The following points helps you in understanding NetScaler SD-WAN best path determination:

• Per-packet determination
• Variety of factors in determining packets assigned path
• Received packet from any WAN path calculates:
  • One-way trip latency
  • One-way loss
  • One-way bandwidth
  • One-way jitter

• Sent packet first references latest calculations of NetScaler SD-WAN “Map”
• WAN Path state:
  • DEAD – no Virtual Path packet received for 1.5 seconds
    • Dead paths never used
  • BAD – 3 lost packets out of 10, 4 lost packets out of 10
    • Bad paths only used if all other paths are dead
    • If all paths are bad, uses the largest capacity path
    • Bad to good transition – 10 second path validation time
  • GOOD
    • Every 2-3 packets of incoming packets are processed as a sample size used to report conditions back to the local device

• CTX201618 - Path DEAD on Newly Installed or Existing WAN Link of NetScaler SD-WAN.
• CTX201619 - Path Continuously Flipping Between GOOD/BAD/DEAD on a Newly Installed WAN Link of NetScaler SD-WAN.