ccm 4300 lecture 3
play

CCM 4300 Lecture 3 Computer Networks: Wireless and Mobile - PowerPoint PPT Presentation

CCM 4300 Lecture 3 Computer Networks: Wireless and Mobile Communication and Mobile Communication Systems


  1. CCM 4300 Lecture 3 Computer Networks: Wireless and Mobile Communication and Mobile Communication Systems ������������������ �������������������������������� �

  2. ��������������������� � introduced a classification of computer networks � Introduced circuit and packet switching � � described networks with different scale � introduced the various network standards, how they are created and by whom �

  3. ��������������� � Lesson Objectives � Network Topologies � Introduction – an example of human-to-human interaction � What is a protocol? � What is a protocol? � ISO OSI Reference Model - TCP/IP protocol � �������������������������� �

  4. ����������������� � At the completion of this lesson you should be able to � understand network logical and physical topologies � understand the concept of layering and structure of the ISO Reference Model � describe the functionality of each layer in the ISO � describe the functionality of each layer in the ISO Reference Model � understand the basic concepts of the client server architecture �

  5. ������������������������������� � ������������������������������������������� � �������!�������� ����������������������������"� � �������������������#���������������������� � $�����������������������%��������������������������� ����������������"� � &�����������������������������!��������������������� � &�����������������������������!��������������������� �����������������������������"� � (�����������������!���������������������� �������������������������������������������������� ����������������"�� '

  6. Bus � Each computer is connected to a single cable which connects all of the computers. � This is the cheapest network topology as the smallest amount of cabling is required. � If the network cable breaks anywhere then none of the computers can access the network. )

  7. Ring � Each computer is connected to the two computers on either side of it. � The last computer is linked to the first to form a ring. � If the network cable breaks anywhere then none of the computers can access the network. � Long cable length *

  8. Mesh � Any computer can be connected to any other computer. � There are multiple routes. If one link fails messages can go another way so this topology is very reliable. � The Internet has a mesh topology. +

  9. Star � All communication takes place via a central computer. � If the central computer fails the whole network will break down. � If one of the network cables breaks only the computer connected to that cable is affected. ,

  10. Extended Star � An extended star topology is like a star topology except that each device that links to the centre device is also the centre of another star. � Each of these devices acts as the centre of another star. another star. � An apparent advantage of this is to extend the length and the size of the network. � Limits the number of devices and the numbers of cables needed to interconnect to the central device. � Logically, the information in an extended star topology stays local �-

  11. ����(�����!�����.�������$� � ����������������������� ������� � ���������������� /�������. ������������ �����������������������0 � �����������������. �����������������. ���������������������� ����.�������������� � ���!��1���������. ����� �������������������� ���������2����!�3 ��

  12. ������������������� � Represent the “rules” for communication: � how do the computers initiate communication? � what features can be negotiated at the start? � the communication vocabulary - i.e. what requests (commands) can be given and what are the valid responses? � what kinds of data can be exchanged ? � how the communication can be closed in an orderly way ? ��

  13. ��������������������� ���� � A human protocol and a computer network protocol: �� �������������� �������������� ��*# �� �������������� ������� �����# ��$�� ( )) �������� !!"""#$�%#��#&' +����, ��$� ��

  14. ��������������������� ���� � $����������������������������������������������������� �4������� Header Header Data Data Control Message Information ��

  15. ��������������������� ���� � For two networked devices to communicate they must speak the same language (i.e. use the same protocol) � The protocols must be able to: - indicate who (what address) they want to talk to - indicate who (what address) they want to talk to - provide any required delivery assurances / recovery - control the flow of information � Must specify how to initiate, maintain and conclude the communications exchange �'

  16. ��������������������� ���� � Several protocols are involved in a network � Operate together in a layered manner - each layer builds upon the services of its lower layer(s) File Transfer Workstation End-to-end integrity Remote Internetworking Server Router WAN LAN �)

  17. ��������������������� ���� � A protocol (or more typically a protocol suite) is needed for communications - some organisations may use multiple suites (e.g. Novell and TCP/IP protocols) � Protocols are specified in the form of documents and usually implemented in software � A separate software package is needed for each different protocol suite to be supported �*

  18. -�.�.�-�����������/���� � Open Systems Interconnection � Developed by International Standards Organisation (ISO) - 1981 - revised in 1994 � Described in ISO-7498 standard � Proposes 7 layers � Provides: - a common terminology - a framework for networking �+

  19. ��������������.�-��������� � A layer should be created where a different level of abstraction is needed � Each layer should perform a well-defined function � The function of each layer should be chosen with a view to defining internationally standardised protocols � The layer boundaries should be chosen to minimise The layer boundaries should be chosen to minimise the information flow across the interfaces � The number of layers should be: - large enough that distinct functions are not thrown together - small enough that the architecture is not unwieldy �,

  20. .�-�����������/���� Source : Computer Networks 1996 ��5��--6����-+ �-

  21. .�-��������� ���� � Application - contains a number of standard protocols of general use - e.g. file transfer protocols, email, virtual - e.g. file transfer protocols, email, virtual terminals, telnet, etc... - any service program may define an application level protocol that clients must use. ��

  22. .�-��������� ���� � Presentation - concerned with the representation of data (e.g. between different hardware, Operating Systems etc.) � Session - allows clients of an OS on one machine to establish and use sessions with clients of an OS on another machine - Controls the dialogue between applications in end systems. -Controls the direction of traffic. - Other functions: recovery, synchronisation, etc.. ��

Download Presentation
Download Policy: The content available on the website is offered to you 'AS IS' for your personal information and use only. It cannot be commercialized, licensed, or distributed on other websites without prior consent from the author. To download a presentation, simply click this link. If you encounter any difficulties during the download process, it's possible that the publisher has removed the file from their server.

Recommend


More recommend