Networking Media

1
Networking Media

• Chapter 1

All Material Taken from Faster Smarter Network
Certification by Melissa Craft
2
Topologies

• Physical Topologies
• Point-to-point connections
• Multipoint connections
• Logical Topologies
• How does the data flow?

3
Physical Star Topology

• A central hub connects to each device
• Central hub can also be a switch, multipoint
  repeater, or Multi-station Access Unit (MAU or
  MSAU)
• Most common topology

4
Physical Bus Topology

• Single cable used to connect multiple devices
  with termination at both ends

5
Physical Mesh Topology

• All devices are connected to each other

Full mesh topology
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Hierarchical Mesh Topology

• Devices are not connected directly to every other
  device, but a connection path can be made.

7
Physical Ring Topology

• Closed loop of cabling connecting each device in
  a ring.
• Data can flow in either direction, depending on
  configuration.

8
Wireless Topology

• Areas capable of transmitting data arranged in
  cells
• Access points are used

9
Logical Ring Topology

• Physically a star, but data flows in one
  direction, thus creating a circular path for data

10
Cellular Topology

• Basically a logical bus topology
• Devices can seamlessly move between cells
• See P. 16 in text

11
Accessing the Media

• Contention
• CSMA/CD
• CSMA/CA

12
CSMA/CD

• Carrier Sense Multiple Access/Collision Detection
• Walking in without ringing the bell!
• Just make sure the door is open, even if someone
  else is in the doorway.
• When a collision occurs, each sending device must
  resend the message.

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CSMA/CD (cont.)

• Advantages
• Easy to implement
• Requires few resources
• Very fast when traffic is light
• Disadvantages
• Speed can decrease significantly in high traffic
• Only detects collisionsdoesnt avoid them
• All data is treated equally

14
CSMA/CA

• Carrier Sense Multiple Access/Collision Avoidance
• Ring the bell before entering!
• If someone is in the doorway, wait for them to
  get out of the way.
• Uses special contention protocols and time slices

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CSMA/CA (cont.)

• Advantages
• Less administrative overhead than CSMA/CD
• Allows more messages to be seemingly sent
  simultaneously by using time slices
• Significantly reduces collisions, increases data
  throughput
• Disadvantages
• Collisions still occur
• All data still treated equally

16
Token Passing

• If you dont have it, you cant get in!
• A special data packet (token) is passed around
  the network
• Only the device which has the token can transfer
  data

17
Token Passing (cont.)

• Advantages
• No data collisions!
• Highest amount of data throughput in high traffic
  networks
• Utilizes demand priority (not all data is treated
  equally)

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Token Passing (cont.)

• Disadvantages
• Much more expensive to implement
• Requires more processing power to deal with the
  token
• Each device must be aware of its neighboring
  devices so that the token can be received
  passed along
• Low data throughput in low traffic networks
• Low priority data can have trouble being sent

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Media Types

• Unshielded Twisted Pair (UTP)
• Uses twisted pairs of wires
• Subject to crosstalk
• See table on p. 21
• Shielded Twisted Pair (STP)
• Heavy outer covering (shield)
• Much more resistant to noise
• More expensive
• Difficult to install due to lack of flexibility

20
Coaxial Cable

• Standard Cable TV cable
• Copper conductor surrounded by insulation
• Braided or mesh outer cover surrounds the
  insulation (also a conductor)
• PVC plastic jacket encases cover

21
ThickNet (RG-8)

• Older type of coaxial cable
• Physical bus topology
• Very thick shielding
• Difficult to work with because it is so rigid
• 50 ohm terminators at both ends of bus
• Uses vampire tap connectors

22
ThinNet (RG-58)

• Much more flexible than ThickNet
• Physical bus
• Maximum of 30 devices on 185 meter length of
  cable
• BNC connectors are crimped onto the cable for
  connectivity
• Terminators at both ends

23
Fiber Optic Cable

• Thin strand of glass enclosed in a glass tube
• Shielded with PVC plastic
• Very brittle, not very flexible
• Immune to crosstalk
• Supports very long distances
• Requires specialized installation
• More expensive option

24
Wireless Media

• IEEE 802.11 specification
• Radio frequency (RF) 2.4 gigahertz range for
  wireless data transmissions
• Data rate depends upon type of protocol
  implemented. (802.11-B, 802.11-G)
• No cables, easy to install configure
• Poor security
• Distance can be limited

25
Media Connectors

• RJ-11
• Common telephone connector
• RJ-45
• Most common network connection type
• Looks like a fat telephone connector

26
Media Connectors

• AUI (Attachment Unit Interface)
• Used in ThickNet and ThinNet cables
• 15 pins on the end that connects to the network
  interface card. (NIC)
• Other end connects to a short cable which
  connects to a transceiver, which connects to the
  main cable.

Transceiver
AUI
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Media Connectors

• BNC (British Naval Connectors)
• Used in ThinNet 10Base2 Ethernet
• Resemble cable TV connectors

28
Media Connectors

• ST
• Used in duplex fiber optic connections

29
Media Connectors

• SC
• Used in simplex fiber optic connections

30
Media Connectors

• RS-232
• 9 or 25 pins connectors
• Used only in serial communications with analog
  modems

31
IEEE Specifications

• 802.2 (LLC)
• Logical Link Control
• Protocol Specification used by all 802 standards

32
IEEE Specifications

• 802.3 (Ethernet)
• 10BaseT
• 10Base2
• 10Base5

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IEEE Specifications

• 802.3u (Fast Ethernet)
• 100BaseT

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IEEE Specifications

• 802.4
• Token Bus
• 802.5
• Token Ring

35
IEEE Specifications

• 802.6
• Metropolitan Area Networks (MAN) based on
  bidirectional fiber optic bus

36
IEEE Specifications

• 802.11(a b)
• Wireless networks

37
FDDI

• Fiber Distributed Data Interface
• Dual ring topology (uses token passing)
• If one ring fails, the other takes over
• Good for long distances
• Large data capacity