Network Model (Protocol and Layering)

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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

2017

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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 speedData 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