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Internetworking Concept and Architectural Model

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Internetworking Concept and Architectural Model Chapter 3 – PowerPoint PPT presentation

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Title: Internetworking Concept and Architectural Model


1
Internetworking Concept and Architectural Model
  • Chapter 3

2
Introduction
  • Now that we know the technology that is used for
    transmission, how do we create a coordinated unit
    for communication?
  • Goal
  • To hide details of the underlying network, and
    build the necessary software to provide a
    framework for communication
  • Two approaches to hiding details
  • Application programs translate for their hardware
  • Intermediate computers computers pass data, dont
    look at it

3
Network Level Interconnection
  • Small packets of data are sent from source to
    destination without using intermediate
    application programs
  • This separates the application from the transfer
    of packets
  • It also allows the underlying network structure
    to change without modifying the application
  • Separation of communication details from the
    messages being sent

4
Design of communication systems
  • No single network hardware technology can satisfy
    all constraints
  • speed, distance, cost
  • Users desire universal interconnection
  • Therefore, we need a unified, cooperative
    interconnection of (heterogeneous) networks which
    supports a universal communication service

5
Design of communication systems
  • New software, inserted between the
    technology-dependent communication mechanisms and
    application programs will make the collection of
    networks appear to be a single large network

6
Design of the Internet
  • Do not want to require users to understand the
    hardware details
  • Do not want to mandate which hardware to use
  • Do want to allow users to connect with computers
    that are not directly connected
  • Do want to allow users to connect to all others
    connected to the Internet (or an internet)

7
Internet Architecture
  • How is one network connected to another?
  • It involves more than just a cable the two
    networks need to each be connected to a computer
    that will pass packets between them
  • Called a router or a gateway See Figure 3.1
  • Each router needs to know something of the
    networks beyond those directly connected to it -
    see Figure 3.2
  • Each router needs to know the destination
    network, not necessarily the actual computer
    within the network
  • Routers in TCP/IP internets are usually small and
    have little memory

8
The Users View
  • Think of an internet as a single, virtual network
    to which all machines connect, despite the
    physical connections, as in Figure 3.3
  • The network software is all that needs to be
    reconfigured when to networks topology changes
  • Figure 3.3b shows that not all networks need to
    be directly connected to all others (see the
    routers)
  • The intermediate networks agree to handle traffic
    in exchange for being connected themselves

9
All Networks are Equal
  • A network is a network, regardless of whether it
    is the smallest LAN or the largest WAN

10
Unanswered Questions
  • What do the internet addresses look like?
  • What does a packet look like?
  • What happens when too many packets arrive too
    quickly?
  • How can multiple application programs executing
    concurrently on a single computer send and
    receive packets to multiple destinations without
    getting entangled?

11
Summary
  • Interconnected systems agree to conventions so
    that they can communicate with other computers
  • An internet allows two computers to communicate
    even if they are not connected within the same
    network, or directly connected networks
  • Computers must agree on a set of universal
    identifiers and a set of procedures for moving
    data
  • Connections between networks are made with
    routers which attach to two or more networks
  • Routers forward packets from one network to
    another

12
For Next Time
  • Read Chapter 4
  • See exercises, write your own notes
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