P2PRG                                                           S. Kamei
Internet-Draft                                           NTT Corporation
Intended status: Informational                                 T. Momose
Expires: March 8, 2012                                     Cisco Systems
                                                                T. Inoue
                                                            T. Nishitani
                                                      NTT Communications
                                                       September 5, 2011

 ALTO-Like Activities and Experiments in P2P Network Experiment Council


   This document introduces experiments to clarify how ALTO-like
   approach was effective to reduce network traffic made by a Council in
   Japan to harmonize P2P technology with the infrastructure.  And this
   also provides some suggestions that might be useful for ALTO
   architecture learned through our experiments.

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Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Background in Japan  . . . . . . . . . . . . . . . . . . . . .  3
     2.1.  P2P traffic  . . . . . . . . . . . . . . . . . . . . . . .  3
     2.2.  Impact on network infrastructure . . . . . . . . . . . . .  3
     2.3.  The object of P2P Network Experiment Council . . . . . . .  4
   3.  The details of the experiments . . . . . . . . . . . . . . . .  5
     3.1.  Dummy Node . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Hint Server ('08)  . . . . . . . . . . . . . . . . . . . . . .  6
   5.  High-Level Trial Results . . . . . . . . . . . . . . . . . . . 11
     5.1.  Peer Selection with P2P  . . . . . . . . . . . . . . . . . 11
     5.2.  Peer Selection with the Hint Server  . . . . . . . . . . . 11
   6.  Considerations . . . . . . . . . . . . . . . . . . . . . . . . 11
     6.1.  Next steps . . . . . . . . . . . . . . . . . . . . . . . . 12
     6.2.  Feedback to ALTO WG  . . . . . . . . . . . . . . . . . . . 12
       6.2.1.  Hierarchical architecture for ALTO servers . . . . . . 12
       6.2.2.  Measurement mechanism  . . . . . . . . . . . . . . . . 13
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   9.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 14
   10. Informative References . . . . . . . . . . . . . . . . . . . . 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14

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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 the 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 council, focusing
   on the experiments made from 2007 to 2008.

2.  Background in Japan

2.1.  P2P traffic

   As of 2008, the world most popular P2P file sharing application
   Bittorrent isn't widely deployed in Japan.  Instead, other Japan
   specific file sharing P2P applications such as Winny [1], Share [2],
   PerfectDark, and so on, still occupy 40% of the Internet traffic in
   Japan even though many those P2P users were arrested for sharing
   illegal files with these P2P apps.

   Each P2P file sharing application has their original protocol.
   Therefore, it is more difficult to control one by one unlike

2.2.  Impact on network infrastructure

   One of the advantage of using P2P technology for content delivery is
   that peers exchange content directly among themselves.  This reduces
   the 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.

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   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.  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.

   In some cases, traffic on the Internet used to be limited by the
   capacity of servers.  For those cases, 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[3].

   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

2.3.  The object of P2P Network Experiment Council

   In order to reduce Internet traffic and encourage legitimate use of
   P2P technologies, the Japanese government led to establish a new
   council called P2P Network Experiment Council conjunction with
   commercial P2P application vendors and ISPs in 2006.

   Then the council had started to develop regulations that include
   several guidelines such like an advance notice to restrict bandwidth
   to heavy traffic users.  In accordance with the regulations, some
   ISPs introduced solutions that reduce traffic caused by P2P file
   sharing applications .

   Besides this activity, the council also looked for new ways to avoid
   traffic conjunction by commercial P2P applications with ISPs,
   carriers, contents providers and P2P system vendors.  In this work,
   the council had experiments that introduced ALTO-like system and
   observed how the traffic was reduced by redirecting to proper peers
   on the real Internet in Japan.

   This memo describes the overview of the experiments.

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3.  The details of the experiments

   The council has already learned that the server cost could be reduced
   with using P2P technology for contents delivering by investigating
   data offered by the members of the council.  For example, the data
   brought by the vendors shows as follows:

      90% of traffic was reduced with UG Live by Utagoe Inc[4].

      The costs of delivering to tens of thousand subscribers was
      reduced to 1/5 with BBbroadcast with TV Bank Corp.[5]

   On the other hand, these reduced server costs may affect network
   load.  One of the goals of our experiments are to visualize the
   impacts and propose an architecture to reduce network load caused by
   these new technologies.

   To satisfy the above goals, the framework to be proposed should be
   well generalized as possible that doesn't rely specific P2P
   application behaviors because multi P2P application vendors join
   these experiments.  In addition, the traffic should be captured
   beyond multi ISPs.

3.1.  Dummy Node

   As mentioned before, while the effect of delivery using P2P
   technology on reducing the traffic and the load on servers is well
   known, traffic behavior in the inter-ISP is not known.  In Japan,
   there is a backbone traffic report cooperated with ISPs and IXes [6].
   However, this measurement requires to capture packets on subscribers
   line to know end user's activity.  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

   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 and P2P
   applications are running on the nodes.

   By introducing dummy nodes, we can observe and evaluate how much P2P
   applications have affected networks by measuring the traffic on dummy
   nodes.  Since this method can't measure every subscriber's traffic,
   the accuracy would be less than other methods.  But this make it
   possible to adapt to situations many different P2P applications
   coexist on a network.  We can say this is suitable for these

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   A dummy node consists of Intel PC server, Linux(CentOS), VMWare and
   Windows XP works on VMWare.  With this configuration, all packets can
   be captured without any impacts to the network, nodes and application
   behaviors.  And it enable us to use different P2P applications for
   windows and evaluate them generally.

   To see behaviors of the node, incoming and outgoing packets are
   captured on Linux because every packets are transmitted through it.
   In these experiments, we captured source/destination address, port
   number, amount of traffic and start/end time to see flow information.

   60 Dummy nodes are put on access networks that are closest subscriber
   as possible in different 40 networks.

   ||| P2P Application  |||
   |||    WindowsXP     |||
   |||        +--+      |||
   ||+--------|N |------+||
   ||  VMware |e |       ||
   |+---------|t |-------+|
   |   Linux  |IF| capture|
   +----------|  |--------+

   Dummy nodes

                                 Figure 1

4.  Hint Server ('08)

   In Japan, bottleneck in IP networks have been shifting 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 these circumstances, the Council proposed a less
   restrictive and more flexible cooperation between ISPs than existent
   P4P experiments [7].  The proposed method consists of the following
   elements: (1) P2P clients, (2) P2P control servers, and (3) a hint
   server: a peer selection 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 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 through

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   providing information about the physical network to P2P applications.

   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 publicly, 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
   experiments 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 difficulties to achieve
   coordination among providers.  In consideration of these
   difficulties, the council has been limiting the implementation and
   experiments to the following scope since 2006.

   Figure 2 shows an outline of the hint server.

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   +---------+   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 |-->| +--Priority Node Selection System--+ |
   |         |  |    List   |   | |                                  | |
   |         |  +-----------+   | |     Peer candidate ranking       | |
   |         |  +-----------+   | |                                  | |
   |         |--|  Ranking  |-->| +----------------------------------+ |
   |         |  +-----------+   +--------------------------------------+

                        Peer selection hint server

                                 Figure 2

   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.

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                      | 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)

      AS path length 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 of both ISPs is too
      large.  To avoid this, we use multiple BGP information gotten at
      different ISPs and combine them.  Based on this concept, we used
      BGP routing information's offered by three ISPs operated by big
      telecommunication couriers and made a topology tree.  Then it
      enables to calculate the shortest path between given two ASes.

   o  Geographical 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.

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   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_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]

   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
      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

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5.  High-Level Trial Results

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 these experiments 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 these experiments 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.  Considerations

   We clarified followings throughout our experiments.

   1.  Dispersed dummy nodes can figure out the behavior of peers and
       traffic between inter-ISP networks, which peers are selected by
       each peer.  Therefore it proves that the importance of peer

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       selection control mechanism proposed in ALTO.

   2.  Using our peer selection control mechanism, called hint server,
       could achieve significant differences.  Our hint server can lead
       each peer to select nearer peer.

   In the experimental result of peer selection control, it is smaller
   in intra-ISP traffic than other experiments[8] We think that it is
   because there are smaller 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 small peers in one ISP, it is
   difficult to select peers in the same ISP.  In the situation of our
   experiments, there are many ISPs of peers belonging, and there are
   relatively smaller peers exist in same ISP.

   Moreover, we didn't force P2P vendors to limit their implementation
   policy, therefore we can observe differences how each implementations
   weigh the information from the hint servers.  Especially, in tree
   overlay topology P2P applications, such mechanism is very effective,
   on the other hand, in mesh overlay system, less effective.

6.1.  Next steps

   The experiments are on going as of 2011.  Current experiments in
   2011, we've changed the communication protocol to hint servers to
   ALTO based because it is nearly standardized.  In our implementation,
   PIDs and the value of cost are mapped to ISP subnets, and ISP
   distance respectively.  We also implement services for compatibility
   required by ALTO such as Service Capability and Map Services.  But
   the Endpoint Cost Service is mainly used because of backward
   compatibility of our experiments.

   We also study hierarchical hint server structure, in order to control
   in coarse inter-ISPs and in detail intra-ISP.  It is also effective
   for limiting the area of information disclose.

6.2.  Feedback to ALTO WG

   This section describes what the authors learned with these
   experiments would be useful for the ALTO WG.

6.2.1.  Hierarchical architecture for ALTO servers

   In our experiments, we present the possibility of traffic control
   among multi-ISPs and multi-P2P applications using ALTO mechanism.  On
   the other hand, we found several problems in ISP operations to adapt
   the mechanism.  One is the granularity of network information.  Among
   inter-ISP area, it is relatively easy to treat information for public

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   purpose using BGP full route.  On the other hand, among intra-ISP
   area, it may be difficult to disclose private information of each
   ISP. [9] propose some modification for 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 and moreover it is difficult to exchange the
   fine-grained information between ISPs.  Considering this situation,
   the authors use only coarse-grained information to control backbone
   traffic in the experiments this year, though demand of controlling
   traffic within an ISP using fine-grained information will arise in
   the near future.  Therefore it led us that introducing hierarchical
   structure into ALTO is necessary to cope with both situations.
   Actually, the authors plan to adapt a hierarchical control mechanism
   in the next steps, which include the following two steps.

   o  In the first step, coarse-grained information about whole the
      network is used to select ISPs.

   o  Next, fine-grained information within the ISP is used to select a

6.2.2.  Measurement mechanism

   In the 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.

7.  Security Considerations

   This document does not propose any kind of protocol, practice or

8.  IANA Considerations

   No need to describe any request regarding number assignment.

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9.  Acknowledgments

   Thanks to strong support by MIC (Ministry of Internal Affairs and
   Communications of Japanese government), the council was established.
   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
   experiments.  The authors appreciate Tohru Asami, Hiroshi Esaki and
   Tatsuya Yamshita for their constructive comments.

10.  Informative References

   [1]  "Winny on Wikipedia", <http://en.wikipedia.org/wiki/Winny>.

   [2]  "Share on Wikipedia",

   [3]  Taniwaki, "Broadband Competition Policy in Japan", 2008,

   [4]  Utagoe Inc., "UGLive technology introduction",
        http://www.utagoe.com/en/technology/grid/live/index.html, March,

   [5]  TVBank, "Live Delivery using `BB Broadcast'Achieving 96% Saving
        in Traffic!", http:.wwww.tv-bank.com/jp/20081031.html, 2008 (in

   [6]  Cho, Fukuda, Esaki, and Kato, "The Impact and Implications of
        the Growth in Residential User-to-User Traffic",  SIGCOMM2006,
        pp207-218, Pisa, Italy, September 2006.

   [7]  Open P4P, "P4P Field Tests: Yale-Pando-Verizon",
        http://www.openp4p.net/front/, 2009.

   [8]  "RFC5632: Comcast's ISP Experiences in a Proactive Network
        Provider Participation for P2P (P4P) Technical Trial", September

   [9]  "ALTO H12,draft-kiesel-alto-h12-02 (work in progress)", March

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Authors' Addresses

   Satoshi Kamei
   NTT Service Integration Laboratories
   3-9-11, Midori-cho
   Musashino-shi, Tokyo  180-8585

   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

   Phone: +81-3-5324-4154
   Email: tmomose@cisco.com

   Takeshi Inoue
   NTT Communications
   3-4-1, Shibaura
   Minato-ku, Tokyo  108-8118

   Phone: +81-3-6733-7177
   Email: inoue@jp.ntt.net

   Tomohiro Nishitani
   NTT Communications
   1-1-6, Uchisaiwaicho
   Chiyodaku, Tokyo  100-8019

   Phone: +81-50-3812-4742
   Email: tomohiro.nishitani@ntt.com

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