PPSP                                                      Yunfei. Zhang
Internet Draft                                             China Mobile
Intended status: Informational                             March 5, 2009
Expires: September 5, 2009

                Introduction of Distributed Services Network

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Internet-Draft  Introduction of Distributed Services Network                                                                  March 2009


   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

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

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Internet-Draft  Introduction of Distributed Services Network                                                                  March 2009

2. Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   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

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

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Internet-Draft  Introduction of Distributed Services Network                                                                  March 2009

   |  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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Internet-Draft  Introduction of Distributed Services Network                                                                  March 2009

   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

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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Internet-Draft  Introduction of Distributed Services Network                                                                  March 2009

   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

   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

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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Internet-Draft  Introduction of Distributed Services Network                                                                  March 2009

   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

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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Internet-Draft  Introduction of Distributed Services Network                                                                  March 2009

   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

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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Internet-Draft  Introduction of Distributed Services Network                                                                  March 2009

7.  References

7.1. Normative References

   [1]  ITU-T DSN, Proposed scope of DSN,

   [2]  ITU-T DSN scenario, Initial draft of supplement Y.dsnscen
         Supplement on DSN scenarios, http://www.itu.int/md/T09-SG13-

   [3]  ITU-T DSN requirements,Initial draft of recommendation Y.dsnreq
         "Recommendation on DSN requirements", http://wwwtu.int/md/T09-

   [4]  DSN whitepaper,unpublished.

7.2. Informative References

Author's Addresses

   Yunfei Zhang
   China Mobile

   Phone: 86 13601032119
   Email: zhangyunfei@chinamobile.com

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