Introduction to Networking

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Introduction to Networking
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Key Terms

• packet
• envelope of data sent between computers
• server
• provides services to the network
• client
• requests actions from a server (i.e. makes
  requests to a server)

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Local Area Network (LAN)

• computers and peripherals directly linked
  together in a single area
• room, office, or building
• enables sharing of peripherals (e.g. printer)
• commonly uses client-server model
• one machine acts as the central node (server)
• all others are clients
• LANs may connect to other LANs or to the outside
  using a gateway

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Wide Area Network (WAN)

• a really, really big network
• your house ? ISP ? Internet
• Washington-Lee ? Yorktown ? etc.
• allows a computer to connect to other computers
  over a wide geographic area

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Hardware

• network cable
• Network Interface Card (NIC)
• hub
• connects together multiple computers or segments
• any incoming data will be broadcasted out to all
  ports
• switch
• connects together multiple computers or segments
• analyzes network traffic and learns which
  machines are connected to particular ports
• incoming data is forwarded through proper port
• router
• forwards traffic to proper destination
• programmable (e.g. filter traffic)
• gateway
• a computer that connects users of a LAN to
  another network

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Topologies

• network layout
• in what configuration are the computers connected
  together
• Example configurations
• star
• bus
• hybrid

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Bus topology

• single cable used to link all computer together
• all computers can see all traffic, but only
  grab their respective data

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Star Topology

• computers are connected to a switch or hub
• if any client machine fails, the network keeps on
  truckin

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Hybrid Topology

• a combination of two or more topologies
• Example star-bus topology

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Packets

• an envelope of data sent between computers
• typically contains
• source (origin) address
• destination address
• sequence numbers (for packets that combine into
  one larger piece of data)
• timestamp (i.e. postmark)

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More Key Terms

• data integrity
• making sure that what is received is what was
  transmitted
• how does data integrity compromised?
• noise / interference on a line ? error in message
• hacking (hax0ring)
• data security
• preventing unauthorized access to data
• examples
• required user logins
• data encryption
• permissions (one user cannot access another
  users data)

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Protocols

• technical word for agreed set of rules
• Jack Bauer breaks protocol
• networking protocols define how two computers
  exchange information
• initiating a message (multiple packets!)
• acknowledging that a message has been received
• error checking
• compression

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Detecting Errors

• Check sums ? SEE 3.6 ERRORS SLIDES
• Parity checking
• even parity
• count the number of 1s in a bit string
• if the of 1s is even
• append a 0 to maintain the total number of 1s as
  even
• if the of 1s is odd
• append a 1 to make the total number of 1s even
• odd parity
• count the number of 1s in a bit string
• if the of 1s is even
• append a 0 to make the total number of 1s odd
• if the of 1s is odd
• append a 1 to maintain the total number of 1s as
  odd

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Detecting Errors contd

• Assume we use one of the parity checks, then the
  destination computer knows if a messages bits
  are messed up EXCEPT when?

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Random Questions

• Why is speed important in data transmission?
• How can speed be increased?
• What is the function of a web browser?
• What is the function of a search engine?

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Practice Question

• You are asked to backup all the contents of a
  1000 GB server. You may backup the servers
  contents via networking or tape backup, and the
  backup copy must be stored at the backup
  location. Assume you have a 3 Mbit / s data
  connection to the backup location. If you
  physically mailed the servers tape backups, it
  would take a week to reach the backup location.
  Which option is best to save time?