Cloud transactions and caching for improved performance in clouds and DTNs

In distributed transactional systems deployed over some massively decentralized cloud servers, access policies are typically replicated. Interdependencies ad inconsistencies among policies need to be addressed as they can affect performance, throughput and accuracy. Several stringent levels of policy consistency constraints and enforcement approaches to guarantee the trustworthiness of transactions on cloud servers are proposed. We define a look-up table to store policy versions and the concept of Tree-Based Consistency approach to maintain a tree structure of the servers. By integrating look-up table and the consistency tree based approach, we propose an enhanced version of Two-phase validation commit (2PVC) protocol integrated with the Paxos commit protocol with reduced or almost the same performance overhead without affecting accuracy and precision. A new caching scheme has been proposed which takes into consideration Military/Defense applications of Delay-tolerant Networks (DTNs) where data that need to be cached follows a whole different priority levels. In these applications, data popularity can be defined not only based on request frequency, but also based on the importance like who created and ranked point of interests in the data, when and where it was created; higher rank data belonging to some specific location may be more important though frequency of those may not be higher than more popular lower priority data. Thus, our caching scheme is designed by taking different requirements into consideration for DTN networks for defense applications. The performance evaluation shows that our caching scheme reduces the overall access latency, cache miss and usage of cache memory when compared to using caching schemes --Abstract, page iv

Cloud Transactions Adhere to Strict Policy Consistency for Improved Performance

In distributed transactional systems deployed over some massively decentralized cloud servers, access policies are typically replicated. Interdependencies and inconsistencies among policy versions can affect performance, throughput, and accuracy, which can increase the transaction failure rate and cause long delays. Thus, policy and user credential inconsistencies need to be addressed. Several stringent levels of policy consistency constraints and enforcement approaches to guarantee the trustworthiness of transactions on cloud servers are proposed. However, there are performance issues associated with the policies proposed while retrieving the latest policy versions present in various cloud servers. In this paper, first, we define a look-up table in which the policy versions used for authorization is stored and updated on a regular basis and this information can be easily retrieved by the transaction manager. Next, we use the concept of Tree-Based Consistency approach to maintain a tree structure of the servers where a data item is replicated. By integrating look-up table for policy versions and the consistency tree based approach, finally, we propose an enhanced version of Two-Phase Validation Commit (2PVC) protocol integrated with the Paxos commit protocol to increase the number transaction commits with reduced or almost the same performance overhead (transaction execution time) without affecting accuracy and precision, but reducing the number of transaction aborts in comparison with a most recent work

Opportunistic Distributed Caching for Mission-Oriented Delay-Tolerant Networks

In this paper, a new caching scheme has been proposed which takes into consideration mission-oriented applications of Delay-tolerant Networks (DTNs) such as in Military. In such applications data need to be cached following different criteria and priority levels. In these applications, other than data popularity based on request frequency, the importance is also given to who created and ranked POIs (point of interest) in the data (images), when and where it was created; higher rank data belonging to some specific location may be more important though the frequency of those may not be higher than frequency based popular data. Thus, our caching scheme for DTNs is designed by taking different requirements into consideration for defense applications so that access latency for higher priority but lesser accessed data is reduced. The performance evaluation shows that our caching scheme based on criteria other than popularity reduces the overall access latency, cache miss and cache memory when compared to other caching schemes