Excessive packet round-trip time (RTT) detected

The longest round-trip time recorded during the test exceeds some threshold.

Recommended action

  • Observe secondary messages. If it appears that these delays are affecting the end-to-end path, check for media errors, especially wireless and unseated fiber-optic and copper connections.
  • Check for Frame Relay vendors who exceed maximum packet delay as agreed to in their contract or SLA. Typically no packet should be delayed greater than 250ms beyond the minimum trip time.
  • Check for the existence of legacy networking hardware along the test path. Some older devices contain excessively large queues which can lead to disruptive delays.

Detailed explanation

Usually this indicates that your network path has either media errors, or misdesigned networking equipment.

RTT or round-trip time is the time required for a network communication to travel from the source to the destination and back. RTT is used by some routing algorithms to aid in calculating optimal routes. This will vary depending on the amount of data sent, the speed of the link, the length of the link, and how busy the link is.

Often when packets are excessively delayed, duplication of data can occur on the network, leading to poorer response time than if the packet had simply been dropped.

Possible secondary messages

  • "May be media error or routing hardware fault"
  • "May indicate an unusually large (Mbyte) queue in use"
  • "Intermediate device CPU effect only - not present on end-to-end path"
  • "Under network load, voice applications may experience quality degradation due to jitter" </ul>

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