1. Network Models CCNA Instructor Training Course October 12-17, 2009
Department of Computer Engineering
Kasetsart University

2. Real World Example Communication between managers of two companies
Communicate

3. What Actually Happens Communication takes place thru many layers
Logical communication
Secretary: reads and reports the message
Secretary: types a letter
Delivery boy: drops the letter
Delivery boy: takes the letter
Postal truck
Post office:
Processes and routes the letter

4. Internet Model The Internet Protocol Stack User Application Layer
Transport Layer
Network Layer
Data Link Layer
Physical Layer
Software
Network Access
Hardware
Transmission Medium

5. Internet Model Application Transport Network Data Link Physical
router
sender
router
receiver
Application
Transport
Network
Data Link
Physical
Application
Transport
Network
Data Link
Physical
Network
Data Link
Physical
Network
Data Link
Physical
Transmission medium

6. Responsible for providing services to the user
Application Layer
Responsible for providing services to the user
The only layer to interact with user
Data
Data
Logical communication
Application Layer
SMTP
FTP
HTTP
SMTP
FTP
HTTP
Data H5
Data H5
to Transport
from Transport

7. Responsible for delivery of a message from one process to another
Transport Layer
Responsible for delivery of a message from one process to another
Duties/services
Port addressing
Segmentation and reassembly
Connection control
Flow control (end-to-end)
Error control (end-to-end)

8. Transport Layer Data Data Transport Layer (segments) to Network
App-A
App-B
App-C
Sending Host
App-A
App-B
App-C
Receiving Host
Data
Data
Transport Layer
Data1 H4
Data2 H4
Data3 H4
Data1 H4
Data2 H4
Data3 H4
(segments)
to Network
from Network

9. Network Layer Duties/services
Responsible for the delivery of packets from the original source to the destination
Duties/services
Logical addressing
Routing

10. Network Layer from Transport to Transport Data Data Network Layer DataH3
Data H3
(packet)
to Data Link
from Data Link

11. Network Layer A1, A2, B1, B3, ... are logical addresses A1 A2
Data A1 C7
A1, A2, B1, B3, ... are logical addresses A1 A2
Network A R1 B1
Network B B6 B3 R3 R2 C2
Router D3
Network C C7
Network D D8

12. Responsible for transmitting frames from one node to the next
Data Link Layer
Responsible for transmitting frames from one node to the next
Duties/services
Framing
Physical addressing
Flow control (hop-to-hop)
Error control (hop-to-hop)
Access control

13. Data Link Layer from Network to Network Data Data Data Link Layer T2H2 T2
Data H2
(frame)
to Physical
from Physical

14. Data Link Layer 10, 35, 82, 97, ... are physical addresses Data 97 35

15. Data Link Layer A1 A2 97 32 Network A 25 R1 B1 79 Network B B6 B3 62C7 A1 A2 97 32
Network A 25
Data A1 C7 97 25 R1 B1 79
Network B
Data A1 C7 79 62 B6 B3 62 12 R3 R2 C2 54 88 D3
Data A1 C7 54 74
Network C C7 74
Network D D8

16. Responsible for transmitting individual bits from one node to the next
Physical Layer
Responsible for transmitting individual bits from one node to the next
Duties/services
Physical characteristics of interfaces and media
Representation of bits
Data rate (transmission rate)
Synchronization of bits

17. Physical Layer from Data Link to Data Link Data Data Physical Layer
(bits)
Transmission medium

18. Internet Protocol Suite
Layer
Protocols
Application
HTTP, FTP, Telnet, SMTP, ...
Transport
TCP, UDP, SCTP, ...
Network
IP (IPv4), IPv6, ICMP, IGMP, ...
Data Link
Ethernet, Wi-Fi, PPP, ...
Physical
RS-232, DSL, 10Base-T, ...