Files: exercises-network-performance.txt

APRICOT 2010: Kuala Lumpur, Malaysia

LOCAL NETWORK ANALYSIS TOOLS

Notes:
------
* Commands preceded with "$" imply that you should execute the command as
  a general user - not as root.
* Commands preceded with "#" imply that you should be working as root.
* Commands with more specific command lines (e.g. "RTR-GW>" or "mysql>") 
  imply that you are executing commands on remote equipment, or within 
  another program.

Exercises
---------

1. lsof and netstat
   ----------------

See what services are running on your machine. You can use the
presentation as a reference.

Or, utilize "man lsof", "man netstat", "lsof -h" and "netstat -h" to see
the available options (there are a lot!). Remember to use
sudo when using lsof and netstat to give yourself necessary permissions
to view everything.

* Using lsof, what IPv4 services are listening on your machine?

* Using netstat, what IPv4 and IPv6 services are listening on your machine?


2. tcpdump and Wireshark
   ---------------------

To use tcpdump you need to use sudo, or be root. To use wireshark you need 
to open a terminal and use sudo as a normal user (i.e., userid "inst"):

Use tcpdump like this:

        $ sudo tcpdump -i lo -A -s1500 -w /tmp/tcpdump.log

Now, generate some traffic on your lo interface in another terminal.

For example:

        $ ping localhost
        $ ssh localhost
 
etc. Afterwords press CTRL-C to terminate the tcpdump session.

Note: ssh generates much more "interesting" output.

Now install wireshark:

        $ sudo apt-get install wireshark

Once installed, in another terminal as a normal user ("inst") open
wireshark like this:

        $ sudo wireshark -r /tmp/tcpdump.log

Now you can play with the wireshark interface to start and understand 
how it works. Can you figure out how to follow packets by protocol? 
By Session?

Now try something like this (note the "eth1"):

        $ sudo rm /tmp/tcpdump.log
        $ sudo tcpdump -i eth0 -A -s1500 -w /tmp/tcpdump.log

In another terminal do:

        $ ftp limestone.uoregon.edu
 
        Connected to limestone.uoregon.edu.
        220 FTP Server ready.
        Name (limestone.uoregon.edu:sysadmin): anonymous
        Password: <anything you want>
        ftp> exit

End the tcpdump session in the other terminal (CTRL-C). Now view the 
contents of the log file:

        $ sudo wireshark -r /tmp/tcpdump.log

Can you see your password? Sniffing unencrypted passwords on wireless 
lans is very easy with a tool like this.


3. Using iperf
   -----------

Use "man iperf" or "iperf -h" for help.

First install iperf:

        $ sudo apt-get install iperf

Ask your neighbor to run:

        $ iperf -s

Connect to your neighbor's machine using:

        $ iperf -c ipNeighbor

How is the throughput between  your machines?

Consider connecting both your PCs directly together (one cable, 
no switch). Use a private IP address on both machines, verify
you can ping each other, then repeat the previous steps with
your new connection. Has your throughput improved? 

If you have time continue playing with iperf options. If you have a
remote PC running UNIX or Linux you might want to try installing iperf
and testing your connection from the workshop lab to your remote 
machine.

Some more things to try...

* Test TCP using various window sizes (-2).

* Verify TCP MSS (-m). How does this affect throughput? What is
  Path MTU discovery?

* Test with two parallel threads (-P) and compare the totals. Is
  there any difference? Why?

* Test with different packet sizes and the TCP_NODELAY (-N) option.