An Architecture for A Global Internet Host Distance Estimation Service

越来越多的情况是，给定的互联网交互可以由多个互联网主机中的一个来满足。示例范围从诸如单个网页访问多个相同内容的Web服务器中的任何一个的短期交互到两个新闻(NNTP)服务器之间的长期对等关系。在任何这样的互动中，在所有其他条件相同的情况下，获得“最近”的选择是有利的。我们所说的接近指的是互联网性能指标，如低延迟或高带宽。即使所有其他条件都不相等，例如不同的Web服务器具有不同的响应时间，将到每台候选主机的距离作为选择的几个标准之一仍然很有用。获取此距离信息的一种方法是发起主机自己测量它，使用单播(ping、Traceroute)或组播(扩展环搜索)工具。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Traceroute的成本可能超过网页访问本身的成本。更重要的是，大量主机进行独立且频繁的测量可能会对整体性能产生严重影响。理想情况下，一个系统(主机或路由器)所做的测量应该以较低的成本提供给其他主机。互联网上有用的一般服务应该是主机可以快速有效地获知任意两台主机之间的距离。为了广泛使用，这样的服务应该以比使用该服务所获得的收益更少的延迟和开销来提供答案。用于这种服务(声纳)的简单协议早在1996年2月就在IETF(互联网工程任务组)中讨论过，并在1997年4月作为称为HOPS(主机邻近服务)的更一般的服务进行了讨论。这两项工作都提出了类似于域名系统(域名系统)查询/回复的轻量级客户端/服务器查询/回复协议。这两个方案都要求服务器能够在非常短的时间内产生答案-优选地，尽管不一定，通过使用已经存储在本地的信息。该建议涉及这样的声纳/跳跃服务中的服务器如何能够获得回答查询所需的距离信息的问题。具体地说，我们探讨以下问题：-哪些系统最初产生距离信息，它是如何产生的？-距离信息是如何从这些产生系统到服务器的？-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产生答案？在讨论了上述问题的基本方面之后，本提案提出了提供声纳/跳跃服务所使用的基本信息的基础服务的一般体系结构。这项底层服务被称为IDMaps，即互联网距离地图服务。这项工作是由PI Sugih Jamin和联合PI张丽霞并行提出的。Sugih Jamin之前的研究是在互联网流量特征和基于测量的准入控制方面。张丽霞一直积极参与可扩展可靠组播的研究。PI将与NTT软件实验室的保罗·弗朗西斯和LBNL的弗恩·帕克森密切合作。Paul Francis一直活跃在分布式层次结构构建算法的研究中。Vern Paxson活跃在互联网性能测量方面，是NSF资助的国家互联网测量基础设施(NIMI)工作的PI。IDMaps可以构建在NIMI衬底上。保罗·弗朗西斯和弗恩·帕克森确认合作的信件附在这份提案上。

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.