The ONL NPR Tutorial

NPR Tutorial >> The Remote Laboratory Interface

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Session Sharing

The RLI has a session sharing feature which allows a user to observe another RLI session and converse with that user through a chat window. Session sharing can be useful in two situations:

• Timely Feedback: An instructor/TA can provide timely debugging and feedback to a student/user.
• Peer Programming: Two students (or groups) at different remote locations can work together on an assignment.

This page describes the session sharing concept, and how to share an ONL session. The subsections are:

• The Session Sharing Concept
• How to Share an ONL Session
• The Observer's View
• The Chat Window

The idea behind session sharing is that you (the user) want to allow another RLI user (the observer) to see your RLI session in real-time and want to discuss what is happening in the session with another user. The figure above shows the user's windows on the left and the observer's windows on the right. Once session sharing has been started between a user (kenw) and an observer (onldemo), the observer sees all changes (configuration and monitoring) made by the user. In the figure above, the observer sees that the user has a 2-NPR configuration and that the user is charting some traffic rates in the bandwidth chart. It also shows in the Chat Received box the conversation history. Each message in the chat history box is preceded by the user's name. The observer onldemo is currently responding to the user's question (see arrow). As soon as the observer types the ENTER key, the message will move into both the user's and the observer's Chat Received box.

So, what can and can not be done in session sharing? The basic ideas are outlined below and discussed in more detail in the remainder of this page.

• Starting a Shared Session:

A user must use the RLI to give permission for an observer to join a session AFTER he/she has committed the experiment. The observer must then join the session.

• Visible Actions:

The observer will see all of the user's activities except for mouse movements and individual keystrokes. For example, if the user changes a field in the Route Table, the observer will see the change as soon as the the field value has been accepted by the user's RLI (e.g., after the ENTER or TAB key has been depressed). In most cases, this will occur without selecting File => Commit.

• Observer Actions:

The observer only has read-only access to the configuration. So, the observer can not change the configuration values. But the observer can change the appearance of the windows (e.g., move or resize the RLI window and charts).

• Chatting:

After the session setup protocol has been completed, a chat window appears that will allow both the user and the observer to send text to each other.

The figure above shows the ONL components involved in making session sharing possible: user RLI, observer RLI, ONL Proxy and ONL Central Daemon (with experiment database). The ONL Central Daemon is the master controller. It:

• authenticates users;
• maintains the state of the virtual laboratory; and
• coordinates other daemons running on endhosts and router control processors (CPs).

When session sharing is in progress, the ONL Proxy ensures that the user and the observer see a consistent view of a shared RLI session. Because ONL doesn't know a user is active until the user issues File => Commit, no session sharing can occur until the user has selected File => Commit.

In brief, these are the steps involved in sharing a user's RLI session with an observer:

1. The user adds an observer to his/her experiment
• Commit an experiment
• Select Extras => Add Observer to Experiment.
2. The observer selects an experiment to observe
• Start the RLI
• Select Extras => Get Observable Experiments.
• Enter password into Login dialogue box.
• Select experiment to observe.

A dialogue box appears in the observed users screen informing him/her that someone wants to observe.

3. The user accepts the observer
• Grant access to the observer.
4. Session sharing starts after the user and observer finish their acceptance protocol.

In the example below, the user will share a simple 2-NPR experiment. The user is kenw, and the observer is onldemo. The user's screen shots are shown on the left side of the page, and the observer's screen shots are shown on the right side.

• The user adds an observer to his experiment
• Commit an experiment

Remember: You can not share an experiment with an observer until after you have committed the experiment.

• Select Extras => Add Observer to Experiment.


• The observer selects an experiment to observe

• Start the RLI
• Select Extras => Get Observable Experiments.
• Enter the password into Login dialogue box.

A chat window labeled Observation Window appears.



• Select the experiment to observe.

Select Exps Available for Observation => ....

Note in the example, that the user's login name appears.
An Observation Request window will appear.

• Select Yes in the Observation Request window.

A dialogue box will appear in the user's screen notifying them that someone wants to observe their session.

A Processing Observeration Request window will appear in the observer's screen.

• Select OK in the Processing Observation Request window.

Note that the observer's RLI window is empty since session sharing has not yet started.



• The user accepts the observer

• The user selects Invite to accept the observer.

The dialogue box shows that the observer is ondemo.



• The observer is notified of the user's acceptance
• A RSVP window appears in the observer's screen.
• The observer selects OK, thus enabling sessing sharing.

Note that the observer's RLI window shows a 2-NPR configuration with two hosts and is now identical to the user's RLI window.

Shown to the left in the figure above are the user's RLI window and and the Queue Table at Port 1. On the right is the observer's version of the same Queue Table. Notice that the observer's port rate is shown in a lighter color than the user's, indicating that the field is not writeable by the observer.

Once session sharing has been established, the observer will see any configuration changes enterred by the user. A field value is considered enterred when the user has keyed in the value followed by the ENTER key or the TAB key. The only exception is the Port Rate which isn't shown in the observer's version until after a Commit.

The observer can look at configuration tables somewhat independent of the user. For example, the observer could decide to display the route table at port 1 even though the user is doing something else and not displaying that table. But any changes made by the user will be displayed in the observer's screen even if it requires a new window to appear.

Either participant in a shared session can send a message to the other. The figure below shows an ongoing conversation between the user kenw and the observer onldemo. The chat history box (Chat Received) shows that the conversation was initiated by the user kenw. The observer onldemo is composing a new messagea. This message will be sent as soon as the observer depresses the ENTER key.

NPR Tutorial >> The Remote Laboratory Interface	TOC