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Versions: (draft-deng-aplusp-experiment-results) 00 01

V6OPS                                                             X.Deng
Internet Draft                                                   T.Zheng
Intended status: Informational                               M.Boucadair
Expires: January 9, 2012                                          L.Wang
                                                          France Telecom
                                                                 X.Huang
                                                                  Q.Zhao
                                                                    Y.Ma
                                                                    BUPT
                                                            July 8, 2011



        Implementing AplusP in the provider's IPv6-only network
           draft-deng-v6ops-aplusp-experiment-results-01.txt


Status of this Memo

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

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  Internet-Drafts are draft documents valid for a maximum of six months
  and may be updated, replaced, or obsoleted by other documents at any
  time.  It is inappropriate to use Internet-Drafts as reference
  material or to cite them other than as "work in progress."

  This Internet-Draft will expire on January 9, 2012.

Copyright Notice

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

  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
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  Legal Provisions and are provided without warranty as described in the
  Simplified BSD License.



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Abstract

  This memo describes an implementation of A+P in a provider's IPv6-
  only network. It provides details of the implementation, network
  elements, configurations and test results as well. Besides traditional
  port range A+P, a scattered port sets flavour of A+P is also
  implemented and verified for the sake of distributing incoming ports
  among customers in a more discrete way. The test results consist of
  the application compatibility test, UPnP extension for A+P, port usage
  and BitTorrent behaviour with A+P.

  This memo focuses on the IPv6 flavor of A+P.

Table of Contents


  1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
  2. Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
  3. Implementation environment . . . . . . . . . . . . . . . . . .  4
    3.1. Environment Overview . . . . . . . . . . . . . . . . . . .  4
    3.2. Implementation and Configuration of A+P  . . . . . . . . .  5
      3.2.1. IPv4-Embedded IPv6 Address Format For A+P CPE. . . . .  5
      3.2.2. DHCPv6 Configurations  . . . . . . . . . . . . . . . .  6
      3.2.3. Avoiding Fragmentation . . . . . . . . . . . . . . . .  6
    3.3. Implementing scattered Port Sets for A+P . . . . . . . . .  7
      3.3.1. Scattered Port Sets allocation mechanism   . . . . . .  7
      3.3.2. IPv4-Embedded IPv6 Address Format for Scattered Port
             Sets A+P CPE  . . . . . . . . . . . . . .  . . . . . . 10
      3.3.3. Customize a scattered Ports Set A+P NAT on Linux . . . 10
  4. Application Tests and Experiments in A+P Environment   . . . . 11
    4.1. A+P Impacts on Applications  . . . . . . . . . . . . . . . 12
    4.2. UPnP extension experiment  . . . . . . . . . . . . . . . . 13
    4.3. Port Usage of Applications . . . . . . . . . . . . . . . . 14
    4.4. BitTorrent Behaviour in A+P  . . . . . . . . . . . . . . . 16
  5. Security Considerations  . . . . . . . . . . . . . . . . . . . 17
  6. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 17
  7. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 17
  8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
    8.1. Normative References . . . . . . . . . . . . . . . . . . . 18
    8.2. Informative References . . . . . . . . . . . . . . . . . . 18
  9. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 19

1. Introduction

  A+P [draft-ymbk-aplusp-09] is a technique to share IPv4 addresses
  during the IPv6 transition period without requiring a NAT function in
  the provider's network. The main idea of A+P is treating some bits
  from the port number in the TCP/UDP header as additional end point



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  identifiers to extend the address field, thereby leaving a range of
  ports available to applications. This feature facilitates migration of
  networks to IPv6-only while offering the IPv4 connectivity services to
  customers, because the IPv4 address and the significant bits from the
  port range can be encoded in an IPv6 address and therefore
  transporting IPv4 traffic over IPv6 network by stateless IPv6 routing.

  We have implemented A+P in a residential ADSL access network, where
  IPv6-only access network is provided over PPPoE. In this document, we
  describe the implementation environment including A+P IPv6 prefix
  format and network elements configurations, and results of application
  tests as well. The document focuses on the implementation of the SMAP
  function specified in [draft-ymbk-aplusp-09]:

  o Implement DHCPv6 options to retrieve an IPv4-embedded IPv6 address
     and a port range.

  o Support of those DHCPv6 options in both the DHCPv6 server side and
     the DHCPv6 client side.

  o Support of those DHCPv6 options in both the DHCPv6 server side and
     the DHCPv6 client side.

  For extensive application tests results in A+P environment, please
  refer to [draft-boucadair-behave-bittorrent-portrange-02] and [draft-
  boucadair-port-range-01].

2. Terminology

  This document makes use of the following terms:

  o PRR: Port Range Router

  o A+P CPE: A+P aware Customer Premise Equipment



3. Implementation environment

3.1. Environment Overview

                           public
                           addresses        +----------+
                           realm            |  PRR     |
                                            |          |
                            ===             +----------+
                        IPv4 ^                  ^ ^
                             |                  | |



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                             |                  v v
                             |            +--------------+
                             |            | PPPoE/DHCPv6 |
                        over |            |    Server    |
                             |            +--------------+
                             |       ===        ^ ^
                             |  IPv6  ^         | |
                             |  over  |         | |
                        IPv6 |  PPPoE |         | |
                             V        v         | |
                            ===      ===        v v
                                      ^     +----------+
                                      |     |  A+P     |
                                      |     |  CPE     |
                                      |     +----------+
                              Private |         ^ ^
                              RFC1918 |         | |
                              realm   |         v v
                                      |     +----------+
                                      |     |   Host   |
                                      |     |          |
                                      V     +----------+


                  Figure 1 : Implementation Environment

  We had developed both A+P home gate way function and Port Range Router
  (PRR) function on Linux platform and ported the home gate way function
  to a Linksys wrt 54G CPE, on which an openwrt 2.6.32 (based on Linux
  kernel) is running.

  Figure 2 shows the Parameters of A+P CPE. IPv6 is provisioning over
  PPPoE to CPE while DHCPv6 server offers IPv6 prefix and A+P


  parameters by extended options defined in [draft-boucadair-dhcpv6-
  shared-address-option].



  +--------+------------+-------+-----+------------+-----------+------+
  | Model  | CPU Speed  | Flash | RAM |  Wireless  | Wireless  | Wired|
  |        |      (MHz) |  (MB) | (MB)|    NIC     | Standard  | Ports|
  +--------+---------- -+-------+-----+------------+-----------+------+
  | Linksys|    200     |   8   |  32 | Broadcom   |    11g    |   5  |
  | WRT54GS|            |       |     |(integrated)|           |      |
  +--------+------------+-------+-----+------------+-----------+------+




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                     Figure 2 :Parameters of A+P CPE

3.2. Implementation and Configuration of A+P

  Aplusp CPE, using Netfilter framework, the IPv4 port restricted NAT
  operation performed by CPE has been implemented by simply rules
  through iptables tool on Linux. After the port restriceted NAT
  operation, the IPv4 packets are sent to a TUN interface which is
  described as a virtual network interface in Linux. Using the IPv4-
  Embedded IPv6 address format defined in section 3.2.1, an IPv4-in-
  IPv6 encapsulation/decapsulation is performed by the TUN interface
  handler.

  PRR, located in the interconnection point of the IPv6 network and IPv4
  network, has been implemented with two main functions: 1) IPv4-
  in-IPv6 encapsulation/decapsulation; Like CPE, TUN driver is also used
  in PRR to achieve function IPv4-in-IPv6 encapsulation/decapsulation.
  2) destination port based routing function, which is responsible for
  routing the IPv4 traffic originated from the IPv4 Internet to the Port
  Range restricted A+P CPE. Destination port based routing is
  implemented by generating IPv6 destination address, pre-assigned from
  IPv4 address and port range to each CPE, according to IPv4-Embedded
  IPv6 address format defined in section 3.2.1.

3.2.1. IPv4-Embedded IPv6 Address Format For A+P CPE


























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  |31bits|1bit| 32bits|8 bits|16bits|4bits|1bit|1bit|1bit|1bit|32 bits|
  +------+----+-------+------+------+-----+----+----+----+----+-------+
  |AplusP|flag|Public | EUI64| port |Port |flag|flag|flag|flag|Public |
  |Prefix| 0  |IPv4   |      | Range|Range|  1 |  2 |  3 |  4 |IPv4   |
  |      |    |Address|      |      |Size |    |    |    |    |Address|
  +------+----+-------+------+------+-----+----+----+----+----+-------+


               Figure 3 :IPv4-Embedded IPv6 address format

  flag0: Is this address used by CPE or PRR?

  flag1: Is address shared?

  flag2: Is length of invariable present?

  flag3: Is port range identifying sub network?

  flag4: Reserved?



  To facilitate test and experiment on AplusP solution, recently, we are
  considering release this AplusP implementation under open source
  license. For more implementation details, please refer to
  [Implementing A+P]

3.2.2. DHCPv6 Configurations



  DHCPv6 options defined in [draft-boucadair-dhcpv6-shared-address-
  option] have been implemented. These options allow to configure a
  shared address together with a port range using DHCPv6.

3.2.3. Avoiding Fragmentation



  Normally the TCP protocol stack will employ Maximum Segment Size (MSS)
  negotiation and/or Path Maximum Transmission Unit Discovery (PMTUD) to
  determine

  the maximum packet size, and then try to send as large as possible
  datagram to achieve better throughput. However the IPv4-in-IPv6
  encapsulation and the PPPoE header is very likly to cause a larger
  packet that exceeds the maximum MTU of the wire, and result in
  undesired fragmentation processing and decrease transmission



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  efficiency.

  A simple solution is to enable iptables on A+P CPE to modify the MSS
  value of TCP session, using the command like "iptables -t mangle -A
  FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss
  DESIRED_MSS_VALUE". Here the DESIRED_MSS_VALUE is taken into account
  of common size of IPv4 header without options, common size of TCP
  header and size of basic IPv6 header and PPPoE header as well.

3.3. Implementing scattered Port Sets for A+P

3.3.1. Scattered Port Sets allocation mechanism

  As described in [I-D.ietf-intarea-shared-addressing-issues], a bulk of
  incoming ports can be reserved as a centralized resource shared by all
  subscribers using a given restricted IPv4 address. In order to
  distribute incoming ports as scattered as possible among subscribers
  sharing the same restricted IPv4 address, other than allocating a
  continuous range of ports to per subscriber, a solution to distribute
  bulks of non-continuous ports among subscribers, which also takes port
  randomization of CPE NAT into account, because port randomization is
  one protection among others against blind attacks, is elaborated
  thereby.

  On every restricted IPv4 address, according to port set size N,
  log2(N)bits are randomly chose as subscribers identification bits(s
  bit) among 1st and 16th bits.  Take a sharing ration 1:32 for example,
  Figure 4 shows an example of 5bits (2nd, 5th, 7th, 9th, 11th) being
  chose as s bit.



                   |1st |2nd |3rd |4th |5th |6th |7th | 8th|
                   +----+----+----+----+----+----+----+----+
                   | 0  |  s | 0  | 0  | s  | 0  | s  |  0 |
                   +----+----+----+----+----+----+----+----+

                   |9th |10th|11th|12th|13th|14th|15th|16th|
                   +----+----+----+----+----+----+----+----+
                   | s  | 0  |  s | 0  | 0  | 0  | 0  | 0  |
                   +----+----+----+----+----+----+----+----+

     Figure 4 : An s bit selection example (on a sharing ration 1:32
                                address).



  Subscriber ID pattern is then formed by setting all the s bits to 1



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  and other trivial bits to 0.  Figure 5 illustrates an example of
  subscriber ID pattern which follows the s bit selection of figure 4.
  Note that the subscriber ID pattern can be different, ensured by the
  random s bit selection, per restricted IP address no matter whether
  the sharing ratio varies.

                   |1st |2nd |3rd |4th |5th |6th |7th | 8th|
                   +----+----+----+----+----+----+----+----+
                   | 0  | 1  | 0  | 0  | 1  | 0  | 1  |  0 |
                   +----+----+----+----+----+----+----+----+

                   |9th |10th|11th|12th|13th|14th|15th|16th|
                   +----+----+----+----+----+----+----+----+
                   | 1  | 0  | 1  | 0  | 0  | 0  | 0  | 0  |
                   +----+----+----+----+----+----+----+----+

   Figure 5 : A subscriber ID pattern example (on a sharing ration 1:32
                                address).



  Subscribers ID value is then assigned by setting subscriber ID pattern
  bits (s bits shown in figure 4) to a unique customer value and setting
  other trivial bits to 1. An example of subscriber ID value, having a
  subscriber ID pattern shown in the figure 5 and a customer value 0, is
  shown in the figure 6.



                   |1st |2nd |3rd |4th |5th |6th |7th | 8th|
                   +----+----+----+----+----+----+----+----+
                   | 1  | 0  | 1  | 1  | 0  | 1  | 0  | 1  |
                   +----+----+----+----+----+----+----+----+

                   |9th |10th|11th|12th|13th|14th|15th|16th|
                   +----+----+----+----+----+----+----+----+
                   | 0  | 1  |  0 | 1  | 1  | 1  | 1  | 1  |
                   +----+----+----+----+----+----+----+----+


       Figure 6 : A subscriber ID value example (customer value: 0)



  Subscriber ID pattern and subscriber ID value together uniquely
  defines a restricted port set (Non-contiguous port sets or a
  contiguous port range, depends on Subscriber ID pattern and subscriber
  ID value) on a restricted IP address.



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  Pseudo-code shown in the figure 7 describes how to use subscriber ID
  pattern and subscriber ID value to implement a random ephemeral port
  selection function within the defined restricted port sets on a
  customer NAT.

        do{

            restricted_next_ephemeral = (random()|subscriber_ID_pattern)

                                        & subscriber_ID_value;

            if(five-tuple is unique)

            return restricted_next_ephemeral;

        }



  Figure 7 : Random ephemeral port selection within the restricted port
                                   set

3.3.2. IPv4-Embedded IPv6 Address Format for Scattered Port Sets A+P CPE



  |31bits|1bit| 32bits|8bits|16bits |4bits|1bit|1bit|1bit|1bit|32bits|
  +------+----+-------+------+------+-----+----+----+----+----+-------+
  |AplusP|flag|Public | EUI64|SID_  |Reser|flag|flag|flag|flag|Public |
  |Prefix| 0  |IPv4   |      |Value |-ved |  1 |  2 |  3 |  4 | IPv4  |
  |      |    |Address|      |      |     |    |    |    |    |Address|
  +------+----+-------+------+------+-----+----+----+----+----+-------+

               Figure 8 :IPv4-Embedded IPv6 address format

  SID Value: Subscriber_ID_Value, which is unique for per subscriber
  sharing a given restricted IPv4 address. and has been allocated to
  each subscriber.

  flag0: Is this address used by CPE or PRR?

  flag1: Is address shared?

  flag2: Is length of invariable present?

  flag3: Is port range identifying sub network?

  flag4: Reserved?



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  PRR maintains a mapping table, which consists of restricted IPv4
  address and it's Subscriber ID Pattern. To form an IPv6 destination
  address for incoming packet, PRR could find the right SID Pattern
  according to a destination IPv4 address, and then apply a simple
  operation shown in the figure 9.

                  SID_Value = Destination_Port | (~SID_Pattern).

                   Figure 9 :PRR calculates SID Value





3.3.3. Customize a scattered Ports Set A+P NAT on Linux

  With a linux kernel 2.6.32.36, only one line of linux kernel code is
  changed, as shown in the figure5, and the same IPtables command line
  interface is used with the only one change of semantic that the
  original staring of port range becomes SID_Value and the ending port
  of a port range becomes SID_Pattern. The command line with iptables to
  configure a scattered Ports Set A+P is illustrated in the figure 11.


           bool nf_nat_proto_unique_tuple(...)

             ...

        //The Original code:

         //*portptr = htons(min + off % range_size);

         // was changed to:

           *portptr = htons((ntohs(off) | min ) & max );

            ...



   Figure 10:Function of finding a unique 5-tuple for a scattered port
                              sets A+P NAT









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  iptables -t nat -A POSTROUTING -o eth0 -p tcp -j SNAT --to-source
  a.b.c.d: SID_Value-SID_Pattern --random

  iptables -t nat -A POSTROUTING -o eth0 -p udp -j SNAT --to-source
  a.b.c.d: SID_Value-SID_Pattern --random


      Figure 11: IPtables commands for a scattered ports set A+P NAT


4. Application Tests and Experiments in A+P Environment


  A set of well-known applications have been tested in this IPv6 flavor
  of A+P environment to access A+P impacts on them. The test results
  show that IPv6 flavor of A+P has the same impacts on applications as
  IPv4 flavor A+P does [draft-boucadair-port-range-01]. Web browsing (IE
  and Firefox), Email (Outlook), Instant message(MSN),Skype, Google
  Earth work normally with A+P. For more details, please refer to
  [draft-boucadair-port-range-01].

4.1. A+P Impacts on Applications


  +------------------+--------------------------------------+
  | Application      |     A+P impacts                      |
  +------------------+--------------------------------------+
  | IE               |     None                             |
  +------------------+--------------------------------------+
  | Firefox          |     None                             |
  +------------------+--------------------------------------+
  | FTP(Passive mode)|     None                             |
  +------------------+--------------------------------------+
  | FTP(Active mode) | require opening port forwarding      |
  +------------------+--------------------------------------+
  | Skype            |     None                             |
  +------------------+--------------------------------------+
  | Outlook          |     None                             |
  +------------------+--------------------------------------+
  | Google Earth     |     None                             |
  +------------------+--------------------------------------+
  | BitComet         | UPnP extensions may be required, when|
  |                  | listening port is out of A+P range;  |
  |                  | other minor effects(see section 4.4) |
  +------------------+--------------------------------------+
  | uTorrent         | UPnP extensions may be required, when|
  |                  | listening port is out of A+P range;  |
  |                  | other minor effects(see section 4.4) |



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  +------------------+--------------------------------------+
  | Live Messenger   |     None                             |
  +------------------+--------------------------------------+


                 Figure 12:Aplusp impacts on applications



  For P2P (Peer-to-Peer) applications, when some of them listening on
  specific port to expect inbounding connection, it is likely to fail
  due to the listening port is out of A+P port range. Some UPnP
  extensions may be required to make P2P applications work properly with
  A+P. Other minor effects of A+P are discussed in section 4.4.

4.2. UPnP extension experiment



  To make P2P application work properly with port restricted NAT , we
  have designed extensions including new variables, new errorcodes as
  well as new actions to UPnP 1.0, and have them implemented with
  [Emule], [open source UPnP SDK 1.0.4 for Linux] and [Linux UPnP IGD
  0.92].



  In figure 5, a new error code is proposed for the existing
  "AddPortMapping" action to explicitly indicate the situation that the
  requested external port is out of range.



  +----------+-----------------------+-----------------------------+
  | ErrorCode| errorDescription      |  Description                |
  +----------+-----------------------+-----------------------------+
  | 728      |ExternalPortOutOfRange |  The external port is out   |
  |          |                       |  of the port range assigned |
  |          |                       |  to this external interface |
  +----------+-----------------------+-----------------------------+


           Figure 13:New ErrorCode for "AddPortMapping" action



  New state variables have been introduced to reflect the valid port
  range. The definitions of these state variables are shown in figure 6.



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  +-------------+-------+------+----------+---------+-------+
  |Variable     |Req. or| Data |  Allowed | Default | Eng.  |
  | Name        |   Opt.| Type |   Value  |  Value  | Units |
  +-------------+-------+------+----------+---------+-------+
  |PortRangeLow |   O   | ui2  |   >=0    |    0    |  N/A  |
  +-------------+-------+------+----------+---------+-------+
  |PortRangeHigh|   O   | ui2  |  <=65535 |  65535  |  N/A  |
  +-------------+-------+------+----------+---------+-------+


              Figure 14: New state variables for port range



  Correspondingly, new actions, GetPortRangeLow and GetPortRangeHigh,
  defined to retrieve port range information are illustrated in figure
  7. An IP address should be provided as argument to invoke the new
  actions, for the port range is associated with a specific IP address.



  +----------------+-----------------------+----+--------------------+
  |  Action Name   |   Argument            |Dir.|  Related           |
  |                |                       |    |  StateVariable     |
  +----------------+-----------------------+----+--------------------+
  |GetPortRangeLow | NewExternal IPAddress | IN |  ExternalIPAddress |
  |                +-----------------------+----+--------------------+
  |                | NewPortRange Low      | OUT|  PortRangeLow      |
  +----------------+-----------------------+----+--------------------+
  |GetPortRangeHigh| NewExternal IPAddress | IN |  ExternalIPAddress |
  |                +-----------------------+----+--------------------+
  |                | NewPortRange High     | OUT|  PortRangeHigh     |
  +----------------+-----------------------+----+--------------------+


                  Figure 15: New actions for port range



  Please refer to [UPnP Extension] for more details of UPnP extension
  experiment in A+P.

4.3. Port Usage of Applications


  Port consumptions of applications not only impact the deployment
  factor (i.e., port range size) for AplusP solution but also play an
  important role in determining the port limitation of per customer on



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  AFTR for Dual-Stack Lite.

  Therefore we have also developed and deployed a Service Probe in our
  IPv6 network, which use IPv6 TCP socket to ask AplusP CPE for NAT
  session usage, and store AplusP NAT statistics in a Mysql database for
  further analysis of application behaviors in terms of port and session
  consumptions.

  In figure 8, the maximum port usage of each application is the peak
  number of port consumption per second during the whole communication
  process. The duration time represents the total time from the first
  NAT binding entry being established to the last one being destroyed.


  +-----------+--------------------------+--------------+----------+
  |Application|    Test case             | Maximum      | Duration |
  |           |                          | port usage   | (seconds)|
  +-----------+--------------------------+--------------+----------+
  |           | browsing a news website  |  20-25       |    200   |
  | IE        +--------------------------+--------------+----------+
  |           | browsing a video website |  40-50       |    337   |
  +-----------+--- ----------------------+--------------+----------+
  |           | browsing a news website  |  25-30       |    240   |
  | Firefox   +--------------------------+--------------+----------+
  |           | browsing a video website |  80-90       |    230   |
  +-----------+--------------------------+--------------+----------+
  |           | browsing a news website  |  50-60       |    340   |
  | Chrome    +--------------------------+--------------+----------+
  |           | browsing a video website |  80-90       |    360   |
  +-----------+--------------------------+--------------+----------+
  | Android   | browsing a news website  |  40-50       |    300   |
  | Chrome    +--------------------------+--------------+----------+
  |           | browsing a video website |  under 10    |    160   |
  +-----------+--------------------------+--------------+----------+
  | Google    | locating a place         |  30-35       |    240   |
  | Earth     |                          |              |          |
  +-----------+--------------------------+--------------+----------+
  | Android   |                          |              |          |
  | Google    | locating a place         |  10-15       |    240   |
  | Earth     |                          |              |          |
  +-----------+--------------------------+--------------+----------+
  | Skype     | make a call              |  under 10    |    N/A   |
  +-----------+--------------------------+--------------+----------+
  | BitTorrent| downloading a file       |  200         |    N/A   |
  +-----------+--------------------------+--------------+----------+


                  Figure 16: Port usage of applications



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4.4. BitTorrent Behaviour in A+P



  [draft-boucadair-behave-bittorrent-portrange] provides an exhaustive
  testing report about the behaviour of BiTtorrent in an A+P
  architecture. [draft-boucadair-behave-bittorrent-portrange] describes
  the main behavior of BitTorrent service in an IP shared address
  environment.  Particularly, the tests have been carried out on a
  testbed implementing [ID.boucadair-port-range] solution.  The results
  are, however, valid for all IP shared address based solutions.


  Two limitations were experienced.  The first limitation occurs when
  two clients sharing the same IP address want to simultaneously
  retrieve the SAME file located in a SINGLE remote peer.  This
  limitation is due to the default BitTorrent configuration on the
  remote peer which does not permit sending the same file to multiple
  ports of the same IP address.  This limitation is mitigated by the
  fact that clients sharing the same IP address can exchange portions
  with each other, provided the clients can find each other through a
  common tracker, DHT, or Peer Exchange.  Even if they can not, we
  observed that the remote peer would begin serving portions of the file
  automatically as soon as the other client (sharing the same IP
  address) finished downloading.  This limitation is eliminated if the
  remote peer is configured with bt.allow_same_ip == TRUE.

  The second limitation occurs when a client tries to download a file
  located on several seeders, when those seeders share the same IP
  address.  This is because the clients are enforcing bt.allow_same_ip
  parameter to FALSE.  The client will only be able to connect to one
  sender, among those having the same IP address, to download the file
  (note that the client can retrieve the file from other seeders having
  distinct IP addresses).  This limitation is eliminated if the local
  client is configured with bt.allow_same_ip == TRUE, which is somewhat
  likely as those clients will directly experience better throughput by
  changing their own configuration.

  Mutual file sharing between hosts having the same IP address has been
  checked.  Indeed, machines having the same IP address can share
  files with no alteration compared to current IP architectures.

5. Security Considerations

  TBD

6. IANA Considerations




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  This document includes no request to IANA.

7. Conclusion

  Despite A+P introduces some impacts on existence applications, issues
  of P2P applications due to the port restricted NAT have been resolved
  by UPnP extension experiment in our test bed, and other issues are
  shared by other IP address sharing solutions. Therefore, from our
  work, it has been proved that deploying A+P in the Service Provider's
  IPv6 network during IPv6 transition period is feasible.

8. References

8.1. Normative References

  [Implementing A+P]

            Xiaoyu ZHAO.,"Implementing Public IPv4 Sharing in IPv6
            Environment", ICCGI 2010

  [UPnP Extension]

            Xiaoyu ZHAO., "UPnP Extensions for Public IPv4 Sharing in
            IPv6 Environment", ICNS 2010

8.2. Informative References

  [1]  Faber, T., Touch, J. and W. Yue, "The TIME-WAIT state in TCP
        and Its Effect on Busy Servers", Proc. Infocom 1999 pp. 1573-
        1583.

  [Fab1999] Faber, T., Touch, J. and W. Yue, "The TIME-WAIT state in TCP
            and Its Effect on Busy Servers", Proc. Infocom 1999 pp.
            1573-1583.

  [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate

             Requirement Levels", BCP 14, RFC 2119, March 1997.

  [draft-ymbk-aplusp-09]

            R. Bush., " The A+P Approach to the IPv4 Address Shortage",
            draft-ymbk-aplusp-09 (work in progress), February 17, 2011.

  [draft-boucadair-dhcpv6-shared-address-option]

            M. Boucadair., "Dynamic Host Configuration Protocol (DHCPv6)
            Options for Shared IP Addresses Solutions", draft-



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            boucadair-dhcpv6-shared-address-option-01 (work in
            progress), December 21, 2009

  [draft-boucadair-port-range-01]

            "IPv4 Connectivity Access in the Context of IPv4 Address
            Exhaustion",  draft-boucadair-port-range-01(work in
            progress), January 30, 2009

  [Emule]

            http://www.emule-project.net/. [Accessed October 26, 2009]

  [UPnP SDK 1.0.4 for Linux]

            http://upnp.sourceforge.net/. [Accessed October 26, 2009].

  [Linux UPnP IGD 0.92].

            http://linuxigd.sourceforge.net/. [Accessed October 26,
            2009].

  [draft-boucadair-behave-bittorrent-portrange]

            M. Boucadair.,"Behaviour of BitTorrent service in an IP
            Shared Address Environment", draft-boucadair-behave-
            bittorrent-portrange-02.txt

9. Acknowledgments

  The experiments and tests described in this document have been
  explored, developed and implemented with help from Zhao Xiaoyu, Eric
  Burgey and JACQUENET Christian.

  Thanks to Jan Zorz for comments.
















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Authors' Addresses

   Xiaohong Deng
   France Telecom
   Hai dian district, 100190, Beijing,
   China

   Email: xiaohong.deng@orange-ftgroup.com

   Mohamed BOUCADAIR
   France Telecom
   Rennes,35000 France

   Email: mohamed.boucadair@orange-ftgroup.com

   Lan Wang
   France Telecom
   Hai dian district, 100190, Beijing, China

   Email: lan.wang@orange-ftgroup.com

   Tao Zheng
   France Telecom
   Hai dian district, 100190, Beijing, China

   Email: tao.zheng@orange-ftgroup.com

   Xiaohong Huang
   Beijing University of Post and Telecommunication
   Email: huangxh@bupt.edu.cn


   Qin Zhao
   Beijing University of Post and Telecommunication
   Email: zhaoqin.bupt@gmail.com

   Yan MA
   Beijing University of Post and Telecommunication
   Email: mayan@bupt.edu.cn












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