一种混合式P2P下的大规模地形数据传输机制  

A Large-scale Terrain Transmission Mechanism Based on Hybrid P2P

作　　者：喻占武[1] 郑胜[2] 李忠民[1] 

机构地区：[1]武汉大学测绘遥感信息工程国家重点实验室,湖北武汉430079 [2]武汉大学电子信息学院,湖北武汉430079

出　　处：《测绘学报》2008年第2期243-249,共7页Acta Geodaetica et Cartographica Sinica

基　　金：国家973重点基础研究发展计划项目(2004CB318206);国家863计划项目(2007AA12Z214)

摘　　要：海量地形数据的网络传输和可视化是实现网络环境下大规模地形漫游的关键。传统的客户端/服务器结构,随着用户的增加,面临着负载过大,性能下降等问题。基于对等网结构,提出一种混合式对等网络模型下的地形数据传输机制PeerVOLT,能够以较小的服务器代价实现大规模地形数据的传输。PeerVOLT中每个节点都分配有一定的数据空间缓存接收的地形数据,同时缓存组成员列表和地形数据索引列表,同组成员节点通过交换地形数据缓冲映射表共享地形数据。通过实验原型系统比较测试表明,PeerVOLT系统的服务器负载和地形数据的平均传输速率优于传统的客户端/服务器的单播模式。In large scale terrain roaming systems, the terrain visualization components are usually running on the local host and terrain datasets are stored in the remote server. The server should guarantee the certain response delay and realize the real-time rendering of large-scale terrain when the number of user is limited. However, as the number of clients is quickly increasing, the server performance will drop too rapidly to satisfy the client real-time rendering requirement. Peer-to-peer （P2P） technologies can efficiently reduce the bandwidth consumption of the server by the means of utilizing the client nodes＇resource. The paper combines the C/S and peer-to-peer into a new data transmission mode for large terrain data transmission. First, it gives a new model for data transmission and new structure for client node. Then it presents the management of peers and the look-up of terrain blocks in the new mode. Also it presents a kind of optimal algorithm for terrain block scheduling. The optimal algorithm can improve the terrain data transmitting speed and be adapted to the network change. Fault-tolerance and security are also considered in the paper. We build a prototype system and compare the new mechanism with traditional unicast mode. Experimental results have shown that the new mechanism can make the server＇s load lighter than the old mode in the case of equal number of user requests and improve greatly the response time of the terrain block request.

关 键 词：每量数据 并行传输 地形可视化 点对点方式 

分 类 号：P208[天文地球—地图制图学与地理信息工程]