2.0 OPEN SYSTEMS

INTERCONNECTION (OSI) MODEL

AND NETWORK PROTOCOLS

Prepare by:

Pn. Wan Fazlini Idayu Wan Fakari

CLO 2: apply network connection using straight-

through or crossover UTP cables complying to

TIA/EIA-568-B wiring standard (C3)

CLO 4 : create a simple network connection

using Wireless Local Area Network (WLAN) in

accordance to IEEE 802.11 protocols. (P7) note: C3 = application

P7 = origination

• Chapter 2 will appear in:-

– Lab session (1)

– Quiz (2)

2.1 Network Communication

� The OSI (Open System Interconnection) model is developed by ISO in 1984.

� It provide a reference model for the complex aspects related to network communication.

� It divides the different functions and services providedby network hardware and software in 7 layers.

� Helps to isolate problems and allows vendors to focus on just the layer(s) in which their hardware or software is implemented and be able to create products that are compatible, standardized and interoperable.

THE OSI MODEL

7 LAYERS OF THE OSI MODEL

TEKSI

NAIK

DOLLAH

PAK

AWAL

SUPAYA

PULANG

*Pak Dollah Naik Teksi Supaya Pulang Awal

Data travel down the layer in the sending device….

and up the layers in the receiving device.

CABLE

HOST A HOST B

LAYER 7 : APPLICATION LAYER

• Does not contain any of the application, such as a word processor or Internet Explorer.

• It provides services to facilitate the communication between software application and lower network services.

• Protocols:

1. FTP (File Transfer Protocol): used for uploading

and downloading files from and to FTP server.

2. SMTP (Simple Mail Transfer Protocol): send

and received e-mail from e-mail server.

3. HTTP (Hypertext Transfer Protocol): use by web

browser to send/receive information.

LAYER 6 : PRESENTATION LAYER

• The presentation layer is primarily concerned

with the format of the data.

• Data is formatted so that one type of

application (host) can understand data from

another type of application.

• Encoding , decoding, compressing and

decompressing .

LAYER 6 : PRESENTATION LAYER

• Data and text can be formatted as ASCII files, EBCDIC

files or can even be Encrypted.

• Sound may become a Midi file.

• Video files can be formatted as MPEG video files or

QuickTime files.

• Graphics and visual images can be formatted as PICT,

TIFF, JPEG, or even GIF files.

LAYER 5 : SESSION LAYER

• Establish, maintain and terminates the

communication between two computer over

a network.

• This layer is primarily concerned with coordinating

applications as they interact on different hosts.

• Protocols: Apple talk, NetBIOS

LAYER 4 : TRANSPORT LAYER

• Manipulate data and prepare it for delivery

(transport) through the network.

• Transport layer protocols break large data unit

received from Session layer into smaller units called

segments. This process is known as segmentation.

• Segmentation helps in data transmission efficiency.

• It also establishes the end-to-end connection, from

your host to another host.

LAYER 4 : TRANSPORT LAYER continue…..

• Essentially the transport layer opens up the connection from your system through a network and then through a wide area cloud to the receiving system at the other end.

• Protocols:

TCP (Transmission Control Protocol)

UDP (User Datagram Protocol)

LAYER 3 : NETWORK LAYER

• Determine the path for data from the source to the

destination computer.

• It manage switching and routing of data packets

based on network addresses.

• Protocols:

IP (Internet Protocol)

IPX (Internet Protocol Exchange)

LAYER 2 : DATA LINK LAYER

• This layer is where the network packets are translated into

raw bits (00110101) to be transmitted on the physical layer.

• This is also a layer that uses the most basic addressing

scheme, MAC Addresses.

• Protocols:

CSMA (Carrier-Sense Multiple Access)

TOKEN RING

FRAME RELAY

MAC ADDRESS

ETHERNET

WIFI

LAYER 1 : PHYSICAL LAYER

• Is the physical connection between network devices.

• Cables, connections, hubs , switch, Router and Network Interface Cards (NIC) operate at this layer.

• Protocols:

IEEE 802

ISDN

(Integrated Services

Digital Network)

1. The Application, Presentation and Session layer take user input and

converts it into data.

2. The Transport layer adds a segment header converting the data into

segments.

3. The Network layer adds a network header and converts the segments into

packets.

4. The Data Link layer adds a frame header and frame trails converting the

packets into frames.

5. The MAC sublayer layer converts the frames into a bits which the Physical

layer can put on the wire.

What basically happens when data passes from Host A to Host B ?

Host A Host B

This whole process of moving data from host A to host B is

known as DATA ENCAPSULATION

– the data is being wrapped in the appropriate

protocol header so it can be properly received.

DATA ENCAPSULATION

Let’s say we compose an email that we wish to send from host A to host B.

�The application we are using is EUDORA. We write the letter

end then hit send.

�Now, the computer translates the numbers into ASCII and then

into binary (1s and 0s).

�If the email is a long one, then it is broken up and mailed in

pieces. This all happens by the time the data reaches the

Transport layer - SEGMENT.

�At the network layer, a network header is added to

the data.

�This header contains information required to

complete the transfer, such as source and

destination logical addresses.

�In this layer the data is called PACKET.

�The packet from the network layer is then passed

to the data link layer where a frame header and a

frame trailer are added thus creating a data link

frame.

�Finally, the physical layer provides a service to the

data link layer.

�This service includes encoding the data link frame

into a pattern of 1s and 0s for transmission on the

medium (usually a wire).

Example of how the OSI Layers work using an e-mail sent from the computer on the left.

E-mail sent from JULIANA:Meet me at JJ 7:00 for breaking fast.

JULIANA

E-mail received from JULIANA:Meet me at JJ 7.00 for breaking fast.

JULIANA

Identify sender and intended receiver; is there an e-mail application available? APPLICATION

layer 7

Identified sender and intended receiver; found e-mail application.

Encode data with X coding key; use ASCII characters.

PRESENTATIONlayer 6

Decoded data with X decoding key; used ASCII characters.

Initiate and terminate the session according to X protocol. SESSION

layer 5

Initiated and terminated the session according to X protocol.

Make sure all data is sent intact.

TRANSPORTlayer 4

Make sure all data has arrived intact.

Keep track of how many hops;open shortest path First;Go to IP address 255.65.0.123

NETWORKlayer 3

Keep track of how many hops;opened the shortest path First;Went to IP address 255.65.0.123

Is the initial connection set up? Put data into frames according to X standard. DATA LINK

layer 2

The initial connection set up. Decoded data in frame according to X standard.

Send as electrical signal over the network cable at X voltage, and X Mbps. PHYSICAL

layer 1

Receive electrical signal over the network cable at X voltage, and X Mbps.

Data Packets• A small chunk of data transmitted over the Internet.

• A packet is a formatted unit of data carried by a packet mode computer network.

• A packet consists of two kinds of data: control information and user data.

• The control information provides data the network needs to deliver the user data, for example: source and destination addresses, error detection codes like checksums, and sequencing information

JULIANA

The Internet

AINUL

Frame

• A frame is a data packet on the Layer 2 of the OSI model.

• A frame is "the unit of transmission in a link layer protocol, and consists of a link-layer header followed by a packet.

• Examples are Ethernet frames (maximum 1500 byte plus overhead), PPP frames and V.42 modem frames

OSI MODEL

LAYER PROTOCOLS DEVICE

3 NETWORK LAYER

Routes data to different LANs

and WANs based on network

address.

IP/ IPX Router, ATM Switch

2 DATA LINK LAYER

Transmits packet from node to

node based on address

CSMA/CD, Token

Ring

Switch , Bridge, NIC

1 PHYSICAL LAYER

Electrical signal and cabling.

IEEE 802, ISDN Cable, Repeater,

Hub, Amplifier

SUMMARY

DATA ENCAPSULATION

Let’s say we compose an email that we wish to send from host A to host B.

�The application we are using is EUDORA. We write the letter

end then hit send.

�Now, the computer translates the numbers into ASCII and then

into binary (1s and 0s).

�If the email is a long one, then it is broken up and mailed in

pieces. This all happens by the time the data reaches the

Transport layer - SEGMENT.

�At the network layer, a network header is added to

the data.

�This header contains information required to

complete the transfer, such as source and

destination logical addresses.

�In this layer the data is called PACKET.

�The packet from the network layer is then passed

to the data link layer where a frame header and a

frame trailer are added thus creating a data link

frame.

�Finally, the physical layer provides a service to the

data link layer.

�This service includes encoding the data link frame

into a pattern of 1s and 0s for transmission on the

medium (usually a wire).

Example of how the OSI Layers work using an e-mail sent from the computer on the left.

E-mail sent from JULIANA:Meet me at JJ 7:00 for breaking fast.

JULIANA

E-mail received from JULIANA:Meet me at JJ 7.00 for breaking fast.

JULIANA

Identify sender and intended receiver; is there an e-mail application available?

APPLICATIONlayer 7

Identified sender and intended receiver; found e-mail application.

Encode data with X coding key; use ASCII characters.

PRESENTATIONlayer 6

Decoded data with X decoding key; used ASCII characters.

Initiate and terminate the session according to X protocol.

SESSIONlayer 5

Initiated and terminated the session according to X protocol.

Make sure all data is sent intact. TRANSPORTlayer 4

Make sure all data has arrived intact.

Keep track of how many hops;open shortest path First;Go to IP address 255.65.0.123

NETWORKlayer 3

Keep track of how many hops;opened the shortest path First;Went to IP address 255.65.0.123

Is the initial connection set up? Put data into frames according to X standard.

DATA LINKlayer 2

The initial connection set up. Decoded data in frame according to X standard.

Send as electrical signal over the network cable at X voltage, and X Mbps.

PHYSICALlayer 1

Receive electrical signal over the network cable at X voltage, and X Mbps.

OSI MODEL

LAYER PROTOCOLS DEVICE

7 APPLICATION LAYER

Interaction at the user or

application level:

E-mail, file transfer,

client/server

FTP, SMTP, HTTP Gateway

6 PRESENTATION LAYER

Translation of data:

Encoding, compression,

conversion. ASCII to EBCID, BCD

to binary.

JPEG, GIFF, MPEG Gateway

5 SESSION LAYER

Starts, stops session. Maintain

order.

Apple Talk, NetBIOS Gateway

4 TRANSPORT LAYER

Ensure delivery of entire file or

message

TCP, UDP Gateway, Router

SUMMARY

OSI MODEL

LAYER PROTOCOLS DEVICE

3 NETWORK LAYER

Routes data to different LANs

and WANs based on network

address.

IP/ IPX Router, ATM Switch

2 DATA LINK LAYER

Transmits packet from node to

node based on address

CSMA/CD, Token

Ring

Switch , Bridge, NIC

1 PHYSICAL LAYER

Electrical signal and cabling.

IEEE 802, ISDN Cable, Repeater,

Hub, Amplifier

SUMMARY