Negative Caching Research Articles

Analysis of Flooding DoS Attacks Utilizing DNS Name Error Queries

The Domain Name System (DNS) is a critical Internet infrastructure that provides name to address mapping services. In the past decade, Denial-of-Service (DoS) attacks have targeted the DNS infrastructure and threaten to disrupt this critical service. While the flooding DoS attacks may be alleviated by the DNS caching mechanism, we show in this paper that flooding DoS attacks utilizing name error queries is capable of bypassing the cache of resolvers and thereby impose overwhelming flooding attacks on the name servers. We analyze the impacts of such DoS attacks on both name servers and resolvers, which are further illustrated by May 19 China’s DNS Collapse. We also propose the detection and defense approaches for protecting DNS servers from such DoS attacks. In the proposal, the victim zones and attacking clients are detected through monitoring the number of corresponding responses maintained in the negative cache. And the attacking queries can be mitigated by the resolvers with a sample proportion adaptive to the percent of queries for the existent domain names. We assess risks of the DoS attacks by experimental results. Measurements on the request rate of DNS name server show that this kind of attacks poses a substantial threat to the current DNS service.

Limited Preemption EDF Scheduling of Sporadic Task Systems

The optimality of the Earliest Deadline First scheduler for uniprocessor systems is one of the main reasons behind the popularity of this algorithm among real-time systems. The ability of fully utilizing the computational power of a processing unit however requires the possibility of preempting a task before its completion. When preemptions are disabled, the schedulability overhead could be significant, leading to deadline misses even at system utilizations close to zero. On the other hand, each preemption causes an increase in the runtime overhead due to the operations executed during a context switch and the negative cache effects resulting from interleaving tasks' executions. These factors have been often neglected in previous theoretical works, ignoring the cost of preemption in real applications. A hybrid limited-preemption real-time scheduling algorithm is derived here, that aims to have low runtime overhead while scheduling all systems that can be scheduled by fully preemptive algorithms. This hybrid algorithm permits preemption where necessary for maintaining feasibility, but attempts to avoid unnecessary preemptions during runtime. The positive effects of this approach are not limited to a reduced runtime overhead, but will be extended as well to a simplified handling of shared resources.

Performance Study and Effects of Route Caching Mechanisms in On-Demand Routing Algorithms for MANET

Route caching strategy is an important part of any on-demand routing protocols to influence performance of wireless networks. Performance metrics like overhead and delay were found to vary with utilization levels of route cache for protocols like Dynamic Source Routing (DSR) and Highest Energy Routing (HER). Hence variations to these protocols are presented in this paper to improve reliability of service and reduce the effects of cache staleness and network partitions. The variation is with respect to identification of route and cache validation of errors using different techniques namely Update Route Caching (URC), Temporal Cache Validation (TCV), Negative Cache Validation (NCV) and combined cache validation (CCV). These techniques refresh cache more often than the DSR and HER thereby initiating route requests earlier, when a route still being used is broken, thus reducing peer-to-peer delay to transmit packets. The results of GloMoSim simulator validates higher cache hit percentage and reliable delivery of packets in the technique Combined Cache Validation (CCV) when in comparison to DSR and HER.