Wed Jul 06 1:14pm MDT
Vers: 4.773 Build: 07/05/2022

Emulab Client Interface

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Emulab Client GUI (Alpha)

Note: This software is still under development, so it will be slow, buggy, and lacking in features for some time to come. However, it should still be usable enough to do basic tasks on small scale topologies.

Introduction The Emulab Client GUI is a Java-based front-end to the Emulab network testbed. It is designed to lower the bar to creating new experiments in the testbed and provide a smooth, consistent interface for interacting with an experiment. Using the client you can construct a topology with several nodes, links, LANs, and specify many of their constituent properties (bandwidth, latency, etc...). Once your topology is completed, you can export it as an NS file, or switch into interactive mode where you can login to the nodes, change link parameters, and perform several other tasks.

Emulab Client Screen Shot
[Screen Shot]
Features The current list of features are:
  • Build and interact with the topology from a single interface.
  • Interact with existing topologies.
  • Support for Emulab-specific extensions to the NS syntax.
  • Uses the Emulab XML-RPC interface.
  • Integrated access to node consoles.
Requirements Currently, we can only support a limited set of configurations in order to keep things manageable. The current requirements are:
  • A recent installation of FreeBSD or Linux.
  • Version 1.4 of the Sun JDK.
We plan to expand support to other platforms in the future, but only after the major problems have been addressed. Also, to take advantage of the integration with Emulab's XML-RPC interface, you will need:
  • An Emulab account.
  • SSH and a properly configured ssh-agent. (You just need to be able to ssh in without specifying a password).
Note that network access and an Emulab account are not required to run the client, the software will not make any network connections unless explicitly requested by the user.
Download The client is currently distributed as a self-contained JAR file and a source tar ball:
netlab-client.jar (370K) v0.1.1 Nov 2, 2005
netlab-client-0.1.1.tar.gz (787K) v0.1.1 Nov 2, 2005
Simply save it to any directory you choose and you can move on to the tutorial.

Tutorial Starting the client is just a matter of executing the Java JAR file:
[michael@bluth1 ~] java -jar netlab-client.jar
Next, we will do a brief overview of the three major parts of the interface and then create a simple topology and Emulab experiment.

The interface has a typical layout: a main menu bar at the top, an editing field in the middle, and a status bar at the bottom. The main menu bar has the usual set of actions for opening and saving files, as well as items for accessing your Emulab site and experiments. Most of your time will be spent in the topology field in the middle of the window, editing and interacting with your nodes and links. Inside of the field are two dialog boxes, the palette that is the source for objects to be added to the field, and the properties dialog that shows the details of the currently selected object. The bottom of the window holds the status bar which provides you with at-a-glance information about your topology and the corresponding experiment in Emulab. At the moment, this bar is devoid of any useful information, but, it will be updated as you add nodes or make changes to a running experiment.

Now that you have a passing familiarity with the interface, we can create a topology with two nodes linked together.

Add two nodes Your first task will be to add two nodes to the topology field. Each node represents a physical machine that will be allocated and automatically configured to your specifications. Adding a node is simply a matter of dragging a node object from the palette and dropping it on the field. This will create a new node object with the default properties and add it to the field. Notice that the object has also been given a name, "node0". Naming of newly added or copied objects is handled automatically by the client so that the names are unique and have a consistent style.

Another effect of adding a node to the topology field is that the dialog window in the upper right has changed to show this node's properties. Currently, most of the fields are empty, indicating that the default values will be used. You might want to take a little time and explore the interface to see what options can be specified.

Finally, lets create a friend for our current node by selecting the node and then doing a copy & paste. Your new node should appear a little below the old one, simply drag it to whatever position you prefer, and we can move on to networking the nodes.

Drag & drop node
Create a link You may have noticed a line following your mouse pointer when it approached a node object, this is the "wire" used to network nodes together. To actually make a connection, you simply need to get close to the object, drag the wire to another object, and release. Try this now with your two nodes.

Wire following mouse Dragging wire Connecting nodes
1. Follow 2. Drag 3. Connect

As you can see, the wire from the other node comes out to meet your mouse pointer, making it clear what will be the other endpoint for the connection. You can use this same technique to connect nodes to switches and vice-versa.

Your newly created link, similar to the one at right, represents a Point-to-Point connection that will be establised between the nodes. Normally, this link behaves like an ethernet cable connecting two 100Mbps network interface cards (NICs). However, by changing the "bandwidth", "latency", and "loss rate" properties, you can emulate other types of links. To make things interesting, change the latency of the link from zero to fifty. Later on when we are interacting with the nodes, this delay will be seen when pinging one node from the other.

The newly created link New link
Save your topology Now that the topology is complete, you should save it to a file for future reference. If you are going to create an Emulab experiment from this topology, you probably want to give the file the same name as your experiment. Also, be aware that once you create the experiment, you will not be able to edit the topology until the experiment is terminated. So, if you want to reuse the topology in multiple experiments, you need to save it to a separate file now.

Check your preferences From this point on, you will need an account on an Emulab site and an SSH configured to use public/private keys instead of passwords. If all of these preconditions are met, check the preferences in "Edit / Preferences" to ensure that your user name and Emulab domain name are correct. Also, the client uses its own SSH config file, so you might need to edit the "SSH Config Template" to suit your needs. For example, a common change will be to use version two of the protocol by changing the line "Protocol 1,2" to "Protocol 2". These values are needed to properly communicate with your Emulab's XML-RPC interface.

Create an Experiment With everything in order, you can now instantiate this topology as an experiment in Emulab. First, you need to select the "Experiment / Create..." menu item to open the experiment creation dialog. Since this is your initial attempt to create an experiment, the client needs to contact Emulab to download your account information. Once that has completed, it will also do a one-time check for recently added news items so that you can keep up-to-date with the happenings at your Emulab site.

After getting up-to-date with the news, make sure the Project and Group settings are correct, and then enter a meaningful description for your new experiment. Note that, by default, Emulab will immediately try to allocate and configure your nodes. So, if you do not plan on using the topology right away, uncheck the "Swap in immediately" check box.

Because it can take several minutes to allocate and configure the machines, the client will not block waiting for this process to complete. Instead, you are expected to wait for the Emulab E-mail confirming the completion of the swap in and then manually use the "Experiment / Synchronize" menu. Assuming the swap in was successful, and you resynchronized, the client will switch into "interactive mode". This change disables the editing parts of the client and enables the monitoring and manipulating portions. An example of the simple monitoring done by the client is the change in the node icons, they should have all turned green, meaning the node is up and well. In addition, the properties dialog will now show how the nodes and links mapped into reality. For example, the properties for "link0" will show the IP addresses that were automatically picked for the nodes, instead of the "(auto)" value they had while you were editing. Note that the client does not automatically track the state of nodes, so you must manually resynchronize your view with Emulab every so often. Of course, monitoring the nodes is not very exciting so lets do something with them.

Login to your nodes Logging in to your nodes is simply a matter of bringing up the context-menu for the node and selecting the "Login" item. This action will download the host keys for the node and open an SSH session in a new xterm. Similarly, you can connect to the node's serial console by selecting the "Console" item. Most of the time you will want to use SSH to communicate with your nodes and only use the console if the node has become unreachable via the network.

If you need to perform some other task besides login, you can address the node using its fully qualified domain name, which has the form "<node>.<exp>.<proj>". For example, the name of "node0" in experiment "foo" of project "bar" is "". To save you some typing, the client provides a "Copy DNS Name" item in the node's context-menu which copies the name to the system clipboard.

Now that you are logged into the nodes, you can try pinging one node from the other:

[michael@node0 ~] ping
PING pc82 ( 56(84) bytes of data.
64 bytes from icmp_seq=1 ttl=64 time=0.315 ms
64 bytes from icmp_seq=2 ttl=64 time=0.131 ms
64 bytes from icmp_seq=3 ttl=64 time=0.125 ms
64 bytes from icmp_seq=4 ttl=64 time=0.169 ms
As you can see, the ping worked fine, but the delay you added to the link does not seem to be taking effect. Also, the IP addresses do not match those displayed in the properties dialog for "link0". Well, it turns out that there is another active network interface on your node, called the "control interface", that is not displayed in the client. This control interface is the node's connection to the outside world and provides a route for logging in to the node, mounting shared file systems, and so on. As you may have guessed, the domain name for the control interface is the fully qualified name of the node (e.g. ""). So, in order to reach the node through the link displayed in the client, you need to use the unqualified name:
[michael@node1 ~] ping node1
PING node1 ( 56(84) data bytes
64 bytes from icmp_seq=1 ttl=64 time=99.9 ms
64 bytes from icmp_seq=2 ttl=64 time=99.9 ms
64 bytes from icmp_seq=3 ttl=64 time=99.9 ms
64 bytes from icmp_seq=4 ttl=64 time=99.8 ms
You can read more about the intricacies of the experimental and control networks here.
Context Menu
Change link behavior Now that we have ping working correctly, lets change the link latency and watch the ping behavior change. First, click on the link object to bring up its properties. Then change the latency to 75 and hit return. You may have noticed at this point that the "Synchronized" menu at the bottom of the interface changed to "Unsynchronized", meaning that client's display is out-of-sync with the experiment in Emulab. In other words, your latency change has not yet taken effect. In order for the change to happen, you must do a manual synchronize (CTRL-Y), to upload any changes you have made and then redownload the status of your experiment. Finally, rerun ping to see change in the latency.

Synchronized Unsynchronized Review Changes
1. No changes 2. Latency Changed 3. Review Changes

Try making more changes to the link and watch the change in behavior of ping or other programs, just remember you have to resynchronize to see the effect.

Once you have finished playing around with this simple topology, you can terminate it and try to use the client with one of your existing topologies.

Existing Experiments Besides creating topologies, you can also use the client to interact with existing experiments in Emulab. You can load an experiment into the client through the "Experiment / Bind to existing..." menu item. This menu will display a listing of experiments you have created, then you simply need to select one to load. After the client has finished retrieving information about the experiment, you should be able to use the client like in the previous sections to login to your nodes, change link parameters, and swap in/out your experiment.
Troubleshooting We will try and cover some of the more common problems and their solutions in this section:

"Bad Response" when trying to connect to Emulab.
This error is usually due to the client not configuring SSH correctly. First, check your preferences to make sure they are correct. It is easy to overlook minor details in the defaults, for example, the client assumes that the user name on your desktop machine is the same as your Emulab user name, which is not always the case.

If those settings all look correct, you may want to go into the "SSH Config Template" page of the preferences dialog and change the line "Protocol 1,2" to "Protocol 2". This is required if your keys are for version 2 of the SSH protocol, since the client currently assumes version 1.

If all else fails, leave the client running and execute the following in another terminal:

$ ssh -v -v -v -F ~/.netlab-client/
This should give you an idea of what might be going wrong. If you cannot figure out the output on your own, send the output to the testbed operators.

In the future, we will hopefully be able to make the client figure this all out on its own.

History The release history:
  • v0.1.1 - Add support for nodes with non-routable control networks.
  • v0.1.0b - Add ability to customize the SSH config template. Ask the user before swapping/terminating an experiment. Fix some other minor bugs.
  • v0.1.0 - Initial release