14. Error Model

This chapter describes the implementation and configuration of error models, which introduces packet losses into a simulation.

In addition to the basic class ErrorModel described in details below, there are several other types of error modules not being completely documented yet, which include:

• SRMErrorModel, PGMErrorModel: error model for SRM and PGM.
• ErrorModel/Trace: error model that reads a loss trace (instead of a math/computed model)
• MrouteErrorModel: error model for multicast routing, now inherits from trace.
• ErrorModel/Periodic: models periodic packet drops (drop every nth packet we see). This model can be conveniently combined with a flow-based classifier to achieve drops in particular flows
• SelectErrorModel: for Selective packet drop.
• ErrorModel/TwoState: Two-State: error-free and error
• ErrorModel/TwoStateMarkov, ErrorModel/Expo, ErrorModel/Empirical: inerit from ErrorModel/TwoState.
• ErrorModel/List: specify a list of packets/bytes to drop, which could be in any order.

Their definitions can be found in ~ns/queue/errmodel.{cc, h} and ~ns/tcl/lib/ns-errmodel.tcl, ns-default.tcl.