Download Media:Networking

Introduction to Networking
Key Terms
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packet
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server
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envelope of data sent between computers
provides services to the network
client
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requests actions from a server (i.e. makes
requests to a server)
Local Area Network (LAN)
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computers and peripherals directly linked together in
a single area
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enables sharing of peripherals (e.g. printer)
commonly uses client-server model
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room, office, or building
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”
Wide Area Network (WAN)
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a really, really big network
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your house  ISP  Internet
Washington-Lee  Yorktown  etc.
allows a computer to connect to other
computers over a wide geographic area
Hardware
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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
Types of Network Cables
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Modes of communication
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Telephone lines ~ dialup
Coaxial cable ~ cable internet
Twisted pair ~ ethernet
Fiber-optic ~ FIOS
Microwave (high frequency radio) ~ wifi
Satellite
Topologies
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network layout
in what configuration are the computers
connected together
Example configurations:
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star
bus
hybrid
Bus topology
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single cable used to link all computer together
all computers can “see” all traffic, but only grab their respective
data
Star Topology
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computers are
connected to a switch
or hub
if any client machine
fails, the network keeps
on truckin’
Hybrid Topology
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a combination of two or more topologies
Example: star-bus topology
More Key Terms
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data integrity
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making sure that what is received is what was transmitted
how does data integrity compromised?
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noise / interference on a line  error in message
hacking (hax0ring)
data security
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preventing unauthorized access to data
examples:
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required user logins
data encryption
permissions (one user cannot access another user’s data)
Packets
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an envelope of data sent between computers
typically contains:
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source (origin) address
destination address
sequence numbers (for packets that combine into
one larger piece of data)
timestamp (i.e. postmark)
Packet-switched vs. Circuit-switched
Networks
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http://vimeo.com/10347883
Packet Switching
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Break data up into packets & transmit
Individual packets are not all necessarily
transmitted through the same links
Each packet travels over the best available
link at the time
Packets may arrive at destination out of order
 must be re-ordered and reassembled
(protocol!)
Protocols
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technical word for “agreed set of rules”
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“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
Internet Protocol
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source (origin) address
destination address
Activity:
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Each person receives an address on a card
One person in each row will be a switch
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Rules:
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The switch will write down on his/her card that he/she is a
switch
The switch will write down the range of addresses on their
card
NO TALKING
Switches can move cards
As a class, we will send several messages
IP Problems
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What happens when we send large data?
Let’s try to send lots of messages now
Problems?
Transmission Control Protocol
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Messages now contain
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sequence numbers (for packets that combine into
one larger piece of data)
timestamp (i.e. postmark)
Now let’s try to send bigger messages
Network Security
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User logins
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Layered access via permissions
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Different levels of user access
Firewall
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Must be an authenticated user to login
Password, smartcard, fingerprint, iris, etc.
Inspect and filter incoming traffic
Encryption
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Encrypt data so that it is unreadable by outsiders