I’ll try to keep it a little shorter this time.

Major issues for converged enterprise networks

  • Available bandwidth: competition among applications
    • Fixes
      • Increase bandwidth: More power!
      • Properly queue based on classification and marking: QoS
      • Compress: cRTP, TCP header compression, etc.
  • Delay: Lead time to get a packet to the destination
    • Types of delay
      • Processing delay: routing, switch delay
      • Queuing delay: how long a frame stays in an output queue
      • Serialization delay:  how long to put the frame on the wire
      • Propagation delay: the time to cross the physical medium
  • Jitter (delay variation): Variation is the delay
    • Different delays mean different arrival times
    • De-jitter buffers save up packets to reduce jitter (like the old CD writers)
    • Fixes
      • More bandwidth
      • Prioritize sensitive data and forward first
      • Remark (reclassify) packets based on sensitivity
      • Enable L2 payload compression: make sure compression delay isn’t worse than the jitter
      • Use header compression
  • Packet loss: Packets are lost in the network somewhere
    • Fixes
      • More bandwidth
      • Increase buffers space: more room for the queue on the interface
      • Provide guaranteed bandwidth: Queuing and QoS
      • Congestion avoidance
        • Random Early Detection (RED) and weighted RED (WRED) drop packets before the queue is full
        • Selective dropping is better than FIFO or LIFO dropping

QoS History