Invalidation Reports Research Articles

An adaptive cache invalidation technique for wireless environments

With an evolution of Internet and related technologies such as 4G, and 5G, there is a need of fast response time for various queries raised by intermediate nodes and mobile terminals from infra structured-based/less networks. Although there has been many efforts in the past to address this issue by using an invalidation report (IR)-based cache management schemes which reduce the bandwidth requirements, and battery consumptions, but when the update rate of data at the server is high, then most of the existing approaches have long query latency due to large and fixed size of IRs, and broadcast time (BT) interval. To address these issues, in this paper, an adaptive cache invalidation technique (ACIT) is proposed. In comparison to the previous approaches, the proposed scheme uses different thresholds update rates for adaptive IR, and BT intervals. In the proposed scheme, only hot data updates in IR are recorded which results a less query delay, and bandwidth consumption. The performance of the proposed scheme was studied by extensive simulations by comparing it with the other state-of-the-art schemes using various metrics. The proposed scheme yields 1.5 times enhancement in query response time with a reduction in IR size to 25 % in comparison to other existing techniques. Moreover, there is a reduction of 119.89 % in broadcast time interval using the proposed scheme.

CACC: A Cooperative Approachto Cache Consistency in WMNs

Cooperative caching is a desirable approach to achieve efficient data access in multi-hop wireless networks. Existing cooperative caching algorithms mostly focus on cache placement. Another key issue, cache consistency, has not been adequately addressed. In this paper, we propose CACC, a cooperative approach to maintain cache consistency for wireless mesh networks. CACC combines push and pull by making use of the hierarchical architecture of mesh networks. The key contribution of CACC lies in two techniques that introduce cooperation among network nodes in delivering invalidation reports (IRs) so as to reduce communication cost and tolerate message losses. The first technique, IR integration, buffers and merges IRs at gateway nodes and periodically broadcasts them. The second technique, cooperative IR re-sending, lets intermediate nodes resend missed IR messages upon request. The interval of IR broadcast is optimized to achieve the optimal tradeoff between push and pull. We conduct numerical analysis to find optimal values for different scenarios. We also perform simulation to confirm our analysis results and compare with existing approaches. The results show that CACC can save message cost significantly (50-70 percent).

User-defined consistency sensitive cache invalidation strategies for wireless data access

In order to fulfill users’ insatiable interests in accessing Internet services and information wirelessly, one of the key optimization techniques is caching frequently accessed data items in a local cache. A strong consistency is implicitly assumed in most caching schemes but it may cause a long query delay. In this paper, we propose a consistency-sensitive cache invalidation scheme, called ConSens, based on the existing Invalidation Report (IR) and Updated IR (UIR) based cache invalidation frameworks. In the ConSens scheme, each user is able to set its own consistency level with a server independently. This user-defined cache consistency can support diverse consistency requirements of applications. We also propose both lazy request and opportunistic data access techniques to effectively balance the data accessibility and query delay. In addition, we enhance the IR-based cache invalidation mechanism and propose a multiple data transmission scheme, called MDT, to further reduce the query delay. Extensive performance evaluation studies show that the proposed strategies can effectively balance the data accessibility, reduce the query delay, and significantly increase the number of opportunistic accesses according to the user-defined consistencies.

Performance analysis of cache consistency strategies for multi-hop wireless networks

Data caching is widely used to facilitate information access in wireless mobile networks. Caching frequently used content on mobile clients brings benefits by reducing bandwidth usage, saving energy, and leveraging server workload. Maintaining cache consistency is an important issue in mobile caching and has received much attention by researchers. However, most existing studies on cache consistency strategies are limited to cellular wireless networks in which the mobile terminals can communicate with the base stations directly. In multi-hop wireless network environment, mobile terminals communicate with data server through multiple unreliable links with a high probability of disconnection from the network, which makes it more challenging for the maintenance of cache data consistency. In this paper, we investigate three cache consistency strategies for multi-hop wireless networks: the pull-based strategy POD (pull on demand), the push-based strategy MAT (modified amnesic terminals) and the store and forward strategy PIR (pull-based invalidation report). Extensive theoretical analysis is provided to compare the cache hit ratio, query delay and communication overhead of these methods, and the impact of system parameters on performance is studied as well. Simulation experiments are used to examine the performance of these three schemes, and it is shown that PIR provides the best overall performance.

Answering queries using cooperative semantic cache in mobile computing environments

In cooperative cache research domain, most of previous work engage in peer-to-peer systems and distributed systems, but do not involve applying cooperative semantic cache in mobile computing environments, which wireless communications disconnect at times and clients move frequently. In this paper, we extend the general semantic cache mechanism by enabling mobile clients to share their local semantic caches in a cooperative matter, and the process way and flow chart of the algorithm are described in detail. In addition, we discuss the methods used in cache consistence maintenance, which focus on confirm receiver of the periodic cache invalidation report and the process of validate client's local cache. The experiment results indicate cooperative semantic cache mechanism could reduce query response time and increase cache hit ratio effectively.

VANET에서 효율적이며 엄격한 데이터 일관성을 유지하는 캐쉬 관리 기법

차량용 애드혹 네트워크 (VANET: Vehicular Ad-hoc Network)는 차량으로 구성된 모바일 애드혹 네트워크로서 기간망의 도움 없이 차량 간 통신을 가능하게 한다. VANET에서 차량 노드는 네트워크의 일원으로 참여하면서 에너지와 자원을 사용한다. 지금까지 VANET에서 질의처리시간과 통신 과부하를 줄이기 위하여 데이터 복제와 협력 캐슁이 연구되어 왔다. 또한 VANET에서 협력 캐슁 기법 관련 연구는 주로 약한 일관성에 중점을 두고 있다. 이 논문에서는 VANET에서 엄격한 데이터 일관성을 유지하면서 효율적인 캐쉬 관리가 가능한 기법을 제안한다. 본 논문에서는 강한 데이터 일관성을 유지하면서 질의 지연과 통신 과부하를 줄일 수 있도록 IR (Invalidation Report)을 방송하는 스케줄링 기법을 제안한다. 성능 평가는 제안한 기법이 질의 지연과 통신 과부하에서 강점을 가지고 있음을 보여준다. A Vehicular Ad-hoc Network (VANET) is a vehicular specific type of a mobile ad-hoc network, to provide temporary communications among nearby vehicles. Mobile node of VANET consumes energy and resource with participating in the member of network. In a VANET, data replication and cooperative caching have been used as promising solutions to improve system performance. Existing cooperative caching scheme in a VANET mostly focuses on weak consistency is not always satisfactory. In this paper, we propose an efficient cache management scheme to maintain strong data consistency in a VANET. We make an adaptive scheduling scheme to broadcast Invalidation Report (IR) in order to reduce query delay and communication overhead to maintain strong data consistency. The simulation result shows that our proposed method has a strength in terms of query delay and communication overhead.

Flexible Data Dissemination Strategy For Effective Cache Consistency In Mobile Wireless Communication Networks

In mobile wireless communication network, caching data items at the mobile clients is important to reduce the data access delay. However, efficient cache invalidation strategies are used to ensure the consistency between the data in the cache of mobile clients and at the database server. Servers use invalidation reports (IRs) to inform the mobile clients about data item updates. This paper proposes and implements a multicast based strategy to maintain cache consistency in mobile environment using AVI as the cache invalidation scheme. The proposed algorithm is outlined as follows – To resolve a query, the mobile client searches its cache to check if its data is valid. If yes, then query is answered, otherwise the client queries the DTA (Dynamic Transmitting Agent) for latest updates and the query is answered. If DTA doesn’t have the latest updates, it gets it from the server. So, the main idea here is that DTA will be multicasting updates to the clients and hence the clients need not uplink to the server individually, thus preserving the network bandwidth. The scenario of simulation is developed in Java. The results demonstrate that the traffic generated in the proposed multicast model is simplified and it also retains cache consistency when compared to the existing methods that used broadcast strategy.

A cache invalidation strategy for mobile networks

The diversity of services delivered over wireless channels has increased people's desire in ubiquitously accessing these services from their mobile devices. However, a ubiquitous mobile computing environment faces several challenges such as scarce bandwidth, limited energy resources, and frequent disconnection of the server and mobile devices. Caching frequently accessed data is an effective technique to improve the network performance because it reduces the network congestion, the query delay, and the power consumption. When caching is used, maintaining cache consistency becomes a major challenge since data items that are updated on the server should be also updated in the cache of the mobile devices. In this paper we propose a new cache invalidation scheme called Selective Adaptive Sorted ( SAS) cache invalidation strategy that overcomes the false invalidation problem that exists in most of the invalidation strategies found in the literature. The performance of the proposed strategy is evaluated and compared with the selective cache invalidation strategy and the updated invalidation report startegy found in the literature. Results showed that a significant cost reduction can be obtained with the proposed strategy when measuring performance metrics such as delay, bandwidth, and energy.

Scalability study of cache access mechanisms in multiple-cell wireless networks

Strong-consistent cache access algorithms have been proposed and studied for wireless networks. In this paper, we carry out a comprehensive study to compare four strong-consistent cache access algorithms including the invalidation report (IR), poll-each-read (PER), call-back (CB), and Lease schemes in multiple-cell wireless/mobile networks. The purpose of this study is to examine the scalability of the IR schemes. To the best of our knowledge, this is the first such study. We focus on the scalability issue of these four fundamental strong-consistent schemes in terms of network transmission costs regarding network size, database size, subscription ratio, and network traffic, through extensive computer simulations. Our results show that: (1) the IR schemes do not perform well in a multiple-cell wireless/mobile networks with a large update rate, database size, and IR window size, and with a small subscription ratio; (2) the IR schemes do scale up well with the IR period and the access rate; however, while good performance can be obtained when the IR period is large, this implies a large access latency; (3) the PER, the CB and the Lease schemes perform well with a large update rate, small subscription ratio, and large database size.

Broadcasting four types of reports to read only transactions in mobile computing environments

PurposeRecently the advances in wireless communication technology and the popularity of portable computers have rendered mobile computing environments from which mobile users with battery‐operated palmtops can access the information via wireless channels, without space and time restriction. In mobile computing environments, mobile users cache the data items to use the bandwidth efficiently and improve the response time of mobile transactions. If the data items cached in mobile users are updated at the server, the server broadcasts an invalidation report for maintaining the cache consistency of mobile users. However, this method has an obstacle that does not guarantee the serializable execution of mobile transactions. The purpose of this paper is to propose the four types of reports for mobile transaction (FTR‐MT) method for ensuring the serializable execution of mobile transactions.Design/methodology/approachThe paper describes the FTR‐MT method, which is composed of four types of algorithms, e.g. group report composition algorithm, immediate commit decision algorithm, cache consistency algorithm, and disconnection cache consistency algorithm. FTR‐MT method for improving the response time of mobile transactions makes a commit decision by using the four types of reports.FindingsWith the FTR‐MT method, mobile users can make a commit decision by using the four types of reports. The response time of mobile transactions can be reduced. Furthermore, the FTR‐MT method can improve the cache efficiency in the case that the disconnection of mobile users is longer than the broadcast interval of the window report.Originality/valueThis paper proposes a new method for guaranteeing the serializable execution of mobile transactions, called FTR‐MT, using four types of reports. Also, it can prevent the entire cache dropping, even though the disconnection of a mobile host is longer than the broadcast interval of a window report. Through the analytical model, this method is felt to be superior to other methods, in terms of the average response time and the commit rate of mobile transactions, and bandwidth usage.

A cache invalidation scheme for continuous partial match queries in mobile computing environments

The continuous partial match query is a partial match query whose result remains consistently in the client's memory. Conventional cache invalidation methods for mobile clients are record ID-based. However, since the partial match query uses content-based retrieval, the conventional ID-based approaches cannot efficiently manage the cache consistency of mobile clients. In this paper, we propose a predicate-based cache invalidation scheme for continuous partial match queries in mobile computing environments. We represent the cache state of a mobile client as a predicate, and also construct a cache invalidation report (CIR), which the server broadcasts to clients for cache management, with predicates. In order to reduce the amount of information that is needed for cache management, we propose a set of methods for CIR construction (in the server) and identification of invalidated data (in the client). Through experiments, we show that the predicate-based approach is very effective for the cache management of mobile clients.

Proxy-based hybrid cache management in Mobile IP systems

In this paper, we propose and analyze a proxy-based hybrid cache management scheme for client–server applications in Mobile IP (MIP) networks. We leverage a per-user proxy as a gateway between the server and the mobile host (MH) such that any communication between the MH and server must pass through the proxy. The proxy has dual responsibilities in our design. It keeps track of the current location of the MH by acting as a regional Gateway Foreign Agent (GFA) as in the MIP Regional Registration protocol for mobility management. The proxy is also responsible for cache consistency management and query processing on behalf of the MH. To reduce the network traffic, a threshold-based hybrid cache consistency management policy is applied. That is, when a data object is updated at the server, the server sends an invalidation report to the MH through the proxy to invalidate the cached data object, provided that the size of the data object exceeds the given threshold. Otherwise, the server sends a fresh copy of the data object through the proxy to the MH. We identify the best “threshold” value that would minimize the overall network traffic incurred due to mobility management, cache consistency management, and query processing, when given a set of parameter values characterizing the operational and workload conditions of the MIP network.

An Efficient Cache Invalidation Method in Mobile Client/Server Environment

In mobile computing environments, cache invalidation techiniques are widely used. However, theses techniques require a large-sized invalidation report and show low cache utilization under high server update rate. In this paper, we propose a new cache-level cache invalidation technique called TTCI (Timestamp Tree-based Cache Invalidation technique) to overcome the above two problems. TTCI also supports selective tuning for a cache-level cache invalidation. We show in our experiment that our technique requires much smaller size of cache invalidation report and improves cache utilization.

Increasing mobile clients' cache reusability in a wireless client‐server environment

AbstractIn a wireless client‐server environment, data broadcasting is an efficient data dissemination method and some of the broadcast data are often cached at each mobile client's cache. Data broadcasting and caching save communication bandwidth, resource usage, and data access time. A server also broadcasts invalidation reports (IRs) to maintain the consistency between server data and clients' cached data. Most existing cache invalidation policies simply purge the entire cache after a client has been disconnected long enough to miss a certain number (window size) of IRs. We present a cache invalidation scheme to increase the reusability of the data in mobile clients' caches after long disconnection. Instead of clearing the entire cache regardless of its consistency after long disconnection, a client estimates the relative cost of purging all data and the cost of a selective purge. If a selective purge is cheaper, the client sends server an uplink message to ask the validity of data whose update rate is low to salvage as many valid data as possible. Simulation results show that our scheme effectively increases cache reusability since our cost functions respect update rates at a server, broadcast intervals, the communication bandwidth, and data sizes as well as disconnection time. Copyright © 2007 John Wiley & Sons, Ltd.

Better mobile client’s cache reusability and data access time in a wireless broadcast environment

Data broadcasting is an efficient data dissemination method in a wireless client–server system. A data server broadcasts data items periodically, and mobile clients cache data items to save communication bandwidth, resource usage, and data access time. The server also broadcasts invalidation reports (IRs) to maintain the consistency between server data and the clients’ cached data. Most existing cache invalidation policies in a wireless environment based on IRs simply purge the entire cache after a client has been disconnected long enough to miss a certain number (window size) of IRs. We present a cache invalidation scheme that provides better cache reusability and better data access time after a long disconnection. Our scheme attempts to increase cache reusability by respecting update rates at a server, broadcast intervals, the communication bandwidth, and data sizes, as well as disconnection time. Simulation results show that the increased cache reusability of our scheme can improve the data access time after a long disconnection.

Cache invalidation strategies for internet-based mobile ad hoc networks

Internet-based mobile ad hoc network ( Imanet) is an emerging technique that combines a mobile ad hoc network ( Manet) and the Internet to provide universal information accessibility. Although caching frequently accessed data items in mobile terminals (MTs) improves the communication performance in an Imanet, it brings a critical design issue when data updates. In this paper, we analyze several push and pull-based cache invalidation strategies for Imanets. A global positioning system (GPS) based connectivity estimation (GPSCE) scheme is first proposed to assess the connectivity of an MT for supporting cache invalidation mechanisms. Then, we propose a pull-based approach, called aggregate cache based on demand (ACOD) scheme that uses an efficient search algorithm for finding the queried data items. In addition, we modify two push-based cache invalidation strategies, proposed for cellular networks, to work in Imanets. They are called modified timestamp (MTS) scheme and MTS with updated invalidation report (MTS + UIR) scheme, respectively. We compare the performance of all these schemes as a function of query interval, cache update interval, and cache size through extensive simulation. Simulation results indicate that the ACOD scheme provides high throughput, low query latency, and low communication overhead, and thus, is a viable approach for implementation in Imanets.

Defending against cache consistency attacks in wireless ad hoc networks

Caching techniques can be used to reduce bandwidth consumption and data access delay in wireless ad hoc networks. When cache is used, the issue of cache consistency must be addressed, and maintaining strong cache consistency is desired in some strategic scenarios (e.g., battlefields). In these situations, the invalidation-based approach is preferred due to its low overhead. However, this approach may suffer from some security attacks. For example, malicious nodes (also called intruders) may drop, insert or modify invalidation messages to mislead receivers to use stale data or unnecessarily invalidate data that are still valid. In this paper, we first propose to employ the Invalidation Report (IR) based cache invalidation strategy to prevent intruders from dropping or modifying invalidation messages. Although digital signatures can be used to protect IRs, this has significantly high overhead in terms of computational and bandwidth overhead. To address this problem, we further propose a family of randomized grouping-based schemes for intrusion detection, damage recovery and intruder identification. Extensive analysis and simulations are performed to evaluate the proposed schemes. The results show that our solution can achieve a satisfactory level of security with low overhead.

Energy efficient cache invalidation in a disconnected wireless mobile environment

Caching of frequently accessed data on the mobile clients can reduce the number of uplink requests, server load and query latency and can increase data availability. As cached data items eventually become invalid due to updates at the server, an invalidation strategy is employed to maintain cache consistency so that no obsolete data would be used to serve queries. The basic cache invalidation strategies make use of periodic invalidation reports (IRs) and updated invalidation reports (UIRs) broadcast by the server. This paper presents a synchronous stateful caching strategy called update report (UR). UR strategy preserves the advantages of IR/UIR strategies and improves on their disadvantages. It reduces the size of IR by filtering out noncached items, handles long disconnection, reduces query latency by broadcasting recently requested items immediately after every UIR, conserves client energy and supports mobility. Simulation results prove that UR yields better performance than IR and UIR strategies.

Dynamic cache consistency schemes for wireless cellular networks

Caching frequently accessed data objects at the local buffer of a mobile user (MU) has been found to be very effective in improving information availability in mobile wireless environments. Several mechanisms have been proposed in the literature to address the challenging problem of cache consistency in cellular wireless networks. However, these mechanisms are limited to single cell systems. In this paper, we develop a novel Dynamic Scalable Asynchronous Cache Consistency Scheme (DSACCS) that can adaptively maintain mobile data objects globally or locally depending on the minimum consistency maintenance cost in multi-cell systems. The cost function is derived by taking into account each data object's update frequency, MUs' access pattern and roaming frequency, number of cells and number of MUs in the system. Extensive simulation studies demonstrate that DSACCS outperforms three existing cache strategies extended to multi-cell environments. The three cache consistency strategies are homogeneous invalidation reports (IRs), inhomogeneous IR without roaming check, and inhomogeneous IR with roaming check. Finally, an improvisation of DSACCS, called DSACCS-G, is proposed for grouping cells in order to facilitate effective cache consistency maintenance in multi-cell systems.

이동 컴퓨팅 환경에서 비동기적 데이터방송을 사용한 동시성 제어 기법

이동 컴퓨팅 환경에서 이동 호스트는 대역폭의 사용을 줄이고 이동 트랜잭션의 응답 시간을 향상시키기 위하여 캐쉬를 사용한다. 그리고 서버는 이동 호스트의 캐쉬 일관성을 유지하기 위해서 주기적으로 갱신된 데이터를 방송한다. 그러나 무효화 보고서를 사용한 캐쉬 일관성 유지기법은 이동 트랜잭션의 완료 결정을 지연한다는 문제점을 가지고 있다. 본 논문에서는 캐슁된 데이터를 사용하여 이동 트랜잭션을 수행하는 경우 이동 트랜잭션의 직렬 가능한 수행을 보장하는 CCM-AD 방법을 제안한다. 제안하는 CCM-AD 방법은 서버에서 이동 호스트에게 방송한 데이터와 갱신된 데이터와의 교집합을 구하여 공통되는 데이터를 요청 데이터와 함께 방송함으로써 이동 트랜잭션의 직렬 가능한 수행을 보장한다. 그리고 수행 후 완료 결정을 위한 이동 트랜잭션의 지연도 줄일 수 있다. 또한 주기적으로 방송하는 무효화 보고서의 메시지 크기도 줄일 수 있다. In mobile computing environments, a mobile host caches the data to use the narrow bandwidth efficiently and improve the response time. A server periodically broadcasts the update data for maintaining the cache consistency of a mobile host. However, a method for maintaining cache consistency using periodic invalidation report has a problem that defers the commit decision of a mobile transaction to guarantee its serializable execution. In this paper, we propose CCM-AD method that guarantees the serializable execution of a mobile transaction even in the case that it is executed using cached data. As CCM-AD method guarantees the serializable execution of mobile transactions by using the intersection between the data broadcast to mobile host and the data updated at server. Then the CCM-AD method can reduce the delay of commitment decision of a mobile transaction. Also our method can reduce the size of invalidation report.