P2PRG S. Kamei Internet-Draft NTT Corporation Intended status: Informational T. Momose Expires: November 21, 2010 Cisco Systems T. Inoue T. Nishitani NTT Communications May 20, 2010 ALTO-Like Activities and Experiments in P2P Network Experiment Council draft-kamei-p2p-experiments-japan-03 Abstract This document provides some suggestions about ALTO architecture through experiments made by P2P Network Experiment Council in Japan. This document also introduces experiments made by the Council in Japan to harmonize P2P technology with the infrastructure. Specifically, this document describes Hint Server technology, which is similar to ALTO technology. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Background in Japan . . . . . . . . . . . . . . . . . . . . . 3 2.1. P2P traffic . . . . . . . . . . . . . . . . . . . . . . . 3 2.2. Impact on network infrastructure . . . . . . . . . . . . . 4 3. The object of P2P Network Experiment Council . . . . . . . . . 5 4. Activity in P2P Network Experiment Council . . . . . . . . . . 6 4.1. Dummy Node . . . . . . . . . . . . . . . . . . . . . . . . 6 4.2. Hint Server ('08) . . . . . . . . . . . . . . . . . . . . 6 4.3. Difference between P4P and Hint Server technology . . . . 10 4.4. Difference between ALTO and Hint Server technology . . . . 12 5. High-Level Trial Results . . . . . . . . . . . . . . . . . . . 12 5.1. Peer Selection with P2P . . . . . . . . . . . . . . . . . 13 5.2. Peer Selection with the Hint Server . . . . . . . . . . . 13 6. Next steps . . . . . . . . . . . . . . . . . . . . . . . . . . 13 7. Feedback to ALTO WG . . . . . . . . . . . . . . . . . . . . . 14 7.1. Harmonizing a Hint Server with ALTO . . . . . . . . . . . 14 7.2. Measurement mechanism . . . . . . . . . . . . . . . . . . 15 8. Security Considerations . . . . . . . . . . . . . . . . . . . 15 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15 11. Informative References . . . . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 Kamei, et al. Expires November 21, 2010 [Page 2] Internet-Draft P2P Experiments Japan May 2010 1. Introduction An overlay network, which is used by P2P and other applications, offers the advantage of allowing flexible provision of services while hiding the lower layer network. The downside is that inefficient routes are often taken in the lower IP network, thereby increasing the network load. Several proposals have been made to build an overlay network that takes account of the information about the lower layer network. Since the management of the Internet is highly distributed, it is difficult to implement such proposals and thus optimize a network without the cooperation of network providers. Recently, the controversy between the overlay network and the network providers have been rekindled. Under these circumstances, some researchers have studied overlay network control technology that takes account of the network topology information obtained from network providers. One of activities concerning this issue has been made by the P2P Network Experiment Council in Japan. This document reports on the issues addressed and experiments being made by the P2P Network Experiment Council in Japan, focusing on the experiments made from 2007 to 2008. 2. Background in Japan 2.1. P2P traffic In Japan, the major of P2P applications used today is Winny. P2P applications are the sources of a considerable volume of traffic. Recent study [1] showed more than 60% of Internet traffic in Japan is generated by P2P applications. Although traffic from P2P applications increased much more rapidly than traffic from client-server-type web applications, it has leveled off lately as a result of legal restrictions advocated by copyright management organizations and traffic control implemented by ISPs. According to [2], video delivery sites using Flash has again increased volume of web traffic per user, making P2P traffic relatively less conspicuous than before. Consequently, some believe that P2P traffic is no longer a threat to the infrastructure. P2P applications, however, rapidly became widely used to get around the limit of the servers' capacity, which was caused by the increase in demand for delivery of music files. It is likely that the traffic of client-server video delivery will shift to P2P delivery. Kamei, et al. Expires November 21, 2010 [Page 3] Internet-Draft P2P Experiments Japan May 2010 In fact, some P2P content delivery systems solve copyright issues, for example, Sharecast, Ocean-Grid, TVBand, and so on. The transmission of President Obama's Inaugural Address, which is the largest-scale transmission of content in recent history, was mostly of the client-server type. However, the delivery by CNN used a P2P plug-in made by Octoshape. Traffic data observed by Illinois University revealed unique traffic patterns that the upstream traffic exceeded the downstream traffic. 2.2. Impact on network infrastructure One of advantage of using P2P technology for content delivery is that peers exchange content directly among themselves. This reduces the physical load on servers . Also, P2P applications can reduce upstream traffic from an original content server. This is significant that the charge for upstream traffic is usually traffic- sensitive for content delivery services, and it is not negligible. Actually, the volume of traffic sent by the content server in TVBank's P2P content delivery was reduced by a maximum of 96% compared with the volume of traffic received by users [3]. This indicates the great cost-saving of P2P technology from the perspectives of the load on server hardware and the traffic relaying cost of data centers. However, the story is quite different for network providers. From 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. Another problem for network providers that an extremely inefficient routing may be selected has been raised. It is because overlay network systems are configured without any regard to the structure of the lower layer network or network geometry. Traffic on the Internet used to be limited by the capacity of servers. Today the improvement in the scalability of servers has made it likely that network resources will be used up before server resources are. Using P2P applications increases the volume of traffic per user remarkably. Faced with increase in the load on network infrastructure, network providers are compelled to take actions to overcome the sudden increase in facilities' cost. Representative actions include placing content in IXs or data centers, introducing bandwidth control, and raising the access fees [2]. In the future, video posting sites, which has been delivered using client-server applications, may adopt P2P system. The increase in traffic arising from such a shift will be a great threat to the network. Kamei, et al. Expires November 21, 2010 [Page 4] Internet-Draft P2P Experiments Japan May 2010 3. The object of P2P Network Experiment Council 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 from 2006 to 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 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 formed a "Working Group on the P2P Network", which carried out an intensive study of P2P networks. The Working Group reported that it is necessary to undertake the following four activities, which are intended to encourage the government to adopt relevant policies [4]: o Formulate guidelines to be self-imposed by the industry on P2P file delivery applications, o Promote feasibility tests of P2P networks, o Study the current state of traffic control and promote the sharing of information, o Hold working group meetings on traffic control. The first two proposals led to the establishment of the P2P Network Experiment Council supported by the Japanese Ministry of Internal Affairs and Communications [5]. 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, which takes a relatively top-down approach of adopting architecture based on a proposal from a university, the Council is characterized by its bottom-up approach. The aim of establishing the Council has been described as follows. The rapid growth of broadband access enables content delivery system 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 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. Kamei, et al. Expires November 21, 2010 [Page 5] Internet-Draft P2P Experiments Japan May 2010 The activities of the P2P Network Experiment Council can be classified into two categories. The first is activities to formulate guidelines for the promotion of the commercial use of P2P technology. These will enable users to use P2P technology safely, and providers to have clear rules they must observe. The other is feasibility tests of P2P technology. The next section mainly reports on experiments conducted from 2007 to 2008. 4. Activity in P2P Network Experiment Council 4.1. Dummy Node While the effect of delivery using P2P technology on reducing the traffic and the load on servers is well known, traffic behavior in the Internet is not known. However, 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. To solve this problem, dummy nodes have been introduced. Dummy nodes have been settled in the Internet and P2P applications have been installed on these nodes. Dummy nodes enable us to measure and analyze communication among peers. Specifically, Linux servers were installed at 40 sites of some ISPs, and a virtual Windows environment was installed on the servers. P2P applications which were target to measure were running on that environment, and packets were captured by a Linux program to obtain information on communication destinations and communication frequencies. 4.2. Hint Server ('08) In Japan, bottleneck in IP networks will shift from access networks to backbone networks and equipments, such as bandwidth between ISPs and capacity in IXs, since FTTH has rapidly spread all over Japan. Under this situation. the Council proposed a less restrictive and more flexible cooperation between ISPs than ALTO. The proposed method consists of the following elements: (1) P2P clients, (2) P2P control servers, and (3) a peer selection hint server, and a Hint Server. (1) and (2) are existing systems but whether (2) exists depends on each application. (3) is a server that provides a hint as to the selection of a peer, and plays a role equivalent to that of iTracker in P4P's study. 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 districts or ISPs through providing information about the physical network to P2P applications. Kamei, et al. Expires November 21, 2010 [Page 6] Internet-Draft P2P Experiments Japan May 2010 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 makes a mapping of the new peer (P2P client) based on network topology information obtained from the ISP, generates a routing table in which peers are listed in the order of priority for selection, and returns the table to the peer. If all information can be made public, the above procedure can produce a result which is close to overall optimization. However, some information held by ISPs can often be confidential. Besides, in some cases, the volume of calculation required to process all information can be excessive. To avoid these problems, it is planned to conduct experiments with a limited set of functions, analyze experiment results, and gradually expand the scope of optimization. A control mechanism that makes use of all possible information is difficult not only technically but also because it is difficult to achieve coordination among providers. In consideration of these difficulties, the P2P Network Experiment Council has been limiting the implementation and experiments to the following scope since 2006. Figure 1 shows an outline of the hint server. +---------+ GetLocation +-------------GeoIP DB Server---------+ | | +-----------+ | +----------+ +-----------+ | | |--|IP Address |-->| | GeoIP DB | |Quagga etc | | | | +-----------+ | +----------+ +-----------+ | | | | +-------------+ +----------------+ | | | +-----------+ | | District | | Routing | | | |--|AS Code: |---| | information | |information(DGP)| | | | |Regional | | | | | | | |P2P Peers| |Information| | | Range of | |AS Code(origin) | | | or | +-----------+ | | IP address | | | | | Contro| | | +-------------+ +----------------+ | | Server | +-------------------------------------+ | | | ^ | | PeerSelection v | | | +-----------+ +--------------------------------------+ | |--|IP Address |-->| +--Prioryty Node Selection System--+ | | | | List | | | | | | | +-----------+ | | Peer candidate ranking | | | | +-----------+ | | | | | |--| Ranking |-->| +----------------------------------+ | | | +-----------+ +--------------------------------------+ +---------+ Figure 1 Kamei, et al. Expires November 21, 2010 [Page 7] Internet-Draft P2P Experiments Japan May 2010 The network information used by the Hint Server is not information solicited from individual ISPs but the AS number and district information, which are more or less already public. 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. When the Hint Server receives an IP address, it returns its attribute information, to achieve the above. A peer can select a peer 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. Although the priority 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 ratio of peers within the same AS or the same prefecture calculated from the distribution of ASs and prefectures in the IP address space from one-day data on a Winny network. +--------------------+--------+ | Conditions | ratio | +--------------------+--------+ | AS matches | 6.70% | | Prefecture matches | 12.76% | | Both match | 2.09% | | Neither match | 78.45% | +--------------------+--------+ Table 1: AS and prefecture distributions Since, in addition to the above, the presence/absence of content affects the result, the control of selecting a peer 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. In consideration of the above, the following two measures are used for the evaluation of proximity between peers in a Hint Server. o AS path length (distance between ISPs) Distances between peers are weighted using the degree of paths' matching from an origin AS to ASs that target peers belong to. The degree of paths' matching means ratio of common paths from an Kamei, et al. Expires November 21, 2010 [Page 8] Internet-Draft P2P Experiments Japan May 2010 origin AS (for example, 4/6 between A-B-C, and A-B-D, 6/8 between A-B-C-D and A-B-C-E). In this year, the OCN is used as an origin AS. Distance is calculated as int((1.0- degree of matching of AS paths)*15). Distance is 15 if either of AS path is indefinite, and is 0 if there is a perfect match. o Physical distance Distances between peers are measured using physical distance of prefectural capitals that target peers belong to. The distance between prefectural capitals is used to calculate physical distance. Distances between prefectural capitals are sorted into ascending order, and then into bands, with weights 1 to 15 assigned to them so that there are a more or less equal number of "capital pairs" in each band. If either of their location is indefinite, distance is equal to 15 and, if they are in the same prefecture, distance is equal to 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 expands the area where the control by a Hint Server is effective. An example of the request and the response o Request 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=transcation ID] [pt=Flag of port type] [ub=upload bandwidth] [db=download bandwidth] Kamei, et al. Expires November 21, 2010 [Page 9] Internet-Draft P2P Experiments Japan May 2010 o Response 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 respond peer n=[src address] dst address / cost / option 4.3. Difference between P4P and Hint Server technology To explain difference between P4P and Hint Server technology, the architecture proposed by P4P is described. P4P aims to control traffic in such a way that traffic is confined within the same district or AS. As shown in Figure 2, iTracker provides an interface for P2P content delivery using appTracker and peers in BitTorrent. This arrangement provides a framework for efficient control based on network information. In this framework, it is proposed that ISPs and applications share the following types of information through iTracker: o Info: information about peers within an ISP - ASID AS number - Group number of PID node (peer) - LOC: virtual and geographical coordinates o Policy: information about policy on usage specified by an ISP - Ratio between outgoing traffic and incoming traffic that flows between domains Kamei, et al. Expires November 21, 2010 [Page 10] Internet-Draft P2P Experiments Japan May 2010 - Desirable daily traffic variation pattern on a link - Specifications about relations between peer groups (PID) o Capability: information about the capability of an ISP - Information about usable service classes - Information about the cache server Note that [6] reports on the results of a field test in which it was attempted to reduce overall traffic by using the above concept to confine traffic exchange destinations to within the same ISP or the same city. It reports that, in an evaluation with a Verizon network, traffic to locations outside an ISP was reduced by 30 to 50% and that the ratio of inter-city traffic to Verizon's total traffic was more or less halved. ISP +------------------------+ Internet | +----------------+ | +------------+ | | iTracker | | | appTracker | | | *Info |--------> +------------+ | | *Policy | | ^ | | *capability | | | | +----------------+ | | | | | | +----------------+ | | | | Peer |----------------+ | +----------------+ | +------------------------+ Figure 2 Comparing P4P with Hint Server technology, the following three differences are observed: o Target of optimization: P4P technology focuses on optimization within an ISP, while Hint Server technology focuses on optimization in backbone traffic. o Target applications: P4P technology focuses on supporting BitTorrent, while Hint Server technology does not specify any P2P applications. Kamei, et al. Expires November 21, 2010 [Page 11] Internet-Draft P2P Experiments Japan May 2010 o Strength of cooperation between P2P providers and ISPs: P4P technology requires close cooperation between ISPs and P2P providers, while Hint Server technology does not require. 4.4. Difference between ALTO and Hint Server technology ALTO technology is more general approach than P4P technology. And Hint Server technology has more similar focus of this technology. Hint Server offers similar information of ALTO service and can easily supports following ALTO Services. o Map Service The cost type is computed by physical distance and AS path length, and the mode is numerical. PID information, it is same as AS and physical location, does not offered to client. o Map Filtering Service o Endpoint Cost Service Hint Server only offers map information associated with requested IP addresses. ALTO framework has more generality but the following two points are not sufficiently improved or some operational solution should be offered. o Target of optimization: ALTO technology focuses on optimization within an ISP, while Hint Server technology focuses on optimization in backbone traffic. o Strength of cooperation between P2P providers and ISPs: ALTO technology requires close cooperation between ISPs and P2P providers, while Hint Server technology does not require. 5. High-Level Trial Results Kamei, et al. Expires November 21, 2010 [Page 12] Internet-Draft P2P Experiments Japan May 2010 5.1. Peer Selection with P2P Table 2 shows the result of the analysis of communication in a node of an ISP installed in Tokyo, as an example of measurement results. +-----------------------------------------+------------+------------+ | Conditions | Experiment | Experiment | | | 1 | 2 | +-----------------------------------------+------------+------------+ | *Peers selected within the same ISP | 22% | 29% | | *Peers selected within the same | 19% | 23% | | district | | | | *Peers selected within the same | 5% | 7% | | district and the same ISP | | | +-----------------------------------------+------------+------------+ Table 2: Percentage of communication within the same ISP The table shows that the probability of communication with peers in the same ISP is proportional to the number of population 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 this experiment explained that the mechanism of selection 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. 5.2. Peer Selection with the Hint Server Since the main objective of this experiment was to verify the operations of the Hint Server and P2P applications, the degree to which traffic in the network was actually reduced was not evaluated. However, 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 mean value of distance after the Hint Server was introduced was reduced by 10% and that 95% value of that was reduced by 5%. 6. Next steps This document has reported on activities aimed at achieving cooperative control between the P2P/overlay network and the network infrastructure. Specifically, it has described issues to be addressed and the activities of the P2P Network Experiment Council in Japan, which was established to address these issues. It has also introduced the Council's activities, from 2007 to 2008, focusing on the use of a Hint Server, which is a feature of the traffic Kamei, et al. Expires November 21, 2010 [Page 13] Internet-Draft P2P Experiments Japan May 2010 engineering mechanism proposed by the Council. The P2P Network Experiment Council has been renamed the Advanced Network Use Promotion Council. The new Council aims to create new network services suitable for the broadband environment and to promote the widespread use of such services in rural areas. It has expanded its scope of work to include all cache technologies, including P2P technology. It will promote more advanced use of the network by encouraging an exchange of views among a broad spectrum of parties on how to use the network effectively, and by supporting a variety of feasibility tests. The Council aims to continue the analysis of the experiment results obtained, and further study by involving a wider spectrum of P2P providers, network providers and delivery service providers. 7. Feedback to ALTO WG This section describes what the authors learned with this experiment would be useful for the ALTO WG. 7.1. Harmonizing a Hint Server with ALTO As described before, a Hint Server control mechanism focuses on control between ISPs, while ALTO does control within an ISP. Generally speaking, control mechanism that a peer chooses a replica from its neighbors shows higher performance when probability of a peer having a content is higher. This means ISP cooperation mechanism that enlarges area in choosing peers will have much impact on P2P performance. The authors consider combination of these two mechanisms produce better P2P performance. The authors propose hierarchical structure to harmonize a Hint Server with ALTO. From viewpoint of cooperation between ISPs, fine information is not necessarily required and it is difficult to exchange fine information between ISPs. Considering this situation, the authors use only coarse information to control backbone traffic in the experiments this year, though demand of controlling traffic within an ISP using fine information will arise in the near future. The authors consider that introducing hierarchical structure into ALTO is necessary to cope with both situations. Actually, the authors plan to try a hierarchical control mechanism in the next steps, which include the following two steps. o In the first step, coarse information about whole the network is used to select ISPs. Kamei, et al. Expires November 21, 2010 [Page 14] Internet-Draft P2P Experiments Japan May 2010 o Next, fine information within the ISP is used to select a peer. 7.2. Measurement mechanism In experiments, there were two difficulties as follows: o Evaluating effect of introducing a Hint Server was difficult, since P2P applications had their own measurement mechanisms. o How to treat priority orders of peers suggested by a Hint Server could not be predetermined for P2P applications. From these experiences, the authors consider that clarifying requirements about measurement mechanisms for P2P applications are necessary also in Alto. 8. Security Considerations There are no security considerations in this document. 9. IANA Considerations No need to describe any request regarding number assignment. 10. Acknowledgments These experiments were performed under cooperation among P2P Network Experiment Council members, and DREAMBOAT co.,ltd., Bitmedia Inc., Utagoe. Inc. and Toyama IX have especially supported analyses of the experimernts. The authors appreciate Tohru Asami, Hiroshi Esaki and Tatsuya Yamshita for their constructive comments. 11. Informative References [1] Hiroshi Esaki, "The State of Traffic and the Effects of P2P", Special Symposium on Broadband, September 2008 (in Japanese). [2] Yoichi Yamazaki, "ISPs have Begun to Explore Tomorrow due to the Expansion of Traffic", Nikkei Communications, December 2007 (in Japanese). [3] TVBank, "Live Delivery using `BB Broadcast'Achieving 96% Saving in Traffic!", http:.wwww.tv-bank.com/jp/20081031.html, 2008 (in Japanese). Kamei, et al. Expires November 21, 2010 [Page 15] Internet-Draft P2P Experiments Japan May 2010 [4] Ministry of Internal Affairs and Communications, "Disclosure of the Report `Working Group on P2P Networks'", http://www.soumu.go.jp/menu_news/s-news/2007/070629_11.html, 2007 (in Japanese). [5] The Foundation for MultiMedia Communications, "The P2P Network Experiment Council", http://www.fmmc.or.jp/P2P/about.htm, 2007 (in Japanese). [6] Open P4P, "P4P Field Tests: Yale-Pando-Verizon", http://www.openp4p.net/front/fieldests, 2009. Authors' Addresses Satoshi Kamei NTT Service Integration Laboratories 3-9-11, Midori-cho Musashino-shi, Tokyo 180-8585 JP Phone: +81-422-59-6942 Email: kamei.satoshi@lab.ntt.co.jp Tsuyoshi Momose Cisco Systems G.K. 2-1-1 Nishi-Shinjuku Shinjuku-ku, Tokyo 163-0409 JP Phone: +81-3-5324-4154 Email: tmomose@cisco.com Takeshi Inoue NTT Communications 3-4-1, Shibaura Minato-ku, Tokyo 108-8118 JP Phone: +81-3-6733-7177 Email: inoue@jp.ntt.net Kamei, et al. Expires November 21, 2010 [Page 16] Internet-Draft P2P Experiments Japan May 2010 Tomohiro Nishitani NTT Communications 1-2-20, Shibaura Minato-ku, Tokyo 108-8118 JP Phone: +81-50-3812-4742 Email: tomohiro.nishitani@ntt.com Kamei, et al. Expires November 21, 2010 [Page 17]