX traffic (IPX is a Novell

protocol that is like IP, but really, really chatty.Typically not used in todays networks.)


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Routers create an internetwork.


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There are two advantages of using routers in yournetwork:

They dont forward broadcasts by default. They can filter the network based on layer 3 (Network

layer) information (e.g., IP address).

Four router functions in your network can be listed asfollows:

Packet switching Packet filtering

Internetwork communication Path selection


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Internetworking devices


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Switched networks creating an internetwork


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Layered Models

The Layered Approach

A reference model is a conceptual blueprint of howcommunications should take place.

It addresses all the processes required for effectivecommunication and divides these processes intological groupings called layers.

When a communication system is designed in thismanner, its known as layered architecture.


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The OSI Model

The OSI isnt a physical model. Rather, its a set ofguidelines that application developers can use to createand implement applications that run on a network.

It also provides a framework for creating andimplementing networking standards, devices, and

internetworking schemes.


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The OSI Model

The upper layers


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The OSI Model

The lower layers


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The OSI Model

The Layer Functions


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The OSI Model

Connection-Oriented Communication


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The OSI Model

Windowing


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The OSI Model

Network Layer Routing Table used in a router


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The OSI Model

Router in an internetwork


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The OSI Model

Data Link Layer

Provides the physical transmission of the data and handles errornotification, network topology, and flow control Ensure that messages are delivered to the proper device on a LAN using

hardware addresses and will translate messages from the Network

layer into bits for the Physical layer to transmit.


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Binary Addressing

Binary to Decimal Memorization Chart10000000 12811000000 19211100000 22411110000 24011111000 24811111100 25211111110 25411111111 255

BINARY 128 64 32 16 8 4 2 1 DECIMAL

10000100 1 0 0 0 0 1 0 0 132

11010010 1 1 0 1 0 0 1 0 210

10111000 1 0 1 1 1 0 00

184

10100110 1 0 1 0 0 1 1 0 166

Conversion Example


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Hexadecimal Addressing [1]

Hex is short for hexadecimal, which is a numbering systemthat uses the first six letters of the alphabet (A through F) to

extend beyond the available 10 digits in the decimal system.Hexadecimal has a total of 16 digits.

Hex Value Binary Value Decimal Value

0 0000 01 0001 1

2 0010 2

3 0011 34 0100 4

5 0101 5

6 0110 6

7 0111 7


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Hexadecimal Addressing [2]

Hex Value Binary Value Decimal Value

8 1000 89 1001 9

A 1010 10

B 1011 11

C 1100 12

D 1101 13

E 1110 14

F 1111 15


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The OSI Model

A hub in an network


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The OSI Model

A Switch in an network


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Ethernet Networking

Ethernet is a contention media access method that allowsall hosts on a network to share the same bandwidth of alink.

Ethernet is popular because its readily scalable, meaningthat its comparatively easy to integrate new technologies,

such as Fast Ethernet and Gigabit Ethernet, into anexisting network infrastructure.

Its also relatively simple to implement in the first place,

and with it, troubleshooting is reasonably straightforward.


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Ethernet Collision Detection

CSMA/CD

Carrier Sense Multiple Access with

Collision Detection (CSMA/CD),a protocol that helps devices share thebandwidth evenly without having twodevices transmit at

the same time on the network medium

CSMA/CD was created to overcomethe problem of those

collisions that occur when packets aretransmitted simultaneously fromdifferent nodes.


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Half and Full Duplex

Half-duplex Ethernet is defined in the original 802.3 Ethernet;Cisco says it uses only one wire pair with a digital signal running inboth directions on the wire.

But full-duplex Ethernet uses two pairs of wires instead of one wirepair like half duplex. And full duplex uses a point-to-pointconnection between the transmitter of the transmitting device and

the receiver of the receiving device.

Full-duplex Ethernet can be used in three situations: With a connection from a switch to a host

With a connection from a switch to a switch With a connection from a host to a host using a crossover cable


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Ethernet Addressing

The MAC, or hardware, address is a 48-bit (6-byte)address written in a hexadecimal format.


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Ethernet at the Physical Layer

The IEEE 802.3 and original Ethernet Physical layer

specifications.


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Ethernet Cabling

Ethernet cabling is an important discussion, especially ifyou are planning on taking the Cisco exams.

Three types of Ethernet cables are available:

Straight-through cable Crossover cable Rolled cable

We will look at each in the following sections.


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Straight Through

The straight-through cable is used to connect Host to switch or hub

Router to switch or hub


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Crossover Cable

The crossover cable can be used to connect Switch to switch Hub to hub Host to host Hub to switch Router direct to host


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Rolled Cable

Although rolled cable isnt used to connect any Ethernet connectionstogether, you can use arolled Ethernet cable to connect a host to a

router console serial communication (com) port.


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Using Hyper Terminal

Notice the settings for Hyper Terminal


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What type of cable is used?


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Data Encapsulation [1]

When a host transmits data across a network to another device, thedata goes through encapsulation:

It is wrapped with protocol information at each layer of the OSImodel.

Each layer communicates only with its peer layer on the receivingdevice.

To communicate and exchange information, each layer uses ProtocolData Units (PDUs). These hold the control information attached tothe data at each layer of the model. They are usually attached to theheader in front of the data field but can also be in the trailer, or end,of it.

Each PDU attaches to the data by encapsulating it at each layer of theOSI model, and each has a specific name depending on theinformation provided in each header. This PDU information is readonly by the peer layer on the receiving device. After its read, its

stripped off and the data is then handed to the next layer up.


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Data Encapsulation [2]


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PDU


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Port Numbers

The Transport layer uses port numbers to define both the virtualcircuit and the upper-layer process.


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Ciscos Three-Layer Model

The following are the three layers and their typical functions: The core layer: backbone The distribution layer: routing The access layer: switching


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Review Question

Hub Hub

How many broadcast domains are shown?


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Review Question

Hub HubHub HubHub Hub

Switch Switch

How many collision domains are shown?

Which of the hosts can transmit simultaneously


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Which of the hosts can transmit simultaneouslywithout causing collisions?

HubSwitch

How many collision and broadcast domains are show?

A FEDB C


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Written Labs and Review Questions

Open your books and go through all the writtenlabs and the review questions.

Review the answers in class.


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Thank You

Documents

Chapter 1 Internet Working