A live demo can be found here.
This is a simple simulation of CSMA/DA on a 5-computer LAN setup written in JavaScript. The computers can send telegrams to each other and use exponential backoff to space out repeated retransmissions of the same block of data.
A red block means collision, all other colors represent data. Darker grey squares below each computer indicate the possible slots the computer can choose for retransmitting. Random choices are indicated by green. Manually chosen slots are colored dark red.
The number on device screens displays the number of retries the device has made to transmit a telegram. The number next to the cable displays the number of slot times left until the device attempts to retransmit the last packet.
Switching on short telegrams illustrates what would happen if the telegrams were too short. – the transmitting device will think the transmission was successful even if there was a collision.
- Click on two computers to send a packet from one to the other;
- For deterministic slot times click on any of the numbered buttons. The device above will then always wait until the given slot time to transmit its telegram. Clicking on the chosen button again will enable random slot time selection;
- The simulation can be paused at any time using the button in the lower left corner. Mouse events won't be disabled so you could for example issue several transmits and unpause to synchronise;
- You can unpause by clicking on the pause button again;
- FPS can be controlled by clicking on the two arrow buttons on the lower left corner;
- To change the packet length, either click on "Long telegram" or "Short telegram";
To run unit tests, you'll need to fire up tests.html in your favorite web browser.
csma-simulator is released under MIT License. See the bundled
LICENSE file for details.