INLS102 Week2: Networking: Clients and servers UNIX file directory system

1
INLS102 Week2Networking Clients and
serversUNIX file directory system

• Date 9/08/05
• Instructor Leo Cao

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Objective for today

• Recognize IP addresses, MAC address, DNS, default
  gateway, and other networking information
• Differentiating client and server
• Knowing where you are in a file directory system,
  and how to move elsewhere

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Transmission Control Protocol (TCP) --- how to
connect

• TCP enables two hosts to establish a connection
  and exchange streams of data.
• Packet disassembly (local host) and re-assembly
  (destination) rules
• Error recovery by verifying correct delivery of
  data

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Packets

• Packets all data are split into small data
  packets prior to being sent over the network,
  then the packets are reassembled at destination
• Packets contain
• Headers (all relevant info about the packet,
  including IP and protocol types)
• Payload (data itself)
• Trailer (typically contains a couple of bits that
  tell the receiving device that it has reached the
  end of the packet
• http//computer.howstuffworks.com/question525.htm

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IP address hierarchy

• IP address hierarchy
• 152.1 ncsu.edu
• 152.2 unc.edu
• 152.2.81 ils.unc.edu
• 152.2.81.123 ils-pc13.ils.unc.edu
• 152.2.81.55 idl55.ils.unc.edu
• 152.2.83 jomc.unc.edu
• 152.2.131 cs.unc.edu
• 152.3 duke.edu
• 152.9 nccu.edu
• The host name is a translation of the IP address
• Try to type 152.2.81.1 in your browser
• nslookup exercise
• Startrun --- nslookup www.ncsu.edu

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Routing

• Routing
• manage internet traffic by deciding where to send
  packets next
• find efficient routes from the source to the
  destination
• Machines on the same network share similar
  starting IPs
• similar to post office service

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Client/Server relationship

• Client-server relationship between two programs
  http//computer.howstuffworks.com/web-server.htm/p
  rintable
• Client send requests to the server
• Server responds and serves files
• This is the model used by TCP/IP for webpages,
  and most networks and systems in use today.
• Every time you click on a link, a request is sent
  to the server, asking for data, and the server
  sends the data back, then its displayed on your
  screen.

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Centralized architecture

• Before PCs, this was the norm of computing
• Telnet still follows this model, your computer
  telnets to that main computer, processing are
  done on the server.
• This type of network is still in use today
• Secure, absolute control
• High processing power

Mainframe computer (size of a house) Process
requests from the terminals
Dumb display terminals
Dumb display terminals
Dumb display terminals
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De-centralized architecture

• In de-centralized or distributed systems, dumb
  terminals got smarter, and could do their own
  processing. Basically, the network is no longer
  solely dependent on the mainframe.
• Inter-connected machines
• Any computer installed with server software can
  act as an server. In a sense, a client computer
  could simultaneously operate as a server.
• Inter-connected clients with file transfer
  capabilities is whats known as the peer-to-peer
  network

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The 7 layer OSI model (Open System
Interconnection)

• OSI is another protocol, serves similar functions
  as TCP/IP, they dont conflict
• There are differences between them, if you take
  networking classes in the future, see
  http//www.cellsoft.de/telecom/tcpiposi.htm for
  details
• For now, just know that theres something called
  OSI model, and it has 7 layers.
• This is optional material

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Class Exercise for Network Configuration

• Windows commands hostname, ipconfig, nslookup,
  ping, tracert, arp
• Open Windows command interpreter Start / Run /
  type 'cmd'
• hostname (hostname of a host computer) hostname
• ipconfig (network configuration settings)
  ipconfig /all
• nslookup (domain name server lookup) nslookup
  isis.unc.edu (nslookup 152.2.1.217)
• ping (send an echo request to a host for response
  times) ping www.unc.edu
• tracert (trace the route to a host) tracert
  www.ils.unc.edu (www.jomc.unc.edu,
  www.cs.unc.edu, www.lis.uiuc.edu)
• arp (Address Resolution Protocol IP to Ethernet
  address map or to a physical machine address)
  arp -a
• To get help, type 'command /help' ping /help,
  ipconfig /help, arp /help
• type 'exit' or 'c' (CTRL-c) when in trouble

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Unix file directory system

• Picture the upside down tree, the first level is
  called the root
• The branches, or folders, can contain sub-folders
• You are currently located in one of those boxes,
  if you are in the mary folder, your current
  location is, /users/mary

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Trees and trees

• The windows file directory system is based off
  the unix one, so its just about the same
• Burn the tree structure into your head, know
  where you are, and be able to move to where you
  want to be
• Example in windows

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For next week

• Assignment 1 Due on Thursday
• Readings as usual