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IPv6 Operations                                               M. Defeche
Internet-Draft                                       University of Liege
Intended status: Informational                            E. Vyncke, Ed.
Expires: April 26, 2012                                    Cisco Systems
                                                        October 24, 2011


             Measuring IPv6 Traffic in BitTorrent Networks
            draft-vyncke-ipv6-traffic-in-p2p-networks-00.txt

Abstract

   This document is a follow-up of a University thesis which aims to
   measure the evolution over time of IPv6 traffic and to analyze the
   geographical distribution of IPv6 nodes.  The first measurements were
   done during the Summer 2009 using a specific-purpose program which
   connects to the BitTorrent peer-to-peer network and this document
   adds measurements done with the same program but in October 2011 (2
   years later).

   The study was made in Peer-to-Peer (P2P) networks because they are
   responsible for most Internet traffic and because their structure and
   functioning permit a rapid discovery of a large number of nodes from
   all over the world.  In addition, the P2P users are more likely to be
   interested by IPv6 as IPv6 does not have the same NAT problems as
   IPv4.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on April 26, 2012.

Copyright Notice

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



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   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.  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 Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Some explanations about BitTorrent . . . . . . . . . . . . . .  3
     2.1.  Peer Wire Protocol . . . . . . . . . . . . . . . . . . . .  4
     2.2.  Tracker  . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.3.  Peer Exchange  . . . . . . . . . . . . . . . . . . . . . .  5
     2.4.  Distributed Hash Table . . . . . . . . . . . . . . . . . .  5
     2.5.  Local Service Delivery . . . . . . . . . . . . . . . . . .  5
   3.  Tools used for Measurement . . . . . . . . . . . . . . . . . .  6
   4.  What was measured  . . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  IPv6 Addresses . . . . . . . . . . . . . . . . . . . . . .  7
       4.1.1.  Native IPv6  . . . . . . . . . . . . . . . . . . . . .  7
       4.1.2.  Teredo . . . . . . . . . . . . . . . . . . . . . . . .  8
       4.1.3.  6to4 . . . . . . . . . . . . . . . . . . . . . . . . .  8
       4.1.4.  ISATAP . . . . . . . . . . . . . . . . . . . . . . . .  9
       4.1.5.  Other Addresses  . . . . . . . . . . . . . . . . . . .  9
     4.2.  Traffic Measurements . . . . . . . . . . . . . . . . . . .  9
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11















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1.  Introduction

   An IPv6 vs. IPv4 measurement was made in Peer-to-Peer (P2P) networks
   because they are responsible for most Internet traffic [TFE3] and
   because their structure and functioning permit a rapid discovery of a
   large number of nodes from all over the world.  In addition, the P2P
   users are more likely to be interested by IPv6 as IPv6 does not have
   the same NAT problems as IPv4.

   The measurements were made in October 2011 re-using the application
   developped in October 2009 and presented in
   [I-D.defeche-ipv6-traffic-in-p2p-networks].  This was part of the
   Master Thesis [THESIS].

   Measurements include: number of IPv4 vs. IPv6 nodes, which kind of
   IPv6 connectivity and geographical distribution.


2.  Some explanations about BitTorrent

   Let's start with some explanations about BitTorrent.

   BitTorrent is based on an hybrid decentralized network which is
   particularly well suited to the transfer of large files.  BitTorrent
   generates the largest amount of traffic of all P2P networks and was
   installed on 28.20% of PCs in September 2007, and this number is
   certainly higher at present.  BitTorrent also includes different
   protocols to discover peers, namely DHT, PEX and LSD which will be
   discussed later.  Thanks to these mechanisms BitTorrent can be
   completely decentralized.  The different clients are all compatible
   with the core protocol but some divergences concerning PEX, DHT and
   LSD appear between Azureus and the mainline, which represents at
   least the BitTorrent and A[micro]Torrent clients.  Swarming is one of
   the basis of the protocol and IPv6 specification exists although it
   is not implemented by all clients.

   Since BitTorrent is the only protocol that offers in theory a good
   support to IPv6, our choice is limited.  But there are other reasons
   why BitTorrent is the network protocol that best matches our needs.

   o  The number of different copies of the same file(s) is far smaller
      than in other networks.  This leads to a larger number of peers
      sharing the same file(s).  Therefore swarming can be more
      efficient thanks to a larger number of sources.

   o  As BitTorrent is generally used to share large files, peers stay
      connected longer, giving us more time to discover them.




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   o  BitTorrent is responsible for the largest part of the P2P traffic
      throughout the world.

   o  BitTorrent is widely used in most regions of the world.

   o  Thanks to many different extensions like PEX (Section 2.3), DHT
      (Section 2.4) and LSD (Section 2.5), the discovery of peers is
      improved greatly.

2.1.  Peer Wire Protocol

   The Peer wire Protocol [TFE5], or PWP, specifies the way peers
   communicate in an asynchronous fashion with each other to exchange
   data and signalling messages.  It is based on TCP connections that
   function in Full-Duplex and Pipelining mode to get better
   performances.  This protocol does not define how to choose pieces to
   request, nor how to select peers to download from and to upload to.
   Certain algorithms, which are explained below, give some solutions to
   attain a good propagation of pieces in the swarm and to make peers
   happy with their download rate compared to their upload rate.

2.2.  Tracker

   The trackers [TFE5] act like servers but do not deal with the
   transfer of files ; their only purposes are to manage the swarm and
   to respond to periodic client requests for information about peers
   sharing the same torrent.  Since the transfer of files is completely
   supported by peers, the bandwidth requirement is very low and thus a
   single tracker can handle many swarms, each one containing a large
   number of peers.  This protocol commonly called THP is used by
   clients to communicate over HTTP with trackers.  As a matter of fact,
   the trackers run an HTTP server.  Peers contact trackers that are
   present in the metadata file for the following purposes :

   o  to enter a swarm

   o  to leave a swarm

   o  to inform the tracker that the download is complete

   o  to periodically give information on the download state and
      retrieve information about a random peer set.  This time interval
      is defined by the tracker.  If a peer misses a periodical request
      it can be considered as disconnected by the tracker and thus not
      present in the swarm any more

   This communication permits trackers to keep track of peers that are
   in the swarm and to avoid referencing disconnected peers.



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   Tracker responses do not support IPv6 peers without this extension
   [TFE12] which means that they do not include IPv6 peers in their
   responses.  This extension adds two new parameters for the tracker
   requests:

   o  ipv6 : the client IPv6 address.  It can be added when the client
      contacts the tracker over IPv4;

   o  ipv4 : the client IPv4 address.  Conversely, when communication is
      made over IPv6.

   It permits clients having a dual stack to advertize both its
   addresses in the swarm.  The port of the additional address is the
   same as the primary one.

2.3.  Peer Exchange

   The Peer Exchange or PEX is a means to discover new peers through
   peers that the client is already connected to.  As a matter of fact,
   peers trade information concerning the peers they are connected to.
   Only few initial peers are needed to rapidly find a large number of
   peers.  This mechanism permits a reduction of the tracker load and an
   improvement in the robustness as the tracker dependency is decreased.

2.4.  Distributed Hash Table

   The DHT technology [TFE13] is a way to store a hash table over a
   network, thus in a distributed way, each peers contains a part of it.
   Files and nodes are identified by a same length key, which is 20
   bytes in BitTorrent.  Each peer also maintains a list of different
   peers to efficiently route its searches.  DHT in BitTorrent is an
   implementation of Kademlia which is based on the XOR metric that is
   the distance between two nodes or between a node and a file can be
   determined by a XOR of their keys.

   This technology is used to decentralize the tracking mechanism to
   once more decrease the dependence on trackers.  Even if the trackers
   are down or if no trackers are specified in the metadata file, the
   DHT technology permits the discovery of peers sharing the same
   torrent thanks to the info key hash as identifier.  Conversely to
   PEX, no initial peers are needed.

2.5.  Local Service Delivery

   The Local Service Discovery or LSD permits the discovery of peers
   that are downloading the same torrent in the same local network.  The
   transfer rate is much higher between two peers in the same local
   network than between two peers in different networks since the



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   bandwidth limitation is that of the local network and not the one of
   the Internet connection which is far smaller, especially the upload
   stream.  Briefly, LSD works as follows : the hash of the info key is
   broadcasted in the local network to find out peers sharing the same
   torrent.


3.  Tools used for Measurement

   As millions of pieces of information can be reached, the choice of a
   MySQL database came naturally for effectiveness reasons and because
   concurrent access is managed.  Each program requests, inserts, and/or
   updates information in this database.

   The computer that holds the database and executes the programs has
   native IPv6 and IPv4 connectivity, which will permit a better
   evaluation of the two versions than if we use Teredo, for instance.

   Our specialized BitTorrent client joins different swarms and
   periodically changes to other swarms.  While in a swarm we try to get
   connected to as many peers as possible thanks to all protocols
   supported by BitTorrent.  In this way we are able to easily,
   automatically and efficiently discover peers.  Ideally we should
   choose swarms with large numbers of peers in order to effectively
   retrieve information.  Concerning the legality issue, we can use a
   trick to avoid downloading and uploading any files.  In fact, we
   claim that we are not interested in any pieces so we will not
   download anything and we will not upload either since we have nothing
   to upload.  So we are present in the swarm but without taking part in
   the sharing of files.


4.  What was measured

   The measurements were done in two periods:

   o  May 2009 to July 2009: 5,000,000 peers were discovered but we were
      only able to to establish a BitTorrent connection with 1,500,000
      peers;

   o  1 day in October 2009: 100,000 peers were discovered.

   o  1 day in October 2011: 180,000 peers were discovered.








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4.1.  IPv6 Addresses

   We will now analyze the 2,177 distinct IPv6 addresses found via the
   different protocols and classify them into different categories.  The
   next section will explain the utilization of these addresses over the
   world in greater detail.

   +----------------+--------+--------+--------+--------+--------------+
   |                | Native | Teredo | 6to4   | ISATAP | Tunnel       |
   |                |        |        |        |        | Brokers      |
   +----------------+--------+--------+--------+--------+--------------+
   | Number in 2009 | 1,216  | 99,634 | 41,425 | 24     | 102          |
   | Percentage in  | 0.85   | 69.72  | 28.99  | 0.02   | 0.08         |
   | 2009           |        |        |        |        |              |
   | Number in 2011 | 258    | 1,280  | 636    | 3      | n/a          |
   | Percentage in  | 11.85  | 58.80  | 29.22  | 0.14   | n/a          |
   | 2011           |        |        |        |        |              |
   +----------------+--------+--------+--------+--------+--------------+

                Table 1: Different Types of IPv6 Addresses

   The next table describes which weird and plain wrong IPv6 address our
   probe has received.  It can be expected that a normal BitTorrent
   client will try to contact those addresses and therefore will
   generate packets whose destination IPv6 address is illegal.

   +--------------+-------+---------+--------------+-----------+-------+
   |              | 6bone | Site    | IPv4         | IPv4      | Bogon |
   |              |       | Local   | Compatible   | Mapped    |       |
   +--------------+-------+---------+--------------+-----------+-------+
   | Number in    | 436   | 24      | 1            | 94        | 74    |
   | 2009         |       |         |              |           |       |
   | Percentage   | 0.31  | 0.02    | 0.00         | 0.07      | 0.05  |
   | in 2009      |       |         |              |           |       |
   | Number in    | 0     | 0       | 0            | 0         | 61    |
   | 2011         |       |         |              |           |       |
   | Percentage   | 0     | 0       | 0            | 0         | 100   |
   | in 2011      |       |         |              |           |       |
   +--------------+-------+---------+--------------+-----------+-------+

            Table 2: Different Types of IPv6 Addresses (Cont.)

4.1.1.  Native IPv6

   In the 2011 study, only 197 distinct native IPv6 addresses were
   discovered in 25 different countries during our study.  More than 40
   % of these addresses came from the French ISP Free.




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4.1.2.  Teredo

   Teredo with 59 % of IPv6 addresses found is clearly the most utilized
   way to get IPv6 connectivity.  This ratio is also unsually high
   compared to other Internet measurements.  It is probably linked to:

   o  users: BiTorrent users are mainly residential and not
      professional, therefore Teredo is allowed to traverse the firewall
      while most enterprises block all outbound UDP traffic (and
      blocking Teredo in the same shot) and the most common Teredo
      implementation (Microsoft) also disables Teredo when used in an
      Active Directory network;

   o  application: Teredo is only used by Windows to connect to an IPv6
      which does not have any IPv4 address (in other word [RFC3484]
      severelly limits the normal use of Teredo), but, with BitTorrent
      the peers appear always as single stack (i.e. it appears like
      having only an IPv6 address even if it actually have both version
      of the IP protocol).

   When we analyze the servers employed to configure these addresses we
   notice that only four servers represent 100 % of the utilized ones.
   Their addresses are as follows :

   1.  65.55.158.118 : is deployed by Microsoft (56.44 %);

   2.  94.245.115.184 : is deployed by Microsoft ( 2.42 %);

   3.  94.245.121.251 : is deployed by Microsoft (17.49 %);

   4.  94.245.121.253 : is deployed by Microsoft (23.65 %);

   while in October 2009, three different servers represented 99 % of
   the traffic:

   1.  213.199.162.214 : is deployed by Microsoft (46.12%);

   2.  65.55.158.80 : is also set up by Microsoft (41.33%);

   3.  207.46.48.150 : is once more owned by Microsoft (12.41%).

   Thus 100 % of the peers that were using Teredo were likely to be
   using one of the Microsoft Operating Systems.

4.1.3.  6to4

   6to4 is also broadly used to provide IPv6 connectivity as 29.21 % of
   the addresses found in 2011 and was 28.99 % in 2009 were created by



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   this transition mechanism.  Nevertheless, it is still far behind
   Teredo.  It must be noted that the proportion of 6to4 nodes has not
   decreased as indicated by other measurements, but, the other
   measurements count only the web access to dual-stack servers where
   happy eye-balls [I-D.ietf-v6ops-happy-eyeballs] and [RFC3484] can
   influence the browser behavior in order to avoid all tunneling (this
   includes Teredo and 6to4).

4.1.4.  ISATAP

   We only discovered 3 different peers that used ISATAP ([RFC5214]) to
   get IPv6 connectivity in a non IPv6-capable infrastructure.  This
   mechanism is less common than Teredo ([RFC4380]) and 6to4
   ([RFC3056]).  However, this bad result can be moderated by the fact
   that ISATAP is mostly destined to enterprises which often have a
   strict control on applications used by their employees.  Thus
   installing a BitTorrent client is not often possible, and even if it
   is the firewall can filter its traffic.

4.1.5.  Other Addresses

   Although IPv6 addresses with the 6bone prefix should not exist
   anymore, in October 2009 we found up to 436 addresses with this
   prefix.  In fact, all these addresses have the old Teredo prefix
   3ffe:831f::/32 which was used in the 6bone network.

   In October 2009, we found 94 IPv4-mapped addresses that were all
   discovered by PEX.

   The good news is that in October 2011, we found neither a single
   6bone address not an IPv4-mapped address in our peers.

   Bogons are IP blocks that are reserved for private or special uses
   plus those that are not yet allocated by the IANA.  Thus a bogon is
   an illegal IP address that must not appear on the Internet since they
   are theoretically unroutable.  At present, the IPv6 unicast space is
   limited to the 2000::/3 prefix.  During our study we discovered up to
   61 bogons via PEX.

4.2.  Traffic Measurements

   Most of the European countries have at least 1 % of their peers that
   can use IPv6 with better results for Finland (3.25%), France (2.53%),
   Latvia (2.41%), Denmark (2.40%) and Belgium (2.00%).  Another
   surprising fact is that China has only 1.40 % of its peers using IPv6
   which seems strange since China is one of the leading countries in
   IPv6 deployment.  This result may be negatively affected by the
   filter set up in this country.  Other countries having peers which



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   are IPv6-enabled are Chile (3.07%), Mexico (2.10%), Korea (1.98%) as
   well as Japan (1.88%), USA (1.34%) and Canada (1.40%).

   As explained in the analysis of IPv6 addresses section, we only found
   few native IPv6 addresses.  This analysis confirms what we discussed
   previously, which is that Japan and France have the highest rate with
   1.09% in 2009 (and 1.62% in 2011) and 0.65% in 2009 (and 0.63% in
   2011) respectively.  China with 0.65% in 2009 and 1.01% in 2011, has
   a good percentage in comparison with other countries as well as
   growth.


5.  IANA Considerations

   There are no extra IANA consideration for this document.


6.  Security Considerations

   This I-D does not describe any specific protocol, so, the security
   section is mostly irrelevant.  The measures were done with the
   specific security issues in mind:

   o  copyrighted content: only a first fragment is downloaded and never
      stored on long term storage, so, it is assumed that even if
      copyrighted content is actually received it will never be user or
      propagated further to other peers;

   o  denial of services: timers and rate limiters are used when getting
      the list of torrents from our directory, when contacting other
      peers, and so on


7.  Acknowledgements

   Many thanks to Professor Guy Leduc of the University of Liege and his
   research assistants, Cyril Soldani and Sylvain Martin.  Martin is
   also grateful to Arvid Norberg who implemented the LibTorrent
   Rasterbar library [TFE23].  We also exchanged ideas with Nathan Ward.


8.  References

8.1.  Normative References

   [TFE12]    Hazel, G., "IPv6 Tracker Extension", May 2008,
              <http://www.bittorrent.org/beps/bep_0007.html>.




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   [TFE13]    Maymounkov, P., "Kademlia : A Peer-to-peer Information
              System Based on the XOR Metric".

   [TFE5]     Cohen, B., "The BitTorrent Protocol Specification", 2008,
              <http://www.bittorrent.org/beps/bep_0003.html>.

8.2.  Informative References

   [I-D.defeche-ipv6-traffic-in-p2p-networks]
              Defeche, M. and E. Vyncke, "Measuring IPv6 Traffic in
              BitTorrent Networks",
              draft-defeche-ipv6-traffic-in-p2p-networks-00 (work in
              progress), October 2009.

   [I-D.ietf-v6ops-happy-eyeballs]
              Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with
              Dual-Stack Hosts", draft-ietf-v6ops-happy-eyeballs-04
              (work in progress), September 2011.

   [RFC3056]  Carpenter, B. and K. Moore, "Connection of IPv6 Domains
              via IPv4 Clouds", RFC 3056, February 2001.

   [RFC3484]  Draves, R., "Default Address Selection for Internet
              Protocol version 6 (IPv6)", RFC 3484, February 2003.

   [RFC4380]  Huitema, C., "Teredo: Tunneling IPv6 over UDP through
              Network Address Translations (NATs)", RFC 4380,
              February 2006.

   [RFC5214]  Templin, F., Gleeson, T., and D. Thaler, "Intra-Site
              Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214,
              March 2008.

   [TFE23]    Norberg, Arvid., "LibTorrent Rasterbar Library",
              <http://www.rasterbar.com/products/libtorrent/>.

   [TFE3]     Schulze, H., "Internet Study 2008/2009", 2009.

   [THESIS]   Defeche, M., "Measure and Analysis of IPv6 Traffic in
              Peer-to-Peer Networks. Master Thesis", August 2009.

   [geoip]    Maxmind, "GeoLite Country", 2011,
              <http://www.maxmind.com/app/geolitecountry>.








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Authors' Addresses

   Martin Defeche
   University of Liege

   Email: martin.defeche@gmail.com


   Eric Vyncke (editor)
   Cisco Systems
   De Kleetlaan 6a
   Diegem  1831
   Belgium

   Phone: +32 2 778 4677
   Email: evyncke@cisco.com



































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