Internet Research Task Force (IRTF) S. Kamei
Request for Comments: 6875 NTT Communications
Category: Informational T. Momose
ISSN: 2070-1721 Cisco Systems
T. Inoue
T. Nishitani
NTT Communications
February 2013
Internet Research Task Force (IRTF) S. Kamei
Request for Comments: 6875 NTT Communications
Category: Informational T. Momose
ISSN: 2070-1721 Cisco Systems
T. Inoue
T. Nishitani
NTT Communications
February 2013
The P2P Network Experiment Council's Activities and Experiments with Application-Layer Traffic Optimization (ALTO) in Japan
P2P网络实验委员会在日本开展的应用层流量优化（ALTO）活动和实验
Abstract
摘要
This document describes experiments that clarify how an approach similar to Application-Layer Traffic Optimization (ALTO) was effective in reducing network traffic. These experiments were performed in Japan by the P2P Network Experiment Council in an attempt to harmonize peer-to-peer (P2P) technology with network infrastructure. Based on what was learned from these experiments, this document provides some suggestions that might be useful for the ALTO architecture and especially for application-independent ALTO-like server operation.
本文档描述了一些实验，阐明了类似于应用层流量优化（ALTO）的方法如何有效地减少网络流量。这些实验是由P2P网络实验委员会在日本进行的，目的是使P2P技术与网络基础设施相协调。基于从这些实验中学到的知识，本文提供了一些建议，这些建议可能对ALTO体系结构，特别是对独立于应用程序的ALTO-like服务器操作有用。
Status of This Memo
关于下段备忘
This document is not an Internet Standards Track specification; it is published for informational purposes.
本文件不是互联网标准跟踪规范；它是为了提供信息而发布的。
This document is a product of the Internet Research Task Force (IRTF). The IRTF publishes the results of Internet-related research and development activities. These results might not be suitable for deployment. This RFC represents the individual opinion(s) of one or more members of the Peer-to-Peer Research Group of the Internet Research Task Force (IRTF). Documents approved for publication by the IRSG are not a candidate for any level of Internet Standard; see Section 2 of RFC 5741.
本文件是互联网研究工作组（IRTF）的产品。IRTF发布互联网相关研究和开发活动的结果。这些结果可能不适合部署。本RFC代表互联网研究任务组（IRTF）对等研究小组一名或多名成员的个人意见。IRSG批准发布的文件不适用于任何级别的互联网标准；见RFC 5741第2节。
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6875.
有关本文件当前状态、任何勘误表以及如何提供反馈的信息，请访问http://www.rfc-editor.org/info/rfc6875.
Copyright Notice
版权公告
Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2013 IETF信托基金和确定为文件作者的人员。版权所有。
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document.
本文件受BCP 78和IETF信托有关IETF文件的法律规定的约束(http://trustee.ietf.org/license-info)自本文件出版之日起生效。请仔细阅读这些文件，因为它们描述了您对本文件的权利和限制。
Table of Contents
目录
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Background in Japan . . . . . . . . . . . . . . . . . . . . . 4
2.1. P2P Traffic . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Impact on Network Infrastructure . . . . . . . . . . . . . 4
2.3. Overview of the P2P Network Experiment Council . . . . . . 5
3. Objectives of the P2P Network Experiment Council . . . . . . . 6
4. Details of the Experiment . . . . . . . . . . . . . . . . . . 7
4.1. Dummy Node . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Hint Servers . . . . . . . . . . . . . . . . . . . . . . . . . 9
6. High-Level Trial Results . . . . . . . . . . . . . . . . . . . 13
6.1. Peer Selection with P2P . . . . . . . . . . . . . . . . . 13
6.2. Peer Selection with the Hint Server . . . . . . . . . . . 13
7. Considerations . . . . . . . . . . . . . . . . . . . . . . . . 14
7.1. Next Steps . . . . . . . . . . . . . . . . . . . . . . . . 14
7.2. Feedback to the ALTO WG . . . . . . . . . . . . . . . . . 15
7.2.1. Hierarchical Architecture for ALTO Servers . . . . . . 15
7.2.2. Measurement Mechanism . . . . . . . . . . . . . . . . 15
8. Security Considerations . . . . . . . . . . . . . . . . . . . 16
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
10. Informative References . . . . . . . . . . . . . . . . . . . . 16
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Background in Japan . . . . . . . . . . . . . . . . . . . . . 4
2.1. P2P Traffic . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Impact on Network Infrastructure . . . . . . . . . . . . . 4
2.3. Overview of the P2P Network Experiment Council . . . . . . 5
3. Objectives of the P2P Network Experiment Council . . . . . . . 6
4. Details of the Experiment . . . . . . . . . . . . . . . . . . 7
4.1. Dummy Node . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Hint Servers . . . . . . . . . . . . . . . . . . . . . . . . . 9
6. High-Level Trial Results . . . . . . . . . . . . . . . . . . . 13
6.1. Peer Selection with P2P . . . . . . . . . . . . . . . . . 13
6.2. Peer Selection with the Hint Server . . . . . . . . . . . 13
7. Considerations . . . . . . . . . . . . . . . . . . . . . . . . 14
7.1. Next Steps . . . . . . . . . . . . . . . . . . . . . . . . 14
7.2. Feedback to the ALTO WG . . . . . . . . . . . . . . . . . 15
7.2.1. Hierarchical Architecture for ALTO Servers . . . . . . 15
7.2.2. Measurement Mechanism . . . . . . . . . . . . . . . . 15
8. Security Considerations . . . . . . . . . . . . . . . . . . . 16
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
10. Informative References . . . . . . . . . . . . . . . . . . . . 16
An overlay network, which is used by P2P and other applications, offers the advantage of allowing flexible provisioning of services while hiding the lower-layer network. The disadvantage is that inefficient routing without considering the lower-layer network may cause increasing the network load. Several proposals have been made to build an overlay network that takes into account the information about the lower-layer network [1] [2]. Since the management of the Internet is highly distributed, it is difficult to implement such proposals, and thus to optimize a network, without the cooperation of network providers.
P2P和其他应用程序使用的覆盖网络具有允许灵活提供服务，同时隐藏底层网络的优点。缺点是没有考虑下层网络的低效路由可能导致网络负载增加。已经提出了几项建议，以建立一个覆盖网络，该网络考虑了有关下层网络的信息[1][2]。由于互联网的管理是高度分布式的，如果没有网络供应商的合作，很难实施这些建议，从而优化网络。
Recently, the controversy between the overlay network and the network providers about network resource wastefulness has been rekindled. Under these circumstances, some researchers have studied overlay-network control technology that takes into account the network topology information obtained from network providers.
最近，覆盖网络和网络供应商之间关于网络资源浪费的争论重新燃起。在这种情况下，一些研究人员研究了覆盖网络控制技术，该技术考虑了从网络提供商处获得的网络拓扑信息。
One research effort regarding this issue were experiments planned and performed by the P2P Network Experiment Council in Japan. This document reports on these experiments and the issues they addressed.
关于这个问题的一项研究工作是由日本P2P网络实验委员会计划和执行的实验。本文件报告了这些实验及其解决的问题。
These experiments were performed from 2007 to 2008, because P2P traffic decreased after Japanese copyright law was revised. While more recently, the dominant traffic in Japan, the United States, and elsewhere has been HTTP-based flash streaming, a large amount of traffic in Asia (outside Japan) is still P2P traffic, like P2P streaming [3], and P2P technology is very useful in such a real-time streaming area.
这些实验是从2007年到2008年进行的，因为日本版权法修订后P2P流量减少了。最近，日本、美国和其他地方的主要流量是基于HTTP的flash流，而亚洲（日本以外）的大量流量仍然是P2P流量，如P2P流[3]，P2P技术在此类实时流领域非常有用。
Our experience in this experiment might be useful for ALTO architecture, especially for application-independent and multi-application ALTO-like server operations. We suggest that a generic measurement mechanism is important because each application has different mechanism, which makes it difficult to compare their effectiveness.
我们在这个实验中的经验可能对ALTO体系结构有用，特别是对于独立于应用程序和类似ALTO的多应用程序服务器操作。我们认为一个通用的度量机制很重要，因为每个应用程序都有不同的机制，这使得比较它们的有效性非常困难。
This document is a product of the P2P Research Group (RG). The views in this document were considered controversial by the P2P RG, but the RG reached a consensus that the document should still be published.
本文档是P2P研究组（RG）的产品。P2P RG认为本文件中的观点存在争议，但RG一致认为该文件仍应发布。
As of 2008, the world's most popular P2P file-sharing application, BitTorrent, was not widely deployed in Japan. Instead, other file-sharing P2P applications specific to Japan, such as Winny [4] and Share [5], still account for 40% of the Internet traffic in Japan, even though many those P2P users were arrested for sharing illegal files with these P2P applications.
截至2008年，全球最流行的P2P文件共享应用程序BitTorrent尚未在日本广泛部署。相反，日本特有的其他文件共享P2P应用程序，如Winny[4]和Share[5]，仍占日本互联网流量的40%，尽管许多P2P用户因与这些P2P应用程序共享非法文件而被捕。
Each P2P file-sharing application has a unique protocol and none have a large market share, therefore making it hard to control them effectively.
每个P2P文件共享应用程序都有一个独特的协议，并且没有一个具有很大的市场份额，因此很难有效地控制它们。
One advantage of using P2P technology for content delivery is that peers exchange content directly among themselves without server bottleneck. This reduces the load on servers. Also, P2P applications can reduce upstream traffic from an origin content server. This reduces server cost dramatically.
使用P2P技术进行内容交付的一个优点是，对等点之间可以直接交换内容，而不会出现服务器瓶颈。这减少了服务器上的负载。此外，P2P应用程序可以减少来自源内容服务器的上游流量。这大大降低了服务器成本。
It is also known that server cost could be reduced with P2P technology. However, the story is quite different for network providers. From the viewpoint of network providers, the traffic that content servers generate has shifted to the edge network and the amount of traffic has not necessarily been reduced by using P2P technology for reducing server cost. Another problem for network providers is that extremely inefficient routing may be selected because overlay network systems are configured without any regard to the structure of the lower-layer network or network geometry.
众所周知，P2P技术可以降低服务器成本。然而，网络提供商的情况却大不相同。从网络提供商的角度来看，内容服务器产生的流量已经转移到边缘网络，并且使用P2P技术来降低服务器成本并不一定会减少流量。网络提供商的另一个问题是，可能会选择效率极低的路由，因为覆盖网络系统的配置不考虑下层网络的结构或网络几何结构。
In some cases, the total amount of traffic on the Internet used to be limited by the capacity of servers. For those cases, P2P technology can improve the scalability of servers; however, it may exhaust network resources. Moreover, using P2P applications remarkably increases the volume of traffic per user.
在某些情况下，Internet上的总流量过去受到服务器容量的限制。对于这些情况，P2P技术可以提高服务器的可伸缩性；但是，它可能会耗尽网络资源。此外，使用P2P应用程序显著增加了每个用户的流量。
Faced with an increase in the load on network infrastructure, network providers are compelled to take actions to overcome the sudden increase in facilities' costs. Representative actions include placing content in Internet Exchanges (IXs) or data centers, introducing bandwidth control, and raising access fees [6].
面对网络基础设施负荷的增加，网络供应商不得不采取措施克服设施成本的突然增加。有代表性的行动包括将内容放在互联网交换机（IX）或数据中心、引入带宽控制和提高访问费[6]。
As mentioned above, the dominant traffic currently in Japan, the US, and elsewhere, is HTTP-based flash streaming. However, a large amount of traffic in Asia (outside Japan) is P2P traffic, like P2P
如上所述，目前日本、美国和其他地方的主要流量是基于HTTP的闪存流。然而，亚洲（日本以外）的大量流量是P2P流量，就像P2P一样
Streaming [3], and P2P technology is very useful in such real-time streaming. The increase in traffic arising from such a shift may be a great threat to the network.
流媒体[3]，P2P技术在这种实时流媒体中非常有用。由于这种转移而导致的流量增加可能对网络构成巨大威胁。
In order to reduce Internet traffic and encourage legitimate use of P2P technologies, in 2006 the Japanese government established a new council called the P2P Network Experiment Council, in conjunction with commercial P2P application vendors and ISPs.
为了减少互联网流量并鼓励合法使用P2P技术，2006年，日本政府与商业P2P应用程序供应商和ISP共同成立了一个名为P2P网络实验委员会的新委员会。
The council developed regulations that include guidelines such as giving advance notice to heavy users before restricting their bandwidth. In accordance with the regulations, some ISPs introduced solutions that reduce traffic caused by P2P file-sharing applications.
该委员会制定了一些规定，其中包括一些指导原则，如在限制带宽之前提前通知重度用户。根据规定，一些ISP推出了减少P2P文件共享应用程序造成的流量的解决方案。
In addition, the council, along with ISPs, carriers, contents providers, and P2P system vendors, looked for new ways to control traffic by commercial P2P applications. In this work, the council performed experiments that introduced an ALTO-like system and observed how the traffic was reduced when it was redirected to proper peers on the real Internet in Japan.
此外，该委员会与ISP、运营商、内容提供商和P2P系统供应商一起，寻找通过商业P2P应用程序控制流量的新方法。在这项工作中，委员会进行了一些实验，引入了一个类似ALTO的系统，并观察了在日本，当流量被重定向到真实互联网上的适当对等方时，流量是如何减少的。
In our experiment, the council deployed hint servers, which are described in Section 5. Hint servers run a protocol that offers network distances to peers, and these distances are disclosed to P2P application vendors.
在我们的实验中，委员会部署了提示服务器，如第5节所述。提示服务器运行一个协议，该协议提供了到对等方的网络距离，并且这些距离向P2P应用程序供应商公开。
Using hint servers, P2P application vendors can introduce ALTO concepts easily into their P2P distribution systems. Because the protocol used by hint servers, as defined by the council, is independent of specific P2P application vendors like BitTorrent. The protocol needs to gather network information from ISPs so it can provide network distance to peers. However, many ISPs dislike disclosing such information to others. Therefore, hint servers are designed to offer little information about an ISP's network architecture to P2P application vendors.
通过使用提示服务器，P2P应用程序供应商可以轻松地将ALTO概念引入其P2P分发系统。因为委员会定义的提示服务器使用的协议独立于特定的P2P应用程序供应商，如BitTorrent。该协议需要从ISP收集网络信息，以便提供到对等方的网络距离。然而，许多ISP不喜欢向他人披露此类信息。因此，提示服务器的设计目的是向P2P应用程序供应商提供有关ISP网络架构的少量信息。
To monitor the traffic of peers, the council also deployed a dummy node, which is described in Section 4.1.
为了监控对等节点的流量，委员会还部署了一个虚拟节点，如第4.1节所述。
The remainder of this memo provides an overview of the experiments.
本备忘录的其余部分对实验进行了概述。
The Japanese Ministry of Internal Affairs and Communications, which has jurisdiction over information and communication systems in Japan, held meetings of an advisory panel on network neutrality in 2006 and 2007 in order to study issues related to next-generation networks, such as how to ensure fairness in the use of networks and how to define fairness in the cost burden. The panel took an interest in P2P technology as a solution to the impending traffic saturation in the backbone network resulting from the rapid expansion of broadband access in Japan, and it formed a "Working Group on the P2P Network", which carried out an intensive study of P2P networks.
对日本信息和通信系统拥有管辖权的日本内务省和通信省于2006年和2007年举行了网络中立性咨询小组会议，以研究与下一代网络有关的问题，比如如何确保网络使用的公平性，如何在成本负担中定义公平性。专家组对P2P技术感兴趣，认为这是解决日本宽带接入迅速扩张导致主干网流量即将饱和的一种方法，并成立了一个“P2P网络工作组”，对P2P网络进行了深入研究。
The working group reported that it would be necessary to undertake the following four activities, which are intended to encourage the government to adopt relevant policies [7]:
工作组报告说，有必要开展以下四项活动，旨在鼓励政府采取相关政策[7]：
o Formulate guidelines on P2P file-delivery applications to be self-imposed by the industry.
o 制定行业自行制定的P2P文件交付应用程序指南。
o Promote feasibility tests of P2P networks.
o 推动P2P网络的可行性测试。
o Study the current state of traffic control and promote the sharing of information.
o 研究交通管制现状，促进信息共享。
o Hold working group meetings about traffic control.
o 召开交通管制工作组会议。
The first two proposals led to the establishment of the P2P Network Experiment Council, supported by the Japanese Ministry of Internal Affairs and Communications [8] [9]. The Council, with membership from P2P delivery providers, content holders, and network providers, began a variety of delivery experiments, which were expected to strengthen cooperative control between different layers. In contrast to P4P (Proactive Network Provider Participation for P2P), which takes a relatively top-down approach of adopting an architecture based on a proposal from a university, the Council is characterized by its bottom-up approach. The aim of establishing the Council was described as follows (translated from [10]).
前两项提案促成了P2P网络实验委员会的成立，该委员会得到了日本内务省和交通省的支持[8][9]。该委员会的成员来自P2P交付提供商、内容持有者和网络提供商，开始了各种交付实验，有望加强不同层面之间的合作控制。与P4P（P2P的主动网络提供商参与）不同，P4P采取相对自上而下的方法，采用基于大学提案的体系结构，理事会的特点是自下而上的方法。成立该委员会的目的描述如下（翻译自[10]）。
The rapid growth of broadband access enables content delivery systems to deliver high-quality and high-volume videos securely and efficiently. Although P2P technology is an effective technology for this requirement, it still has some issues to be coped with. Therefore, the "P2P Network Experiment Council" was established with the support of the Japanese Ministry of Internal Affairs and Communications, with its secretariat set up within the
宽带接入的快速增长使内容交付系统能够安全高效地交付高质量和高容量的视频。尽管P2P技术是满足这一需求的有效技术，但它仍然存在一些问题需要解决。因此，在日本内务省和交通省的支持下成立了“P2P网络实验委员会”，其秘书处设在日本政府内部
Foundation for MultiMedia Communications (FMMC), in order to formulate guidelines for providers and conduct feasibility tests so that users can receive video delivery services safely.
多媒体通信基金会（FMMC），以制定供应商的指导方针和进行可行性测试，以便用户可以安全地接收视频传递服务。
The activities of the P2P Network Experiment Council can be classified into two categories. The first is formulating guidelines for promoting the commercial use of P2P technology. These guidelines will enable users to use P2P technology safely and will give providers clear rules they must observe. The second is feasibility testing of P2P technology. Section 4 describes experiments conducted in 2007 and 2008.
P2P网络实验委员会的活动可分为两类。第一是制定促进P2P技术商业化使用的指导方针。这些指南将使用户能够安全地使用P2P技术，并将为提供商提供他们必须遵守的明确规则。二是P2P技术的可行性测试。第4节描述了2007年和2008年进行的实验。
The Council investigated data offered by the members of the Council and learned that the server cost could be reduced by using P2P technology for content delivery. For example, the data from the vendors showed the following:
委员会调查了委员会成员提供的数据，了解到使用P2P技术进行内容交付可以降低服务器成本。例如，来自供应商的数据显示如下：
Traffic was reduced by 90% with UGLive by Utagoe, Inc. [11].
Utagoe，Inc.的UGLive将流量减少了90%。[11]。
The cost of delivering to tens of thousands of subscribers was reduced by 80% with BBbroadcast with TV Bank Corp. [12]
通过电视银行公司的BBbroadcast，向数万用户提供服务的成本降低了80%。[12]
On the other hand, these reduced server costs may have affected the network load. One of the goals of our experiments was to visualize the impact and propose an architecture to reduce network load caused by these new technologies.
另一方面，这些服务器成本的降低可能会影响网络负载。我们实验的目标之一是将影响可视化，并提出一种架构来减少这些新技术造成的网络负载。
In order to visualize the reduction of network cost, we modeled P2P applications and a multi-ISP environment. This model was also needed for visualizing the effectiveness of the ALTO-like approach.
为了可视化降低网络成本，我们对P2P应用程序和多ISP环境进行了建模。该模型还需要用于可视化ALTO-like方法的有效性。
As mentioned above, while the effect of using P2P technology to reduce the traffic and the load on servers is well known; however, traffic behavior in the inter-ISP area is not known. In Japan, the ISPs and IXes cooperated to create a backbone traffic report [13]. However, the measurements gathered for that report required capturing packets on subscribers' lines in order to determine the end users' activities. It is not realistic to measure the behavior of P2P applications at user terminals connected to the Internet because that would require a large-scale arrangement for measurement, such as using deep packet inspection (DPI) on aggregated lines.
如上所述，使用P2P技术降低服务器流量和负载的效果是众所周知的；但是，ISP间区域的流量行为尚不清楚。在日本，ISP和IXE合作创建主干流量报告[13]。然而，为该报告收集的度量需要捕获订阅者线路上的数据包，以便确定最终用户的活动。在连接到Internet的用户终端上测量P2P应用程序的行为是不现实的，因为这需要大规模的测量安排，例如在聚合线路上使用深度数据包检查（DPI）。
To solve these problems, we put several nodes called 'dummy nodes' in the ISP's networks. The dummy nodes emulate an end user's PC running P2P applications. Every P2P node provided by participating vendors in the experiment was configured so it always contacted the hint server.
为了解决这些问题，我们在ISP的网络中放置了几个称为“虚拟节点”的节点。虚拟节点模拟最终用户运行P2P应用程序的PC。参与实验的供应商提供的每个P2P节点都进行了配置，因此它总是与提示服务器联系。
By introducing dummy nodes and measuring the traffic on them, we were able to observe and evaluate how much the P2P applications affected the networks. Since this method can't measure every subscriber's traffic, the accuracy is less than other methods. However, using dummy nodes makes it possible to adapt to situations in which many different P2P applications coexist on a network. We decided that using dummy nodes was suitable for these experiments.
通过引入虚拟节点并测量其流量，我们能够观察和评估P2P应用程序对网络的影响程度。由于该方法不能测量每个用户的流量，因此其精度低于其他方法。然而，使用虚拟节点可以适应许多不同的P2P应用程序在网络上共存的情况。我们认为使用虚拟节点适合这些实验。
A dummy node consisted of an Intel PC server running Linux (CentOS), VMWare, and Windows XP on VMWare. With this configuration, all packets can be captured without any impact on the behavior of the network, nodes, or applications. Also, this configuration enabled us to use different P2P applications for Windows and evaluate them generally.
虚拟节点由在VMWare上运行Linux（CentOS）、VMWare和Windows XP的Intel PC服务器组成。通过此配置，可以捕获所有数据包，而不会对网络、节点或应用程序的行为产生任何影响。此外，这种配置使我们能够在Windows上使用不同的P2P应用程序，并对其进行总体评估。
To see behaviors of the node, incoming and outgoing packets are captured on Linux because every packet is transmitted through it. To see flow information in these experiments, we captured the source and destination addresses, port number, amount of traffic, and start and end times.
为了查看节点的行为，在Linux上捕获传入和传出的数据包，因为每个数据包都是通过它传输的。为了在这些实验中查看流信息，我们捕获了源地址和目标地址、端口号、通信量以及开始和结束时间。
We placed 60 dummy nodes on access networks of 40 different ISPs. They were placed as close as possible to the subscriber in each network.
我们在40个不同ISP的接入网络上放置了60个虚拟节点。它们被放置在每个网络中尽可能靠近订户的位置。
+----------------------+
|+--------------------+|
||+------------------+||
||| P2P Application |||
||| Windows XP |||
||| +--+ |||
||+--------|N |------+||
|| VMware |e | ||
|+---------|t |-------+|
| Linux |IF| capture|
+----------| |--------+
+--+
+----------------------+
|+--------------------+|
||+------------------+||
||| P2P Application |||
||| Windows XP |||
||| +--+ |||
||+--------|N |------+||
|| VMware |e | ||
|+---------|t |-------+|
| Linux |IF| capture|
+----------| |--------+
+--+
Figure 1: Dummy node
图1：虚拟节点
Since fiber to the home (FTTH) has rapidly spread all over Japan, bottlenecks in IP networks have been shifting from access networks to backbone networks and equipment, such as bandwidth between ISPs and capacity in IXs. Under these circumstances, the Council proposed less restrictive and more flexible cooperation between ISPs than existent P4P experiments [14]. The proposed method consists of the following elements: (1) P2P clients, (2) P2P control servers, and (3) a hint server (specifically, a peer selection hint server). P2P clients and control servers are existing systems, but whether the P2P control servers exist is application dependent. The hint server is a server that provides a hint for peer selection and plays a role equivalent to that of the ALTO server. Note that this proposal was based on results of experiments using dummy nodes. The results showed that it was possible to reduce unnecessary traffic that flows across the boundaries of geographical districts or ISPs by providing information about the physical network to P2P applications.
自从光纤到户（FTTH）在日本各地迅速蔓延以来，IP网络中的瓶颈已经从接入网络转移到骨干网络和设备，如ISP之间的带宽和IXs中的容量。在这种情况下，委员会建议ISP之间的合作比现有的P4P实验更少限制，更灵活[14]。所提出的方法由以下元素组成：（1）P2P客户端，（2）P2P控制服务器，（3）提示服务器（特别是对等选择提示服务器）。P2P客户端和控制服务器是现有的系统，但是P2P控制服务器是否存在取决于应用程序。提示服务器是一个为对等选择提供提示的服务器，其作用相当于ALTO服务器。请注意，此建议基于使用虚拟节点的实验结果。结果表明，通过向P2P应用程序提供有关物理网络的信息，可以减少跨越地理区域或ISP边界的不必要流量。
When a peer joins the network, it registers its location information (IP address) and supplementary information (line speed, etc.) with the hint server. The hint server calculates the network distance between peers (P2P clients) based on network topology information obtained from the ISP and generates a priority table for peer selection. The hint server returns the table to the peer.
当对等方加入网络时，它向提示服务器注册其位置信息（IP地址）和补充信息（线路速度等）。提示服务器根据从ISP获得的网络拓扑信息计算对等点（P2P客户端）之间的网络距离，并生成用于对等点选择的优先级表。提示服务器将表返回给对等方。
If all information is public, the above procedure can produce results that are nearly optimal. However, some information held by ISPs is often confidential. Also, in some cases, the volume of calculation required to process all information can be excessive. To avoid these problems, the plan is to conduct experiments with a limited set of functions, analyze the results, and gradually expand the scope of optimization.
如果所有信息都是公开的，上述程序可以产生接近最优的结果。然而，ISP持有的一些信息通常是保密的。此外，在某些情况下，处理所有信息所需的计算量可能过大。为了避免这些问题，计划是使用有限的函数集进行实验，分析结果，并逐步扩大优化范围。
A control mechanism that makes use of all possible information is difficult not only technically but also because it requires coordination among providers. In light of these difficulties, the council has been limiting the implementation and experiments to the technical scope.
利用所有可能信息的控制机制不仅在技术上是困难的，而且因为它需要提供者之间的协调。鉴于这些困难，理事会一直将实施和试验限制在技术范围内。
Figure 2 shows an outline of the hint server.
图2显示了提示服务器的概要。
+---------+ GetLocation +-------------GeoIP DB Server---------+
| | +-----------+ | +----------+ +-----------+ |
| |--|IP Address |-->| | GeoIP DB | |BGP daemon | |
| | +-----------+ | +----------+ +-----------+ |
| | | +-------------+ +----------------+ |
| | +-----------+ | | District | | Routing | |
| |--|AS Code: |---| | Information | |Information(BGP)| |
| | |Regional | | | | | | |
|P2P Peers| |Information| | | Range of | |AS Code(origin) | |
| or | +-----------+ | | IP Addresses| | | |
| Control | | +-------------+ +----------------+ |
| Server | +-------------------------------------+
| | | ^
| | PeerSelection v |
| | +-----------+ +--------------------------------------+
| |--|IP Address |-->| +--Priority Node Selection System--+ |
| | | List | | | | |
| | +-----------+ | | Peer Candidate Ranking | |
| | +-----------+ | | | |
| |--| Ranking |-->| +----------------------------------+ |
| | +-----------+ +--------------------------------------+
+---------+
+---------+ GetLocation +-------------GeoIP DB Server---------+
| | +-----------+ | +----------+ +-----------+ |
| |--|IP Address |-->| | GeoIP DB | |BGP daemon | |
| | +-----------+ | +----------+ +-----------+ |
| | | +-------------+ +----------------+ |
| | +-----------+ | | District | | Routing | |
| |--|AS Code: |---| | Information | |Information(BGP)| |
| | |Regional | | | | | | |
|P2P Peers| |Information| | | Range of | |AS Code(origin) | |
| or | +-----------+ | | IP Addresses| | | |
| Control | | +-------------+ +----------------+ |
| Server | +-------------------------------------+
| | | ^
| | PeerSelection v |
| | +-----------+ +--------------------------------------+
| |--|IP Address |-->| +--Priority Node Selection System--+ |
| | | List | | | | |
| | +-----------+ | | Peer Candidate Ranking | |
| | +-----------+ | | | |
| |--| Ranking |-->| +----------------------------------+ |
| | +-----------+ +--------------------------------------+
+---------+
Figure 2: Hint server for peer selection
图2：用于对等选择的提示服务器
The network information used by the hint server is not information solicited from individual ISPs but is the Autonomous System (AS) number and district information, which are more or less public already. Routing tables are not generated. Instead, peers within the same ISP or the same district are selected with higher priority in order to confine traffic to within the same ISP or the same district.
提示服务器使用的网络信息不是从单个ISP请求的信息，而是自治系统（AS）号码和地区信息，这些信息或多或少已经公开。不生成路由表。相反，选择同一ISP或同一地区内具有较高优先级的对等方，以便将流量限制在同一ISP或同一地区内。
When the hint server receives an IP address, it returns its attribute information, in order to confine the traffic to within the nearer ISP or district. A peer can select another based on the returned information. This operation is called GetLocation. However, in preparation for the time when it becomes necessary to hide topology information, an interface is provided through which a priority order is returned in response to an input of a list of candidate peers. This operation is called PeerSelection.
当提示服务器收到IP地址时，它会返回其属性信息，以便将通信量限制在较近的ISP或地区内。对等方可以根据返回的信息选择另一个。此操作称为GetLocation。然而，为了准备需要隐藏拓扑信息时，提供了一个接口，通过该接口，响应候选对等点列表的输入，返回优先级顺序。此操作称为PeerSelection。
Although the target node is selected based on the criterion that it is within the same ISP or the same district, this type of selection is not very effective if the number of participating peers is small. Table 1 shows the percentage of peers within the same AS or the same prefecture calculated from the distribution of ASes and prefectures in the IP address space from one-day data on a Winny network.
尽管目标节点是基于其位于同一ISP或同一地区内的标准来选择的，但是如果参与节点的数量很小，这种类型的选择不是非常有效。表1显示了根据Winny网络上的一天数据在IP地址空间中的ASE和郡县分布计算出的相同或相同郡县内的对等点百分比。
+--------------------+------------+
| Conditions | Percentage |
+--------------------+------------+
| AS matches | 6.70% |
| Prefecture matches | 12.76% |
| Both match | 2.09% |
| Neither match | 78.45% |
+--------------------+------------+
+--------------------+------------+
| Conditions | Percentage |
+--------------------+------------+
| AS matches | 6.70% |
| Prefecture matches | 12.76% |
| Both match | 2.09% |
| Neither match | 78.45% |
+--------------------+------------+
Table 1: AS and prefecture distributions
表1：AS和地区分布
Because, in addition to the above, the presence or absence of content affects the results, controlling peer selection within the same district may be inadequate. Therefore, it is necessary to introduce the weight of a continuous quantity that reflects the physical distance or the AS path length as an indicator of the proximity of the areas involved.
由于除上述内容外，内容的存在或不存在也会影响结果，因此在同一地区内控制同行选择可能是不够的。因此，有必要引入反映物理距离或AS路径长度的连续量的权重，作为相关区域接近程度的指标。
In consideration of this, the following two measures are used to evaluate the proximity of peers in a hint server.
考虑到这一点，使用以下两个度量来评估提示服务器中对等点的接近程度。
o AS path length (distance between ISPs)
o 作为路径长度（ISP之间的距离）
AS path length is calculated from BGP full routes. Since a full routing table retrieved at an ISP can show only a best path, it may not get an accurate length if the AS hop count of both ISPs is too large. To avoid this, we use BGP information received from different ISPs and combine them. Based on this concept, we used BGP routing information offered by three ISPs operated by big telecommunication couriers and made a topology tree. Then, we were able to calculate the shortest path between two given ASes.
因为路径长度是根据BGP完整路由计算的。由于在ISP上检索的完整路由表只能显示最佳路径，因此如果两个ISP的AS跃点计数过大，则可能无法获得准确的长度。为了避免这种情况，我们使用从不同ISP收到的BGP信息，并将它们结合起来。基于这一概念，我们利用由三家大型电信运营商运营的ISP提供的BGP路由信息，构建了一个拓扑树。然后，我们能够计算两个给定ASE之间的最短路径。
o Geographical distance
o 地理距离
Distances between peers are measured using the physical distance between the capitals of the prefectures to which the peers belong. Distances between prefectural capitals are sorted into ascending order, and then into bands, with weights 1 to 15 assigned to them so that each band contains roughly the same number of "capital pairs". If either of the peer's locations is indefinite, the distance is equal to 15; if they are in the same prefecture, the distance is equal to 0.
同龄人之间的距离是使用同龄人所属州首府之间的实际距离来衡量的。县府首府之间的距离按升序排序，然后按带排序，并分配权重1至15，以便每个带包含大致相同数量的“首府对”。如果对等方的任一位置不确定，则距离等于15；如果他们在同一个县，则距离等于0。
Evaluation of distances between peers showed that the distribution of distances was almost uniform when distances between peers are normalized. This result suggests that using normalized distances
对等点之间的距离评估表明，对等点之间的距离被归一化后，距离分布几乎是均匀的。这一结果表明，使用标准化距离
expands the area where the control by a hint server is effective. The geographical distance is used only when the AS path length is the same between some candidates.
扩展提示服务器控件有效的区域。仅当某些候选路径之间的AS路径长度相同时，才使用地理距离。
An example of the request and the response follows.
下面是请求和响应的示例。
o Request
o 要求
POST /PeerSelection HTTP/1.1
Host: ServerName
User-Agent: ClientName
Content-Type: text/plain; charset=utf-8
POST /PeerSelection HTTP/1.1
Host: ServerName
User-Agent: ClientName
Content-Type: text/plain; charset=utf-8
v=Version number
[application=Application identifier]
ip=IP address of physical interface
port=Port number of physical interface
[nat={no|upnp|unknown}]
[nat_ip=Global IP address using UPnP]
[nat_port= Global port number using UPnP]
[trans_id=transaction ID]
[pt=Flag of port type]
[ub=upload bandwidth]
[db=download bandwidth]
v=Version number
[application=Application identifier]
ip=IP address of physical interface
port=Port number of physical interface
[nat={no|upnp|unknown}]
[nat_ip=Global IP address using UPnP]
[nat_port= Global port number using UPnP]
[trans_id=transaction ID]
[pt=Flag of port type]
[ub=upload bandwidth]
[db=download bandwidth]
o Response
o 回答
HTTP/1.1 200 OK
Date: Timestamp
Content-Type: text/plain; charset=utf-8
Cache-control: max-age=max age
Connection: close
HTTP/1.1 200 OK
Date: Timestamp
Content-Type: text/plain; charset=utf-8
Cache-control: max-age=max age
Connection: close
v=Version number ttl=ttl server=hint server name ... trans_id=transaction ID pt=Flag of port type client_ip=Peer IP address observed from server client_port=Peer port number observed from server numpeers=number of responding peers n=[src address] dst address / cost / option
v=版本号ttl=ttl服务器=提示服务器名称。。。trans_id=事务id pt=端口类型客户端标志\u ip=从服务器客户端观察到的对等ip地址\u port=从服务器观察到的对等端口号NUMPERS=响应对等端口数n=[src地址]dst地址/成本/选项
Table 2 shows the result of the analysis of communication in a node of an ISP in Tokyo, as an example of measurement results.
表2显示了东京ISP节点中的通信分析结果，作为测量结果的示例。
In these two experiments, we evaluated different P2P applications. In the first experiment, the P2P topology was generated by a tree algorithm; in the second experiment, it was generated by a mesh algorithm. Both resulted in similar performance.
在这两个实验中，我们评估了不同的P2P应用程序。在第一个实验中，通过树算法生成P2P拓扑；在第二个实验中，它是由网格算法生成的。两者的表现相似。
+-----------------------------------------+------------+------------+
| Conditions | Experiment | Experiment |
| | 1 | 2 |
+-----------------------------------------+------------+------------+
| Peers selected within the same ISP | 22% | 29% |
| | | |
| Peers selected within the same district | 19% | 23% |
| | | |
| Peers selected within the same district | 5% | 7% |
| and the same ISP | | |
+-----------------------------------------+------------+------------+
+-----------------------------------------+------------+------------+
| Conditions | Experiment | Experiment |
| | 1 | 2 |
+-----------------------------------------+------------+------------+
| Peers selected within the same ISP | 22% | 29% |
| | | |
| Peers selected within the same district | 19% | 23% |
| | | |
| Peers selected within the same district | 5% | 7% |
| and the same ISP | | |
+-----------------------------------------+------------+------------+
Table 2: Percentage of communication within the same ISP
表2：同一ISP内的通信百分比
Table 2 shows that the probability of communication with peers in the same ISP is proportional to the population size and the share of the ISP in each district. The data show that peers were selected at random. Note that the vendor of a P2P application used in these experiments demonstrated that the mechanism for selecting a peer using network information can be implemented. However, peer selection is normally based on past information because users often cannot actually perceive the effect of using network information.
表2显示，与同一ISP中的同行通信的概率与每个地区的人口规模和ISP的份额成正比。数据显示，同龄人是随机挑选的。注意，在这些实验中使用的P2P应用程序的供应商证明了使用网络信息选择对等点的机制是可以实现的。然而，对等选择通常基于过去的信息，因为用户通常无法实际感知使用网络信息的效果。
The main objective of these experiments was to verify the operation of the hint server and P2P applications. The distances between a dummy node and a peer were obtained from data on the dummy nodes. An examination of the distances between a dummy node and a peer revealed that the mean value of distance after the hint server was introduced was reduced by 10% and that the 95th percentile was reduced by 5%. The results show that introducing a hint server can reduce the network loads that result from P2P applications.
这些实验的主要目的是验证hint服务器和P2P应用程序的操作。从虚拟节点上的数据获得虚拟节点和对等节点之间的距离。对虚拟节点和对等节点之间距离的检查显示，引入提示服务器后距离的平均值减少了10%，第95个百分位减少了5%。结果表明，引入提示服务器可以减少P2P应用程序带来的网络负载。
We clarified the following during our experiments.
我们在实验中澄清了以下内容。
1. Dispersed dummy nodes can determine the behavior of peers and traffic between inter-ISP networks and can determine the peer that each peer selects. Therefore, this result proves the importance of the peer-selection control mechanism that is proposed by ALTO.
1. 分散的虚拟节点可以确定对等点的行为和ISP网络之间的通信量，并可以确定每个对等点选择的对等点。因此，这一结果证明了ALTO提出的对等选择控制机制的重要性。
2. Using our peer-selection control mechanism, called hint servers, can result in significant differences. Hint servers can lead each peer to select a closer peer.
2. 使用我们的对等选择控制机制（称为提示服务器）可能会导致显著的差异。提示服务器可以引导每个对等方选择一个更接近的对等方。
3. The 10% reduction of network cost is not satisfactory for ISPs, but the controllability of P2P applications is the most important point. When ISPs apply this mechanism to their real networks, they will set a very large cost for the most expensive network link.
3. 网络成本降低10%对ISP来说并不令人满意，但P2P应用的可控性是最重要的一点。当ISP将这种机制应用于他们的真实网络时，他们将为最昂贵的网络链路设置非常大的成本。
In the experimental results for peer-selection control, the selection is smaller in intra-ISP traffic than in other experiments [15]. We think this is because there are fewer peers in each area of traffic control. When there are many peers in one ISP, it is easy to select peers in the same ISP. However, when there are fewer peers in one ISP, it is difficult to select peers in the same ISP. In our experiments, most of the ISPs had many peers in their networks, i.e., there were a small number of ISPs that had few peers in their networks.
在对等选择控制的实验结果中，ISP内部流量中的选择比其他实验中的选择要小[15]。我们认为这是因为在交通控制的每个领域都有较少的对等点。当一个ISP中有多个对等点时，很容易选择同一ISP中的对等点。但是，当一个ISP中的对等点较少时，很难在同一ISP中选择对等点。在我们的实验中，大多数ISP的网络中都有许多对等点，也就是说，有少数ISP的网络中几乎没有对等点。
Moreover, we didn't force P2P vendors to limit their implementation policy; therefore, we observed differences in how each implementation weighs the information from the hint servers. Specifically, in P2P applications when a tree topology is used, the hint-server mechanism is very effective; on the other hand, when a mesh topology is used, it less effective.
此外，我们没有强迫P2P供应商限制其实施策略；因此，我们观察到每个实现如何衡量来自提示服务器的信息的差异。具体来说，在P2P应用中，当使用树拓扑时，提示服务器机制非常有效；另一方面，当使用网格拓扑时，其效率较低。
In recent research, we've changed to an ALTO-based communication protocol on hint servers because the requirements of ALTO are documented in RFC 6708 [16] and the ALTO protocol is a work in progress [17]. In our implementation, protocol identifiers (PIDs) and the cost value are mapped to ISP subnets and to ISP distance, respectively. We also implement services for compatibility required by ALTO such as Map Services and Endpoint Cost Service. The Endpoint Cost Service (defined in [17]) is mainly used because of backward compatibility with our experiments.
在最近的研究中，我们在提示服务器上更改为基于ALTO的通信协议，因为ALTO的要求记录在RFC 6708[16]中，并且ALTO协议是一项正在进行的工作[17]。在我们的实现中，协议标识符（PID）和成本值分别映射到ISP子网和ISP距离。我们还实现了ALTO所需的兼容性服务，如Map服务和Endpoint Cost服务。端点成本服务（定义见[17]）主要是因为与我们的实验具有向后兼容性。
We are also studying a hierarchical structure of hint servers, in order to control traffic at a coarse level (in inter-ISP areas) and at a finer level (in intra-ISP areas). It is also effective for limiting the areas where information is disclosed.
我们还在研究提示服务器的层次结构，以便在粗略级别（在ISP间区域）和更精细级别（在ISP内区域）控制流量。它还可以有效地限制信息披露的领域。
This section describes what the authors learned from these experiments that might be useful to the ALTO WG.
本节描述了作者从这些实验中学到的可能对ALTO工作组有用的东西。
In our experiments, we present the possibility of traffic control among multiple ISPs and multiple P2P applications using an ALTO mechanism. We found several problems when ISPs try to adopt the mechanism. One is the granularity of network information from Council members. Among inter-ISP areas, it is relatively easy to handle information for public purposes by using BGP full routes. On the other hand, among the intra-ISP areas, it may be difficult to disclose the private information of each ISP. Kiesel [18] proposes some modifications for the ALTO protocol in order to hide ISP information. We propose hierarchical structures. From the viewpoint of cooperation between ISPs, fine-grained information is not necessarily required. Moreover, it is difficult to exchange the fine-grained information between ISPs. Considering this situation, we used only coarse-grained information to control backbone traffic in these experiments; however, in the future, there may be a demand for controlling traffic within an ISP using fine-grained information. Therefore, we decided to introduce hierarchical structures into ALTO in order to cope with both situations. Actually, adopting a hierarchical control mechanism that includes the following two steps will be useful.
在我们的实验中，我们提出了使用ALTO机制在多个ISP和多个P2P应用程序之间进行流量控制的可能性。当ISP尝试采用这种机制时，我们发现了几个问题。一是安理会成员提供的网络信息的粒度。在ISP之间的区域中，使用BGP全路由为公共目的处理信息相对容易。另一方面，在ISP内部区域中，可能很难披露每个ISP的私人信息。Kiesel[18]建议对ALTO协议进行一些修改，以隐藏ISP信息。我们提出了层次结构。从ISP之间合作的角度来看，不一定需要细粒度的信息。此外，ISP之间很难交换细粒度信息。考虑到这种情况，在这些实验中，我们仅使用粗粒度信息来控制主干流量；然而，未来可能需要使用细粒度信息控制ISP内的流量。因此，我们决定在ALTO中引入层次结构，以应对这两种情况。实际上，采用包括以下两个步骤的分层控制机制将非常有用。
o First, use coarse-grained information about whole the network to select ISPs.
o 首先，使用整个网络的粗粒度信息来选择ISP。
o Second, use fine-grained information within the ISP to select a peer.
o 其次，使用ISP中的细粒度信息来选择对等方。
In these experiments, there were two difficulties as follows.
在这些实验中，有以下两个困难。
o Evaluating the effect of introducing a hint server was difficult because the P2P applications had their own measurement mechanisms.
o 评估引入提示服务器的效果很困难，因为P2P应用程序有自己的度量机制。
o How to treat the priority order of peers suggested by a hint server could not be predetermined for P2P applications.
o 对于P2P应用程序，如何处理提示服务器建议的对等点的优先级顺序无法预先确定。
From these experiences, the authors consider that clarifying the requirements about measurement mechanisms for P2P applications is necessary in ALTO.
从这些经验，作者认为，澄清在P2P应用程序的测量机制的要求是必要的在阿尔托。
This document does not propose any kind of protocol, practice, or standard.
本文件未提出任何类型的协议、实践或标准。
The P2P Network Experiment Council was established thanks to strong support by the Japanese Ministry of Internal Affairs and Communications. These experiments were performed with cooperation among the P2P Network Experiment Council members. DREAMBOAT Co., Ltd., Bitmedia, Inc., Utagoe, Inc., and Toyama IX have especially supported the analyses of the experiments. The authors appreciate Tohru Asami, Hiroshi Esaki, and Tatsuya Yamashita for their constructive comments.
P2P网络实验委员会是在日本内务省和交通省的大力支持下成立的。这些实验是在P2P网络实验委员会成员的合作下进行的。DREAMBOAT Co.，Ltd.，Bitmedia，Inc.，Utagoe，Inc.，和富山九号公司特别支持实验分析。作者们对浅井富郎、以崎广史和山下达也的建设性评论表示赞赏。
The authors would also like to thank Martin Stiemerling, Stefano Previdi, and Vijay K. Gurbani for their comments on this document.
作者还要感谢Martin Stieemerling、Stefano Previdi和Vijay K.Gurbani对本文件的评论。
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Authors' Addresses
作者地址
Satoshi Kamei NTT Communications Corporation Granpark Tower 16F, 3-4-1 Shibaura Minato-ku, Tokyo 108-8118 Japan
佐藤龟井新田通讯公司日本东京新田区Shibaura Minato ku 3-4-1 Granpark大厦16楼108-8118
Phone: +81-50-3812-4697
EMail: skame@nttv6.jp
Phone: +81-50-3812-4697
EMail: skame@nttv6.jp
Tsuyoshi Momose Cisco Systems G.K. 9-7-1 Akasaka Minato-ku, Tokyo 107-6227 Japan
Tsuyoshi Momose Cisco Systems G.K.9-7-1 Akasaka Minato ku，日本东京107-6227
Phone: +81-3-6738-5154
EMail: tmomose@cisco.com
Phone: +81-3-6738-5154
EMail: tmomose@cisco.com
Takeshi Inoue NTT Communications Corporation Kuredo Hakushima Building 3F, 14-15 Higashihakushimacho Chuo-ku, Hiroshima-City, Hiroshima 730-0004 Japan
井上武NTT通信公司日本广岛市东白岛町中区14-15号黑田东白岛大厦3楼730-0004
Phone: +81-82-563-5030
EMail: inoue@jp.ntt.net
Phone: +81-82-563-5030
EMail: inoue@jp.ntt.net
Tomohiro Nishitani NTT Communications Corporation 1-1-6, Uchisaiwaicho Chiyodaku, Tokyo 100-8019 Japan
日本东京千代湖内石卫1-1-6号西谷智博NTT通信公司，日本东京100-8019
Phone: +81-50-3812-4742
EMail: tomohiro.nishitani@ntt.com
Phone: +81-50-3812-4742
EMail: tomohiro.nishitani@ntt.com