The Internet is a large-scale, complex, loosely coupled distributed system made of many imperfect components. All Internet-based applications rely on a dependable packet delivery service provided by the Internet routing infrastructure. However, Faults of varying scale and severity occur from time to time. The article presents a survey of the past research efforts aimed at enhancing the dependability of the routing infrastructure. To provide a comprehensive overview of the various efforts, a threat model based on known threats has been presented initially, then a sketch out a defense framework, and puts each of the existing efforts at appropriate places in the framework based on the faults and attacks against which it can defend. This analysis shows that although individual defense mechanisms may effectively guard against specific faults, no single fence can counter all faults. Thus, a resilient Internet routing infrastructure calls for integrating techniques from cryptographic protection mechanism, statistical anomaly detection, protocol syntax checking, and protocol semantics checking to build a multifence defense system.