ITR/SI - A Networking Protocol for Underwater Acoustic Networks

我们建议开发一种必要的网络层协议，以增加浅水环境中声通信的效用。人们越来越重视收集各种活动难以进入的沿海水域的数据，包括科学研究、工商业关切和军事应用。活动的优势集中在开发可靠的方法，通过时间变化困难的浅水介质传输收集的信息。然而，当前负责确定业务路由的网络层协议不提供有保证的服务质量。目前的协议也可能造成不必要的消息延迟。由于声速在水中的传播速度导致的过度传播延迟，使得声学网络中的流量传递变得复杂。这种传播速度的影响是使通过短跳连接的声学网络的性能类似于在相邻节点之间具有超过100,000公里链路的有线网络。然而，无线水下网络的实施带来了潜在的好处和更大的应用开发潜力，因此有必要探索减轻传播延迟影响的方法。网络流量的路由确定问题的核心是网络拓扑的发现，网络节点从中提取下一跳信息，作为流量转发决策的基础。发现路径信息的方法主要有两种。主动路由方法在网络流量生成之前预先计算路由数据，因此，当网络应用程序提交流量时，适当的路由已经知道。反应式路由响应于流量提交确定路由信息。这种方法被称为按需路由，通过只确定支持实际流量模式所需的路由来最小化路由发现流量。这些路由信息被缓存以增加对提交流量的响应能力和对拓扑变化的适应性。这两种方法都有各自的优点，但都不能充分支持保证服务质量所需的资源分配。我们提出了一种新的网络协议，它既提供了主动路由的许多优点，又保持了反应式协议的适应性。我们的协议基于一个中央主节点，它周期性地探测网络中的活动参与者节点。在响应探测时，节点向主节点提供足够的信息，以便主节点确定通过网络的所有可能的数据路径。主节点根据该信息做出网络的所有路由决策，并向每个非主节点提供不合适的信息，从而减少了非主节点上的工作量。该信息还使得主节点能够优化业务网络路径的分配，从而提供对延迟的主动管理，从而确保延迟差异和数据容量在所建立的服务质量承诺之内。这种分离允许在不必首先等待传统握手机制来提供对信道的访问的情况下传输数据。网络层协议的进步将扩大水声网络的用途，使其超出仅限于极低数据速率和非时间敏感型数据类型的应用。这项研究活动的具体受益者包括可部署的自主分布式系统、SeaWeb技术演示、自主海洋采样网络和国家海洋合作计划的前端分辨率遥测观测网络(前端)项目。

We propose development of a network layer protocol necessary to increase the utility of acousticcommunications in the shallow water environment. Increasing attention has been given to collecting datafrom difficult to access coastal waters for diverse activities, to include scientific research, industrial andcommercial concerns, and military applications. The preponderance of activity has focused ondeveloping reliable methods for transmitting the information collected through the difficult time-varyingshallow water medium. However, current network layer protocols, which are responsible for determiningtraffic routing, do not provide for guaranteed quality of services. Current protocols also may causeunnecessary message delays.The delivery of traffic in an acoustic network is complicated by the excessive propagation delaysresulting from the speed of sound in water. The effect of this propagation speed is to cause an acousticnetwork connected by short hops to perform similar to a wire-based network with links betweenneighboring nodes of over 100,000 kilometers. However, the potential benefits and increased potentialfor application developments that stem from the implementation of wireless underwater networks make itworthwhile to explore means of mitigating the effects of the propagation delays.Central to the problem of route determination for network traffic is the discovery of the networkstopology from which network nodes extract next-hop information upon which to base traffic forwardingdecisions. Two principal methods are used for discovering the route information. Proactive routingmethods pre-compute route data before network traffic is generated, thus when traffic is submitted bynetwork applications the appropriate routes are already known. Reactive routing determines the routeinformation in response to traffic submissions. This method, referred to as on-demand routing, seeks tominimize route discovery traffic by only determining routes necessary to support actual traffic patterns.This routing information is cached to increase responsiveness to submitted traffic and adaptability totopology changes. Both methods have their merits; however, neither adequately supports resourceallocations necessary to assure guaranteed levels of service quality.We proposed a novel network protocol that provides many of the benefits of proactive routing yetretains the adaptability of reactive protocols. Our protocol is based upon a central master node whichperiodically probes the network for active participant nodes. In responding to the probes, the nodesprovide the master node with sufficient information for the master node to determine all possible datapaths through the network. From this information the master node makes all routing decisions for thenetwork and provides irnext-hoply information to each non-master node, thus reducing the workload onnon-master nodes. This information also enables the master node to optimize the allocation of traffic tonetwork paths providing for active management of delays insuring delay variance and data capacity arewithin the established quality of service commitments.Fundamental to this approach is the separation of control traffic from data delivery. This separationallows data to be transmitted without first having to wait for traditional handshake mechanisms to provideaccess to the channel. This separation significantly reduces the expected delay to which traffic issubjected resulting in potentially higher data throughput.Progress in network layer protocols will expand the usefulness of underwater acoustic networksbeyond applications that are limited to very low data rate traffic and non-time sensitive data types.Specific beneficiaries of this research activity include the Deployable Autonomous Distributed System,the SeaWeb Technology Demonstrations, the Autonomous Oceanographic Sampling Network, and theNational Oceanographic partnership Programs Front Resolving Observational Network with Telemetry(FRONT) project.