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Network Model (Protocol and Layering)

รศ. ดร. อนันต์ ผลเพิม่

Asso. Prof. Anan Phonphoem, Ph.D.anan.p@ku.ac.th

http://www.cpe.ku.ac.th/~anan

Computer Engineering Department

Kasetsart University, Bangkok, Thailand

2018

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Outline

◼ Network Model

◼ Layering Concept

◼ Techniques protocols use

Network Model

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Data Communication

Hi

How are you

doing?

How are youdoing?

Hi

01010001 01010001

Hi

10010001 10010001

How are you

01010100 01010100

doing?

Hi

How are you

doing?

UserComputer

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How can it happen?

◼ A lot of work since user inputs data until the data is transmitted.

◼ Should each application program take care all tasks?

◼ NO

User

Communication: App's Viewpoint

◼ Two network applications interact as if there is a dedicate pipe connecting them

◼ But what's going on underneath?

◼ What is inside the "cloud"?5

InternetA

App

B

App

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Computer Communication Model

◼ Modularity

◼ Well-defined interfaces

◼ Well-defined functions and protocol

Lord of the Rings

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http://wallpapercave.com/map-of-middle-earth-wallpaper

Lord of the Rings: Light the Beacons

◼ Gondor (by Gandalf) sends a signal to Rohan asking them for military aid

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Question?

◼ How fast is the Beacon of Gondor?Posted by Rhett Allain on July 30,2010http://scienceblogs.om/dotphysics/2010/07/30/how-fast-is-the-beacon-of-gond/

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Question?

◼ Who is the sender and receiver?

◼ How can the delay occur?

◼ How about the acknowledgement from Rohan?

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Transmit a letter

What Actually Happens

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◼ Communication takes place thru many layers

Logical communication

Secretary:types a letter

Delivery boy:drops the letter

Secretary:reads and reportsthe message

Delivery boy:takes the letter

Post office:Processes and routes the letter

Postal truck

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Layered (Software) Architecture

•Applications

•Allow interoperability

•Ensure reliable data transmission

•Moving data

•Physical connections

User Support

Transport

Network Support

Network

User

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Open Systems Interconnection(OSI) Model

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

User Support

Transport

Network Support

Network

User

OSI Layers in Real World

transmission medium

Reads the

message

Summarizes or

translates letter

Opens letter

Withdraws letter

from mailbox

Checks address

and sorts letter

Unpacks

packages

Unloads

from truck

Handwrites

a message7.Manager

Prepares

final version6.Assistant

Provides address

and packs letter5.Secretary

Delivers letter

to post office4.Driver

Checks address

and sorts letter3.Postal staff

Packs letters

for certain directions2.Postal staff

Loads on truck1.Postal staff

Pictures from Wikipedia

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Old Protocol Stacks

Now they are replaced by TCP/IP

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OSI model “It’s just a model”

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

Applications

TCP/ UDP

IP

Physical

Data Link

TCP/IP

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TCP/IP Protocol Suite (Internet Model)

Applications User service and interface5

Transport Process delivery + Error (TCP/UDP)4

NetworkPacket end-to-end (across network)

3

Data Link2

Physical (mechanical and electrical spec)1

Provide framesNode-to-node (same network segment)

Transmission bit streams

Move packets from source to destination

Reliable end-to-end (whole message)

Homework

1. Draw “The Lord of the Rings: Light the Beacons” in term of TCP/IP protocol suite

◼ Explain

◼ the actors for each layer

◼ The protocol used

2. Give another example of communication

◼ Draw diagram and explain in brief

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Outline

◼ Network Model

◼ Layering Concept

◼ Techniques protocols use

Layering Concept

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Layering Concept

1. Interfaces between layers (Physical)

2. Peer-to-Peer process (Logical)

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1. Interfaces between layers(Physical)

5

4

3

2

1

Above

Below

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2. Peer-to-Peer process(Logical)

5

4

3

2

1

5

4

3

2

1

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Application5

4 Transport

3 Network

2 Data Link

1 Physical

Application5

4 Transport

3 Network

2 Data Link

1 Physical

Direct connection

Identical Message

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Application5

4 Transport

3 Network

2 Data Link

1 Physical

Connection via intermediate nodes

Application5

4 Transport

3 Network

2 Data Link

1 Physical

Network

Lin

kLin

k

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Data Flow in a station

Application5

4 Transport

3 Network

2 Data Link

1 Physical

Hello

Hello543

Hello5432 T

1001101001011101011

4 Hello5

5 Hello

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Data Flow

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OSI Model and data flow

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Physical Layer

Transmitting individual bits from one node to the next.

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1. Physical Layer

◼ Physical characteristics of interface

◼ Stream of Bits (e.g., 001010100100)

◼ Line config. (e.g., point-to-point)

◼ Topology (e.g., bus, star)

◼ Transmission mode (e.g., half-duplex)

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Data Link Layer

Transmitting frames from one node to the next.

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2. Data Link Layer

◼ Physical addressing

◼ Access control

◼ Error control

◼ Node-to-Node delivery (same network)

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Node-to-node delivery

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2. Data Link Layer Example

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3. Network Layer

Delivery of packets from the source to the final destination

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3. Network Layer

◼ Logical Address

(e.g., IP address:158.108.33.66)

◼ Routing (router, gateway)

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Source-to-destination delivery

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3. Network Layer Example

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4. Transport Layer

Delivery of a message from one process to another

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4. Transport Layer

◼ Service-point addressing (port number)

◼ Segmentation and assembly

◼ Flow and error control

◼ End-to-end delivery (across network)

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Process-to-process delivery

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Process-to-process delivery

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5. Application Layer

Providing services to the user

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5. Application Layer

◼ User interfaces

◼ Service supports (e.g., mail, FTP)

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TCP/IP Protocol Suite (Internet Model)

Applications User service and interface5

Transport Process delivery + Error (TCP/UDP)4

NetworkPacket end-to-end (across network)

3

Data Link2

Physical (mechanical and electrical spec)1

Provide framesNode-to-node (same network segment)

Transmission bit streams

Move packets from source to destination

Reliable end-to-end (whole message)

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OSI Model

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

User service

Translate format, encrypt

Session manage, checkpoints

Reliable end-to-end (whole message)

Packet end-to-end (across network)

Node-to-node (same network segment)

Physical

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Outline

◼ Network Model

◼ Layering Concept

◼ Techniques protocols useTechniques protocols use

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Techniques Protocols Use

◼ Sequencing Number

◼ for out-of-order delivery

◼ to eliminate duplicate packets

◼ Retransmission lost packets

◼ Avoiding replay caused by excessive delay

◼ Flow control to prevent data overrun

◼ Mechanisms to avoid network congestion

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Sequencing Number

◼ Sender adds sequence no. in the packet

◼ For out-of-order delivery

◼ sorting in the list

◼ To eliminate duplicate packets

◼ discard the new one

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Retransmission lost packets

◼ To guarantee reliable transfer

◼ Positive acknowledgement (ACK)

◼ Retransmission

Retransmission

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Avoiding replay caused by excessive delay

◼ A packet from previous conversation comes late

◼ Just discard the old packet

◼ Detected by a unique ID (e.g. time)

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Flow control to prevent data overrun

◼ Sender / receiver may operate at different speed➔Data is lost

◼ Flow control

◼ Stop-and-go (Stop-and-wait)

◼ Sliding window

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Stop-and-go (Stop-and-wait)

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Sliding window

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Sliding window

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Comparison

Stop-and-go Sliding window

Can you compare throughput ?

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1

25

3

4

6

7

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Network congestion

Each connection is 3 Mbps

To avoid congestion ➔ control the incoming rate

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Summary

◼ Network Model◼ OSI Model

◼ TCP/IP protocol suite

◼ Layering Concept◼ Data flow

◼ functions of each layer

◼ Techniques protocols use◼ Seq.no. / Retransmission / Congestion