Layering as Optimization Decomposition a cal Theory of Network Archietectures
Network Model (Protocol and Layering)
Transcript of Network Model (Protocol and Layering)
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Network Model (Protocol and Layering)
รศ. ดร. อนันต์ ผลเพิม่
Asso. Prof. Anan Phonphoem, [email protected]
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)
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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)
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4
3
2
1
Above
Below
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2. Peer-to-Peer process(Logical)
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4
3
2
1
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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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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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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)
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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
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3
4
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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