• Bufferbloat is a cause of high latency caused by large buffering of packets in bottleneck nodes of a network.
• Bufferbloat can also cause packet delay variation (also known as jitter), as well as reduce the overall network throughput.
• Oversized buffers can have a damaging effect!
• Bufferbloat test
Bufferbloat simple example
1. The host should be pinged continuously.
2. A several-seconds-long download from the host should be started and stopped a few times.
3. TCP congestion avoidance algorithm will rapidly fill up the bottleneck on the route.
4. If increase of the RTT is reported by ping, then it demonstrates that the buffer of the current bottleneck is bloated.
Goals of the Assignment
• Learn first-hand the dynamics of TCP sawtooth and router buffer occupancy in a network.
• Learn why large router buffers can lead to poor performance.
• Learn how to use Mininet to run traffic generators, collect statistics and plot them.
• Learn how to package your experiments so it’s easy for others to run your code.
• Slow Start: cwnd < ssthresh • Congestion Avoidance: cwnd > ssthresh
• Triple Duplicate ACK: cwnd, ssthresh cwnd/2
• Timeout: ssthresh cwnd/2 & cwnd 1MSS
Installation and Setup
• Download and Install Virtual Box.
• Go to File -> Host Network Manager and add a host-only network adapter.
• Download the PA2 OVM File.
• Import VM: On VirtualBox, go to File->Import Appliance and select the .ova file from your unzipped folder.
• Start and login in your VM
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