Internet Research Task Force (IRTF) E. Marocco
Request for Comments: 6821 A. Fusco
Category: Informational Telecom Italia
ISSN: 2070-1721 I. Rimac
V. Gurbani
Bell Labs, Alcatel-Lucent
December 2012
Internet Research Task Force (IRTF) E. Marocco
Request for Comments: 6821 A. Fusco
Category: Informational Telecom Italia
ISSN: 2070-1721 I. Rimac
V. Gurbani
Bell Labs, Alcatel-Lucent
December 2012
Improving Peer Selection in Peer-to-Peer Applications: Myths vs. Reality
改进对等应用程序中的对等选择：神话与现实
Abstract
摘要
Peer-to-peer (P2P) traffic optimization techniques that aim at improving locality in the peer selection process have attracted great interest in the research community and have been the subject of much discussion. Some of this discussion has produced controversial myths, some rooted in reality while others remain unfounded. This document evaluates the most prominent myths attributed to P2P optimization techniques by referencing the most relevant study or studies that have addressed facts pertaining to the myth. Using these studies, the authors hope to either confirm or refute each specific myth.
对等（P2P）流量优化技术旨在改善对等选择过程中的局部性，已引起研究界的极大兴趣，并已成为许多讨论的主题。这些讨论中的一些产生了有争议的神话，一些植根于现实，而另一些则毫无根据。本文档通过引用与P2P优化技术相关的一项或多项研究，评估了与该神话相关的最突出的神话。通过这些研究，作者们希望确认或反驳每一个具体的神话。
This document is a product of the IRTF P2PRG (Peer-to-Peer Research Group).
本文件是IRTF P2PRG（对等研究小组）的产品。
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 consensus of the Peer-to-peer Research Group 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代表了互联网研究任务组（IRTF）对等研究小组的共识。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/rfc6821.
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/rfc6821.
Copyright Notice
版权公告
Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2012 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 ....................................................4
2. Definitions .....................................................5
3. Myths, Facts, and Discussion ....................................6
3.1. Reduced Cross-Domain Traffic ...............................6
3.1.1. Facts ...............................................6
3.1.2. Discussion ..........................................7
3.1.3. Conclusions .........................................7
3.2. Increased Application Performance ..........................7
3.2.1. Facts ...............................................7
3.2.2. Discussion ..........................................8
3.2.3. Conclusions .........................................9
3.3. Increased Uplink Bandwidth Usage ...........................9
3.3.1. Facts ...............................................9
3.3.2. Discussion ..........................................9
3.3.3. Conclusions .........................................9
3.4. Impacts on Peering Agreements ..............................9
3.4.1. Facts ..............................................10
3.4.2. Discussion .........................................10
3.4.3. Conclusions ........................................11
3.5. Impacts on Transit ........................................11
3.5.1. Facts ..............................................11
3.5.2. Discussion .........................................11
3.5.3. Conclusions ........................................11
3.6. Swarm Weakening ...........................................12
3.6.1. Facts ..............................................12
3.6.2. Discussion .........................................12
3.6.3. Conclusions ........................................12
3.7. Improved P2P Caching ......................................12
3.7.1. Facts ..............................................12
3.7.2. Discussion .........................................13
3.7.3. Conclusions ........................................13
4. Security Considerations ........................................13
5. Acknowledgments ................................................13
6. Informative References .........................................13
Appendix A. Myths/References/Facts Matrix .........................15
1. Introduction ....................................................4
2. Definitions .....................................................5
3. Myths, Facts, and Discussion ....................................6
3.1. Reduced Cross-Domain Traffic ...............................6
3.1.1. Facts ...............................................6
3.1.2. Discussion ..........................................7
3.1.3. Conclusions .........................................7
3.2. Increased Application Performance ..........................7
3.2.1. Facts ...............................................7
3.2.2. Discussion ..........................................8
3.2.3. Conclusions .........................................9
3.3. Increased Uplink Bandwidth Usage ...........................9
3.3.1. Facts ...............................................9
3.3.2. Discussion ..........................................9
3.3.3. Conclusions .........................................9
3.4. Impacts on Peering Agreements ..............................9
3.4.1. Facts ..............................................10
3.4.2. Discussion .........................................10
3.4.3. Conclusions ........................................11
3.5. Impacts on Transit ........................................11
3.5.1. Facts ..............................................11
3.5.2. Discussion .........................................11
3.5.3. Conclusions ........................................11
3.6. Swarm Weakening ...........................................12
3.6.1. Facts ..............................................12
3.6.2. Discussion .........................................12
3.6.3. Conclusions ........................................12
3.7. Improved P2P Caching ......................................12
3.7.1. Facts ..............................................12
3.7.2. Discussion .........................................13
3.7.3. Conclusions ........................................13
4. Security Considerations ........................................13
5. Acknowledgments ................................................13
6. Informative References .........................................13
Appendix A. Myths/References/Facts Matrix .........................15
Peer-to-peer (P2P) applications used for file-sharing, streaming, and real-time communications exchange large amounts of data in connections established among the peers themselves and are responsible for an important part of the Internet traffic. Since applications have generally no knowledge of the underlying network topology, the traffic they generate is frequent cause of congestions in inter-domain links and significantly contributes to the raising of transit costs paid by network operators and Internet Service Providers (ISPs).
用于文件共享、流式传输和实时通信的对等（P2P）应用程序在对等点之间建立的连接中交换大量数据，并负责互联网流量的重要部分。由于应用程序通常不了解底层网络拓扑结构，因此它们产生的流量经常导致域间链路拥塞，并大大增加了网络运营商和互联网服务提供商（ISP）支付的传输成本。
One approach to reduce congestions and transit costs caused by P2P applications consists of enhancing the peer selection process with the introduction of proximity information. This allows the peers to identify the topologically closer resource among all the instances of the resources they are searching through. Several solutions following such an approach have recently been proposed [Choffnes] [Aggarwal] [Xie], some of which are now being considered for standardization in the IETF [ALTO]. While this document serves to inform the protocol work going on in the IETF ALTO working group, this document does not specify a protocol of any kind, nor is this document a product of the IETF.
减少P2P应用程序造成的拥塞和传输成本的一种方法是通过引入邻近信息来增强对等选择过程。这允许对等方在其正在搜索的资源的所有实例中识别拓扑上更接近的资源。最近提出了几种采用这种方法的解决方案[Choffnes][Aggarwal][Xie]，其中一些正在考虑在IETF[ALTO]中进行标准化。虽然本文件旨在告知IETF ALTO工作组正在进行的协议工作，但本文件并未规定任何类型的协议，也不是IETF的产品。
Despite extensive research based on simulations and field trials, it is hard to predict how proposed solutions would perform in a real-world systems made of millions of peers. For this reason, possible effects and side effects of optimization techniques based on P2P traffic localization have been a matter of frequent debate. This document describes some of the most interesting effects, referencing relevant studies that have addressed them and trying to determine whether and in what measure they are likely to happen.
尽管基于模拟和现场试验进行了广泛的研究，但很难预测所提出的解决方案在由数百万对等方组成的现实世界系统中的表现。因此，基于P2P流量定位的优化技术可能产生的影响和副作用一直是一个经常争论的问题。本文件描述了一些最有趣的影响，参考了解决这些影响的相关研究，并试图确定这些影响是否可能发生以及以何种方式发生。
Each possible effect -- or myth -- is examined in three phases:
每种可能的影响或神话都分三个阶段进行研究：
o Facts: in which a list of relevant data is presented, usually collected from simulations or field trials;
o 事实：其中列出了相关数据列表，通常从模拟或现场试验中收集；
o Discussion: in which the reasons supporting and opposing the myth are discussed based on the facts previously listed;
o 讨论：根据前面列出的事实讨论支持和反对神话的原因；
o Conclusions: in which the authors try to express a reasonable measure of the plausibility of the myth.
o 结论：作者试图表达一个合理的神话似是而非的措施。
Note: Even though a myth is an unfounded or false notion, we have nonetheless chosen to provocatively assign a confirmation likelihood to each of the myths in Section 3. This is a
注：尽管一个神话是一个没有根据或错误的概念，我们仍然选择挑衅性地为第3节中的每一个神话指定一个确认可能性。这是一个
whimsical, but we believe effective, attempt that was inspired by the TV show "Mythbusters", wherein each myth was "busted", deemed "plausible", or "confirmed" by the end of the show.
这是一次异想天开但我们相信是有效的尝试，其灵感来自电视节目“Mythbusters”，在节目结束时，每个神话都被“粉碎”，被认为是“合理的”，或是“证实的”。
This document represents the consensus of the P2PRG. The first version of this document appeared in February 2009, and there was a sizeable discussion on the contents of the document thereafter. The document has been improved by incorporating comments from experts in the area of peer-to-peer networks as well as casual, but informed, users of such networks. The IRTF community has helped improve the number of facts and quality of discussion and enhanced the trustworthiness of the conclusions documented.
本文件代表P2PRG的共识。该文件的第一个版本于2009年2月发布，此后对该文件的内容进行了大量讨论。该文件经过改进，纳入了点对点网络领域专家以及此类网络的临时但知情用户的意见。IRTF社区帮助改善了事实的数量和讨论的质量，并提高了记录的结论的可信度。
This document essentially represents the view of the participating P2PRG IRTF community between 2009 and the latter part of 2010; as such, it is like a snapshot: frozen in time. While some aspects are confirmed with references to pertinent literature, other aspects reflect the state of discussions in the RG at the time of writing and may require further investigation beyond the publication date of this document.
本文件主要代表了2009年至2010年下半年期间参与P2PRG IRTF社区的观点；因此，它就像一个快照：在时间上冻结。虽然参考相关文献确认了某些方面，但其他方面反映了撰写本文件时RG中的讨论状态，可能需要在本文件出版日期之后进行进一步调查。
Terminology defined in [RFC5693] is reused here; other definitions should be consistent with the terminology in that document.
此处重复使用[RFC5693]中定义的术语；其他定义应与该文件中的术语一致。
Seeder:
播种机：
A peer that has a complete copy of the content it is sharing, and still offers it for upload. The term "seeder" is adopted from BitTorrent terminology and is used in this document to indicate upload-only peers that are also in other kinds of P2P applications.
拥有共享内容的完整副本，但仍提供用于上传的对等方。术语“种子机”取自BitTorrent术语，在本文档中用于表示在其他类型的P2P应用程序中也仅上载的对等点。
Leecher:
利切：
A peer that has not yet completed the download of a specific content (but usually has already started offering for upload the part it is in possession of). The term "leecher" is adopted from BitTorrent terminology and is used in this document to indicate peers that are both uploading and downloading and are used in other kinds of P2P applications.
尚未完成特定内容下载（但通常已开始提供其拥有的部分的上传）的对等方。术语“leecher”取自BitTorrent术语，在本文档中用于表示正在上载和下载以及在其他类型的P2P应用程序中使用的对等点。
Swarm:
蜂群：
The group of peers that are uploading and/or downloading pieces of the same content. The term "swarm" is commonly used in BitTorrent, to indicate all seeders and leechers exchanging chunks
正在上载和/或下载相同内容片段的对等组。术语“swarm”在BitTorrent中常用，表示所有播种机和韭菜机交换块
of a particular file; however, in this document, it is used more generally (e.g., in the case of P2P streaming applications) to refer to all peers receiving and/or transmitting the same media stream.
一个特定文件的名称；然而，在本文档中，更一般地（例如，在P2P流应用的情况下）使用它来指代接收和/或发送相同媒体流的所有对等方。
Tit-for-Tat:
以牙还牙：
A content exchange strategy where the amount of data sent by a leecher to another leecher is roughly equal to the amount of data received from it. P2P applications, most notably BitTorrent, adopt such an approach to maximize resources shared by the users.
一种内容交换策略，其中由一个leecher发送到另一个leecher的数据量大致等于从该leecher接收到的数据量。P2P应用程序，尤其是BitTorrent，采用这种方法来最大化用户共享的资源。
Surplus Mode:
盈余模式：
The status of a swarm where the upload capacity exceeds the download demand. A swarm in surplus mode is often referred to as "well seeded".
群集的状态，其中上载容量超过下载需求。处于剩余模式的群通常被称为“良好种子”。
Transit:
过境：
The service through which a network can exchange IP packets with all other networks to which it is not directly connected. The transit service is always regulated by a contract, according to which the customer (i.e., a network operator or an ISP) pays the transit provider per amount of data exchanged.
一种服务，通过该服务，网络可以与它未直接连接的所有其他网络交换IP数据包。运输服务始终由合同管理，根据该合同，客户（即网络运营商或ISP）按交换的数据量向运输提供商支付费用。
Peering:
窥视：
The direct interconnection between two separate networks for the purpose of exchanging traffic without requiring a transit provider. Peering is usually regulated by agreements taking in account the amount of traffic generated by each party in each direction.
两个独立网络之间的直接互连，目的是在不需要公交服务提供商的情况下交换流量。对等通常由协议进行管理，考虑到各方在每个方向上产生的通信量。
The reduction in cross-domain traffic (and thus in transit costs due to it) is one of the positive effects P2P traffic localization techniques are expected to cause, and also the main reason why ISPs look at them with interest. Simulations and field tests have shown a reduction varying from 20% to 80%.
跨域流量的减少（以及由此产生的传输成本）是P2P流量定位技术有望带来的积极影响之一，也是ISP对其感兴趣的主要原因。模拟和现场试验表明，降低幅度从20%到80%不等。
1. Various simulations and initial field trials of the P4P solution [Xie] on average show a 70% reduction of cross-domain traffic.
1. P4P解决方案[Xie]的各种模拟和初始现场试验平均显示跨域流量减少了70%。
2. Data observed in Comcast's P4P trial [RFC5632] show a 34% reduction of the outgoing P2P traffic and an 80% reduction of the incoming.
2. Comcast的P4P试验[RFC5632]中观察到的数据显示，传出的P2P流量减少了34%，传入的P2P流量减少了80%。
3. Simulations of the "oracle-based" approach [Aggarwal] proposed by researchers at Technischen Universitat Berlin (TU Berlin) show an increase in local exchanges from 10% in the unbiased case to 60%-80% in the localized case.
3. 柏林理工大学（TU Berlin）研究人员提出的“基于甲骨文的”方法[Aggarwal]的模拟显示，本地交换从无偏情况下的10%增加到局部情况下的60%-80%。
4. Experiments with real BitTorrent clients and real distributions of peers per Autonomous System (AS) run by researchers at INRIA [LeBlond] have shown that ASes with 100 peers or more can save 99.5% of cross-domain traffic with high values of locality. They have also shown that on a global scale, i.e., 214,443 torrents, 6,1113,224 unique peers, and 9,605 ASes, high locality can save 40% of global inter-AS traffic, i.e., 4.56 Petabytes (PB) on 11.6 PB. This result shows that locality would be beneficial at the scale of the Internet.
4. INRIA[LeBlond]的研究人员对真实BitTorrent客户端和每个自治系统（AS）的对等点的真实分布进行了实验，结果表明，具有100个或更多对等点的ASE可以节省99.5%的跨域流量和较高的局部性值。他们还表明，在全球范围内，即214443个Torrent、61113224个唯一对等点和9605个ASE，高局部性可以节省40%的全球AS间通信量，即11.6 PB的4.56 PB。这一结果表明，在互联网的规模上，本地化将是有益的。
Tautologically, P2P traffic localization techniques tend to localize content exchanges, and thus reduce cross-domain traffic.
重复地说，P2P流量定位技术倾向于将内容交换本地化，从而减少跨域流量。
Confirmed.
确认。
Ostensibly, the increase in application performance is the main reason for the consideration of P2P traffic localization techniques in academia and industry. The expected increase depends on the specific application: file-sharing applications witness an increase in the download rate, real-time communication applications observe lower delay and jitter, and streaming applications can benefit by a high constant bitrate.
从表面上看，应用程序性能的提高是学术界和工业界考虑P2P流量定位技术的主要原因。预期的增长取决于具体的应用：文件共享应用见证了下载速率的增长，实时通信应用观察到较低的延迟和抖动，流式应用可以受益于较高的恒定比特率。
1. Various simulations and initial field trials of the P4P solution [Xie] show an average reduction of download completion times between 10% and 23%.
1. P4P解决方案[Xie]的各种模拟和初始现场试验表明，下载完成时间平均减少10%到23%。
2. Data observed in Comcast's P4P trial [RFC5632] show an increase in download rates between 13% and 85%. Interestingly, the data collected in the experiment also indicate that fine-grained localization is less effective in improving download performance compared to lower levels of localization.
2. Comcast的P4P试验[RFC5632]中观察到的数据显示下载率在13%到85%之间增加。有趣的是，实验中收集的数据还表明，与较低级别的本地化相比，细粒度本地化在提高下载性能方面的效果较差。
3. Data collected in the Ono experiment [Choffnes] show a 31% average download rate improvement.
3. 在Ono实验[Choffnes]中收集的数据显示平均下载率提高了31%。
* In networks where the ISP provides higher bandwidth for in-network traffic (e.g., as in the case of a Romanian ISP (RDSNET), described in [Choffnes]), the increase is significantly higher.
* 在ISP为网络内流量提供更高带宽的网络中（例如，如[Choffnes]中所述的罗马尼亚ISP（RDSNET））的情况下，增加的带宽明显更高。
* In networks with relatively low uplink bandwidth (as the case of Easynet, described in [Choffnes]), traffic localization slightly degrades application performance.
* 在上行链路带宽相对较低的网络中（如[Choffnes]中所述的Easynet情况），流量本地化会略微降低应用程序性能。
4. Simulations of the "oracle-based" approach [Aggarwal] proposed by researchers at TU Berlin show a reduction in download times between 16% and 34%.
4. 柏林大学研究人员提出的“基于oracle的”方法[Aggarwal]的模拟显示下载时间减少了16%到34%。
5. Simulations by Bell Labs [Seetharaman] indicate that localization is not as effective in all scenarios and that the user experience can suffer in certain locality-aware swarms based on the actual implementation of locality.
5. 贝尔实验室[Seetharaman]的模拟表明，本地化并不是在所有场景中都有效，并且基于本地性的实际实现，用户体验可能会在某些具有本地性意识的集群中受到影响。
6. Experiments with real clients run by researchers at INRIA [LeBlond] have shown that the measured application performance is a function of the degree of congestion on links on which the locality policy tries to reduce the traffic. Furthermore, they have also shown that, in the case of severe bottlenecks, BitTorrent with locality can be more than 200% faster than regular BitTorrent.
6. INRIA[LeBlond]的研究人员对真实客户机进行的实验表明，测量的应用程序性能是链路拥塞程度的函数，本地策略试图在链路上减少流量。此外，他们还表明，在严重瓶颈的情况下，具有局部性的BitTorrent比常规BitTorrent快200%以上。
It seems that traffic localization techniques often cause an improvement in application performance. However, it must be noted that such beneficial effects heavily depend on the network infrastructures. In some cases, for example, in networks with relatively low uplink bandwidth, localization seems to be useless if not harmful. Also, beneficial effects depend on the swarm size; imposing locality when only a small set of local peers is available may even decrease download performance for local peers.
似乎流量定位技术通常会导致应用程序性能的提高。然而，必须注意的是，这种有益的影响在很大程度上取决于网络基础设施。例如，在某些情况下，在上行链路带宽相对较低的网络中，本地化即使无害也似乎是无用的。此外，有益效果取决于群体规模；当只有一小部分本地对等点可用时强加局部性甚至可能降低本地对等点的下载性能。
Very likely, especially for large swarms and in networks with high capacity.
很有可能，特别是对于大型群集和高容量网络。
The increase in uplink bandwidth usage would be a negative effect, especially in environments where the access network is based on technologies providing asymmetric upstream/downstream bandwidth (e.g., DSL or Data Over cable Service Interface Specification (DOCSIS)).
上行链路带宽使用的增加将是负面影响，尤其是在接入网络基于提供不对称上/下游带宽的技术的环境中（例如，DSL或有线数据服务接口规范（DOCSIS））。
1. Data observed in Comcast's P4P trial [RFC5632] show no increase in the uplink traffic.
1. Comcast的P4P试验[RFC5632]中观察到的数据显示上行通信量没有增加。
Mathematically, average uplink traffic remains the same as long as the swarm is not in surplus mode. However, in some particular cases where surplus capacity is available, localization may lead to local low-bandwidth leechers connecting to each other instead of trying the external seeders. Even if such a phenomenon has not been observed in simulations and field trials, it could occur to applications that use localization as the only means for optimization when some content becomes popular in different areas at different times (as is the case of prime-time TV shows distributed on BitTorrent networks minutes after getting aired in North America).
从数学上讲，只要swarm不处于剩余模式，平均上行链路流量保持不变。然而，在某些特定情况下，如果有剩余容量可用，本地化可能会导致本地低带宽leecher相互连接，而不是尝试外部播种机。即使在模拟和现场试验中未观察到这种现象，但当某些内容在不同时间在不同地区流行时，将本地化作为唯一优化手段的应用程序也可能会出现这种现象（就像在北美播出几分钟后在BitTorrent网络上发布的黄金时段电视节目一样）。
Unlikely.
不大可能发生的
Peering agreements are usually established on a reciprocity basis, assuming that the amount of data sent and received by each party is roughly the same (or, in case of asymmetric traffic volumes, a compensation fee is paid by the party that would otherwise obtain the most gain). P2P traffic localization techniques aim at reducing cross-domain traffic and thus might also impact peering agreements.
对等协议通常建立在互惠的基础上，假设各方发送和接收的数据量大致相同（或者，在通信量不对称的情况下，补偿费由获得最大收益的一方支付）。P2P流量定位技术旨在减少跨域流量，因此也可能影响对等协议。
No significant publications, simulations, or trials have tried to understand how traffic localization techniques can influence factors that rule how peering agreements are established and maintained.
没有任何重要的出版物、模拟或试验试图了解流量定位技术如何影响决定如何建立和维护对等协议的因素。
This is a key topic for network operators and ISPs, and it certainly deserves to be analyzed more accurately. Some random thoughts follow.
这是网络运营商和ISP的一个关键话题，当然值得更准确地分析。一些随机的想法随之而来。
It seems reasonable to expect different effects depending on the kinds of agreements. For example:
根据协议的种类，期待不同的效果似乎是合理的。例如：
o ISPs with different customer bases: the ISP whose customers generate more P2P traffic can achieve a greater reduction of cross-domain traffic and thus could probably be in a position to renegotiate the contract ruling the peering agreement;
o 具有不同客户群的ISP：客户产生更多P2P流量的ISP可以实现跨域流量的更大减少，因此可能能够重新协商裁定对等协议的合同；
o ISPs with similar customer bases:
o 具有类似客户群的ISP：
* ISPs with different access technologies: customers of the ISP that provides higher bandwidth -- and, in particular, higher uplink bandwidth -- will have more incentives for keeping their P2P traffic local. Consequently, the ISP with a better infrastructure will be able to achieve a greater reduction in cross-domain traffic and will be probably in a position to re-negotiate the peering agreement;
* 具有不同接入技术的ISP：提供更高带宽（特别是更高的上行带宽）的ISP客户将有更多的动机保持其P2P流量的本地性。因此，具有更好基础设施的ISP将能够实现跨域流量的更大减少，并且可能能够重新协商对等协议；
* ISPs with similar access technologies: both ISPs would achieve roughly the same reduction in cross-domain traffic; thus, the conditions under which the peering agreement had been established would not change much.
* 具有类似接入技术的ISP：两个ISP将实现大致相同的跨域流量减少；因此，建立对等协议的条件不会有太大变化。
As a consequence of the reasoning above, it seems sensible to expect that the simple fact that one ISP starts localizing its P2P traffic will be a strong incentive for the ISPs it peers with to do that as well.
作为上述推理的结果，一个ISP开始对其P2P流量进行本地化这一简单事实似乎是合理的，这将有力地激励与其对等的ISP也这样做。
It's worth noting that traffic manipulation techniques have been reportedly used by ISPs to obtain peering agreements [Norton] with larger ISPs. One of the most used techniques involves injecting forged traffic into the target ISP's network, in order to increase its transit costs. Such a technique aims at increasing the relevance of the source ISP in the target's transit bill and thus motivate the latter to sign a peering agreement. However, traffic injection is exclusively unidirectional and easy to detect. On the other hand, if
值得注意的是，据报道，ISP使用流量操纵技术与大型ISP达成对等协议[Norton]。最常用的技术之一是将伪造流量注入目标ISP的网络，以增加其传输成本。这种技术旨在增加源ISP在目标传输账单中的相关性，从而促使后者签署对等协议。然而，流量注入完全是单向的，易于检测。另一方面，如果
a localization-like service were used to direct P2P requests toward the target network, the resulting traffic would appear fully legitimate and, since in popular applications that follow the tit-for-tat approach peers tend to upload to the peers they download from, in many cases also bidirectional.
使用类似本地化的服务将P2P请求定向到目标网络，由此产生的流量将完全合法，因为在采用针锋相对方法的流行应用程序中，对等方倾向于上传到他们下载的对等方，在许多情况下也是双向的。
Likely.
可能的
One of the main goals of P2P traffic localization techniques is to allow ISPs to keep local a part of the traffic generated by their customers and thus save on transit costs. However, similar techniques based on de-localization rather than localization may be used by those ISPs that are also transit providers to artificially increase the amount of data exchanged with networks to which they provide transit (i.e., pushing the peers run by their customers to establish connections with peers in the networks that pay them for transit).
P2P流量定位技术的主要目标之一是允许ISP保留其客户产生的部分本地流量，从而节省运输成本。然而，同样是交通服务提供商的ISP可能会使用基于非本地化而非本地化的类似技术，人为地增加与他们提供交通服务的网络交换的数据量（即，推动其客户运行的对等方与网络中为其付费的对等方建立连接）。
No significant publications, simulations or trials have tried to study effects of traffic localization techniques on the dynamics of transit provision economics.
没有重要的出版物、模拟或试验试图研究交通本地化技术对交通供给经济学动态的影响。
It is actually very hard to predict how the economics of transit provision would be affected by the tricks some transit providers could play on their customers making use of P2P traffic localization -- or, in this particular case, de-localization -- techniques. This is also a key topic for ISPs, definitely worth an accurate investigation.
事实上，很难预测公交服务的经济性将如何受到一些公交服务提供商利用P2P流量本地化（或者，在这种特殊情况下，取消本地化）技术对其客户的把戏的影响。这也是ISP的一个关键话题，绝对值得进行准确的调查。
Probably, the only lesson transit and peering agreement have taught us so far [CogentVsAOL] [SprintVsCogent] is that, at the end of the day, no economic factor, no matter how relevant it is, is able to isolate different networks from each other.
也许，到目前为止，传输和对等协议给我们的唯一教训是，归根结底，任何经济因素，无论多么相关，都无法将不同的网络相互隔离。
Likely.
可能的
Peer selection techniques based on locality information are certainly beneficial in areas where the density of peers is high enough, but may cause damages otherwise. Some studies have tried to understand to what extent locality can be pushed without damaging peers in isolated parts of the network.
基于位置信息的对等选择技术在对等点密度足够高的领域肯定是有益的，但在其他方面可能会造成损害。一些研究试图了解在不损害网络孤立部分的对等点的情况下，可以将局部性推到何种程度。
1. Experiments with real BitTorrent clients run by researchers at INRIA [LeBlond] have shown that, in BitTorrent, even when peer selection is heavily based on locality, swarms do not get damaged.
1. INRIA[LeBlond]研究人员对真实BitTorrent客户端进行的实验表明，在BitTorrent中，即使对等选择在很大程度上基于位置，群集也不会受到破坏。
2. Simulations by Bell Labs [Seetharaman] indicate that the user experience can suffer in certain locality-aware swarms based on the actual implementation of locality.
2. 贝尔实验室（Bell Labs）[Seetharaman]的模拟表明，基于本地性的实际实现，用户体验可能会在某些具有本地性的集群中受到影响。
It seems reasonable to expect that excessive traffic localization will cause some degree of deterioration in P2P swarms based on the tit-for-tat approach, and the damages of such deterioration will likely affect most users in networks with lower density of peers. However, while [LeBlond] shows that BitTorrent is extremely robust, the level of tolerance to locality for different P2P algorithms should be evaluated on a case-by-case basis.
基于针锋相对的方法，过度的流量本地化可能会导致P2P集群出现一定程度的恶化，这种恶化的损害可能会影响到节点密度较低的网络中的大多数用户。然而，尽管[LeBlond]表明BitTorrent非常健壮，但不同P2P算法对局部性的容忍程度应根据具体情况进行评估。
Plausible, in some circumstances.
在某些情况下，这是有道理的。
P2P caching has been proposed as a possible solution to reduce cross-domain as well as uplink P2P traffic. Since the cache servers ultimately act as seeders, a cache-aware localization service would allow a seamless integration of a caching infrastructure with P2P applications [EDGE-CACHES].
P2P缓存已经被提出作为一种可能的解决方案，以减少跨域以及上行P2P流量。由于缓存服务器最终充当种子服务器，缓存感知本地化服务将允许缓存基础设施与P2P应用程序的无缝集成[边缘缓存]。
1. A traffic analysis performed in a major Israeli ISP [Leibowitz] has shown that P2P traffic has a theoretical caching potential of 67% byte-hit-rate.
1. 以色列一家主要ISP[Leibowitz]进行的流量分析表明，P2P流量的理论缓存潜力为67%的字节命中率。
P2P caching may be beneficial for both ISPs and network users, and locality-based optimizations may help the ISP to direct the peers towards caches. Anyway, it is hard to figure at this point in time if the positive effects of localization will make caching superfluous or not economically justifiable for the ISP.
P2P缓存可能对ISP和网络用户都有利，基于位置的优化可能有助于ISP将对等点指向缓存。无论如何，现在很难判断本地化的积极影响是否会使缓存变得多余，或者ISP在经济上不合理。
Plausible, if cost-effective for the ISP.
如果对ISP来说是经济高效的，那么这是合理的。
This document is a compendium of observed issues in peer-to-peer networks with an informed look at whether the issue is known to actually exist in the network or whether the issue is, well, a non-issue. As such, this document does not introduce any new security considerations in peer-to-peer networks.
本文件是对点对点网络中观察到的问题的概述，对该问题是否已知在网络中实际存在或该问题是否为非问题进行了了解。因此，本文档不会在对等网络中引入任何新的安全注意事项。
This documents tries to summarize discussions that happened in live meetings and on several mailing lists: all those who are reading this have probably contributed more ideas and more material than the authors themselves.
本文档试图总结现场会议和几个邮件列表中发生的讨论：所有阅读本文档的人可能都比作者自己贡献了更多的想法和材料。
[ALTO] "Application-Layer Traffic Optimization (ALTO) Working Group", <http://ietf.org/html.charters/alto-charter.html>.
[ALTO]“应用层流量优化（ALTO）工作组”<http://ietf.org/html.charters/alto-charter.html>.
[Aggarwal] Aggarwal, V., Feldmann, A., and C. Scheidler, "Can ISPs and P2P systems co-operate for improved performance?", in ACM SIGCOMM Computer Communications Review, vol. 37, no. 3.
[Aggarwal]Aggarwal，V.，Feldmann，A.，和C.Scheidler，“ISP和P2P系统能够合作提高性能吗？”，载于《ACM SIGCOMM计算机通信评论》，第37卷，第3期。
[Choffnes] Choffnes, D. and F. Bustamante, "Taming the Torrent: A practical approach to reducing cross-ISP traffic in P2P systems", in ACM SIGCOMM Computer Communication Review, vol. 38, no. 4.
[Choffnes]Choffnes，D.和F.Bustamante，“驯服洪流：减少P2P系统中跨ISP流量的实用方法”，载于ACM SIGCOMM Computer Communication Review，第38卷，第4期。
[CogentVsAOL] Noguchi, Y., "Peering Dispute With AOL Slows Cogent Customer Access", appeared in the Washington Post, December 17, 2002.
2002年12月17日，《华盛顿邮报》刊登了Y.Noguchi的一篇文章，“与AOL的对等纠纷减缓了可信的客户访问”。
[EDGE-CACHES] Weaver, N., "Peer to Peer Localization Services and Edge Caches", Work in Progress, March 2009.
[边缘缓存]Weaver，N.，“点对点本地化服务和边缘缓存”，正在进行的工作，2009年3月。
[LeBlond] Le Blond, S., Legout, A., and W. Dabbous, "Pushing BitTorrent Locality to the Limit", <http://hal.inria.fr/>.
[LeBlond]Le Blond，S.，Legout，A.，和W.Dabbous，“将BitTorrent本地化推向极限”<http://hal.inria.fr/>.
[Leibowitz] Leibowitz, N., Bergman, A., Ben-Shaul, R., and A. Shavit, "Are file swapping networks cacheable? Characterizing p2p traffic", in proceedings of the 7th Int. WWW Caching Workshop.
[Leibowitz]Leibowitz，N.，Bergman，A.，Ben Shaul，R.，和A.Shavit，“文件交换网络可缓存吗？p2p流量的特征”，发表于第七届国际WWW缓存研讨会论文集。
[Norton] Norton, W., "The art of Peering: The peering playbook", <http://d.drpeering.net/>.
诺顿，W.，“窥视的艺术：窥视剧本”<http://d.drpeering.net/>.
[RFC5632] Griffiths, C., Livingood, J., Popkin, L., Woundy, R., and Y. Yang, "Comcast's ISP Experiences in a Proactive Network Provider Participation for P2P (P4P) Technical Trial", RFC 5632, September 2009.
[RFC5632]Griffiths，C.，Livingood，J.，Popkin，L.，Woundy，R.，和Y.Yang，“康卡斯特在主动网络提供商参与P2P（P4P）技术试验中的ISP经验”，RFC 56322009年9月。
[RFC5693] Seedorf, J. and E. Burger, "Application-Layer Traffic Optimization (ALTO) Problem Statement", RFC 5693, October 2009.
[RFC5693]Seedorf，J.和E.Burger，“应用层流量优化（ALTO）问题陈述”，RFC 5693，2009年10月。
[Seetharaman] Seetharaman, S., Hilt, V., Rimac, I., and M. Ammar, "Applicability and Limitations of Locality-Awareness in BitTorrent File-Sharing".
[Seetharaman]Seetharaman，S.，Hilt，V.，Rimac，I.，和M.Ammar，“BitTorrent文件共享中位置感知的适用性和局限性”。
[SprintVsCogent] Ricknas, M., "Sprint-Cogent Dispute Puts Small Rip in Fabric of Internet", PCWorld Article, October 2008, <http://www.pcworld.com/businesscenter/article /153123/sprintcogent_dispute_puts_small_rip_in_ fabric_of_internet.html>.
[SprintVsCogent]Ricknas，M.，“Sprint Cogent争端在互联网结构中造成了小裂痕”，《PCWorld》文章，2008年10月<http://www.pcworld.com/businesscenter/article /153123/sprintcogent\u争端\u将\u small\u rip\u放入\u internet.html>的\u fabric\u中。
[Xie] Xie, H., Yang, Y., Krishnamurthy, A., Liu, Y., and A. Silberschatz, "P4P: Explicit Communications for Cooperative Control Between P2P and Network Providers", in ACM SIGCOMM Computer Communication Review, vol. 38, no. 4.
[Xie]Xie，H.，Yang，Y.，Krishnamurthy，A.，Liu，Y.，和A.Silberschatz，“P4P：P2P和网络提供商之间合作控制的显式通信”，载于ACM SIGCOMM计算机通信评论，第38卷，第4期。
Appendix A. Myths/References/Facts Matrix
附录A.神话/参考文献/事实矩阵
+----------------------+-------+-----------+------------+-----------+
| | [Xie] | [RFC5632] | [Aggarwal] | [LeBlond] |
+----------------------+-------+-----------+------------+-----------+
| Cross-Domain Traffic | X | X | X | X |
| (Section 3.1) | | | | |
| Application | X | X | X | X |
| Performance | | | | |
| (Section 3.2) | | | | |
| Uplink Bandwidth | | X | | |
| (Section 3.3) | | | | |
| Impacts on Peering | | | | |
| (Section 3.4) | | | | |
| Impacts on Transit | | | | |
| (Section 3.5) | | | | |
| Swarm Weakening | | | | X |
| (Section 3.6) | | | | |
| Improved P2P Caching | | | | |
| (Section 3.7) | | | | |
+----------------------+-------+-----------+------------+-----------+
+----------------------+-------+-----------+------------+-----------+
| | [Xie] | [RFC5632] | [Aggarwal] | [LeBlond] |
+----------------------+-------+-----------+------------+-----------+
| Cross-Domain Traffic | X | X | X | X |
| (Section 3.1) | | | | |
| Application | X | X | X | X |
| Performance | | | | |
| (Section 3.2) | | | | |
| Uplink Bandwidth | | X | | |
| (Section 3.3) | | | | |
| Impacts on Peering | | | | |
| (Section 3.4) | | | | |
| Impacts on Transit | | | | |
| (Section 3.5) | | | | |
| Swarm Weakening | | | | X |
| (Section 3.6) | | | | |
| Improved P2P Caching | | | | |
| (Section 3.7) | | | | |
+----------------------+-------+-----------+------------+-----------+
+------------------------+------------+---------------+-------------+
| | [Choffnes] | [Seetharaman] | [Leibowitz] |
+------------------------+------------+---------------+-------------+
| Cross-Domain Traffic | | | |
| (Section 3.1) | | | |
| Application | X | X | X |
| Performance | | | |
| (Section 3.2) | | | |
| Uplink Bandwidth | | | |
| (Section 3.3) | | | |
| Impacts on Peering | | | |
| (Section 3.4) | | | |
| Impacts on Transit | | | |
| (Section 3.5) | | | |
| Swarm Weakening | | X | |
| (Section 3.6) | | | |
| Improved P2P Caching | | | X |
| (Section 3.7) | | | |
+------------------------+------------+---------------+-------------+
+------------------------+------------+---------------+-------------+
| | [Choffnes] | [Seetharaman] | [Leibowitz] |
+------------------------+------------+---------------+-------------+
| Cross-Domain Traffic | | | |
| (Section 3.1) | | | |
| Application | X | X | X |
| Performance | | | |
| (Section 3.2) | | | |
| Uplink Bandwidth | | | |
| (Section 3.3) | | | |
| Impacts on Peering | | | |
| (Section 3.4) | | | |
| Impacts on Transit | | | |
| (Section 3.5) | | | |
| Swarm Weakening | | X | |
| (Section 3.6) | | | |
| Improved P2P Caching | | | X |
| (Section 3.7) | | | |
+------------------------+------------+---------------+-------------+
Authors' Addresses
作者地址
Enrico Marocco Telecom Italia
Enrico Marocco意大利电信公司
EMail: enrico.marocco@telecomitalia.it
EMail: enrico.marocco@telecomitalia.it
Antonio Fusco Telecom Italia
安东尼奥·福斯科意大利电信公司
EMail: antonio2.fusco@telecomitalia.it
EMail: antonio2.fusco@telecomitalia.it
Ivica Rimac Bell Labs, Alcatel-Lucent
艾维卡Rimac贝尔实验室，阿尔卡特朗讯
EMail: rimac@bell-labs.com
EMail: rimac@bell-labs.com
Vijay K. Gurbani Bell Labs, Alcatel-Lucent
阿尔卡特朗讯Vijay K.Gurbani Bell实验室
EMail: vkg@bell-labs.com
EMail: vkg@bell-labs.com