Transcript No Slide Title

CONSYL
Computer and Data Communications
Department of Computer Engineering, Kasetsart University
204325 Introduction to Computer Communications and Networks
4/11/40 page 1
CONSYL
A Communications Model
input
information
Input
device
input
data
transmitted
received
signal
signal
Transmission
Transmiter
Receiver
medium
output
information
output
data
Output
Devices
data :
information :
A represent of facts ,
concepts in a
formalized manner
suitable for
communication
The meaning that
is currently assigned
to data by means of
the conventions
applied to those data
Department of Computer Engineering, Kasetsart University
204325 Introduction to Computer Communications and Networks
4/11/40 page 2
CONSYL
Data Communication Network
Communication
Network Node
Communication
Network
Department of Computer Engineering, Kasetsart University
Network Station
204325 Introduction to Computer Communications and Networks
4/11/40 page 4
CONSYL
Data communication networks





Public Switched Telephone Network (PSTN)
Local Area Network (LAN)
Leased lines
Public switched data network (PSDN)
Integrated services digital network (ISDN)
Department of Computer Engineering, Kasetsart University
204325 Introduction to Computer Communications and Networks
4/11/40 page 5
CONSYL
PSTN

modem link via PSTN
PSTN
modem
Department of Computer Engineering, Kasetsart University
modem
204325 Introduction to Computer Communications and Networks
4/11/40 page 6
CONSYL
LAN
hub
station
4th floor
hub
station
3rd floor
hub
2nd floor



confined geographical area
under single management
high data rate
station
1st floor
server
hub
router
Department of Computer Engineering, Kasetsart University
204325 Introduction to Computer Communications and Networks
4/11/40 page 7
CONSYL
Leased lines
• Lease pubic circuits to connect different sites
• Communication channel is privated
LAN
leased circuit
Voice
LAN
LAN
Voice
Voice
Department of Computer Engineering, Kasetsart University
204325 Introduction to Computer Communications and Networks
4/11/40 page 8
CONSYL
PSDN
• PSDN is designed specifically for the transmission of data rather than voice
• Comunication is shared
PSDN= Public Switched Data Network
LAN
LAN
PSDN
=
LAN
Department of Computer Engineering, Kasetsart University
204325 Introduction to Computer Communications and Networks
4/11/40 page 9
CONSYL
ISDN
Using ISDN to carry both voice and data
NTE = Network
termination equipment
NTE
NTE
ISDN = Integrated services
digital network
ISDN
NTE
Department of Computer Engineering, Kasetsart University
NTE
204325 Introduction to Computer Communications and Networks
4/11/40 page 10
CONSYL
Computer Communication
Architecture
Computer A
Computer B
File transfer
application
File and file transfer command
Communications
service module
Communication-related messages
Network access
module
Network
interface
Department of Computer Engineering, Kasetsart University
Communication
network
File transfer
application
Communications
service module
Network access
module
204325 Introduction to Computer Communications and Networks
4/11/40 page 11
CONSYL
Three-layers model
Applications
Transport
Network access
Department of Computer Engineering, Kasetsart University
204325 Introduction to Computer Communications and Networks
4/11/40 page 12
CONSYL
Communication architectures
and networks
Service Access Point
1 2
() ()
Applications
1 2 3 4
() () () ()
Network Address
Transport
Network access
Applications
Transport
Network access
Communication
network
Applications
1 2 3
() () ()
Transport
Network access
Department of Computer Engineering, Kasetsart University
204325 Introduction to Computer Communications and Networks
4/11/40 page 13
CONSYL
Protocol layers
Computer A
Computer B
Application protocol
Application
Application
Transport protocol
Transport
Transport
Network Access Protocol
Network access
Network access
Computer B
Department of Computer Engineering, Kasetsart University
204325 Introduction to Computer Communications and Networks
4/11/40 page 14
CONSYL
Protocol data unit
Application data
Transport
header
Application
data
Transport
header
Application
data
Transport protocol
data unit (TPDU)
Network Transport
header
header
Application
data
Network Transport
header
header
Application
data
Network protocol
data unit (NPDU)
 control info + data in each layer = protocol data unit (PDU)
Department of Computer Engineering, Kasetsart University
204325 Introduction to Computer Communications and Networks
4/11/40 page 15
CONSYL
OSI reference Model
Layer 7
Application layer
Layer 6
Presentation layer
Layer 5
Session layer
Layer 4
Transport layer
Layer 3
Network layer
Layer 2
Data link layer
Layer 1
Physical link
Department of Computer Engineering, Kasetsart University
• developed by ISO
204325 Introduction to Computer Communications and Networks
4/11/40 page 16