Internet DRAFT - draft-wu-ppsp-mtn-introduction

draft-wu-ppsp-mtn-introduction






PPSP                                                               J. Wu
Internet-Draft                                                   B. Long
Intended status: Informational                                   T. Pang
Expires: January 7, 2010                                        H. Huang
                                                           China Telecom
                                                            July 6, 2009


                          Introduction of MTN
                   draft-wu-ppsp-mtn-introduction-00

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Abstract

   This draft briefly introduces MTN, the Median Telecom Network built



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   by China Telecom to support streaming and file download services with
   peer to peer technologies.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
     2.1.  MTN  . . . . . . . . . . . . . . . . . . . . . . . . . . .  3
     2.2.  Center node  . . . . . . . . . . . . . . . . . . . . . . .  3
     2.3.  Area node  . . . . . . . . . . . . . . . . . . . . . . . .  3
     2.4.  Static node  . . . . . . . . . . . . . . . . . . . . . . .  3
     2.5.  User node  . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  MTN architecture . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Key components . . . . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  Content storage and delivery system  . . . . . . . . . . .  6
     4.2.  Resource management and dispatch system  . . . . . . . . .  7
     4.3.  Content management system  . . . . . . . . . . . . . . . .  9
   5.  Deployment . . . . . . . . . . . . . . . . . . . . . . . . . .  9
   6.  Performance evaluations  . . . . . . . . . . . . . . . . . . .  9
   7.  Security considerations  . . . . . . . . . . . . . . . . . . .  9
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10


























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1.  Introduction

   MTN, the abbreviation of media telecom network, is a service network
   built by China Telecom to provide media services in peer to peer
   form.  As far as we know, PPLive has constructed a platform for its
   linear TV and then another different one for VOD because of the lack
   of scalability of the first platform, which weighs both CAPEXP and
   OEXP.  On the contrary, MTN provides linear streaming, VOD, and file
   download on the same platform.  Our aim is to support multiple media
   services over one single platform with carrier's grade manageability
   and operability.  What's more, MTN is designed for both IPv4 and IPv6
   to be compatible with the evolution of NGN.  The concept of MTN was
   proposed in 2004 and we constructed a trial platform in 2008.  Now
   MTN is working as a commercial platform to support P2P services.


2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

2.1.  MTN

   MTN is a distributed, manageable and operable platform which can
   effectively support a wide range of media services such as linear TV,
   VOD, file download and so on.

2.2.  Center node

   Center node is the higher index server containing the content routing
   information of the whole MTN, which responds to inquiries from area
   nodes.

2.3.  Area node

   Area node is the lower index server with the knowledge of the content
   routing information of its own responsible region, which receives
   requests from user nodes of its area, replies to user nodes or
   forwards the requests to center node, and supplies center node with
   its area routing information for aggregation.

2.4.  Static node

   Static node refers to a special server deployed by carriers to offer
   better performance experiences, which acts as either a supplement
   content seed or a relay, or both.




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2.5.  User node

   User node refers to electronic terminal used to consume the services
   by users, e.g.  PCs, mobile terminals, etc.


3.  MTN architecture

   MTN uses the distributed-transport and central-control design along
   with integrated services supporting platform and carrier's existing
   BSS/OSS to achieve the goal of manageability and operability.  To
   make it clear, we divided the architecture into several sub-layers as
   follows:






































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   +-----------------------------------------------------------------+
   |   Operation  Supporting Sub-Layer                               |
   | +-----------------------------------------------------------+   |
   | |   +--------+ +--------+ +----------+ +-------------+      |   |
   | |   |Users & | |Billings| |Statistics| |Terminals &  |      |   |
   | |   |CPs mgmt| |        | |          | |Networks mgmt|      |   |
   | |   +--------+ +--------+ +----------+ +-------------+      |   |
   | +-----------------------------------------------------------+   |
   |  Service Applying Sub-Layer                                     |
   | +-------------------------------------------------------------+ |
   | | +---------+ +---+ +--------------+ +----------------------+ | |
   | | |Linear TV| |VOD| |File Downloads| |Extending Applications| | |
   | | +---------+ +---+ +--------------+ +----------------------+ | |
   | | +--------------------------------+ +----------------------+ | |
   | | |Digital Right Management System | |                      | | |
   | | +--------------------------------+ |Extending Applications| | |
   | | +--------------------------------+ |Supportive Systems    | | |
   | | | Content Management System      | |                      | | |
   | | +--------------------------------+ +----------------------+ | |
   | | +---------------------------------------------------------+ | |
   | | |       Information Publication System                    | | |
   | | +---------------------------------------------------------+ | |
   | +-------------------------------------------------------------+ |
   |  Service Controlling Sub-Layer                                  |
   | +-------------------------------------------------------------+ |
   | |       Resource Management and Dispatch System               | |
   | |           ( Center Node & Area Nodes )                      | |
   | +-------------------------------------------------------------+ |
   |  Content Switching Sub-Layer                                    |
   | +-------------------------------------------------------------+ |
   | |       Content Storage and Delivery System                   | |
   | | +--------------+  +--------------+   +--------------------+ | |
   | | |  User Nodes  |  | Static Nodes |   | Content Repository | | |
   | | +--------------+  +--------------+   +--------------------+ | |
   | +-------------------------------------------------------------+ |
   |  Network Carrying Sub-Layer                                     |
   |  +------------------------------------------------------------+ |
   |  | +-------------------------------------------------------+  | |
   |  | |          ChinaNet Internet    or    CN2 Network       |  | |
   |  | +-------------------------------------------------------+  | |
   |  |    +-----------+      +-----------+     +------------+     | |
   |  |    | DSL Access|      | LAN Access|     | WLAN Access|     | |
   |  |    +-----------+      +-----------+     +------------+     | |
   |  +------------------------------------------------------------+ |
   +-----------------------------------------------------------------+


   The bottom in the hierarchy is the carrier's network infrastructures,



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   which consist of various access networks and the backbone networks.
   As for China Telecom, it now has two distinct backbone networks:
   ChinaNet and China Telecom Next Generation Carrying Network (CN2),
   and users can access them in different ways.

   The second is content switching sub-layer, which has content storage
   and delivery system composed of user nodes, static nodes and content
   repository.  The major streaming data flows are occurring among these
   three types of entities.

   The third is service controlling sub-layer, which has the instances
   of center nodes and area nodes.  Its main function is to collect and
   aggregate content routing information and respond the indexing
   queries.

   The forth is service applying sub-layer, which contains the
   application-specific function components, e.g. digital right
   management, content management system, etc.

   Atop is the conventional operation supporting sub-layer, which
   usually has User and CP management, billings, statistics, terminal
   and P2P network management, and so on.


4.  Key components

   The draft doesn't intend to cover all aspects of MTN, instead it
   focuses on several essential components, which we think SHOULD
   include the content storage and delivery system, resource management
   and dispatch system, and content management system.

4.1.  Content storage and delivery system

   For the purpose of P2P share, the content storage needs special
   treatment, so we elaborate on the mechanism used in our design.

   The contents are stored in the unit of segment, whose size is 2M
   bytes.  If the length of content is not multiple of 2M bytes, the
   last segment can be less than 2M bytes with an ending symbol
   appended.  The storage disks of user nodes, static nodes and content
   repository are divided into areas of 512M bytes size and the areas
   are numbered.

   After getting the peer list from area node or center node, user node
   begins the process of content request and delivery.  A user node
   could build connections with at most 20 peers, and SHOULD NOT ask for
   content from more than 10 peers.  A peer could simultaneously upload
   content to no more than 4 user nodes.



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   Before content delivery starts, the receiver assigns a space of size
   256K byte in memory.  The content is delivered in the unit of 64K
   byte, and is first placed in the designated memory space.  It will be
   rewrite to the corresponding segment of 2M bytes in disk once the
   256K memory is full.  As soon as a new segment has been downloaded,
   the receiver will update its indexing information in its area node
   and center node.

4.2.  Resource management and dispatch system

   Resource management and dispatch system consists of one center node
   and various number of area nodes, which in turn compose of a two-
   layer hierarchy with the center node in the higher.  In MTN, each
   area node manages a certain number of user nodes and static nodes,
   which are usually geographically proximate and MAY change
   dynamically.  With the constant join, leave, failure of user nodes,
   an area MAY be split into two when there are too many nodes or two
   sparse areas could be merged into one, all partition and merger
   operations are under the control of center node.  MTN has adopted a
   sophisticated method to implement such an adaptive management.

   The routing computing is simple: user node sends requests to the
   corresponding area node, which will first looks up in its own
   indexing database.  If there are enough seeds, the area node returns
   a list of peers based on the principle of traffic localization; else
   if the area node cannot find REQUIRED number of peers, it forwards
   the query to center node, which will pick another area node based on
   both load balance and traffic optimization to handle the requests.
   Center node will reply to the origin user node directly after all the
   computing.

   The indexing information in MTN is stored using link data structure,
   with the tiny change that the first entity of link uses a different
   format which is specified as follows:

   +------------+------------+---------+----------+-------------+
   |content ID  | shared tag | DRM Tag | Reserved | upload count|
   +----------------------------+-------------------------------+
   |     segment count          |    content length             |
   +----------------------------+-------------------------------+
   |     created date           |    modified date              |
   +----------------------------+-------------------------------+
   |     first segment ID       |    first segment pointer      |
   +----------------------------+-------------------------------+

      content ID: the 40-bits field is the unique identifier of content
      in MTN.




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      shared tag: the 1-bit field specifies whether the content can be
      shared, the value of '0'forbids sharing while '1'permits.

      DRM tag: the 2-bits field specifies whether the content has been
      encrypted, the value of '00'means no encryption, '01'denotes it
      has been encrypted by carriers, '10'encrypted by content
      providers, '11'is reserved.

      Reserved: the 5-bits field is preserved for future use.

      Upload countGBPothe 16-bits field specifies the number of segments
      that have been uploaded.

      Segment count: the 32-bits field specifies the number of segments
      the node has.

      Content length: the 32-bits field specifies the size of content in
      the unit of byte.

      Created date: the 32-bits field specifies the time when the
      indexing information is created.

      Modified date: the 32-bits field specifies the latest update time
      of indexing information.

      First segment ID: the 32-bits field specifies the smallest ID of
      segments of the content it has.

      First segment index: the 32-bits field specifies the pointer to
      the exact storage information of the first segment, which has the
      following format:

   +-----------+---------------+---------------+--------------+
   |segment ID | area sequence | data position | next pointer |
   +-----------+---------------+---------------+--------------+

      Segment ID: the 32-bits field specifies the identifier of the
      segment.

      Area sequence: the 16-bits field specifies which area of storage
      the segment resides in.

      Data pointer: the 32-bits field specifies the exact position of
      the segment in the area.

      Next index: the 32-bits field points to a same format index for
      the next greater segment on the storage.




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4.3.  Content management system

   Content management system is responsible for the upload, edition,
   deletion, storage and other related operation of contents.When a
   specific content is uploaded, an ID of 40 bits length which is unique
   in the scope of MTN will be assigned.  The following metadata SHOULD
   also be provided along with the content:

      Content type, e.g. audio, video, game, etc.

      File type, e.g. .exe, word, etc

      Content status, which indicates whether the content is available.

      Service type, e.g. download, online play, etc.


5.  Deployment

   The deployment of MTN adopted a three-layer hierarchy corresponding
   to the administration regionalism of China: country, province and
   individual.  The center node and the center content repository are
   placed at the country level, while area nodes and provincial content
   repositories are installed at the province level.  A note is that one
   province usually has only one content vault but various number of
   area nodes according to the number of its subscribers.  The lowest
   level contains user nodes and static nodes.  The deployment of static
   nodes by carriers is to provide faster and more stable seeds for
   users and they could also function as relays as needed.


6.  Performance evaluations

   We evaluate the performance of MTN in two ways: large-scale
   simulation based on PDNS and the field trial and test.  Both results
   indicate MTN could provide traffic localization and service of
   quality as well as or better than PPLive, PPStream and BitTorren.


7.  Security considerations

   In MTN, the following security issues have been addressed:

      authentication and authorization: on one hand, the terminal users
      MUST first register with the carrier and provide usernames and
      passwords to enter the MTN through a client software provided by
      the carrier.  Once given the admission, users could consumer the
      services authorized to them.  On the other hand, the content



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      provider MUST also be authenticated and authorized to upload
      contents.

      Content securities: all contents in MTN MUST be creditable and
      legal and their copyrights can be protected.  MTN has its own DRM
      mechanism and external DRMs could also be applied through specific
      interfaces, contents MAY be encrypted by content providers or
      carrier.  Once contents have been uploaded by content providers,
      they will be artificially censored before being published.  The
      contents downloaded by users can be verified against correctness
      and integrity.

      Communication securities: the route queries and responses could be
      encrypted as needed.


8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

8.2.  Informative References


Authors' Addresses

   Wu Juan
   China Telecom
   109 West Zhongshan Ave, Tianhe District
   Guangzhou, Guangdong Province  510630
   P.R.China

   Phone: +86-20-38639132
   Fax:   +86-20-38639457
   Email: wuj@gsta.com














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   Long Bin
   China Telecom
   109 West Zhongshan Ave, Tianhe District
   Guangzhou, Guangdong Province  510630
   P.R.China

   Phone: +86-20-38639453
   Fax:   +86-20-38639457
   Email: longbin@gsta.com


   Pang Tao
   China Telecom
   109 West Zhongshan Ave, Tianhe District
   Guangzhou, Guangdong Province  510630
   P.R.China

   Phone: +86-20-38639769
   Fax:   +86-20-38639457
   Email: pangt@gsta.com


   Huang Hai
   China Telecom
   109 West Zhongshan Ave, Tianhe District
   Guangzhou, Guangdong Province  510630
   P.R.China

   Phone: +86-20-38639582
   Fax:   +86-20-38639457
   Email: Huanghai@gsta.com




















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