Testing switch rules in software defined networks

SDN-technology is efficiently used for implementing service function chains can be efficiently implemented utilizing common resources and their management principles in virtual networks. The network is based on a connected undirected graph of physical links called usually referred to as resource network connectivity topology (RNCT); graph nodes are network switches and hosts and each host is connected exactly with one switch. Switches operate based on rule tables that are configured by a controller that operates independently of network equipment. The configuration of network switches provides the transmission of packets from the initial to final hosts depending on the values of the packet parameters. The paper discusses the relationship between switch configurations and paths which are created for trasmitting packets depending on RNCT properties. It is shown that, in general, not any configuration of any switch is verifiable. Testing abilities depend on the accepted hypotheses about the switch operating. Two hypotheses are discussed in the paper: the switch hypothesis assumes that the switch operation does not depend on the settings of other switches; a stronger hypothesis about the rule, besides this, assumes that the switch operation according to this rule does not depend on other rules in the configuration of this switch. Section 2 contains preliminaries while Section 3 is devoted to the relationship between switch rules and sets of paths to be implemented. In Section 4, the problem of testing the switch configuration is considered based on the rule hypothesis; a number of statements are estableshed, in particular, the necessary and sufficient conditions of the ability of testing a given rule of a given switch. Section 5 discusses and proves the necessary (but not sufficient) condition and sufficient (but not necessary) condition for checking any switch configuration based on the switch hypothesis. In conclusion, the problems of establishing the necessary and sufficient conditions for verifiability of any switch configuration are discussed.