Router behavioral complexity (network complexity from a testing perspective) Marco Canini EPFL, Switzerland 02/05/2011Marco Canini, RIPE 621

Network complexity Behavior – Extensive range of possible behaviors Flexibility of routing software implementations Support for programmability to enhance functionalities Highly expressive configuration constructs but low level of network-wide semantic gives rise to complexity – As in a distributed system, network behavior is aggregate result of interleaved actions of many routers Heterogeneous and failure-prone environment 02/05/2011Marco Canini, RIPE 622

Whole is sum of the parts Difficult to reason about all possible behaviors – Unanticipated interactions of pieces of software with rather extensive behavior – Subtle differences in inter-operable router implementations – System-wide conflicts under locally admissible decisions – Seemingly valid local fault handling – Different recipes to reach the same network-design objectives – More programmability adds flexibility but extends behavioral complexity 02/05/2011Marco Canini, RIPE 623

Inputs Messages Failures Configuration changes Random choices Timeouts Code, configuration and inputs drive router behavior Code Configuration Behavior 02/05/2011Marco Canini, RIPE 624

Testing can help to manage complexity Our vision – Harness the increases in computational power and bandwidth to improve reliability Our goal – Use online testing to explore system behavior – Make routers aware of the consequences of their actions Subject the routing system to many possible inputs and let things play out in isolation Observe the system-wide impact of router actions 02/05/2011Marco Canini, RIPE 625

Time Space Shadow snapshot 1 Shadow snapshot n Explore system behavior Live system Exploring behavior 02/05/2011Marco Canini, RIPE 626

Wrap up Ongoing work – Online testing for BGP Prototype built into BIRD – Papers: LADIS ’10, USENIX ATC ’11 Ultimately – Network itself would be the test platform Come and see the full talk at the Routing WG session (Wed. at 2pm) 02/05/2011Marco Canini, RIPE 627