SubNet Standards

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SubNet Standards

• 802.3 Ethernet
• 802.5 Token Ring
• Fiber Distributed Date Interface (FDDI)
• 802.11 Wireless LANs

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10Base5 Standard

• 802.3 10Base5
• Trunk cable (backbone)
• Transceiver (media attachment unit)
• AUI (attachment unit interface
• Segments
• 5-4-3 Rule for connecting segments by repeaters
• Collision domain (group of segments)

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10Base2 Standard

• 802.3 10Base2
• Thinner Cable
• BNC Plug
• T-Connector
• Segments
• 5-4-3 Rule
• A segment can have 30 stations
• Proper termination required

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Mixed Networks

• Use coax (10Base5) or fiber (10BaseF) for
  backbone
• Use hub with multiple plugs to connect different
  type segments
• Mixing cable types (Physical layer standards) has
  no impact on MAC layer operation

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Figure C.5 802.2 Logical Link Control (LLC)
Layer Frame Formats  
 
  Notes DSAP Destination Service Access Point
SSAP Source Service Access Point SNAP Subnet
Access Protocol
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802.5 Token Ring Standard

• Token circulates on the ring
• Token message is passed from sending station to
  receiving station
• Possible errors
• Broken Ring use dual rotating rings that are
  self-healing
• Losing Token One station must monitor token as
  it traverses the ring. New tokens are generated
  as needed and duplicate tokens are removed by
  monitor.
• Monitor failure another station can issue a
  claim token and become the new monitor

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Status of Token-Ring

• 4 to 16 Mbps, 100 Mbps in development
• 11 of NICs sold in 1997 were Token Ring
• 85 were Ethernet NICs
• Updating has probably come too late

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FDDI

• Ring topology at physical layer
• Token passing at MAC layer
• 802.2 at LLC layer
• Derived from 802.5 technology
• Designed to run at 100 Mbps
• Fiber or copper media

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More on FDDI

• FDDI ring has maximum circumference of 200 km
  (125 miles)
• Backbone network for individual LANs
• IEEE compatible ANSI standard
• Never really caught on because of single speed
  (not scalable) and expensive NICs
• Prices have fallen, but still exceed other 100
  Mbps LAN technologies

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Figure C.9 802.11 Wireless Network Standards