This section details the process a user takes to construct and simulate a scenario in a virtual world to support the earlier design goals for education and interaction. From this process, each of the encompassed components is detailed in a systematic way providing its purpose, representation in- world, input and output and its structure. Figure 61 details the components, their interactions and a numerical guide to the process from a user’s perspective.
109
6.4.1
Node
A node is a networking component which is
The virtual world representation is that of a modern day Macintosh laptop and is extended from an open source creation [278]. The components
interaction methodology are provided in section 1. it provides a visual reference to
the user
2. it displays the results of the animation after it has been simulated in 3. it provides visual confirmation that the user has constructed a
Figure 62: Screenshot of a networking component in Second
Representation Purpose Method of Interaction
Input Output
Table 18: Summary of the key elements involved in the Node component
6.4.2
All Seeing Orb
The “All Seeing Orb” is represented in the virtual world as a
Seeing Orb contains the scripts required for eliciting Node configuration and gateway management. The All Seeing Orb acts as:
• a central point for configuration is detailed as the Broadcast Census in • a translation of in-world
vice-versa.
110
node is a networking component which is placed in a user’s inventory and is shown in
The virtual world representation is that of a modern day Macintosh laptop and is extended from an . The components’ interactions are through touch only and the details of the interaction methodology are provided in section 6.6. The output from the node is three
it provides a visual reference to the node location in the virtual environment
it displays the results of the animation after it has been simulated in ns-2
visual confirmation that the user has constructed a traffic link between two nodes
Screenshot of a networking component in Second Life
Model of a laptop (see Figure 62)
Provide a visual reference for the location of the node in a constructed scenario
Touch
Touch from the user, signals from other nodes on the island on a pre-assigned communication channel Animation of signals
Summary of the key elements involved in the Node component
The “All Seeing Orb” is represented in the virtual world as a sphere shown in Figure
Seeing Orb contains the scripts required for eliciting Node configuration and gateway management.
configuration aggregation – details of a scenario for execution; this attribute Broadcast Census in 6.7.2.
world information such as Second Life keys into identifiers used in
is shown in Figure 62. The virtual world representation is that of a modern day Macintosh laptop and is extended from an
interactions are through touch only and the details of the put from the node is three-fold:
in the virtual environment as deployed by
traffic link between two nodes
Life
Provide a visual reference for the location of the node in
Touch from the user, signals from other nodes on the
Summary of the key elements involved in the Node component
Figure 63. The All Seeing Orb contains the scripts required for eliciting Node configuration and gateway management.
etails of a scenario for execution; this attribute
111
• an invocation of the WiFiCS which supports WiFiSL through HTTP as described in the Gateway section 6.7.3.
• the timely execution of events which result from the simulation as described in the Execution Scheduler section 6.7.4
The input is the location, identity and traffic connection details of all nodes on the island that are involved in the simulation. Through the WiFiCS, the output is a series of commands sent through a channel causing the networking components to animate certain network events.
Representation Spherical object (see Figure 63)
Purpose
Provide a central controlling point for the initiation of the simulation of the scenario, the request for the simulation to be completed and then instructing networking components to execute resulting events at the correct playback time.
Input
Console or touch commands, location of networking components on the island and any traffic connections between them.
Output
Broadcast requests to networking components, HTTP requests to the WiFiCS and instructions on which signal to animate at which particular networking component. Table 19: Summary of the key elements involved in the All Seeing Orb component
Figure 63: Screenshot of the WiFiSL All Seeing Orb attached to the avatar’s left hand
6.4.3
WiFi Constructor and Simulator
The WiFi Constructor and Simulator (WiFiCS) component in Figure 61 represents a part of several components as described in section 5. These reusable components are server-side and contain methods for constructing a representation of a scenario in Java. This representation is translated, using the Java OTcl Build API (jOBA) into an OTcl file that can be simulated in ns-2. WiFiCS compresses the discrete event results from the simulator into a more space efficient format (see section 6.7.3).
112
6.4.4
Process Description
A scenario refers to a user’s construction of networking components, the traffic interactions between them and advanced parameter settings. The steps a user takes to deploy a network, construct a scenario and review the results were shown in Figure 61 with a textual description below.
A user deploys networking components into the virtual environment from their inventory. Connections are created by touching the networking components. Touching two in succession creates a connection, the order of which denotes the sender and receiver. Visual confirmation is animated to the user. The confirmation animation is automatically stopped after 4 seconds. The connection created by the user is recorded as a file transfer between the two networking components. The start time for the transfer is assigned by the orb. This removes the necessity for the user to specify valid start and finish times during scenario construction.
The gateway broadcasts a request to all networking components to respond with traffic configurations and position reporting. Each node is identified by its 128 bit key assigned by Second Life on first creation (a process known as rezzing [279]). A traffic link consists of sender and receiver keys, which is then translated into a numbering system beginning at 0 and going to n-1 (where n is the number of nodes). This translation and storage is important as the key is used for specifying the destination of animation of network events. The traffic descriptions also contain start and finish times specified by the networking components’ wall clock time value.
Once all the information has been collated, a special URL is constructed and submitted to the system used by both WiFiVL and WiFiVL II (WiFiCS). This URL can be taken and used in any of the other virtual laboratories created (WiFiVL I & WiFiVL II).
The WiFiCS translates the URL into a description and then executes the simulation, returning the results to the orb in a compressed format detailing every network event.
The orb controls the animation of events in the virtual world with an execution scheduler. Nodes are instructed to perform animations by the scheduler on a pre-assigned channel.