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ENG224 INFORMATION TECHNOLOGY – Part I. 6. Network Model. 6. Network Model. ENG224 INFORMATION TECHNOLOGY – Part I. 6. Network Model. Why Network Protocol Models?. Network communication is an extremely complex task Need cooperative efforts from all nodes involved

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slide1
ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

6. Network Model

slide2
ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

Why Network Protocol Models?

  • Network communication is an extremely complex task
  • Need cooperative efforts from all nodes involved
  • A standard model helps to describe the task of a networking product or service
  • Also help in troubleshooting by providing a frame of reference
slide3
ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

Who define Network Model?

  • Need non-profit making organizations
    • ISO - International Standards Organization
    • e.g. OSI, MPEG-1, 2, 4, etc. (http://www.iso.ch/)
    • IEEE - Institute of Electrical & Electronic Engineers
    • e.g IEEE 802, IEEE 754, etc. (http://www.ieee.org)
    • ITU - International Telecommunication Union
    • e.g. V.34, H.323, H.324, etc. (http://www.itu.int)
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ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

The OSI 7-layer Model

  • OSI - Open Systems Interconnection
  • Defined in 1984 and become an international standard

All

Away

People

Pizza

Seem

Sausage

To

Throw

Need

Not

Data

Do

Processing

Please

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ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

Layered Architecture

  • Layering specifies different level of functions and services
  • Each layer works with the layer below and above it
  • Each layer provides services to next layer
  • Shield the upper layer from the details of actual implementation
slide6
ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

Relationship of OSI layers

Virtual

Communication

Physical

Communication

slide7
ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

Protocols in a layered architecture

  • Network communication is possible only if machines speaking the same languages (protocols)
  • Since each layer work independently, each layer speaks different languages (protocols)
  • Lead to the concept of a Protocol Stack
  • Network communication is possible only if the Protocol Stacks on two machines are the same
slide8
ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

  • To identify the language (protocol) of each layer, identifier (header and trailer) are added to data
slide9
ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

1. Physical Layer

Example protocols: Ethernet, Token Ring (Physical part)

Appl.

Appl.

  • Define how cable is attached to the Network Adapter Card
    • How many pins in the connector?
    • The impedance?
    • Max/min electrical voltage?
  • Responsible for transmitting bits from one computer to another

Pres.

Pres.

Sess.

Sess.

Tran.

Tran.

Netw.

Netw.

Data.

Data.

Phys.

Phys.

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ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

2. Data Link Layer

Example protocols: Ethernet, Token Ring

Appl.

Appl.

  • Make data frames
  • Provide error-free frame transfer by acknowledgment and retransmission

Pres.

Pres.

Sess.

Sess.

Tran.

Tran.

Frame

Netw.

Netw.

Data.

Data.

Phys.

Phys.

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ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

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ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

3. Network Layer

Example protocols: IP, IPX

  • Logical address to physical address translation
  • For TCP/IP running on Ethernet
  • Logical address: IP address
    • 158.132.148.99
  • Physical address: Ethernet address
    • 00 00 E2 15 1A CA
  • Determine the route from source to destination computer

Appl.

Appl.

Pres.

Pres.

Sess.

Sess.

Tran.

Tran.

Netw.

Netw.

Data.

Data.

Phys.

Phys.

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ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

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ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

Receiving

Sending

1

3

2

1

2

3

4. Transport Layer

Example protocols: TCP, SPX, NWLink

  • Ensure packets are delivered error free, insequence
  • Translate between packets and message

Appl.

Appl.

Pres.

Pres.

Sess.

Sess.

Tran.

Tran.

Netw.

Netw.

Data.

Data.

Phys.

Phys.

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ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

5. Session Layer

Example application program: Winsock, UNIX Socket

Appl.

Appl.

  • Establishment, maintaining and release of session
  • Provide dialog management
    • Regulate which side transmit, when, for how long (Sync.)
  • Provide synchronization between user tasks

Pres.

Pres.

Sess.

Sess.

Tran.

Tran.

Netw.

Netw.

Data.

Data.

Phys.

Phys.

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ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

What is a Session?

A. Consecutive sessions on a transport layer connection

B. Consecutive sessions on a multiple transport layer connections

1

2

3

1

2

3

C. Both

1

2

3

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ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

6. Presentation Layer

Example application program: redirector (NT), SSL

Appl.

Appl.

  • Translate data from Application Layer to the format suitable for session layer (the network)
  • Provide data encryption, compression
  • Changing or converting character set, graphic, and file format

Pres.

Pres.

Sess.

Sess.

Tran.

Tran.

Netw.

Netw.

Data.

Data.

Phys.

Phys.

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ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

7. Application Layer

Example protocols: FTP, Telnet, HTTP

  • Entry point for application to access network
  • Directly support user applications
  • E.g. File transfer, email
  • General capabilities:
  • Network access, flow control, Error recovery

Appl.

Appl.

Pres.

Pres.

Sess.

Sess.

Tran.

Tran.

Netw.

Netw.

Data.

Data.

Phys.

Phys.

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ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

PictureTel

Example: File Transfer

  • The most traditional network task
  • Implemented by a simple Application Layer protocol called FTP

FTP Client

FTP Server

Network

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ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

Utility: WS_FTP

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ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

PictureTel

WS_FTP

FTP

FTP

FTP Client

FTP Server

Layers 5-7

Layers 5-7

Layer 4

TCP

TCP

Layer 4

Layer 3

IP

IP

Layer 3

Ethernet

Ethernet

Layers 1,2

Layers 1,2

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ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

The 802 Project Model

  • IEEE launched the Project 802 in 1980 February
  • Predate the ISO standard, but the development was performed in roughly the same time
  • Objective: To clearly define the network standards for different kind of physical components of a network - the interface card and the cabling
  • Enhance the Data Link and Physical layers of the OSI model
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ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

IEEE 802 Categories

802.1 Internetworking 802.2 Logical Link Control (LLC)

802.3 Carrier-Sense Multiple Access with Collision Detection (CSMA/CD) LAN (Ethernet)

802.4 Token Bus LAN 802.5 Token Ring LAN

802.6 Metropolitan Area Network (MAN)

802.7 Broadband Technical Advisory Group

802.8 Fiber-Optic Technical Advisory Group

802.9 Integrated Voice/Data Networks

802.10 Network Security 802.11 Wireless Networks

802.12 Demand Priority Access LAN, 100 BaseVG-AnyLAN

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ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

Enhancements to the OSI Model

  • Divide the Data Link layer into 2 sub-layers
  • Logical Link Control Sub-layer
    • Define the use of service access points (SAPs) as an interface for higher layer to Data Link layer
  • Media Access Control Sub-layer
    • Directly interface with the network card
    • For delivering error-free data communications
slide25
ENG224

INFORMATION TECHNOLOGY – Part I

6. Network Model

802.1

Logical Link Control (LLC)

802.2

Media Access

Control (MAC)

802.3

802.4

802.5

802.12

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