One document matched: draft-zhang-ppsp-dsn-introduction-00.txt
PPSP Yunfei. Zhang
Internet Draft China Mobile
Intended status: Informational March 5, 2009
Expires: September 5, 2009
Introduction of Distributed Services Network
draft-zhang-ppsp-dsn-introduction-00.txt
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zhang Expires September 5,2009 [Page 1]
Internet-Draft Introduction of Distributed Services Network March 2009
Abstract
This draft briefly introduces DSN,a Distributed Service Network
proposed by China Mobile in ITU-T as the evolution of NGN.PPSP is a
protocol DSN plans to develop to support streaming services in future
Internet.
Table of Contents
1. Introduction................................................2
2. Terminology.................................................3
2.1. DSN....................................................3
2.2. Core node..............................................3
2.3. User node..............................................3
3. DSN architecture............................................3
4. DSN Scenarios[4]............................................5
4.1. Service Scenarios......................................5
4.1.1. Multimedia telephony services.....................5
4.1.2. Streaming services................................6
4.1.3. Content distribution service......................6
4.1.4. Large-scale High Bandwidth Multi-media Service....7
4.2. Carrier Deployment Scenarios...........................7
4.2.1. Carrier private network-based Deployment..........7
4.2.2. Internet Deployment...............................7
5. Relationship between DSN and PPSP...........................8
6. Security Considerations.....................................8
7. References..................................................9
7.1. Normative References...................................9
7.2. Informative References.................................9
1. Introduction
DSN[1],the abbreviation of Distributed Services Network, is a new
question being standardized in ITU-T proposed by China Mobile. The
first DSN conference was held on January 11th to 23rd,2009 in ITU-T
SG13 plenary meeting in Geneva. Two work items, DSN scenarios[2] and
requirements[3] of DSN capabilities were approved to set up in
current stage. In ITU-T DSN is defined as the evolution of NGN which
uses distributed technologies such as P2P to rebuild the core network
with lower CAPEX/OPEX and more flexible application support to suit
with mobile Internet and FMC development. Therefore it's important to
introduce DSN in related STDs like IETF and 3GPP to accelerate
NGN/NGI development. PPSP can be used in DSN for p2p streaming
applications.
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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 RFC 2119 [RFC2119].
2.1. DSN
DSN is the evolution of NGN driven by p2p technology which provides
distributed, operatable and managable characteristics to support
more carrier's grade rich multimedia services beyond current NGN
scope.
2.2. Core node
Core node refers to the DSN node deployed in service provider domain,
e.g. DSL/Wireless access and aggregation network, IP/MPLS core, etc.
2.3. User node
User node refers to the DSN node in user domain, e.g. PCs, mobile
terminals, etc.
3. DSN architecture
DSN focuses on overlay network layer, which may belong to
application-layer in ISO/OSI model. The traditional Internet is a
dumbbell structure, which places most of the intelligence in the
terminal system and leaves the network as simple as possible. Along
with overlay network introduced in the migration of internet, it
stresses more intelligence in the middle of the network. To make it
clear for designers, we divide this layer into several sub-layers as
follows:
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+-----------------------------------------------------------------+
| Application Sub-Layer |
| +-------------------------------------------------------------+ |
| | +-----+ +---+ +----------+ +-----------+ +-------+ +------+ | |
| | |VoIP | |IM | |Streaming/| |Downloading| |Search | | Game | | |
| | | | | | |Mobile TV | | | |Engine | | | | |
| | +-----+ +---+ +----------+ +-----------+ +-------+ +------+ | |
| +-------------------------------------------------------------+ |
|============================ API ================================|
| Service EnablerSub-layer |
| +-------------------------------------------------------------+ |
| | +-----------+ +-----------+ +-----------+ +-----------+ | |
| | |Distributed| |Distributed| |Distributed| |Distributed| | |
| | |Cache | |Storage | |Relay | |Computing | | |
| | +-----------+ +-----------+ +-----------+ +-----------+ | |
| +-------------------------------------------------------------+ |
| Enhanced P2P Control Sub-layer |
| +-------------------------------------------------------------+ |
| |+----------+ +------+ +---------+ +------------+ +----------+| |
| || P2P | | P2P | | P2P | |Overlay | | Platform || |
| || Mobility | | QoS | | Security| |Interworking| |&User mgmt|| |
| |+----------+ +------+ +---------+ +------------+ +----------+| |
| +-------------------------------------------------------------+ |
| Basic P2P Routing Sub-layer |
| +-------------------------------------------------------------+ |
| | +----------+ +-------------------------+ +-----------+ | |
| | |Index | |Distributed Content | |Topo-Aware | | |
| | |Mechanism | |Publish/Update/Amendment | |P2P Routing| | |
| | +----------+ +-------------------------+ +-----------+ | |
| +-------------------------------------------------------------+ |
|=================================================================|
| +-------------------------------------------------------------+ |
| | IP Network | |
| +-------------------------------------------------------------+ |
+-----------------------------------------------------------------+
Figure 1 DSN Architecture.
The bottom in the overlay layer is Pbasic p2p sub-layer where basic
p2p functions are involved e.g.,index mechanism, distributed content
publish/update/amendment and topology-aware P2P routing.
The second is the enhanced p2p control sub-layer where some
additional management and control functions for the basic p2p network
are developed such as mobility in p2p,QoS mechanism based on p2p
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technology, different p2p system inter-working and distributed
management functions to monitor the p2p system running condition and
individual nodes.
The third is service enabler sub-layer, which is the basic components
to develop applications. They can also be used jointly. For
example, VoIP uses distributed relay module and streaming uses
distributed cache and storage module where gaming uses both.
Atop is application sub-layer where DSN operators open API to expose
network capability to both self-run applications and 3rd applications.
4. DSN Scenarios[4]
DSN applies the P2P technology to provide operators with reduced
CAPEX/OPEX, improved scalability/ubiquity, self
organization/maintenance and fault tolerance.
DSN enables the core architecture of wireless Internet with the
combination of P2P technology and other distributed technologies.
With DSN, carriers are able to build scalable telecom network
platform that deliver multimedia applications and content
applications. In DSN application system, the following services are
enabled:
4.1. Service Scenarios
4.1.1. Multimedia telephony services
With DSN, carriers can build cost effective and large scale MMTel
service system.
Compared with existing MMTel system, DSN's service control node is
named as core node who collaborate with each other in a peer to peer
paradigm. There is no central server for session processing.
Core Nodes compose of a P2P overlay which has its own addressing and
routing mechanisms. Users are registered in different Core Nodes in
the P2P overlay. Core Nodes communicate with each other by exchanging
the application routing information.
Since there is no central server, a single node failure will not
cause system failure. When parts of the nodes are not available in
the system, other nodes can continue to provide services as an entire
system with the organization of P2P technology without any impact
from the unavailable hosts.
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It is unnecessary to configure the added hosts specifically, instead
it only requires that the application layer supports P2P related
protocols in the system, and the system will be expanded
automatically. All the application layer addressing and routing
information are communicated by P2P protocols without manual
configuration. And system capacity can be enlarged by adding new Core
Nodes even by using user equipment as it can also runs Core Node
functions.
In a complicated IP environment, end to end QoS is hard to realize
because congestion may happen along the media path, "Best of effort"
feature may ignores the service requirements of real-time
applications such as MMTel. With DSN, a peer acting as a relay node
can be inserted to the media path to enhance the performance of real-
time service. The relay mechanism can also provides good NAT traverse
capability, which allows users to access high quality service after
NAT.
4.1.2. Streaming services
Streaming services become more and more popular in current Internet.
Conventional C/S model suffers from performance bottleneck and poor
scalability when the number of streaming service subscribers keeps
growing. Operators thus would have to maintain the service quality by
deploying more and more streaming servers, which increases their
CAPEX/OPEX of the network. While in P2P mode, each user acts as a
peer that not only downloads the streaming content but uploads the
content to other users, thus effectively reduce the burden of
streaming server and improve the scalability of streaming service.
Streaming across different network domains may cause increased
network traffic where a network domain usually means a subnetwork
with peers having the vicinity in network topology (e.g. same LAN,
same service PoP). Therefore, it is important for DSN to realize
traffic localization.
4.1.3. Content distribution service
DSN enables very large data storage and content delivery with the
help of p2p overlay distribution network. In P2P-enabled system,
network resources are distributed across peer nodes. Users can
provide and obtain resources and data simultaneously. Such features
make it easier for very large data storage. For carriers, these
features allow maximization of edge network resources and reduce the
load of the server. For users, the new technology provides a richer
resource and a faster resource-sharing channel.
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The Content distribution network based on DSN should closely combine
with underlying routing and the transmission mechanism to realize the
optimization of traffic.
4.1.4. Large-scale High Bandwidth Multi-media Service
Bandwidth exhausting multimedia service in the future may become the
killer application. However it has higher requirements on the network
bandwidth and node processing capability. These applications have
very high requirements on the carrier network: Presence system
requires 3-10M network bandwidth, less than 100ms delay, and 10ms
jitter, and also have high requirement on route setup process as well
as QoS. DSN intelligent routing mechanism provides routing function
for the system, and provides QoS guarantee for large capacity
multimedia service on the basis of P2P bandwidth aggregation
capability.
4.2. Carrier Deployment Scenarios
For the real deployment of DSN, it can be classed into private
network-based deployment and Internet-based deployment for different
applications from the perspective of carriers.
4.2.1. Carrier private network-based Deployment
Carriers can deploy DSN in the mode of private network. Private
network deployment means deploying DSN on the carrier's private
network, e.g. IP private network of China Mobile. DSN serving modes
are deployed on the private network of carrier, which can NOT be
accesses from Internet. They deliver services in a trusted
environment, and DSN network will provide the required high security
and manageability. This deployment mode, however, only optimizes the
serving nodes of its owns compared with the deployment in Internet
environment, without maximizing the resources in Internet environment.
Private network-based DSN can provide traditional telecom service,
including basic voice/video call, supplementary services, value-added
service and IM communication, it also provides service interface for
future new services (e.g. VoIP service, content delivery, real-time
file download and large-capacity multimedia service etc.) with
enhanced service capability. Private network-based DSN can interact
with traditional telecommunication networks via gateway.
4.2.2. Internet Deployment
In this mode, DSN node can be deployed over Internet, or services
provided by DSN node can be accessed from Internet. DSN node on
Internet includes the equipment of carrier and also a large number of
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user nodes on the Internet. The sufficient resources of Internet can
be better utilized, which will drive the carrier to reduce the
network deployment cost. In addition, DSN allows the diversity of
services. With the service interface provided by carriers, a number
of practical service modes will emerge in the open Internet
environment. However, a lot of DSN service nodes on the Internet may
be the users nodes, whose security and stability can not be
guaranteed, and increase the difficulty to control and manage network.
Internet-based DSN can help carriers converge Internet service and
address the service mode shift from voice to data. Internet-based DSN
can also interact with traditional telecommunication networks via
gateway.
5. Relationship between DSN and PPSP
As shown in last section, p2p streaming and other content services
are important types in DSN. Therefore we need a uniform p2p streaming
protocol run among core nodes and user nodes. It can also be used
when there are multiple DSN implementations which can be inter-worked
each other for streaming service.
6. Security Considerations
The motivation of this draft is to introduce Distributed Service
Network (DSN). We don't consider security issues in this draft.
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7. References
7.1. Normative References
[1] ITU-T DSN, Proposed scope of DSN,
http://www.itu.int/md/meetingdoc.asp?lang=en&parent=T09-SG13-
090112-C&PageLB=50.
[2] ITU-T DSN scenario, Initial draft of supplement Y.dsnscen
Supplement on DSN scenarios, http://www.itu.int/md/T09-SG13-
090112-TD-WP5/en.
[3] ITU-T DSN requirements,Initial draft of recommendation Y.dsnreq
"Recommendation on DSN requirements", http://wwwtu.int/md/T09-
SG13-090112-TD-WP5/en.
[4] DSN whitepaper,unpublished.
7.2. Informative References
Author's Addresses
Yunfei Zhang
China Mobile
Phone: 86 13601032119
Email: zhangyunfei@chinamobile.com
Zhang Expires September 5, 2009 [Page 9]
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