Survivability is one of research focuses of network security. This paper classified the target systems of survivability into Bounded Systems and Unbounded Systems and deemed Emergent Algorithms as a suitable solution to enhance the survivability of Unbounded Systems. A pattern of Emergent Algorithms is proposed using Multi-agent System and protocol to model the system. By deploying survivability control agents and designing the protocol among agents the survivability of the target Unbounded Systems is enhanced. Simulation framework to verify and evaluate Emergent Algorithms is also proposed.