Network Concepts

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• Network Concepts

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Networks

• LAN
• WAN

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• Main Concepts

• Protocol
• Media
• Topology

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• Peer -to -Peer

Client Server
Client Server
Client Server
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• Client/Server

Server
Client
Client
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• Bus

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• Ring

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• Star

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• Star - cable
• Bus - signal

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• Star - cable
• Ring - signal

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• Media

• Coax
• Twisted Pair
• Fiber Optic
• Wireless

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• OSI Reference Model

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Application
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Presentation
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Session
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Transport
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Network
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Data Link
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Physical
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OSI Layers

• Physical
• Signal encoding (voltage, amps, timing)
• Connectors (BNC, RJ-45, ST)
• Bit oriented
• Data Link
• Frame oriented
• Error detection
• Media access control (token, CSMA/CD)

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OSI

• Network
• packet (datagram) oriented
• Route data from network to network
• Fragment and reassemble packets
• Transport
• Reliable connection ACK, NACK
• Sequenced delivery
• Flow control

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OSI Layers

• Session
• Logical connections
• Presentation
• Character codes (EBCDIC vs. ASCII), encryption,
  Compression (nice theory, usually done in other
  layers)
• Application
• Like ftp, telnet, email, www, file and printer
  sharing

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• IEEE vs. OSI

IEEE
LLC Logical Link Control
OSI
MAC Media Access Control
Data Link
Physical
Physical
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• IEEE Standards

• 802.2 Logical Link Control
• 802.3 CSMA/CD (Ethernet)
• 802.4 Token Bus
• 802.5 Token Ring

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• 802.3

10BaseF
10Base5
10Base2
10BaseT
1000BaseT
100BaseTX
10Broad36
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• DIX

Ethernet

• Digital
• Intel
• Xerox

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• IEEE vs. Ethernet
• Terminology

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• Ethernet Frame

Preamble
Destination Address
Source Address
Length/ Type
LLC/ Data
Frame Check Sequence
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• Ethernet Frame

Preamble
Destination Address
Source Address
Length/ Type
LLC/ Data
Frame Check Sequence
64 bits of alternating ones and zeroes, for
hardware synchronization, ending with two ones
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• Ethernet Frame

Preamble
Destination Address
Source Address
Length/ Type
LLC/ Data
Frame Check Sequence
48-bit address of station frame is being sent to
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• Ethernet Frame

Preamble
Destination Address
Source Address
Length/ Type
LLC/ Data
Frame Check Sequence
48-bit address of station sending the frame
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• Ethernet Frame

Preamble
Destination Address
Source Address
Length/ Type
LLC/ Data
Frame Check Sequence
16-bit field, length of frame in 802.3, type of
frame in DIX
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• Ethernet Frame

Preamble
Destination Address
Source Address
Length/ Type
LLC/ Data
Frame Check Sequence
46 to 1500 bytes of data, includes LLC fields in
802.3
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• Ethernet Frame

Preamble
Destination Address
Source Address
Length/ Type
LLC/ Data
Frame Check Sequence
32-bit cyclic redundancy check (CRC) code
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• Ethernet Addresses

• 48 bit
• normally shown in HEX
• e.g. 02-60-8C-44-59-E0
• first 24 bits are obtained from IEEE by hardware
  manufacturers
• one bit is used to distinguish unicast from
  multicast addresses
• one bit is used to distinguish locally assigned
  addresses(rare) from globally assigned addresses
  (typical)

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• Transmission Types

• Unicast - intended for one specific station
• Broadcast - intended for all stations
• Multicast - intended for a group of stations

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• CSMA/CD

• Carrier Sense, Multiple Access with Collision
  Detection
• Carrier sense - don't transmit if there is
  already a signal
• Collision detection - if a collision is detected
  stop, wait, and retransmit

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• No Carrier

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• Transmission

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• Transmission

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• End of Transmission

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• Transmission

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• Second Transmission

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• Collision

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• Collision detected

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• Wait

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• Repeater Hub

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• Repeater Hub

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• Repeater Hub
• one station transmits

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• Repeater Hub
• signal repeated on all other ports

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• Repeater Hub
• end of transmission

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• Repeater Hub