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Computer Network

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4122102 : Computer Network & Distributed Computer Network and Distributed Rachphat Sriprom Rajabhat Institute Chandrakasem – PowerPoint PPT presentation

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Title: Computer Network


1
4122102
Computer Network
Distributed
Computer Network and Distributed
Rachphat Sriprom
Rajabhat Institute Chandrakasem
2
Computer Network
  • A network is a set of devices (nodes) connected
    by media links
  • A node can be a computer, printer, etc.
  • The links are called communication channels

3
Simplified Network Model
4
LAN Local Area Network
5
WAN Wide Area Network
6
WAN Dial On Demand-PSTN
7
WAN Leased line - PSTN
8
WAN PSDN
9
WAN ISDN
10
Enterprise Network
11
Network Criteria
12
Performance
The performance of a network depends on a
number of factors
  • Number of users
  • Type of transmission medium
  • Hardware
  • Software

13
Reliability
  • Frequency of failure
  • Recovery time of a network after failure
  • Catastrophe

14
Security
  • Unauthorized access
  • For a network to be useful, sensitive data must
    be protected from unauthorized access. Protection
    can be accomplished at a number of levels
  • Viruses
  • A good network is protected from viruses by
    hardware and software designed specifically for
    that purpose.

15
Computer Networks Computer Communications
  • Computer Networks two or more computer
    interconnected via a communication network
  • Computer Communications the exchange of
    information between two computers for purpose of
    cooperative action

16
Communications Tasks
  • Transmission system utilization
  • Interfacing
  • Signal generation
  • Synchronization
  • Exchange Management
  • Error detection and correction
  • Flow control
  • Addressing
  • Routing
  • Recovery
  • Message formatting
  • Security
  • Network management

17
Protocols
  • Protocol - a set of rules governing the exchange
    of data between two entities in a system
  • Must speak the same language
  • Entities
  • User applications
  • e-mail facilities
  • terminals
  • Systems
  • Computer
  • Terminal
  • Remote sensor

18
Key Elements of a Protocol
  • Syntax
  • Data formats
  • Signal levels
  • Semantics
  • Control information
  • Error handling
  • Timing
  • Speed matching
  • Sequencing

19
Protocol Data Unit (PDU)
20
Protocol Data Unit (PDU)
  • The sending application generates a block of data
    and passes this to the transport layer
  • Each of these blocks the transport layer appends
    a transport header, containing protocol
    information
  • The combination of data from the next higher
    layer and control information is known as a
    protocol data unit (PDU)

21
Encapsulation in PDU
  • Addition of control information to data
  • Address information
  • Error-detecting code
  • Protocol control

22
Protocol Data Unit (PDU)
23
Standard or Nonstandard
24
OSI Model
  • The Open Systems Interconnection model is a
    layered framework for the design of network
    systems that allows for communication across all
    types of computer systems
  • It consists of seven separate but related layers
  • An ISO standard

ISO is the organization. OSI is the model.
25
OSI seven layers
  • Application layer
  • Presentation layer
  • Session layer
  • Transport layer
  • Network layer
  • Data Link layer
  • Physical layer

26
OSI layers
27
The OSI Environment
Headers are added to the data at layers 6, 5, 4,
3, and 2. Trailers are usually added only at
layer 2.
28
Functions Of The Layers
  • Physical Layer
  • Physical interface between devices
  • Information Transmission
  • Medium Signal
  • Mechanical (Connector)

29
Data Link Layer
  • Control the information transfer over Physical
    link
  • Physical addressing
  • Framing
  • Flow control
  • Error control
  • Synchronization
  • Access control

30
Data Link Layer
Figure shows Framing
31
Data Link Layer Example
32
Network Layer
  • The network layer is responsible for the
    source-to-destination delivery of a packet
    possibly across multiple networks (links)
  • Switching Routing
  • Logical Addressing
  • Higher layers do not need to know about
    underlying technology
  • Not needed on direct links

33
Network Layer Example
34
Network Layer Example
35
Transport Layer
  • Control for information transfer between end user
    system
  • Segmentation Reassembly
  • In sequence
  • Connection control
  • Flow control
  • Error control
  • Quality of service (QoS)

36
Transport Layer
37
Transport Layer Example
38
Session Layer
  • Control of dialogues between applications in end
    systems
  • Dialogue discipline (full duplex or half duplex)
  • Grouping
  • Recovery

39
Presentation Layer
  • The presentation layer is concerned with the
    syntax and semantics of the information exchanged
    between two systems
  • Data formats and Encoding
  • Data compression
  • Encryption (senders transforms the original
    information to another from and sends it out over
    the network)

40
Presentation Layer
41
Application Layer
  • The application layer provides user interface and
    support for services such as electronic mail,
    remote file access and transfer, shared database
    management, etc.
  • Network virtual terminal (allows a user to log on
    to a remote host)
  • File transfer, access, and management (FTAM)
  • Mail services
  • Directory services

42
Application Layer
43
Summary of Layer Functions
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