One document matched: draft-wu-ppsp-mtn-introduction-00.txt
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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