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Example Experiment - Layer 3 Deflect

In this example experiment, you will configure and run an OpenFlow experiment. In this experiment we are going to deflect service requests from one server to another. We are going to use:

  • 1 ProtoGENI host to run our OpenFlow controller
  • 3 myPlc hosts, 1 will be the client and 2 will be the servers
  • OpenFlow resources that will connect the three hosts

Please note that you can't just cut and paste all of the commands. There are additional instructions in the text.

1. Add another user to your experiment

Omni gives you the capability of giving access to other users on your compute resources. Depending on which AM you are using to get resources from, this is done in a different way. Ask the team next to you about their username and do the following:

  1. While in a terminal, download their public key under ~/.ssh/ :
      cd ~/.ssh
  1. Follow the instructions these instructions? and add another user for ProtoGENI AMs

1. Create your experiment

In this step, we are going to setup the experiment. In this tutorial we assume that you are sufficiently comfortable with omni to verify that a listresources command works and to know when your slice is ready using sliverstatus.

  1. Create a slice, use the slicename given to you in the paper slip: createslice <slicename>
  2. Create all the slivers using the rspecs from the URL given in your paper slip: createsliver -a <AM_nickname> <slicename> <rspec_url>
  3. Check the status of your sliver sliverstatus -a <AM_nickname> <slicename>

2. Install scripts

While you wait for your sliver to become ready, we will see how we can automate the installation of our experiment with install scripts. In this experiment we are going to use software routers in order to write our own forwarding scheme. This means that in any experiment we are going to run we want the basic installation of the software router to always be present. The configuration might change from run to run, but the software should always be installed. The software to be installed, and the scripts to be executed at boot time, are defined in the rspecs. Follow these steps to locate your install script and identify the different parts.

  1. Download your rspec you used in the pg-utah AM.
     cd /tmp
     wget <rspec_url>
  2. Open your rspec and look for the install tag and copy the value of the URL attribute.
  3. Download and untar the software
    cd /tmp
    wget <software_url>
    tar xvfz <software_name>
  4. Look in your rspec and locate the execute tag. Note what script is being executed at boot time.
  5. Locate the script and open it. Can you identify the different parts?

3. Configure your hosts

Once our slivers iare ready we will go ahead and configure our myPlc hosts. Instead of logging into each host to install the necessary softwarem we are going to use remote execution and install it from our VM.

3a. Login and remote execution

Run the script to get information about logging in to nodes. The script has a lot of output so lets put that in a file so that we can easily search for the information we want. -a <AM_nickname> <slicename> > login.out 2>&1

You'll get a big chunk of information, but you're interested in the ssh configuration info information near the end.

... <lots of output> ...
  Port 22
  User pgenigpolabbbncom_testdeflect 
  IdentityFile /home/nriga/.ssh/geni_key 

  Port 22
  User pgenigpolabbbncom_testdeflect 
  IdentityFile /home/nriga/.ssh/geni_key 

...<more output>...

Copy all the above information and paste it into your .ssh/config file, and do the same for all the AMs, then you can very easily login into your nodes, just by using the name that is after the Host attribute.

Your ~/.ssh/config file should look like

IdentityFile /home/geni/.ssh/geni_key

  Port 22
  User pgenigpolabbbncom_testdeflect 
  IdentityFile /home/nriga/.ssh/geni_key 
  Port 22
  User pgenigpolabbbncom_testdeflect 
  IdentityFile /home/nriga/.ssh/geni_key 

  Port 22
  User pgenigpolabbbncom_testdeflect 
  IdentityFile /home/nriga/.ssh/geni_key 

Host ofctrl
  Port 22
  User inki 
  IdentityFile /home/nriga/.ssh/geni_key

Let's login to our two hosts, the nicknames are hostA and hostB

  1. Open two new terminals
  2. In one terminal type
    ssh -A hostA
    and in the other
    ssh -A hostB

Test remote execution

You can execute commands in a remote host using ssh. To do this just follow your ssh command with the command you want to execute in quotes.

  1. In your local terminal type :
    ssh -A top "ls -a"
    This will list all the files under the home directory on host top. The output should look like:
    geni@geni-VirtualBox:~$ ssh -A top "ls -a"

If you get something similar you are all set for controlling your nodes from your computer.

3b. Configure your routers

We are going to use remote execution to configure our routers.

  1. On a local terminal run the following command four time, each time substituting the <router_nickname> with one of the top, bottom, left, right:
    geni@geni-VirtualBox:~$ ssh -A <router_nickname> "/local/click-example/ "
    You'll get output something like this:
    Your host information:
    (If you are prompted for a password, check to make sure that you provided the -A switch in your ssh command above.)
  1. The extractClickConfig script produces router configurations for your experiment. It also creates a diagram of your experiment. Get a copy locally from one of the routers, by typing in a local terminal:
     scp top:myslice.png
  2. View the diagram by typing :
    eog myslice.png &
    Your slice will look something like the one below (see myslice.png). The overall configuration should be the same, with two end hosts, named hostA and hostB, and four routers (top, left, right, bottom) in a diamond configuration. The host names, interface names, and MAC addresses will be different, depending on the actual resources assigned to your slice.

No image "myslice.png" attached to GEC15Agenda/AdvancedGENITopoOmni/Instructions/L3DeflectExperiment

The four routers interconnected by solid lines are your "core network," which will run a non-standard, non-IP protocol. The dashed lines out to the end hosts carry standard IP traffic.

4. Turn off internet protocol

At this point, your network is still running IP. You can check by running a ping. In your hosta terminal window, run this command.

ping -c 3 hostb

The command should succeed, with output like this:

PING hostB-link-B ( 56(84) bytes of data.
64 bytes from hostB-link-B ( icmp_seq=1 ttl=61 time=1.38 ms
64 bytes from hostB-link-B ( icmp_seq=2 ttl=61 time=1.19 ms
64 bytes from hostB-link-B ( icmp_seq=3 ttl=61 time=1.53 ms

--- hostB-link-B ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2004ms
rtt min/avg/max/mdev = 1.193/1.370/1.531/0.138 ms

Since our experiment doesn't want IP, let's turn it off :

  1. On a local terminal run the following command four time, each time substituting the <router_nickname> with one of the top, bottom, left, right:
    ssh -A <router_nickname> "sh ./"

You'll get output like this (the interface names may be different):

Disabling IP on interface mv10.9
Disabling IP on interface mv10.10
  1. Verify that IP is really off, try another ping. On hosta:
    ping -c 3 hostb
    The command should take twelve seconds to time out, then fail with output like this:
    PING hostB-link-B ( 56(84) bytes of data.
    --- hostB-link-B ping statistics ---
    3 packets transmitted, 0 received, 100% packet loss, time 11999ms

5. Start your routers

The extractor script produces a click configuration file for each of your routers.

  1. On a local terminal run the following command four time, each time substituting the <router_nickname> with one of the top, bottom, left, right:
    ssh -A <router_nickname> "sh ./"
    You'll get output like this. (Don't worry about the warning messages, Click is just reminding you that you have no IP addresses in your core network.) The output of the click router is redirected to /tmp/click.out on each host.
Stopping any running Click routers
Starting Click router While initializing ‘FromDevice@18 :: FromDevice’:
  warning: eth2: no IPv4 address assigned While initializing ‘FromDevice@21 :: FromDevice’:
  warning: eth4: no IPv4 address assigned

Congratulations! You are now running a non-IP core network on your four routers, along with a (primitive) non-IP multipath routing algorithm. You're ready to experiment with this configuration.

6. Send some traffic

Now you'll use your two edge hosts, hostA and hostB to send traffic along your network. Since these end hosts are not running your modified protocol, they'll rely on the top and bottom routers to transform their IP packets into your modified protocol on entry to the core network and back into IP packets on exit.

  1. In your terminal window on hostB, instruct nc to listen for a UDP connection on port 24565 (or some other port that catches your fancy).
    [mberman@hostb ~]$ nc -ul 24565
  2. Connect to it from your terminal window on hostA:
    [mberman@hosta ~]$ nc -u hostb 24565

You've established a simple text chat connection. Enter a line of text in either window, and it should appear in the other. Of course to do this, the text is travelling through your core network, using your non-standard protocol and routing. So type a message into each window, and make sure it appears in the other.

That's it! Now, let's look inside to see what's going on.

7. Looking under the hood

Please note: the interface names and MAC addresses below are for the sample configuration shown in the figure above. You will want to refer to your network diagram to get the correct interfaces and addresses for your configuration.

Let's take a look at what's happening in the four routers in your configuration. There are two basic router configurations. (You can find all of these files on any of your router hosts.)

7b. Packet transformation

  1. The more interesting configuration appears here, in the configuration file. In a local terminal type:
     ssh -A top "cat"
    The output will look like :
    // This portion accepts IP packets,
    // reformats them, and routes them
    // to an internal router.
    route :: Classifier(27/01%01,-);
    modify :: Unstrip(2) ->
        StoreData(0, "AliceWasHere3546") ->
    FromDevice(eth3, PROMISC true) -> 
        Classifier(12/0800) ->
    route[0] -> left :: EtherEncap(0x7744, 00:04:23:b7:14:76, 00:04:23:b7:18:fa) ->
        SimpleQueue ->
        Print(outL) ->
    route[1] -> right :: EtherEncap(0x7744, 00:04:23:b7:1c:e0, 00:04:23:b7:19:2e) ->
        SimpleQueue ->
        Print(outR) ->
    // This portion accepts non-IP packets
    // with an ether type of 0x7744
    // from an internal router, restores
    // them to IP format, and forwards.
    restore :: SimpleQueue ->
        Strip(30) ->
        EtherEncap(0x800, 00:04:23:b7:14:77, 00:04:23:b7:20:00) ->
    FromDevice(eth2) -> Classifier(12/7744) -> Print(inL) -> restore;
    FromDevice(eth4) ->  Classifier(12/7744) -> Print(inR) -> restore;

As indicated in the comments, the top portion of the configuration listens (FromDevice) for IP packets arriving on the interface connected to hostA (that's eth3 in this example). It then creates a new 16-byte field at the head of the packet (two bytes added by the Unstrip operation, plus the existing 14-byte Ethernet header. It fills that field with what could be important routing instructions, but in this case is just graffiti (StoreData). The route operation then routes the packet via either the left or right router toward hostB. In either case, it wraps the packet in a fresh Ethernet header (EtherEncap) with a distinctive ether type code (0x7744), logs the new packet on its way out (Print) and sends it out on the correct interface (ToDevice).

The bottom portion of the configuration is intended for packets coming out of the core network to hostA. It accepts packets from either the left or right router, logs them, strips off thirty bytes (Ethernet header plus your 16-byte new header field), puts on a fresh Ethernet header, and sends them along to hostA.

The configuration for the bottom router is exactly symmetric, routing packets between hostB and the core network, but using different graffiti.

7b. Simple Forwarding

The left router configuration is much simpler. In a local terminal type:

 ssh -A left "cat"

The output will look like :

// Copy packets from top to bottom.
FromDevice(eth2) ->
    StoreEtherAddress(00:04:23:b7:42:b6, dst) ->
    StoreEtherAddress(00:04:23:b7:18:fb, src) ->
    SimpleQueue ->
    Print(top) ->
// Copy packets from bottom to top.
FromDevice(eth3) ->
    StoreEtherAddress(00:04:23:b7:14:76, dst) ->
    StoreEtherAddress(00:04:23:b7:18:fa, src) ->
    SimpleQueue ->
    Print(bottom) ->

This configuration just blindly forwards packets. It picks up any packet from the top router, updates the Ethernet header, and passes it along to the bottom router. The same applies in the reverse direction. Again, the configuration for the right router is exactly analogous.

7c. Monitoring your core network

Let's watch how the packets travel through the network.

  1. In a local terminal type:
    ssh -A top "tail -f /tmp/click.log"
  2. Go to your window for hostA, where your nc command is still running. Type a message into this window. You should see a log message in three of your four router windows. In this example, you might see:
  3. In the local terminal you will see:
    outR:   76 | 000423b7 192e0004 23b71ce0 7744416c 69636557 61734865
    This log entry says that the top router received a packet from hostA, modified it, and sent it out to the right router. If the entry started with outL, that would indicate that it sent the packet out to the left router. Let's look a bit at the start of the packet (the first 24 bytes are logged). It starts with an Ethernet header. The first six bytes are the MAC address of the destination interface, that's 00:04:23:B7:19:2E, the MAC address of eth4 on right. The next six bytes are the MAC address of the source interface, 00:04:23:B7:1C:E0, or eth4 on top. Next comes your ether type, 0x7744. The remaining bytes, "416c 69636557 61734865" are the start of the first field in your new protocol, "AliceWasHe" in ASCII.
  4. Try typing a few different lines to hostA. You should see some packets routed to the left and some to the right. The routing decision is based on the route :: Classifier(27/01%01,-); entry in the top router configuration. Here, the router is looking at the low-order bit of the checksum on the initial IP packet (now at byte position 27 with the addition of the new sixteen byte field at the start of the header). Packets with odd checksums go to the left; those with even checksums go right.

9. Clean up

When you're done, please release your resources so they'll be available to others. deletesliver -a pg-utah <slicename>