Reduce Server Load Research Articles

Peer-assisted multimedia delivery using periodic multicast

Multimedia content distribution is one of the most popular services available on the Internet, and several approaches have been developed to satisfy user requirements and reduce server load. IP multicast is one efficient mechanism for distributing content to multiple users with minimal server and network loads. Because its single stream of data is transmitted simultaneously to multiple users, IP multicast is well-suited for real-time broadcasting. However, it is difficult to offer on-demand multimedia services with IP multicast in which users request content without synchronization. In this paper, we propose an on-demand based multimedia delivery system using IP multicast. In our system, the multimedia server starts multicasting content upon receiving the first content request. Subsequent users then join the multicast session at any time during the transmission. The content that subsequent users have missed is provided by the users (peers) that joined earlier, or by server unicasts. To minimize server load, we quantitatively analyzed the optimal multicast starting point. Through simulation, we show that our proposed system outperforms prior related systems based on peer-to-peer delivery and multicasting.

효율적 메시지 제어방식을 사용한 XMPP/SIP 프레즌스 서비스 시스템

In this paper a new message control method that can reduce server load and network traffic in XMPP/SIP presence service system has been proposed. This presence service system can process both XMPP(Extensible Massaging and Presence Protocol) based presence information and SIP(Session Initiation Protocol) based presence information. A new XMPP stanza architecture with added elements for presence stanza and IQ stanza has been designed, and a new presence information data processing method which can reduce size of SIP notification message and SIP PUBLISH message has been suggested. Furthermore a messages exchanging procedure that can transfer presence information between XMPP domain and SIP domain has been also suggested. The performance of the proposed system has been analysed by simulation.

Push Technology Based on Analytic Hierarchy Process

First of all, three current server push modes are elaborated in this paper, including ​​a detailed analysis and comparison. Due to a single server push mode is used by the current push frame, most application requirements can not be meet. Push techniques based on analytic hierarchy process is proposed in this paper, which selects optimal push mode in different situations by theory of operations research. This method not only improves server performance but also reduces server load. Finally, experimental results show that the proposed method is superior to other single mode.

Optimizing Cloud Resources for Delivering IPTV Services Through Virtualization

Virtualized cloud-based services can take advantage of statistical multiplexing across applications to yield significant cost savings. However, achieving similar savings with real-time services can be a challenge. In this paper, we seek to lower a provider's costs for real-time IPTV services through a virtualized IPTV architecture and through intelligent time-shifting of selected services. Using Live TV and Video-on-Demand (VoD) as examples, we show that we can take advantage of the different deadlines associated with each service to effectively multiplex these services. We provide a generalized framework for computing the amount of resources needed to support multiple services, without missing the deadline for any service. We construct the problem as an optimization formulation that uses a generic cost function. We consider multiple forms for the cost function (e.g., maximum, convex and concave functions) reflecting the cost of providing the service. The solution to this formulation gives the number of servers needed at different time instants to support these services. We implement a simple mechanism for time-shifting scheduled jobs in a simulator and study the reduction in server load using real traces from an operational IPTV network. Our results show that we are able to reduce the load by ~24%(compared to a possible ~31.3% as predicted by the optimization framework).

Time-Shifted Streaming in a Tree-Based Peer-to-Peer System

We propose a peer-to-peer (P2P) streaming system that multicasts live video as well as provides the live video as Video-on-Demand (VoD) during the live session. The proposed system allows users to individually pause and resume a live video stream, and to view video that was streamed before the particular user joined the session. Since live video content naturally results in many users watching it online at the same time, the P2P concept is leveraged to reduce server load. We extend our Stanford Peer-to-Peer Multicast (SPPM) protocol, originally designed for live video multicast, to support playback control. To achieve this in a P2P fashion, peers store received video packets in their local buffer and forward them at a later time when requested by other peers, which is called time-shifted streaming. To understand interaction between live and time-shifted traffic, we analyze video availability of the proposed system, which refers to how many peers possess video contents of a particular position. Motivated by the analysis, we propose fast prefetching and a parent selection scheme suitable for fast prefetching in order to further reduce server load by disseminating video quickly. Fast prefetching is possible because the relaxed transfer deadline of time-shifted streams and peers’ extra uplink bandwidths are exploited. With simulations and mathematical analysis, it is shown that fast prefetching not only alleviates the requirement of server bandwidth by expediting video dissemination, but also mitigates video disruption due to peer churn.

수요에 따른 교체 우선 순위 기반 모바일 데이터베이스 캐쉬 동기화 정책

모바일 데이터 캐슁 기법은 로컬 데이터 전송 과정에서 속도를 향상시키거나 서버의 오버로드를 줄이기 위한 효과적인 기법으로 많이 사용되었고 모바일 컴퓨팅 환경의 저전력, 접속지연 및 간헐적인 인터넷 연결 등의 제약 사항의 해결을 위해 캐싱 기법을 사용하는 다수의연구가 진행되었다. 그러나 최근 스마트폰이 대량 보급되면서 서버 기반 어플리케이션 등 다양한 어플리케이션들에서 모바일 데이터베이스에서 전송해야 되는 데이터 량이 급증하는 등 문제가 발생하고 있으며, 이런 환경에서는 기존 기법들의 사용이 적합하지 않아 어플리케이션의 서버 대기 시간이 길어지는 등 서비스 품질 저하로 연결된다. 본 논문에서는 데이터 캐쉬의 사용률을 높이고 통신횟수를 줄이고 무선 통신망에서의 데이터 전송량을 줄이고 모바일 데이터베이스 시스템의 성능을 향상시키기 위하여 수요에 따른 교체 우선순위기반모바일동기화정책을제안한다. 또한성능평가를통하여제안기법이데이터전송량을줄이고데이터 전송 성공 확률을 향상시켜 모바일 클라이언트가 대량의 데이터의 전송을 요청할 때 데이터 전송 효율이 향상됨을 보인다. Mobile data caching is usually used as an effective way to improve the speed of local transaction processing and reduce server load. In mobile database environment, due to its characters - low bandwidth, excessive latency and intermittent network, caching is especially crucial. A lot of mobile data caching strategies have been proposed to handle these problems over the last few years. However, with smart phone widely application these approaches cannot support vast data requirements efficiently. In this paper, to make full use of cache data, lower wireless transmission quantity and raise transaction success rate, we design a new mobile data caching synchronization strategy based on in-demand and replacement priority. We experimentally verify that our techniques significantly reduce quantity of wireless transmission and improve transaction success rate, especially when mobile client request a large amount of data.

Sensor Based Real-Time Remote Patient Monitoring System: A Study on Mobile DB Construction of Minimum Network Traffic in Use of HTML5 WebSQL

Rapid spread of mobile, a core for leading smart society is influencing not only education, traffic, economy but also health. U-health technology and related market which were loose in development for the past are also developing due to suggestion of new direction by mobile. This study collects biological information of remote patients using sensor out of u-health and develops real-time transmitting system which can give a doctor in charge. Local DB is automatically constructed in mobile by using HTML5 WebSQL to reduce load of server which maintains client (mobile) connection and transmits patient information the biological information can be searched in off-line environment, reduce server load, and reduce network traffic by only bring recent biological information.

Efficient data replication for the delivery of high-quality video content over P2P VoD advertising networks

Recent advances in modern television systems have had profound consequences for the scalability, stability, and quality of transmitted digital data signals. This is of particular significance for peer-to-peer (P2P) video-on-demand (VoD) related platforms, faced with an immediate and growing demand for reliable service delivery. In response to demands for high-quality video, the key objectives in the construction of the proposed framework were user satisfaction with perceived video quality and the effective utilization of available resources on P2P VoD networks. This study developed a peer-based promoter to support online advertising in P2P VoD networks based on an estimation of video distortion prior to the replication of data stream chunks. The proposed technology enables the recovery of lost video using replicated stream chunks in real time. Load balance is achieved by adjusting the replication level of each candidate group according to the degree-of-distortion, thereby enabling a significant reduction in server load and increased scalability in the P2P VoD system. This approach also promotes the use of advertising as an efficient tool for commercial promotion. Results indicate that the proposed system efficiently satisfies the given fault tolerances.

Scalable Brain Atlas: From Stereotaxic Coordinate to Delineated Brain Region

Scalable Brain Atlas: From Stereotaxic Coordinate to Delineated Brain Region

NFS-CD: Write-Enabled Cooperative Caching in NFS

We present the network file system with cluster delegation (NFS-CD), an enhancement to the NFSv4 that reduces server load and increases the scalability of distributed file systems in computing clusters. The cluster delegation feature of NFS-CD allows data sharing among clients by extending the NFSv4 delegation model so that multiple clients manage a single file without interacting with the server. Based on cluster delegation, we implement a fast-commit primitive, cooperative caching, and the ability to recover the uncommitted updates of a failed computer. NFS-CD supports both read and write operations in the cooperative cache without degrading the consistency model of NFSv4. We have implemented NFS-CD by modifying the Linux NFSv4 client only. Because the server remains unchanged, NFS-CD preserves the simple administration model of NFSv4 and interoperates with standard NFS clients. NFS-CD offers improved performance when compared to NFSv4 at the expense of slightly weaker reliability guarantees. An experimental evaluation of our implementation, using industry standard benchmarks and application workloads, reveals that NFS-CD reduces server load by more than half. It also demonstrates that under most workloads, file systems must support writes to the cooperative cache to achieve scale.

On the Design of the Peer-Assisted UGC VoD System

User Generated Content (UGC) VoD services such as YouTube are becoming more and more popular, and their maintenance costs are growing as well. Many P2P solutions have been proposed to reduce server load in such systems, but almost all of them focus on the single-video approach, which only has limited effect on the systems serving short videos such as UGC. The purpose of this paper is to investigate the potential of an alternative approach, the multi-video approach, and we use a very simple method called collaborative caching to show that methods using the multi-video approach are generally more suitable for current UGC VoD systems. We also study the influence of the major design factors through simulations and provide guidelines for efficiently building systems with this method.

GridCast

Video-on-Demand (VoD) is a compelling application, but costly. VoD is costly due to the load it places on video source servers. Many have proposed using peer-to-peer (P2P) techniques to shift load from servers to peers. Yet, nobody has implemented and deployed a system to openly and systematically evaluate how these techniques work. This article describes the design, implementation and evaluation of GridCast, a real deployed P2P VoD system. GridCast has been live on CERNET since May of 2006. It provides seek, pause, and play operations, and employs peer sharing to improve system scalability. In peak months, GridCast has served videos to 23,000 unique users. From the first deployment, we have gathered information to understand the system and evaluate how to further improve peer sharing through caching and replication. We first show that GridCast with single video caching (SVC) can decrease load on source servers by an average of 22% from a client-server architecture. We analyze the net effect on system resources and determine that peer upload is largely idle. This leads us to changing the caching algorithm to cache multiple videos (MVC). MVC decreases source load by an average of 51% over the client-server. The improvement is greater as user load increases. This bodes well for peer-assistance at larger scales. A detailed analysis of MVC shows that departure misses become a major issue in a P2P VoD system with caching optimization. Motivated by this observation, we examine how to use replication to eliminate departure misses and further reduce server load. A framework for lazy replication is presented and evaluated in this article. In this framework, two predictors are plugged in to create the working replication algorithm. With these two simple predictors, lazy replication can decrease server load by 15% from MVC with only a minor increase in network traffic.

NFS-CD: Write-Enabled Cooperative Caching in NFS

We present the network file system with cluster delegation (NFS-CD), an enhancement to the NFSv4 that reduces server load and increases the scalability of distributed file systems in computing clusters. The cluster delegation feature of NFS-CD allows data sharing among clients by extending the NFSv4 delegation model so that multiple clients manage a single file without interacting with the server. Based on cluster delegation, we implement a fast-commit primitive, cooperative caching, and the ability to recover the uncommitted updates of a failed computer. NFS-CD supports both read and write operations in the cooperative cache without degrading the consistency model of NFSv4. We have implemented NFS-CD by modifying the Linux NFSv4 client only. Because the server remains unchanged, NFS-CD preserves the simple administration model of NFSv4 and interoperates with standard NFS clients. NFS-CD offers improved performance when compared to NFSv4 at the expense of slightly weaker reliability guarantees. An experimental evaluation of our implementation, using industry standard benchmarks and application workloads, reveals that NFS-CD reduces server load by more than half. It also demonstrates that under most workloads, file systems must support writes to the cooperative cache to achieve scale.

Biased Replacement Policies for Web Caches: Differential Quality-of-Service and Aggregate User Value

Disk space in shared Web caches can be diverted to serve some system users at the expense of others. Cache hits reduce server loads, and if servers desire load reduction to different degrees, a replacement policy which prioritizes cache space across servers can provide differential quality-of-service (QoS). We present a simple generalization of least-frequently-used (LFU) replacement that is sensitive to varying levels of server valuation for cache hits. Through trace-driven simulation we show that under a particular assumption about server valuations our algorithm delivers a reasonable QoS relationship: higher byte hit rates for servers that value hits more. We furthermore adopt the economic perspective that value received by system users is a more appropriate performance metric than hit rate or byte hit rate, and demonstrate that our algorithm delivers higher social welfare (aggregate value to servers) than LRU or LFU.

PeerStreaming: design and implementation of an on-demand distributed streaming system with digital rights management capabilities

We have developed PeerStreaming, an on-demand peer-to-peer (P2P) media streaming system. The behavior of a PeerStreaming client is very much like an ordinary media player: it streams and plays whatever media the user desires, starting at whatever point he/she desires. Under the hood, however, the media is delivered from multiple peers to the client. The serving peers can be the media server, but more commonly they are the clients that have received the media in a previous streaming session. Leveraging the network and storage resources of the P2P network and retrieving a major part of the media from nearby peers, PeerStreaming greatly improves streaming media quality, reduces server load, and eases traffic on the network. We describe the design and implementation of the PeerStreaming system in this paper, with a focus on a number of key components. They include: (1) peer discovery and content location, (2) scalable coded and randomly accessible media format, (3) receiver-driven streaming, (4) digital rights management, and (5) architecture for the media rendering, caching and serving system.

Inventions on Data Searching in LDAP - A TRIZ Based Analysis

Searching is one of the most basic operation provided by an LDAP server. LDAP offers a rich set of searching capabilities. The search operation allows a client to request the server to perform a search on its behalf. The search operation locates specific users or services in the directory tree. The LDAP server executes the search (or update) command and returns a response to the client. Upon receipt of a Search Request, a server will perform the necessary search of the DIT. The server will then return to the client a sequence of responses in separate LDAP messages. The search responses may contain SearchResultEntry (the attributes and values satisfying the search conditions), SearchResultReference (URL of the referral servers), ExtendedResponse or SearchResultDone (success or failure of search operation) data types. Faster searching increases server load and network traffic. An overloaded server and congested network slows down the performance. This makes a loop of contradiction. It is necessary to reduce server load and reduce network traffic while increasing speed of searching. This article is a TRIZ based study of patents on Lightweight Directory Access Protocol (LDAP) data Searching. Data searching is one of the most important operations of LDAP. The objective of this article is to find the major concerns in LDAP data searching, find the IFR and trends of LDAP data searching and predict the future lines of inventions on LDAP searching. This article is a part of the main study made on LDAP based on 60 patents selected from US patent database.

Hierarchy-aware algorithms for CDN proxy placement in the Internet

The wide adoption and explosive growth of the Internet has led to increasing demand for near instantaneous response from users. Caching is an important avenue to save network bandwidth, reduce server load and the response time experienced by web clients. Content Distribution Networks (CDNs) have emerged as a powerful solution to improve the client response time and to reduce the traffic in the Internet. CDNs consist of a set of distributed proxy servers replicating the content for better performance and availability than centralized servers. The key factor in determining the effectiveness of a CDN is the placement of proxy servers. Network topology and routing policies play an important role on the effectiveness of proxy server placement. However, existing studies on proxy server placement either consider simplified topology (i.e. tree topology) or focus on a particular snapshot of Internet topology. In addition, none of the studies have taken into consideration of the routing policies imposed by Internet Service Providers (ISPs), which is crucial in determining the performance of web access. In this paper, we present heuristic algorithm for CDN proxy server placement by taking into account the hierarchical Internet structure and the routing policy constraint resulting from it. Our experimental results on the Internet topology over three years show that the heuristic algorithms adapt to the Internet growth well.

Refreshment policies for Web content caches

Web content caches are often placed between end users and origin servers as a mean to reduce server load, network usage, and ultimately, user-perceived latency. Cached objects typically have associated expiration times, after which they are considered stale and must be validated with a remote server (origin or another cache) before they can be sent to a client. A considerable fraction of cache “hits” involve stale copies that turned out to be current. These validations of current objects have small message size, but nonetheless, often induce latency comparable to full-fledged cache misses. Thus, the functionality of caches as a latency-reducing mechanism highly depends not only on content availability but also on its freshness. We propose policies for caches to proactively validate selected objects as they become stale, and thus allow for more client requests to be processed locally. Our policies operate within the existing protocols and exploit natural properties of request patterns such as frequency and recency. We evaluated and compared different policies using trace-based simulations.

WebCaL — a domain specific language for web caching

Web caching aims to improve the performance of the Internet in three ways — by improving client latency, alleviating network traffic and reducing server load. A web cache is basically a limited store of information which helps in presenting a faster web-access environment to the clients. The performance of a cache depends on proper management of this information and effective inter-cache communication. The existing web caches have simple and hard-coded policies which are not best suited for all environments. They offer limited flexibility just in the form of changing some simple parameters such as cache size, peer caches, etc. This drawback motivates the need for a framework for building new web caches tailored to specific environments. In this paper, we describe a domain specific language based on an event-action model using which new local web cache policies and inter-cache protocols can be easily specified. This should make it possible to write a new policy or protocol quickly, evaluate its performance and test it thoroughly using the complete program-execute-debug cycle.

Tune to Lambda patching

A recent paper by Hua, Cai and Sheu [7] describes Patching as a technique for reducing server load in a true video-on-demand (TVoD) system. It is a scheme for multicast video transmissions, which outperforms techniques such as Batching in response time and Piggybacking in bandwidth savings for titles of medium popularity, and probably in user satisfaction as well. It achieves TVoD performance by buffering part of the requested video in the receiving end-system.In a further study, the authors give analytical and simulation details on optimized patching windows under the assumptions of the Grace and Greedy patching techniques. In our view, this does not exploit fully the calculation that was performed in that study. We state that temporal distance between two multicast streams for one movie should not be determined by a client policy or simulation. Rather, it can be calculated by the server on a per video basis, since the server is aware of the average request interarrival time for each video. Since we model the request arrivals as a Poisson process, which is defined by a single variable that is historically called λ, we call this variation "λ Patching". Furthermore, we present an optimization option "Multistream Patching" that reduces the server load further. We accept that some near video-on-demand-like traffic is generated with additional patch streams, and achieve additional gains in server load.