An Architecture for A Global Internet Host Distance Estimation Service

越来越多的情况是，一个给定的互联网交互可以由许多互联网主机之一来满足。 示例范围从短暂的交互（例如单个网页访问多个内容相同的Web服务器中的任何一个）到两个新闻（NNTP）服务器之间的长期对等关系。 在任何这样的相互关系中，在所有其他条件相同的情况下，最好选择“最近的”。 所谓接近，我们指的是互联网性能指标，如低延迟或高带宽。 即使其他条件不相同，例如不同的Web服务器有不同的响应时间，将到每个候选主机的距离作为进行选择的几个标准之一仍然是有用的。获得此距离信息的一种方法是由发起主机使用单播（ping，traceroute）或多播（扩展环搜索）工具自己测量它。 虽然这些工具有广泛的用途，但它们的实用性通常受到其开销的限制。 例如，运行单个跟踪路由的成本可能超过网页访问本身的成本。 更重要的是，大量主机进行独立和频繁的测量可能会对整体性能产生严重影响。 理想情况下，由一个系统（主机或路由器）进行的测量应该以较低的成本提供给其他主机。Internet的一个有用的通用服务是主机可以快速有效地了解任何两个主机之间的距离。 为了广泛使用，这样的服务应该提供一个答案，其延迟和开销小于使用该服务所获得的收益。 早在1996年2月，IETF（Internet Engineering Task Force，互联网工程任务组）就讨论了一种用于这种服务的简单协议（SONAR），并在1997年4月讨论了一种更通用的服务，称为HOPS（Host Proximity Service，主机邻近服务）。 这两项工作都提出了轻量级客户机/服务器查询/应答协议，沿着DNS（域名系统）查询/应答的路线。 两者都要求服务器能够在很短的时间内产生一个答案-最好是，虽然不是必须的，通过使用已经存储在本地的信息。这个建议关注的问题是，在这样的声纳/HOPS服务的服务器如何能够获得回答查询所需的距离信息。 具体来说，我们探讨以下问题：-哪些系统最初产生的距离信息，它是如何产生的？-距离信息是如何从这些生产系统到达服务器的？距离信息采取什么形式，以及如何使用它来为特定的互联网主机对生成答案？在讨论了上述问题的基本方面之后，本提案提出了一种用于提供SONAR/HOPS服务所使用的基本信息的底层服务的通用体系结构。 这个基础服务被称为IDMaps，即Internet距离地图服务。这项工作由PI Sugih Jamin和共同PI Lixia Zhang同时提出。 Sugih Jamin之前的研究是互联网流量特征和基于测量的准入控制。 张丽霞是可扩展可靠组播研究的积极参与者。 PI将与NTT软件实验室的Paul弗朗西斯和LBNL的Vern Paxson密切合作。 Paul弗朗西斯一直活跃于分布式层次结构构造算法的研究。 Vern Paxson活跃于互联网性能测量领域，是NSF资助的国家互联网测量基础设施（NIMI）工作的PI。 IDMap可以构建在NIMI基板上。 保罗弗朗西斯和弗恩帕克森确认这些合作的信件附在这个建议。

It is increasingly the case that a given Internet interaction could be satisfied by one of a number of Internet hosts. Examples range from short-lived interactions such as a single web page access to any one of multiple equal-content web servers to a long-term peering relationship between two news (NNTP) servers. In any such interatction, all other things being equal, it is advantageous to access the "nearest" choice. By near we mean interms of Internet performance metrics, such as low latency or high bandwidth. Even when all other things are not equal, such as the case where different web servers have different response times, it is still useful to include distance to each candidate host as one of several criteria for making a selection.One approach to obtaining this distance information is for the initiating host to measure it itself, using either unicast (ping, traceroute) or multicast (expanding ring search) tools. While these tools have a wide range ofuses, their utility is generally limited by their overhead. For instance, the cost of running a single traceroute can exceed the cost of the web page access itself. More important still, a large number of hosts making independent and frequent measurements could have a severe impact on performance overall. Ideally, measurements made by one system (host or router) should be made available, at low cost, to other hosts.A useful general service for the Internet would be one whereby a host could quickly and efficiently learn the distance between any two hosts. To be widely useful, such a service should provide an answer with a delay and overhead less than those of the gains achieved by using the service. A simple protocol for such a service (SONAR) was discussed in the IETF (Internet Engineering Task Force) as early as February 1996, and in April 1997 as a more general service called HOPS (Host Proximity Service). Both of these efforts proposed lightweight client/server query/reply protocols along the lines of a DNS (Domain Name System) query/reply. Both also required that the server be able to produce an answer in a very short time---preferably, though not necessarily, by using information already stored locally.This proposal is concerned with the problem of how servers in such a SONAR/HOPS service can obtain the distance information needed to answer queries. Specifically, we explore the following questions:- Which systems originally produce the distance information, and how is it produced?- How does the distance information get from these producing systems to the servers?- What form does the distance information take, and how is it used to produce answers for specific pairs of Internet hosts?After discussing basic aspects of the questions outlined above, this proposal presents a general architecture for an underlying service that provides the basic information used by a SONAR/HOPS service. This underlying service is called IDMaps, forInternet Distance Map Service.This work is being proposed in parallel by the PI, Sugih Jamin, and the co-PI, Lixia Zhang. Sugih Jamin's prior research has been in Internet traffic characterization and measurement-based admission control. Lixia Zhang has been an active participant in research on scalable reliable multicast. The PIs will work closely with Paul Francis of NTT Software Labs and Vern Paxson of LBNL. Paul Francis has been active on research in distributed hierarchy construction algorithms. Vern Paxson is active in Internet performance measurement and is the PI of the NSF-funded National Internet Measurement Infrastructure (NIMI) effort. IDMaps can be built on the NIMI substrate. Letters from Paul Francis and Vern Paxson confirming thesecollaborations are attached to this proposal.