01a Osi Layered Model
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ISO / OSI The Layered Model
Why a Layered Network Model? 7
Application
6
Presentation
5
Session
4
Transport
3
Network
2
Data Link
1
Physical
• Reduces complexity • Standardizes interfaces • Facilitates modular engineering • Ensures interoperable technology • Accelerates evolution • Simplifies teaching and learning
2
Layer Functions 7
Application
Network processes to applications
3
Layer Functions 7
Application
6
Presentation
Network processes to applications Data representation
4
Layer Functions 7
Application
6
Presentation
5
Session
Network processes to applications Data representation Interhost communication
5
Layer Functions 7
Application
6
Presentation
5
Session
4
Transport
Network processes to applications Data representation Interhost communication End-to-end connections
6
Layer Functions 7
Application
6
Presentation
5
Session
4
Transport
3
Network
Network processes to applications Data representation Interhost communication End-to-end connections Addresses and best path
7
Layer Functions 7
Application
6
Presentation
5
Session
4
Transport
3
Network
2
Data Link
Network processes to applications Data representation Interhost communication End-to-end connections Addresses and best path Access to media
8
Layer Functions 7
Application
6
Presentation
5
Session
4
Transport
3
Network
2
Data Link
1
Physical
Network processes to applications Data representation Interhost communication End-to-end connections Addresses and best path Access to media Binary transmission
9
Peer-to-Peer Communications HOST A
HOST B
Application
Application
Presentation
Presentation
Session
Session
Transport
Transport
Network
Network
Data Link
Data Link
Physical
Physical
10
Peer-to-Peer Communications HOST A
HOST B
Application
Application
Presentation
Presentation
Session
Session
Transport
Transport
Network
Network
Data Link
Data Link
Physical
Physical
11
Peer-to-Peer Communications HOST A
HOST B
Application
Application
Presentation
Presentation
Session
Session
Transport Network Data Link Physical
segments packets frames bits
Transport Network Data Link Physical
12
Data Encapsulation Application
Application
Presentation
Presentation
Session
Session
Transport
Transport
Network
Network
Data Link
Data Link
Physical
Physical
13
Data Encapsulation Application Presentation Session
Application Data Header Presentation Header Session Header
Application
Data
Presentation
Data
Session
Transport
Transport
Network
Network
Data Link
Data Link
Physical
Physical
14
Data Encapsulation Application Presentation Session Transport
Application Data Header Presentation Header
Application
Data
Presentation
Session Header
Data
Session
Transport Header
Data
Transport
Network
Network
Data Link
Data Link
Physical
Physical
15
Data Encapsulation Application Presentation Session Transport Network
Application Data Header Presentation Header
Application
Data
Presentation
Session Header
Data
Session
Transport Header
Data
Transport
Data
Network
Network Header
Data Link
Data Link
Physical
Physical
16
Data Encapsulation Application Data Header
Application
Presentation Header
Data
Presentation
Session Header
Data
Session
Transport Header
Data
Transport
Data
Network
Data
Data Link
Presentation Session Transport Network Data Link Physical
Application
Network Header Frame Header
Physical
17
Data Encapsulation Application Data Header
Application
Presentation Header
Data
Presentation
Session Header
Data
Session
Transport Header
Data
Transport
Data
Network
Data
Data Link
Presentation Session Transport Network Data Link Physical
Application
Network Header Frame Header
0101101010110001
Physical
18
Data Encapsulation Example E-mail message Data
Data
19
Data Encapsulation Example E-mail message Data Segment Data Header
Data Segment
20
Data Encapsulation Example E-mail message Data
Data
Segment Data Header Network Segment Data Header Header
Segment Packet
21
Data Encapsulation Example E-mail message Data
Data
Segment Data Header
Segment
Network Segment Data Header Header Frame Network Segment Data Header Header Header
Packet Frame Trailer
Frame (medium dependent)
22
Data Encapsulation Example E-mail message Data
Data
Segment Data Header
Segment
Network Segment Data Header Header Frame Network Segment Data Header Header Header
Packet Frame Trailer
0111111010101100010101101010110001
Frame (medium dependent)
Bits
23
ISO / OSI Reference Model Network Applications
7
Application
6
Presentation
5
Session
24
ISO / OSI Reference Model Network Applications End-to-End Services
7
Application
6
Presentation
5
Session
4
Transport
25
ISO / OSI Reference Model 7
Application
6
Presentation
End-to-End Services
5
Session
4
Transport
Data Transmission
2
Data Link
1
Physical
Network Applications
26
ISO / OSI Reference Model 7
Application
6
Presentation
End-to-End Services
5
Session
4
Transport
Routing
3
Network
Data Transmission
2
Data Link
1
Physical
Network Applications
27
Why a Layered Network Model? 7
Application
6
Presentation
5
Session
4
Transport
3
Network
2
Data Link
1
Physical
• Reduces complexity • Standardizes interfaces • Facilitates modular engineering • Ensures interoperable technology • Accelerates evolution • Simplifies teaching and learning
2
Layer Functions 7
Application
Network processes to applications
3
Layer Functions 7
Application
6
Presentation
Network processes to applications Data representation
4
Layer Functions 7
Application
6
Presentation
5
Session
Network processes to applications Data representation Interhost communication
5
Layer Functions 7
Application
6
Presentation
5
Session
4
Transport
Network processes to applications Data representation Interhost communication End-to-end connections
6
Layer Functions 7
Application
6
Presentation
5
Session
4
Transport
3
Network
Network processes to applications Data representation Interhost communication End-to-end connections Addresses and best path
7
Layer Functions 7
Application
6
Presentation
5
Session
4
Transport
3
Network
2
Data Link
Network processes to applications Data representation Interhost communication End-to-end connections Addresses and best path Access to media
8
Layer Functions 7
Application
6
Presentation
5
Session
4
Transport
3
Network
2
Data Link
1
Physical
Network processes to applications Data representation Interhost communication End-to-end connections Addresses and best path Access to media Binary transmission
9
Peer-to-Peer Communications HOST A
HOST B
Application
Application
Presentation
Presentation
Session
Session
Transport
Transport
Network
Network
Data Link
Data Link
Physical
Physical
10
Peer-to-Peer Communications HOST A
HOST B
Application
Application
Presentation
Presentation
Session
Session
Transport
Transport
Network
Network
Data Link
Data Link
Physical
Physical
11
Peer-to-Peer Communications HOST A
HOST B
Application
Application
Presentation
Presentation
Session
Session
Transport Network Data Link Physical
segments packets frames bits
Transport Network Data Link Physical
12
Data Encapsulation Application
Application
Presentation
Presentation
Session
Session
Transport
Transport
Network
Network
Data Link
Data Link
Physical
Physical
13
Data Encapsulation Application Presentation Session
Application Data Header Presentation Header Session Header
Application
Data
Presentation
Data
Session
Transport
Transport
Network
Network
Data Link
Data Link
Physical
Physical
14
Data Encapsulation Application Presentation Session Transport
Application Data Header Presentation Header
Application
Data
Presentation
Session Header
Data
Session
Transport Header
Data
Transport
Network
Network
Data Link
Data Link
Physical
Physical
15
Data Encapsulation Application Presentation Session Transport Network
Application Data Header Presentation Header
Application
Data
Presentation
Session Header
Data
Session
Transport Header
Data
Transport
Data
Network
Network Header
Data Link
Data Link
Physical
Physical
16
Data Encapsulation Application Data Header
Application
Presentation Header
Data
Presentation
Session Header
Data
Session
Transport Header
Data
Transport
Data
Network
Data
Data Link
Presentation Session Transport Network Data Link Physical
Application
Network Header Frame Header
Physical
17
Data Encapsulation Application Data Header
Application
Presentation Header
Data
Presentation
Session Header
Data
Session
Transport Header
Data
Transport
Data
Network
Data
Data Link
Presentation Session Transport Network Data Link Physical
Application
Network Header Frame Header
0101101010110001
Physical
18
Data Encapsulation Example E-mail message Data
Data
19
Data Encapsulation Example E-mail message Data Segment Data Header
Data Segment
20
Data Encapsulation Example E-mail message Data
Data
Segment Data Header Network Segment Data Header Header
Segment Packet
21
Data Encapsulation Example E-mail message Data
Data
Segment Data Header
Segment
Network Segment Data Header Header Frame Network Segment Data Header Header Header
Packet Frame Trailer
Frame (medium dependent)
22
Data Encapsulation Example E-mail message Data
Data
Segment Data Header
Segment
Network Segment Data Header Header Frame Network Segment Data Header Header Header
Packet Frame Trailer
0111111010101100010101101010110001
Frame (medium dependent)
Bits
23
ISO / OSI Reference Model Network Applications
7
Application
6
Presentation
5
Session
24
ISO / OSI Reference Model Network Applications End-to-End Services
7
Application
6
Presentation
5
Session
4
Transport
25
ISO / OSI Reference Model 7
Application
6
Presentation
End-to-End Services
5
Session
4
Transport
Data Transmission
2
Data Link
1
Physical
Network Applications
26
ISO / OSI Reference Model 7
Application
6
Presentation
End-to-End Services
5
Session
4
Transport
Routing
3
Network
Data Transmission
2
Data Link
1
Physical
Network Applications
27
