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Lecture 18a - PowerPoint PPT Presentation

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Chapter 1 Introduction to Internetworking (Recommended reading: Comer, Vol 1, Chapters 1, 3) Motivation for Internetworking What is internetworking ? Connect multiple networks of one or more organizations into a large, uniform communication system .

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Chapter 1 introduction to internetworking recommended reading comer vol 1 chapters 1 3 l.jpg
Chapter 1Introduction to Internetworking(Recommended reading: Comer, Vol 1, Chapters 1, 3)

  • Motivation for Internetworking

    • What is internetworking?

      • Connect multiple networks of one or more organizations into a large, uniform communication system.

      • The resulting system is called an internetwork or internet.

        • notion of an unified internet

    • Why internetworking?

      • There are many existing networks located at different places. It is desirable to connect them together for global communication and information exchange.

      • In the future, there will still be multiple types of networks, because no single network technology can fulfill all the needs. It is necessary to connect them for communication.

        • E.g, multinational companies have high speed optical connections, whereas some other companies located in older buildings still use traditional thin-wire or twisted pair Ethernet connections.

Dr. Y.W. Leung

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  • Different networks may not be compatible. Internetworking requires:

    • additional hardware to interconnect the networks,

    • additional software on all the attached computers to execute a common set of internetworking protocols to ensure that these computers can communicate.

      • One vendor’s email program may talk to another vendor’s email program.

  • Internet Architecture

    • Different networks may use different technology and methodology.

      • different transmission media, addressing scheme, packet format, and etc.

      • No single network hardware can satisfy all constraints of different users/networks.

    • Physically, two networks can only be connected by a computer that attaches to both of them.

  • Dr. Y.W. Leung

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    • Routers (or gateways) are used to connect the heterogeneous networks.

      • A router is a special-purpose computer having processor, memory, and I/O interface.

      • A router performs protocol conversion in order to transmit packets between different networks. Example:

      • The router captures packets from Net1 that are destined for Net2, and transfers them.

      • In practice, each router needs to know about the topology of the internet beyond the networks to which it connects.

    Dr. Y.W. Leung

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  • An internet consists of a set of networks interconnected by routers.

  • Each intermediate network must agree to handle transit traffic in exchange for the right to send traffic throughout the internet.

  • Internetworking Protocols

    • In an internet, all the computers and routers must agree on acommon set of internetworking protocols.

      • Even if these computers and routers are attached to different networks, they can still communicate.

  • Dr. Y.W. Leung

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    • What is a protocol? types of networks. Example:

      • A set of syntactic and semantic rules for communication.

      • details of message formats

      • How a computer should respond when a message arrives.

      • How a computer handles errors or other abnormal conditions.

      • Independent of lower layers or hardware

    • The protocols should be transparent, hiding the details of each network and the interconnection of these networks.

      • The users and application programmers are not required to know these details. They see the internet as a single, large network.

      • Users' view on the internet:

    Dr. Y.W. Leung

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  • TCP/IP is the most widely used internetworking protocol suite.

    • TCP: Transmission Control Protocol.

    • IP: Internet Protocol.

  • TCP/IP is now the defacto standard for internetworking protocols.

  • TCP/IP reference model:

    • Network Access Layer: Specify the protocols being used in the underlying networks.

  • Dr. Y.W. Leung

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    • TCP/IP reference model (cont.) types of networks. Example:

      • Internet Layer: Define a common packet format and the internet protocol for packet delivery.

      • Transport Layer: Define transport protocols (transmission control protocol (TCP) for connection-oriented transport, and user datagram protocol (UDP) for connectionless transport).

      • Application Layer: Define application protocols such as file transfer (FTP), email (SMTP), and virtual terminal (TELNET).

    • Possible protocols in each layer of the TCP/IP reference model:

    Dr. Y.W. Leung

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  • Epilogue

    • “Internet" or "internetwork" is composed of a collection of interconnected networks.

    • "Internet" is the single global internet that operates under the TCP/IP protocols.

    • "Intranet" is a private internetwork owned by an organization. It may be connected to the Internet through firewalls (we shall study firewalls later).

  • Dr. Y.W. Leung

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    • Tutorial Problems types of networks. Example:

      • How would your study be affected if there were no Internet?

      • List some networks that you have learnt from COMP 2330.

      • There are many different types of networks. Why?

      • A student argues that it is better to have only one type of networks because this can avoid the overhead of protocol conversion in internetworking. Do you agree?

      • What are the major functions of a router?

      • Many routers are available in the market and they have different prices. What factors would determine the price of a router?

      • If a router can connect to at most K networks, how many routers are required to connect N networks?

    Dr. Y.W. Leung