P2P:Development Situation and Operation Solutions

Dong Zhenjiang,Qi Chen

（Communication Service and Software R&D Center, ZTE Corporation, Nanjing 210012, China）

Abstract:The rapid development of Peer-to-Peer（P2P）technologies and applications has a great impact on telecom services and operations.Operators should refine the pipeline operation and develop characteristic P2P services.They must comply with the rule of Internet services,and design manageable and operational P2P solutions combining the advantages in network,resource and subscriber,providing users with better P2P service experience.ZTE's manageable and operational P2P solution provides operators with customized authorization and accounting functions.Its development is based on the broadband service management platform widely used in the live networks.ZTE's P2P system is stable and reliable.

T he Peer-to-Peer（P2P）architecture allows distributed resource utilization and sharing.It corresponds to the Client/Server（C/S）system architecture predominantly used in the networks.Each node in the P2Pnetwork plays the same role.It acts as both a server and a client.Each node provides services and meanwhile shares services of other nodes.The key technology for the P2Pmode is resource positioning,while the traditional telecom network uses a C/Smode.Figure 1 shows the comparison between the two modes.

P2Pis one of the hottest Internet technologies in recent years.It develops rapidly in Voice over Internet Protocol（VoIP）,download,streaming media and coordination calculation,and is chosen by the Fortune magazine as one of the four great technologies that affect the Internet.

The P2Ptechnology reflects the most basic connotation of the Internet—free and no charge,with the following major advantages:

·High equivalence:Non-centralized.The Internet returns back to the original functions—contact and transmission.

·Good scalability:Users are expanded synchronously with resources,services and systems.

·Great robustness:Services are scattered and self-adaptive,with anti-attack and high fault tolerance.

·High cost-effectiveness:P2P allows low cost and high storage and computing capabilities.

·Load-balanced:Distributed storage and computing ensures load balance in the entire network.

The P2Ptechnology and services have a great impact on the traditional telecom industry.How to deal with and how to use the P2Ptechnology becomes an issue that operators have to face.

1 P2P's Current Situation and Problems

1.1 P2P's Wide Application

P2Phas a variety of applications in the following aspects:

▲Figure 1. Comparison between P2P and C/S modes.

·Content download and sharing:Typical applications include BitTorrent（BT）,eMule,eDonkey and Thunder software,which are preferred tools of a wide range of users for downloading movies,TVprograms,software and materials.

·Instant messaging:Typical software includes MSN,QQ and Skype.QQ is a common communication tool especially for young persons.MSN is the preferred toolfor office-goers.Skype becomes another name of IPPhone,mainly used for the call conversation service.

·Audio and video online sharing:Typical applications include MP3 online playing,and video sharing on such websites as Tudou.com.

·Computing capability sharing:Typical applications include SETI@home and Xenoservers.

·P2Pstreaming media:Typical software includes PPlive,PPstream,UUSee,QQLive and Joost.The software allows users to enjoy sports games and live broadcast of important events,cycling broadcast of movie programs,video on demand,chat-room broadcast,and online radio station.

During the Spring Festival Evening Party 2006,China Central Television（CCTV）provided synchronous video live-broadcast to the world through P2P and Content Distribution Network（CDN）technologies.The number of clicks on the CCTVwebsite that evening reached 296 million.The number of visits to the website reached 47.92 million.4.1 million people watched the live broadcast,in which 0.89 million were overseas.

A statistical report of iResearch［1］shows the average number of daily Chinese Internet users reached 10 million in 2006,in which 25%were P2P streaming media users.It is expected that number will reach 63 million in 2010,in which 40%will be P2Pstreaming media users.

The abovementioned typical applications are widely used and accepted by users.The network TVhas become a hot and major P2Papplication in recent years.

1.2 Negative Proportion of P2P Bandwidth Usage and Profit

Statistics show that the proportion of P2P services to the bandwidth usage is approximately 40%—60%,and 80%—90%in extreme conditions.P2P becomes a bandwidth“killer”that consumes a large number of network resources,which causes congestion of key links in operators'networks and fast performance degradation of other Internet applications［2］.

Operators expand their network capacities continuously every year;however,the added bandwidth is consumed by P2Papplications quickly,with no improvement of network service performance.Moreover,it greatly affects the normal services that generate profits.There are more and more user complaints.All this has a great impact on the enthusiasm of operators for bandwidth expansion.

Statistics on operators'profits show that data services including Multimedia Message Service（MMS）and Short Message Service（SMS）provide more than 90%of their total profits with less than 5%of the bandwidth,whereas the P2Pservices provide only 5%of profits.P2Papplications have an infinite demand for the bandwidth,but operators'network resources are limited.How can the invested system resources obtain a reasonable return?Broadband services including P2Pwillnot have a healthy development if this problem is not resolved.

The negative proportion of bandwidth and profit has become a more serious problem and one of the most important factors that affect the development of broadband services.

1.3 P2P Development Prospect

The statistics from the China Internet Network Information Center（CNNIC）show that China had 137 million netizens in 2006.The number of Chinese netizens was expected to reach 163 million in 2007,and 262 million in 2010,according to a statistical report and forecast of iResearch.In 2006,an average of 40 million Chinese people,which account for 30%of the Chinese netizens,watched P2Pstreaming media programs every month.The number of P2Pstreaming media service users was expected to reach 65 million in 2007,and 158 million in 2010,accounting for 68%of the Chinese netizens.

The above data reflect a promising prospect of broadband service development.Most of the netizens will become P2Pusers,who will have a great influence on the broadband services.The P2Ptechnology and applications have become an important problem that the operators cannot avoid and must face.

1.4 Major Problems of P2P Applications

Although P2Pservices develop rapidly and are widely used,there are problems in the existing technologies and applications.

·The Quality of Service（QoS）is not guaranteed.Existing P2Papplications are implemented based on the best-effort Internet and have no related information of different nodes,so they are unable to consider application QoS.For example,it often occurs that the seed for a BTdownload disappears when download is nearly finished,and all the efforts are in vain.Hot programs of P2P streaming media services seem to be good,however,although some unpopular programs can be seen on the menu,they cannot be used actually,which provides poor experience.Voice services generally have good effects in P2Papplications on PC,however,their quality cannot be guaranteed on some occasions such as festivals and holidays.Besides,these services cannot be connected to traditional telephone terminals in most cases.

·Information sharing and intellectual property right protection—Digital Rights Management（DRM）issue conflict.The information and services on the network have basically no copyright.All resources are used illegally,which greatly affects Content Providers'legal rights and their enthusiasm for making contents,and furthermore,causes serious legal problems.The U.S.-based Joost emphasizes usage of licensed resources now.

·The network security cannot be guaranteed.This is another key problem that confuses P2Papplications,especially for operations of scale.Security problems involve a wide range,including user access security,transmission security,content security,routing,access,inconsistent actions and node overload attack,firewalltraversal and network virus spread.

·Highly-efficient positioning and transmission are not ensured.Available technologies provide low positioning efficiency and result in high pressure on the networks.User experiences are just moderate.Generally,a streaming media service allows users to view contents in more than one minute with minutes of switching time.

·Clients are not uniformed.Different services or features require different clients.

2 Operators'P2P Application Policies

2.1 Great Effort on Broadband Service Development

P2Pservices bring on a great demand on the bandwidth,which greatly improves the development of operators'broadband services.Although P2P services have many negative influences,they are a boost to the operators in expanding the bandwidth to cater for the broadband service development and meet the user requirements for bandwidth and service experience.

Rapid increase of the number of broadband subscribers through P2Pis an aim of the operators.It is also groundwork of large-scale development of broadband services in the future.P2P services require reasonable control policies instead of blocking and restriction.Especially at the levels of provincial network and Metropolitan Area Network（MAN）,the operators must deal with the policies with caution and avoid taking extreme measures that may result in negative effects.

2.2 Fine Pipeline Operations

Good pipeline operation is basic and key to the operators,but the existing pipeline operations are neither good nor fine.P2P traffic makes the operators'international and inter-network links congested points unavoidable,which greatly affects the QoSof the Internet.To guarantee the quality of Internet services and especially valued applications,operators must perform integrated service traffic management,that is,fine pipeline management.The integrated management allows P2Papplication traffic to be distributed within a network which saves outbound bandwidth resources and thus guarantees the Internet QoS.

Fine pipeline operations are generally designed as follows:

·Service-based QoSis used,that is,traffic types and use priority labels are classified based on service types.For example,specialbandwidths are reserved for the services that require high real-time performance to ensure bandwidth quality;dedicated pipelines are allocated with required bandwidths for the services with large traffic but require low real-time performance;and bandwidth resources for some services are reduced to ensure the bandwidth for other services and meanwhile to avoid obvious effects on the users.This solution enables the operators to improve the capability to ensure different QoSand remarkably improve users'experience,which achieves the objective of attracting new subscribers and retaining old ones.

·QoSis used based on subscriber types,and specific bandwidth is reserved or guaranteed for specific user types.Quality of the reserved parts should be ensured,regardless of the condition of other resources,to provide better QoSfor the subscribers who intend to pay for high quality.

·QoSis used based on subscriber type and service.Subscribers can request different qualities of bandwidth according to different fee rates dynamically.Operators are performing such tests.

The healthy development of broadband services depends on the diversity of different bandwidths and tariffs for different subscribers and service types,which allows operators to gain reasonable profits and ensures that subscribers obtain relevant experiences in a win-win situation.

2.3 Characteristic P2P Service Development

Operators are providers of network resources.They fully control the information of subscribers,terminals,networks and services,so they should take advantage of these resources to develop their own characteristic P2P services.P2Pservices that operators like to provide have such features:associated with traditionalservices,scale operation,copyright guarantee and QoS guarantee.For example:

·VoIPservice providers can develop PC-based,telephone-oriented services,which have obvious advantages of resource compared with other services like Skype.Charges of such services can be bound to traditional telephone services.

·Download services can ensure online resources and download rates through“seed”servers.

·Streaming media services ensure good user experiences with high quality of service and picture,copyright guarantee,short access time and complete accessibility,which differentiates such services from ordinary P2Pstreaming media services without QoSguarantee.

2.4 Charging Policies

P2Pservices are typical Internet services using a mechanism different from traditional telecom services.The corresponding operation policies should comply with the rules of Internet services—increasing the number of subscribers rapidly with ordinary services free or charged with a minimum fee.

▲Figure 2. Structure of system functions.

（1）Integrated Client

Similar to the fixed and mobile networks,the Internet requires a scramble for terminals,which are the basis of various services.The fixed-network uses telephones as the terminal.The mobile network uses mobile phones as the terminal.But various terminals are used in the broadband network,such as MSN,QQ,Skype,PPLive,PPStream,BT,eMule and Thunder.Operators recommend the subscribers to install a client,and make it a necessity for them.

To provide P2Pservices,operators must scramble for the subscribers'client,which is essential and basic.The advantage of operators must be the capability to provide integrated services,including the combination with traditional telecom services,which is not supported by common P2PInternet applications.

（2）Advertisement Fee

P2Pservices can be established as a new platform similar to TVmedia to earn advertisement fees.The advertisement revenue in the P2Pstreaming media market in China was increased to 33%in 2006.P2Pstreaming media attract more and more people as a brand new video program.It has wide prospects and will surely share the market of traditional TV advertisements to a certain extent.It is expected that the advertisement revenue will account for a larger proportion of the revenue in the P2Pstreaming media market in 2010.

（3）Enterprise Service Fee

Enterprise service fee will become the most important source in the future.Integrated solutions for enterprise users will be a trend,in which P2Papplications（including voice,data,information and streaming media）will be the main parts and can be charged specific fees.For example,MSNhas launched enterprise solutions now.（4）Charges for Individual Subscribers'Advanced Services

Common applications like QQ are free of charge and provide more and more functions with more convenience for users.However,there are more and more paid contents for enhanced services.Some of the paid value-added applications are accepted by users especially when they become necessary personal communication tools.

（5）Binding Charges

Binding P2Pservices can be used to promote traditional services.On the other hand,the advantages of traditional services may be taken for growing P2P services.For example,operators can provide P2Pterminals similar to Skype,which can dial ordinary calls directly,to increase the revenue of VoIPcall service.Applications like Skype have shared operators'telephone service revenue in the VoIPmarket.Those operators who support VoIPcalls using a client have to get ready to face the challenges.

（6）Content Copyright Charges Operators have the ability to cooperate with content providers and obtain competitive contents in time.Meanwhile,operators ensure content copyrights using the DRM technology to protect the benefits of content providers.The win-win cooperation of the operators and content providers ensures healthy and long development of the industry,which cannot be achieved by common P2Papplication vendors.

3 Operational and Manageable P2P Solutions

General vendors cannot resolve the problems in P2Papplications used in the live networks.Operators take advantages of their own networks,users and resources to provide their P2P services with QoSassurance,security and DRM protection,differentiate them from ordinary Internet P2Pservices,so users are willing to use the services and pay for them.

This chapter uses ZTE's P2Psolution as an example to discuss the operational and manageable P2Psolution and technologies for the implementation.

3.1 Structure of System Functions

Figure 2 illustrates the functional architecture of the system.

3.2 System Functions

The operation support layer provides service management and support for the P2Pplatform,including user management,Service Provider（SP）management,service management,authentication and authorization,accounting,payment and settlement,platform system management,statistics and analysis,terminalmanagement,DRM management and interface management（e.g.authentication interface,accounting interface and payment interface）.

The service application layer provides P2Pservices and applications,including content processing and management,value-added application management,program on-demand,live-broadcast,streaming media services,e-program list,and value-added services such as communications services,games and information services.

The service control layer provides service resource management and scheduling functions for the P2P platform,including the resource management and scheduling center and user terminals.The resource management and scheduling system accomplishes the primary function of centralinfrastructure scheduling for P2P.It also provides the node management function for P2Pnetwork running,that is,the node registration,login and terminal version management functions.User terminals（media nodes）include user nodes（dynamic nodes）and service nodes（such as static nodes,content source centers and edge servers）deployed on the office end,which together compose a P2Pnetwork necessary for system operation.

The service bearer layer provides service bearer for the P2Pplatform,including CDN,bearer network of the operation support layer and the bearer network of service application layer.It mainly provides bearer and control for specific services.The convergence layer includes the network and devices between the service access control point and the service layer border node.It mainly functions as the network bearer between a specific service network and user access network for the service.The access layer includes related network and devices between user terminal and service access control point.It mainly provides P2Pservice access,such as the access from mobile terminals,Asymmetric Digital Subscriber Line（ADSL）,Local Area Network（LAN）and Wireless Local Area Network（WLAN）.

▲Figure 3. Positioning technology illustration.

3.3 Key Technologies

（1）Static,Quasi-Static and Dynamic Nodes

In ZTE's P2Psolution,P2Pclients include static,quasi-static and dynamic nodes,as shown in Figure 3.The static node is a designated node that a operator deploys.It is always online once it goes online.The quasi-static node is a node that is provided by an SPand has a special system resource sharing agreement with the operator.It is online for a long time.Normally it does not provide any services for end users,that is,it does not generate downstream traffic.The dynamic node is an ordinary P2Puser node.The static and quasi-static nodes ensure P2P-issued resources are always online,which is very useful for seldom ordered programs and downloads and can provide users with good experience.Thus,they ensure service quality.

（2）Source Management and Region Management

The Source Management（SM）point divides the contents into segments as the minimum management granularity.It provides a general management of content segments,that is,it knows whether a segment has one or more copies and the number of copies in each Region Management（RM）point.RM is responsible for the regional management of contents,which includes the following:

·Managing the distribution of each content segment on a node and segmented content scheduling（scheduling of adding the number of copies）in a region

·Responding node requests

·Locating the service position of content segments

·Managing the distribution of content segments in the local region

·Collecting the statistics of node resource states and regional real-time user access

（3）Accurate and Highly-Efficient Positioning Technology

The P2Ptechnology has three typical architectures.The centralized catalog architecture is highly manageable and efficient,but the network stability is restricted by the centralized servers.A pure P2Pnetwork architecture has high expandability and fault tolerance,but poor efficiency and large-consumption bandwidth,which may cause network congestion and is subject to malicious attacks of spam information and even viruses.The hybrid network architecture integrates the advantages of the pure P2Pdecentralization and the centralized P2Pfast search.

In ZTE's P2Psolution,the resource positioning policy is designed in the hybrid network architecture.Combining various user information（including type,access feature and user area）,the positioning algorithm generates the optimum routing information for the terminal.To improve user experience in streaming media services,the solution allows preferential selection of the static node,quasi-static node or quality node to obtain required information.This increases the response time which can reach second-level.Generally,the time is at minute-level in ordinary P2P streaming media services.Accordingly,it greatly improves user experience.

（4）Authentication,Authorization and Accounting（AAA）

ZTE's P2Psolution allows customized authorization and accounting according to operator's requirement.It is developed based on the broadband service management platform widely used in the live networks.The system is stable and reliable.The solution provides typical P2Pservices such as program on demand,live broadcast and download,and besides,it can be integrated with traditional telecom services and broadband services to provide users with overall telecom services.Moreover,the solution uses an identity authentication technology to prevent users from malicious attack and ensure user security［3］.

4 Conclusion

The P2Ptechnology has a very promising future.Manageable and operational P2P solutions and technologies are developing,although there are still unsolved problems,such as security and virus problems,further optimization of framework and positioning policy,the effect of jitter to user experience,trust mechanism,and the client with better user experience,which require further improvement.