Cybikos: wireless handheld computers Cybikos specifications: 32-bit processor running at 11mhz 4mhz coprocessor for its radio transmitter 512k of RAM 512k of flash memory (used for storage) 160x100 grayscale LCD display 300 foot range on their wireless communications. Why we picked Cybikos: They’re very cheap They have a full-featured operating system They have built-in support for ad-hoc wireless networking The compiler runs under Windows or Linux, any PC can transfer files to the Cybiko The solution: Each computer keeps a table telling it who it’s connected to. Whenever the user tries to send data through my interface, the computer checks against the table to see if it should allow the data to go through. This check is transparent to the user. What I did: The computers will only talk over the lines colored in blue a d b c abcd a b c d connections -√xx √-√√ x√-x x√x- a b c d a d b c The Problem: I had a wireless network, but I needed to make it behave as if it were a wired network. In a wireless network, any computer can communicate with any other computer. In a wired network, computers can only communicate if they have a wire running between them. What I had: All the computers are interconnected.What I wanted: Only adjacent computers are connected. Virtual network administration: I made one of the nodes an administrator -- not participating in the virtual network as a node, but overseeing the simulation. Virtual network startup routine: 1) The administrator figures out what the network will look like 2) The administrator gathers all the computers it needs and tells them to wait for the network 3) The admin sends its network table, which contains everything the nodes need to know Code structure: My virtual topology is made of multiple layers of abstraction from the Cybiko OS. Cybiko OS Send and receive, names Virtual topology Protocol Provides a familiar interface to send and receive functions and the ability to use strings for source and destination, instead of serial numbers. Keeps a record of the network topology and enforces it. Handles key presses, checking for messages, and provides a basic GUI. Decides how to handle messages from other nodes (by forwarding them on to another Cybiko, for example). Are there system messages? place it in the data queue yes React appropriately used in my interface? yes Pass the key press to the protocol code no Are there messages in the data queue? from another node? key press? yes no Consume the message no Topology change? load the new topology Message from the administrator? Pass it to the protocol code yes pass the data to the protocol code no yes Message system: The single most complicated part of the virtual topology is handling messages. The Cybiko OS sends an application messages for any event: key presses, system events (low battery, etc), and messages from other Cybikos. System messages, and key presses that affect the GUI need to be responded to quickly, and data from other virtual nodes needs to be processed by the protocol code. The system I developed reacts immediately to local messages, and queues messages from remote machines in a separate queue to keep the system’s queue from overflowing. Conclusion: We have three completed protocols, demonstrating flooding, distance vector, and link state routing, and the underlying system is complete. Having successfully tested the programs on students, the simulation of wired networks is finished. We have begun work simulating wireless and low-level networking situations. Nathaniel WaisbrotAdvisor: Professor Brad Richards Vassar College, Poughkeepsie NY Project Goal Create a system for simulating an arbitrary wired network atop hand-held wireless computers. Initial requirements : The system must be robust enough to support a wide variety of protocols The system must provide a layer of abstraction, so that the protocol code can be understood by people without knowledge of the system The eventual goal of this project is to create a series of labs, suitable for supplementing an undergraduate computer science course. These labs will allow students to experience and experiment with both wired and wireless networking in a hands-on fashion. The results of work will be presented to the National Science Foundation, which funded this project through its Course, Curriculum and Laboratory Improvement program. Requirements of a virtual network: There are certain things which all the nodes of a virtual network need to know before they can work together What is the shape of the network? (i.e.: which nodes are connected, and what is the distance or cost of the connection) What are the names of the other nodes? (They can’t talk to each other without knowing their names) Is the network running? (If some of the nodes get their information faster than others, they can’t start networking early)