RTT and packet loss on a lossy link

Objective

Ping 100 times over a link that loses 20 % of the frames in each direction and measure the loss and the RTT.

Procedure

1. Run and read the Summary: loss percentage and RTT.
2. Select the link and set Loss to 0 %: 0 % ping loss.
3. Set it to 5 %: expect 1 − 0.95² ≈ 10 %.

Theory

A ping succeeds only if both the request and the reply survive: P(success) = (1 − p)² = 0.64, so about 36 % of the pings are lost. RTT is unaffected for those that arrive.

Network blocks used

2 × Host / PC

More Computer Networks Lab experiments

• Packet size versus latency
• Queueing delay and loss on an overloaded link
• TCP congestion control (slow start and loss recovery)
• File transfer over TCP: LAN versus WAN
• VLANs across a trunk link