Trace Test
The NQA trace test detects the forwarding path between the source and the destination and collects statistics about each device along the forwarding path. It has a similar function to the tracert command, but provides more output information, including:
- Average delay
- Packet loss ratio
- Time of receiving the last packet
The trace test process is as follows:
The source (SwitchA) constructs a UDP packet, with the time-to-live (TTL) set to 1 and sends it to the destination (SwitchD).
When the first-hop router (SwitchB) receives the UDP packet, its TTL decreases to 0. The first-hop router discards the UDP packet and returns an ICMP Time Exceeded packet.
The source obtains the IP address of the first-hop router from this ICMP Time Exceeded packet. It then constructs another UDP packet with the TTL set to 2.
When the second-hop router (SwitchC) receives the UDP packet, its TTL decreases to 0. The second-hop router discards the UDP packet and returns an ICMP Time Exceeded packet.
The source continues to send UDP packets, with the TTL increasing by 1 each time. This process is repeated until the packet reaches the destination, which then returns an ICMP Port Unreachable packet to the source.
The ICMP packets from each hop give the source information about the forwarding path as well as statistics about each device along the path.
Trace test results and historical records are collected in test instances. You can run commands to view the test results and historical records.