Internetworking

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Internetworking

• Henry C. Co
• Technology and Operations Management,
• California Polytechnic and State University

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(No Transcript)
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Computer Networks

• First computer
• Electronic Numerical Integrator And Calculator
  (ENIAC), U of Penn, 1946.
• 18,000 vacuum tubes, 60,000 lbs, 1,600 sq. feet.
• Businesses establish computer networks
• To let employees exchange documents with other
  employees within the company.
• To separate functions (A/R v. payroll)
• To shared services (printers, databases)
• Reliability
• Networking requires interconnection (wire, fiber,
  infrared, radio) and communication protocols (to
  control the passing of information).

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Network

• Two or more computers connected together
• Allows
• exchange of data
• separation of function (accounts receivable v.
  payroll)
• shared services (printers, databases)
• reliability
• Requires
• interconnection (wire, fiber, infrared, radio)
• communication protocols

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Network Topologies

• More than two computers causes complications
• Each machine on a network must have a unique
  address
• If machine 2 sends a message to machine 4, what
  tells 1, 3 and 5 to ignore it, but 4 to listen?
• Ethernet protocol.

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LAN Local Area Network
LAN Bus Topology
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Routing
Machine 35 wants to send a packet to Machine
249. Routers determine the path the packet will
take.
Router A can send the packet either way
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What Is a Router?

• A router is a device dedicated to the purpose of
  shipping packets between networks using special
  routing tables.
• In the early days of the Internet, routing was
  typically done by general purpose computers
  running special routing software. Today, a router
  is typically a dedicated network device from a
  vendor such as Cisco or 3Com.
• Routing tables are the network roadmap to the
  Internet. They contain rules to tell every router
  how to move a data packet to the next stage of
  the journey, which will usually involve many
  routers.

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The Internet

• The net is composed of
• Various types of wires and cable
• Computer hardware/ software
• Digital switches, and
• Peripheral technologies that support data flow
  and network security

Source http//www.slis.indiana.edu/hrosenba/www/L
561/tx/syll/commprint.html
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Controlling Traffic on the Information
Superhighway
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Client/Server

• Fundamental Internet structure
• Client requests service server provides it
• Data exchanged only through real-time messages
• Server may become a client to a different server.

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Packet Switching

• Digital data sent in small packages called
  packets.
• The packets contained data, address information,
  error-control information and sequencing
  information.
• The address information was used to route the
  packets of data to their destinations.
• The sequencing information was used to help
  reassemble the packets (which, because of complex
  routing mechanism could actually arrive out of
  order) into their original order for presentation
  to the recipient.

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Protocol

• Established and adhered-to way of doing things a
  set of rules that everybody obeys.
• Analogy rules that motorists must obey when
  driving. Imagine the information superhighway not
  having rules!

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Internet Protocols

• Protocols are rules of communication
• Communication consists of small acts
• Protocols formalize the notion of acts
• Protocols relate to other protocols in terms of
  layers

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Transmission Control Protocol (TCP)

• Once one computer establishes a link to another
  (which accepts the link) datagrams flow both ways
  (carries on dialog between client and server)
• Separates information into packets for
  transmission
• Assembles received information if a packet is
  garbled it only asks for that packet again.
  Smarter than most modem protocols

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Internet Protocol (IP)

• The Internetworking Protocol (IP) creates a
  network of networks.
• It defines the basic conditions that all hosts
  and routers on the net must follow to exchange
  data
• It defines the formation and exchange of packets
  (called IP datagrams)
• IP guarantees that the packet sent is the packet
  received and that any computer can send one to
  any other computer

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IP Addresses

• Each host on the Internet has a unique IP address
  
• Assigned by the Internet Corporation for Assigned
  Names and Numbers (ICANN http//www.icann.org/)
• 32-bit address dotted decimal notation, e.g.,
  204.202.129.230
• Each IP number represents one of 256 locations
  (domain.subdomain.organization.host)
• Each number represents an increasingly lower
  level of network (from Class A --gt B --gt C --gt
  Node)

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• IP addresses are stored in domain name servers
  (DNS)
• Once a host knows the IP address of the intended
  receiver, the packets can be sent
• Each packet has an IP for the sender, one for
  the receiver, and a sequence number for
  reassembling
• We use alphabetic address (userID_at_host.institutio
  n.domain)
• Main domains edu, com, gov, mil, org, net
  country codes
• Local DNS converts this address into the IP
  address automatically
• Like phone book, matches the name to the phone
  number
• If it cannot resolve the address, it sends a
  request to the next DNS in the hierarchy
• This continues until the address is resolved or
  an error message is returned

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Internet Host

• What is an Internet Host?
• A computer on the Internet that has a permanent
  IP address.
• A service provider has one IP address for every
  810 customers. Each IP address is associated
  with a phone line. When you dial up and make a
  connection, your computer is associated with the
  IP address allocated to the phone line you are
  connected.
• There are about 100,000,000 IP address on the
  Internet.

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Internet Layering
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Protocol Layers
Different functions in a post-office based
communication system
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ISO-OSI Layers

• The TCP/IP protocol suite is a network model with
  four layers. These layers correspond to the
  layers in the International Standards
  Organization (ISO) reference model.

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ISO Reference Model

• Physical Layer defines electrical and mechanical
  interfaces (e.g., fiber optics) to the network
  and determines the maximum bandwidth
• Data Link Layer transmission of data frames,
  access protocol to physical layer, error
  correction, flow control and frame
  synchronization
• Network Layer switches and routes packets,
  establishes logical association of remote
  stations. Providing services such as addressing,
  internetworking, error handling, congestion
  control, and sequencing of packets.
• Transport Layer provides a process-to-process
  connection.

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• Session Layer coordinates interaction between
  user application processes on different hosts.
  Types of sessions point-to-point, multicast (one
  to many), multidrop (many to one).
• TCP/IP and ATM networks do not explicitly have
  this layer, it is mostly folded into Transport
  Layer.
• Presentation Layer manages abstract data
  structures, conversion of different data
  formats/codes
• In TCP/IP and ATM networks, this layer is merged
  into Application Layer.
• Application Layer contains various protocols,
  e.g., ftp, telnet, SMTP (e-mail), etc.

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Internet Layering

• Network Interface layer
• The Network Interface layer of the TCP/IP model
  maps to both the Data Link and Physical layers of
  the OSI reference model
• Internetwork layer
• The Internetwork layer in the TCP/IP model is a
  direct equivalent to the Network layer in the OSI
  model. Logical addressing information, such as
  the IP address, occurs at this layer.

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• Transport layer
• Main protocols TCP UDP
• TCP provides reliable, connection-oriented
  communications between two hosts. UDP provides
  connectionless, datagram services between two
  hosts.
• TCP requires more network overhead than UDP
  because data is acknowledged as it is received.
• UDP is faster, but less reliable, because the
  recipient does not acknowledge data as it is
  received. UDP leaves communication reliability to
  the Application layer.

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• Application layer
• Includes protocols for e-mail, remote logins,
  file transfers, Web browsing, network management,
  and name management.
• The File Transfer Protocol (FTP) sends data over
  a reliable connection. This protocol can be used
  to send, delete, and move files to and from an
  FTP server and client.
• The Trivial File Transfer Protocol (TFTP) sends
  data using an unreliable connection. This
  protocol functions similarly to FTP, but is
  faster because it is not reliable. Unfortunately,
  a file transferred with TFTP stands a greater
  chance of being corrupted than if it were
  transferred with FTP.

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• The Network File System (NFS) is a distributed
  file system that allows data to be shared across
  a network, regardless of the type of computer,
  operating system, network architecture, or
  protocol. This standard UNIX file system allows
  remote files to be manipulated.
• The Simple Mail Transfer Protocol (SMTP) is the
  messaging or e-mail transfer protocol. This
  protocol allows mail to be transferred on TCP/IP
  networks, including the Internet.
• A Telnet client can use this terminal emulation
  protocol to log onto a remote machine or telnet
  server. The telnet user can then run programs on
  the remote computer.

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• rlogin This command-line utility allows you to
  navigate and manipulate a remote computers
  directory structure.
• SNMP SNMP permits remote tracking and management
  of TCP/IP hosts.
• The Domain Name System (DNS) service provides
  TCP/IP host name to IP address resolution.
• Hypertext Transfer Protocol (HTTP) allows WWW
  users to connect their computers to other
  computers on the Internet.