3COM SuperStack 2 10/100 Baseline Switch 3C16465A

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3COM SuperStack 210/100 Baseline Switch3C16465A

• Naomi Avigdor
• October 25, 2001

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CSMA/CD

• Carrier Sense Multiple Access with Collision
  Detection
• Bus topology shared media
• Half Duplex - CSMA/CD states
• Idle
• Transmission
• Contention if no collision occurs before the end
  of the period, then complete transmission of the
  frame

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Half Duplex MAC (think conference call)

• CS Carrier Sense (Is someone already talking?)
• If not then transmit if you have data
• If yes - wait
• MA Multiple Access (everyone hears everyone)
• Jim Hey Scott, This is Jim, what is the weather
  in Chicago?
• Tony Hey Susan, This is Tony, would you marry
  me?
• CD We are both talking
• everybody stop, we have a collision

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Collision Domain

• Twice the maximum network end to end propagation
  delay
• Defines Network diameter
• Defines minimum frame size

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Full Duplex Ethernet Switch

• UTP Unshielded twisted pair
• Transmit pair separate from receive pair
• Point-To-Point only
• Media not shared, no collision domain
• Aggregate throughput is doubled
• Transmit and receive simultaneously
• Each switch port own MAC

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Switch Internals

• Shared RAM
• Store Forward or Cut Through
• Input queuing versus Output queuing
• Head-of-Line (HOL) blocking
• Scheduling
• Port priority
• Round Robin
• Global FIFO

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Individual Switch Write Performance
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Aggregate Switch Write Performance
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Flow Control

• Ok to mix port speed
• Use MAC Pause Frame for flow control

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Channel Bonding

• Network Interface Cards (NICs) bonded for
  outgoing load balancing
• Does it bond for incoming traffic???

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References

• http//www.iol.unh.edu/training/ge/Ethernet_Evolut
  ion_files/frame.htm
• IEEE 802.3 standards doc.
• Computer Networks Third Ed.by Andrew S. Tanenbaum