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Versions: 00 01 02 03 04                                                
ALTO                                                        Kai.Lee
Internet-Draft                                             China Telecom
Intended status: Informational                             GuangYao.Jian
Expires: April 22, 2011                                   Xunlei network
                                                        October 22, 2010

             ALTO and DECADE service trial within China Telecom

Status of this Memo

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

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   This Internet-Draft will expire on April 22, 2011.

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Copyright Notice

   Copyright (c) 2010 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
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   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.


      This document reports the experience of China Telecom in a recent
   experiment with the ALTO service and P2P caches deployment. It is
   found that the deployment of the ALTO service significantly improves
   the capability of a Service Provider to affect the distribution of
   P2P traffic. It is also found that a traffic localized ALTO policy
   may decrease the download speed of a P2P user. However, the
   deployment of some P2P caches can compensate such influence.

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Table of Contents

   1. Introduction ................................................. 3
   2. High level description of the trial .......................... 4
      2.1. Difference between standard ALTO protocol ............... 4
      2.2. Difference with Comcast's trial ......................... 5
   3. Trial results ................................................ 6
      3.1. ALTO server policy test...................................7
      3.2. P2P cache test .......................................... 8
   4. Methods of data collection.................................... 9
   5. Configurations and algorithms in trial ...................... 10
      5.1. Configuration of PID MAP................................ 10
      5.2. Algorithms of Xunlei using ALTO information ............ 10
      5.3. Configuration of cache system........................... 12
   6. Next steps .................................................. 13
   7. Security Considerations...................................... 14
   8. IANA Considerations ......................................... 14
   9. References .................................................. 14
   Author's Addresses ............................................. 14

1. Introduction

      Although another trial on P4P, the predecessor of the ALTO, is
   available by Comcast, the impact of ALTO on a large scale real
   network has never publicly reported. Such real network should post
   no limitation on either the number of contents or the number of
   users. This draft reports the experience of China Telecom in a
   recent experiment with the deployment of the ALTO service and P2P

      With over 60 million fixed-line broadband subscribers, China
   Telecom   is the largest broadband service provider in China. It has
   one IP   backbone network that cover all of the 31 provinces and
   about 200   MAN networks managed by the provinces respectively.
   This trial was   taken place in one province with 7 million
   broadband subscribers and   about 11 MAN networks.

     Xunlei, the cooperator of this trial, is a leading P2P service
   provider in China. Xunlei supports both file downloads and real time
   media streaming. In 2009, when was this trail occurring, it serves
   over 20 million users each day.

      This trial is a joint effort of China Telecom and Xunlei. During
   this trial, China Telecom provided the following devices: an alto
   server for distribute ALTO information, some P2P caches to test its
   influence on traffic localization and user experience. China Telecom

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   also monitored the traffic load within its backbone. Xunlei provided
   the P2P client and users. To support this trial, Xunlei modified its
   platform to support ALTO, and recorded operational information on
   its platform according to the requirement of China Telecom. Note
   that the client of Xunlei was not changed.

2. High level description of the trial

2.1. Difference between standard ALTO protocol

   Note that ALTO protocol is still on progressing, in this trail, some
   modifications were made to the ALTO.

   First, a notification mechanism for the ALTO server is introduced.
   With this mechanism, the ALTO server notifies its clients the
   changes of network maps and cost maps. Thus, ALTO clients can
   respond fast to the change of traffic optimizing policy.

   One problem that this trail met is to find the effect of ALTO&Cache
   deployment. The traffic within the IP backbone is highly periodical
   For example, the traffic on each weekend is higher than the workday.

   As such, data should be collected in the same workday in different
   week. This can facilitate the comparison of the effects on p2p
   traffic under different ALTO configuration and different policy, and
   to evaluate the effect of ALTO service

   In this trail, ALTO clients were just embedded in the trackers of
   Xunlei, not in the Xunlei clients. The reason for this is mainly for
   deployment consideraton. There are hundreds of millions of Xunlei
   clients in use, To update these clients as the ALTO client in a
   short time is not feasible. However, according to the analysis of
   Xunlei, although both tracker based and tracker-less technology are
   adopted, the traffic does not controlled by the trackers is less
   than 15% of its total traffic. Based on this analysis, in this trial,
   Xunlei clients are not involved in the ALTO service which has
   negligible influence on the final evaluation of this trial. Such
   design can also reduce the load on the ALTO server.

   Secondly, only map service is provided in this trial. Other services
   of ALTO service were not deployed, as they are not essential for
   this trial.

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2.2. Difference with Comcast's trial

   Comcast has a trial with limited swarms, with the cooperation of
   Pando. According to (ref), there are five swarms, and overall 57,000
   peers are involved in that trial.

   There are several differences between our trial and Comcast's trial:

   1. The scope of the trail: This trial covers the whole province with
     over 700 million broadband users. It lasted for over 4 months.
     There are countless swarms with all kinds of contents. Thus, this
     trial is more realistic than the previous trial from Comcast.

   2. The usage of P2P cache: This trail differs from the previous
     trail by the utilization of P2P cache. In this trail, the average
     download speed of a Xunlei client decreases with the increase of
     the level of traffic localization. Thus the usage of P2P cache was
     introduced to compensate the decrease of download speed.

   3. The evaluation method: In contrast to that all test data was
     collected by Pando client in Comcast's trial, we collect test data
     from two ways. Besides the data from Xunlei P2P client, we
     simultaneously collect the data from network operator's NMS
     system.(such as data from SNMP reports and DPI(deep package
     inspection) device deployed on backbone). We can do this because
     Xunlei's p2p traffic occupy 20% of backbone traffic flow. This
     traffic flow will all be affected by our alto policy and it is big
     enough to be observed by network operator's NMS system.

   4. The implementation of ALTO: In this trial, only the P2P trackers
     are ALTO clients, but not those Xunlei clients. There are some
     reasons to do this:

      a) To avoid the update all Xunlei clients and simplify the
         deployment of trial.

      b) To lessen the alto server load.

      c) Above 85% of Xunlei traffic flow is controlled by Xunlei
         tracker, the traffic flow from DHT mechanism is less than 15%.
         An alto server dedicated for Xunlei tracker can control
         majority of Xunlei traffic flow.

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3. Trial results

   This trial used all Xunlei p2p client in the province and all
contents that are requested or served by Xunlei P2P client in the
province. The trial environment is more realistic than comcast's. A
primary objective of this trial is to measure the effects of traffic
localization and change of users download speed in comparison to normal
p2p activity.
   The test process is divided into two parts: first part is just
applied the ALTO server to measure the effects of traffic localization
and change of P2P user experience. The second part is to introduce the
P2P cache to the trial, to measure the improvement of user download
speed, the bandwidth consumption and  their relationship with the scale
of cache and.
   Our trial starts at 2009.6.12 and ends at 2009.10.18, lasting nearly
four months. We do this trial by applying different ALTO policy to
Xunlei tracker. There are two kinds of ALTO policy: One is optimized
policy and the other is normal policy. The optimized policy will try to
localize the traffic as much as possible by utilizing the information
from ALTO server. The normal policy will just use the original Xunlei
peer selection and traffic control rules and no alto policy are
involved. We usually change the alto policy in midnight of a day and
send a notification to Xunlei tracker with notification
   Before we do the trial , we collect the information about Xunlei'S
peer and traffic distribution

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      | No |Data Item   |Description             |The way of          |
      |    |            |                        |collection          |
      +----+---------- -+------------------------+--------------------+
      | 1  |Peer        |24.6% is within         |Random sampling by  |
      |    |distribution|the province,75.4%      |Xunlei tracker 24   |
      |    |            |is out of the           |times one day       |
      |    |            |province                |                    |
      |    |Traffic     |76.9% is                |Random selecting    |
      | 2  |distribution|intra-province traffic  |peers to report     |
      |    |            |23.1% is                |their traffic flow  |
      |    |            |inter-province traffic  |                    |
3.1. ALTO server policy test

   After we applied the alto optimized policy about 60% inter-province
   traffic has became The intra-province traffic. Below is the result
   that we observed on china telecom's network NMS system:

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      | No |Data Item   |Description             |The way of             |
      |    |            |                        |collection             |
      +----+---------- -+------------------------+-----------------------+
      | 1  |Outbound    |Decreased 42.77Gbps,     Collecting max average |
      |    |bandwidth   |about 50.61% of total    outbound traffic of    |
      |    |            |Xunlei outbound         |a day from the DPI     |
      |    |            |traffic                 |system                 |
      |    |Inbound/    |outbound bandwidth      |Collecting max average |
      | 2  |outbound    |decreased 31.58Gbps     |inbound/outbound       |
      |    |bandwidth   |inbound bandwidth        traffic of a day from  |
      |    |            |decreased 10.46Gbps     |the snmp system        |

User's average download speed will decreased if traffic localization
 policy is applied

3.2. P2P cache test

   In this trial we deployed 16 cache devices, each with 1.8TB SAS hard
   disks. The P2P cache system has 15Gbps links connected to the
   internet.  We cached the content according to its popularity.

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      | No |Data Item   |Description             |The way of             |
      |    |            |                        |collection             |
      +----+---------- -+------------------------+-----------------------+
      | 1  |Outbound    |Decreased 40Gbps,        Collecting max average |
      |    |bandwidth   |about 54.47% of total    outbound traffic of    |
      |    |            |Xunlei outbound traffic |a day from the DPI     |
      |    |            |                        |system                 |
      |    |Inbound/    |outbound bandwidth      |Collecting max average |
      | 2  |outbound    |decreased 39.18Gbps     |inbound/outbound       |
      |    |bandwidth   |inbound bandwidth        traffic of a day from  |
      |    |            |decreased 28.3 Gbps     |the snmp system        |
      | 3  |Average     |From 279KBps up to      |Collection from Xunlei |
      |    |download    |294.5KBps               |OAM system             |
      |    |speed       |                        |                       |

   The P2P cache system occupancy ratio is about 80%. Bandwidth
   consumed is about 4-5Gbps.

   After deployed the P2P cache system, the traffic flow in the the
   province has decreased a lot. Meanwhile the average download speed
   of Xunlei client has been increased.

4. Methods of data collection

   In this trial we have two ways for information collection; one is to
   collect from p2p service provider such as Pando and Xunlei just like
   comcast's trial. The other is to collect from ISP's network OAM
   system. Because the Xunlei's inter-province traffic flow is about
   80Gbps that is large enough to be observed by ISP's network OAM

   1. Information from ISP's network OAM system and DPI system

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      a) Inbound/outbound traffic flow statistic

      b) Xunlei traffic flow detected by DPI system. The DPI system
         just monitored the uplink of the province to China telecom's

   2. Information from Xunlei

      a) Inter-province/intra-province traffic flow.

      b) User average download speed.

5. Configurations and algorithms in trial

5.1. Configuration of PID MAP

      a) PID Map: We define 11 PIDs
                PID1-PID11 represent the 11 MANs of the trial network
                PID12 represents rest of the Internet

      b) Cost Map:
                Bidirectional cost between any PIDs from PID1 to PID11 has the
          same value 1
                Bidirectional cost between PID12 and PIDi (1<=i<=11) has the
          same value 2

5.2. Algorithms of Xunlei using ALTO information

     Xunlei is a hybrid application utilizing both trackers and DHT,
   About 85% of Xunlei traffic controlled by Xunlei trackers. In this
   trail ALTO clients just include the xunlei trackers not include the
   xunlei client. Just the traffic controlled by xunlei tracker has
   been affected.

    Before the trial Xunlei tracker peer selection algorithm is:

   Xunlei Peer selection algorithm depends on two properties: ISP ID
   and UC (upload capability), the peer selection priority is :

             Same ISP ID > different ISP ID

             Higher UC > lower UC

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   The peers with same ISP ID with the requesting peer have higher
   priority than those with different ISP ID. If peers have same ISP ID
   then the peers with higher UC have higher priority than those with
   lower UC.

   After applying the ALTO information into the xunlei peer selection
   algorithm. Xunlei changed his Peers select mechanism. All xunlei
   peers are organized in a tree structure which is indexed by
   CID(content ID), in the second level ALTO_ISP and normal_ISP
   represent the network of ISP with and without alto information. In
   this trial 11 MANs in trial province became 11 ALTO_ISPs.The third
   level is defined by different upload capability(UC) of peers. The
   fourth level of normal_ISP branch is the different
   provinces(PRO1,PRO2) of ISP, the fifth level of the normal_ISP is
   different city of ISP.

                                  |        CID        |
                                   /                     \
                      +----------+                    +----------+
                      |NORMAL_ISP|                    | ALTO_ISP |
                      +----------+                    +----------+
                      /     |     \                   /     |     \
                   UC_BIG UC_MID  UC_SMALL         UC_BIG UC_MID  UC_SMALL
                 /   |                              |   \
               PRO1 PRO2                            PEER1  PEER2
             /   |
         CITY1 CITY2
         |   \
      PEER1  PEER2

   The algorithms of cost between origination peer(peer_o) and
   destination peer(peer_d) is :

   If (peer_o and peer_d both from ALTO_ISP)

     If (peer_o and peer_d in the same ALTO_ISP) then cost = 0;

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     Else cost = 100000;

   Else if (peer_o from ALTO_ISP and peer_d from normal_ISP) cost =

   Else if (peer_o from normal_ISP and peer_d from ALTO_ISP) cost =

   Else if (peer_o and peer_d both from normal_ISP){

     If (peer_o and peer_d from different normal_ISP) cost =1000;

     Else if (peer_o and peer_d from different province) cost = 100;

     Else if (peer_o and peer_d from different city) cost = 10;

     Else cost =0;


   The peer select mechanism is lower cost peers will have higher

   The updated peer selection mechanism is not the best mechanism. For
   example a peer in MAN2 is supposed to be better choice than the
   peers which not located in china telecom's network when a peer in
   MAN1 send a content request to tracker. But this mechanism will
   select the peer out of china telecom's network first then select the
   peer in the MAN2. Before we defined the network map with 12 PIDs. We
   first defined a network map with just 2 PIDs. PID1 represent the
   trial province and PID2 represent the other network to test the
   backbone traffic saving effect of ALTO service. The test result show
   that the network map with 12PIDs has almost same backbone traffic
   saving effect compared to the network map with 2 PIDs. So in the
   trial we deployed this mechanism.

   The other change is the number of returned peers from xunlei
   tracker . If a listing request is from the trial province, the
   maximum # of returned peers from xunlei tracker is set to 120, not
   the normal case of 500.

5.3. Configuration of cache system

   Before we deploy the cache system we have made some statistics about
   relationship of content popularity and network traffic caused by
   content with different popularity in trial province.

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   |content    | total   |total     | proportion  |

   | popularity| size(GB)|traffic   |  of total   |

   |           |         |(Gbps)    |traffic(%)   |


   |  top 10   |  18.9   |   1.34   |     9.3     |

   |  top 20   |  29.3   |   1.68   |    11.7     |

   |  top 50   |  51.8   |   2.28   |    15.9     |

   |  top 100  |  93.6   |   2.89   |    20.1     |

   |  top 500  |  418.7  |   4.74   |     33      |

   | top 1000  |  812.4  |   5.88   |    40.9     |

   | top 2000  | 1518.6  |   7.16   |    49.8     |

   | top 5000  |  3551   |   8.89   |    61.9     |


   Our cache system has limited storage and access bandwidth so we need
   to know which content is most "valuable" to be cached. According the
   statistics from xunlei if a downloading task is fed over 100 peers ,
   this task always can get the maximum download speed(this speed
   depends on the peer's access network, in the trial the average
   access speed of user is about 2Mbps). The top 2000
   popular content almost all have over 100 seeds in trial province.
   That means the top 2000 popular contents don't need be cached. Our
   cache policy is just cache the content which's popularity rank
   behind 2000.

6. Next steps

   The alto mechanism is very effective to optimize the traffic flow.
   But when the traffic is localized, the user average download speed

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   is slowed down simultaneously. If alto can cooperate with p2p cache
   or other service performance enhancement mechanism, it will be more
   The ALTO service's effect depends on the SP such as Xunlei,pando how
   to use it. The mechanism such as peer selection mechanism and
   content cache mechanism need to be studied.

7. Security Considerations

   High-level security considerations can be found in the [draft-ietf-

8. IANA Considerations

   This document requests the registration of a new media type:

9. References

   [RFC 5693]
             Seedorf, J. and E. Burger, "Application-Layer Traffic
                 Optimization (ALTO) Problem Statement", RFC 5693,
                 October 2009.

                 Kiesel, S., Popkin, L., Previdi, S., Woundy, R., and Y.
                 Yang, "Application-Layer Traffic Optimization (ALTO)
                 Requirements", draft-ietf-alto-reqs-01 (work in
                 progress),July 2009.

                 Penno, R. and Y. Yang, "ALTO Protocol",
                 draft-ietf-alto-protocol-01 (work in progress),
                 July 2009.

Author's Addresses

   Kai Lee
   China Telecom Beijing Research Institute
   Email: leekai@ctbri.com.cn

   GuangYao Jian
   Xunlei Network
   Email: jianguangyao@xunlei.com

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