dummynet Labs
Network Simulation and Testing
Spring 2005
- Session 1:
- Lab 1. ipfw basics
- Clear all the removable ipfw entries (what ipfw command will do this?)
- Find out if there is any filter remaining (what ipfw command will do this?)
- Can you ping xxx.xxx.xxx.xxx (see the IP written on the whiteboard) at this point?
- If not, set the appropriate ipfw filters to allow ping messages to go out and come back
- Lab 2. Ping delay
- Start tcpdump and take tcpdump traces in the background
- Ping this computer -- xxx.xxx.xxx.xxx -- for 1 minute and save the output file
- Compare the ping delay observed from tcpdump trace vs. the ping output
- Are they different? Are the difference significant?
- Lab 3. Adding delay
- Add a dummynet pipe(s) to add 200ms to the round-trip ping delay to xxx.xxx.xxx.xxx
- Is it 200ms delay being added if you self-ping? If not, why?
- Clear the current setting and set up a dummynet pipe(s) to add 200ms to the
round-trip ping delay to self
- Lab 4. Revisiting the ping delay
- Use the Lab 3 setting to add 200ms to the round-trip ping delay to xxx.xxx.xxx.xxx
- Repeat Lab 2 and compare the ping delay observed from tcpdump trace vs. the ping output
- Are they different? Are the difference significant?
- Lab 5. Limiting the ping bandwidth
- Go back to the setting after completing Lab 2
- Use the -f option for the ping operation
- Take a new tcpdump trace and estimate the bandwidth share used to send ping requests
- Configure for the outgoing pipe to send 1/10 of that estimated bandwidth
- Re-take the tcpdump trace
- Estimate from the new tcpdump trace that the bandwidth share used to send ping requests
- Are the bandwidth used to send ping requests different before vs. after limiting the bandwidth? By how much?
- Session 2:
- Lab 1. FTP
- Download samplefile.tr to your FreeBSD machine.
- Figure out the IP address of your FreeBSD machine.
- Change the loopback interface MTU to 512 (ifconfig).
- Create a new user account (adduser).
- ftp to your own IP address and transfer samplefile.tr to the new user account you just created.
- If your ftp server is not enabled, modify your /etc/inetd.conf and restart inetd.
- Lab 2. TCP Throughput
- tcpdump the loopback interface.
- ftp to your own IP address and transfer samplefile.tr to the new user account you just created.
- Stop tcpdump.
- Identify the data connection of ftp.
- Estimate the throughput of the data transfer (kbps).
- Produce the time and sequence number plot for the data (use the ending seq number) and acks.
- Lab 3. Changing the RTT
- Estimate the RTT of the ftp data connection.
- Use dummynet to add 100ms to the RTT of the ftp connection.
- tcpdump the loopback interface.
- ftp to your own IP address and transfer samplefile.tr to the new user account you just created.
- Stop tcpdump.
- Identify the data transfer ports.
- Estimate the throughput of the data transfer (kbps).
- Produce the time and sequence number plot for the data (use the ending seq number) and acks.
- Lab 4. RTT and Throughput Relationshop
- Repeat 3 by adding 200ms and 400ms to the initial RTT.
- Are the actual throughput and RTT inversely proportional
as derived in Case Studies Paper #1?
- If not, why would the actual data not fitting the model?
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