Contents

Link failure support

Real systems always have a possibility of suffering from link failures, so a realistic simulation must allow for links to fail. Simulator model supports two different kinds of link failures:

• STOP_FAIL and
• INTERMITTENT

Each time and before a specific protocol execution, one of the above types of failures can be selected and an upper bound of the number of links to fail can be determined. The number of links to fail, as can be found in the relevant bibliography, is a fundamental parameter for all the available solutions.

In case of STOP_FAIL link failure, simulator forces each message sent on a faulty link to vanish. In case of INTERMITTENT link failure, faulty links loose messages selectively according to a probabilistic distribution.

In both cases the node that sends a message is not aware of their lost and the receiving node is not aware of the fact that a message was sent to it and it never received it. Debug files contain information about message sending but not about message receiving since the relevant message was never received. Therefore, to help the user study message sequencing easier, in case of a message that is sent on a faulty link, information about the link condition is written to the debug file as a comment.

SEE ALSO: Simulator model (Section 4.1), Experiment Dialogue Window (Section 3.2.3).

The network model in LYDIAN is implemented on the GraphWin module of LEDA [2], which strongly supports for constructing graphs as well as animating graph algorithms. Every time a new network is created via GraphWin for LYDIAN window (section 6), the three following files need to be saved:

*.gw:

save the network topology. These files can be loaded to the GraphWin for LYDIAN window for futher use.

*.ipf:

save the network timing information. These files are used in the Network field on Experiment dialogue window.

*.gsf:

save graph structured needed for graphical animation visualization mode. These files are used in the Graph Structure field on Experiment dialogue window.

2002-11-11