Chapter 1 Introduction to Internetworking Recommended reading: Comer, Vol 1, Chapters 1, 3

1
Chapter 1Introduction to Internetworking(Recomme
nded 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.

2

• Users point of view a set of application
  programs that use the underlying network to carry
  out useful communication tasks, e.g., World Wide
  Web, email, ftp, remote login.
• Interoperability the above applications can run
  on different types of computers.
• 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 vendors email program may talk to another
  vendors 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.

3

• 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.

4

• Different routers can connect different number
  and different types of networks. Example
• 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 a common set of internetworking
  protocols.
• Even if these computers and routers are attached
  to different networks, they can still communicate.

5

• What is a protocol?
• 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

6

• Actual view
• 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

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• TCP/IP reference model (cont.)
• 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

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• TCP/IP reference model versus the OSI model
• 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).

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• Tutorial Problems
• 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?