P2P Technology Analysis and Research

[Streaming media network] Abstract: peer-to-peer (P2P) is a network architecture in which resources (such as computing, storage, communication, and information) are distributed and used and shared, it corresponds to the dominant Client Server (Client/Server, C/S) architecture in the current network.

 

 

I,P2P technology Overview

Peer-to-peer (P2P) is a network architecture that distributes and shares resources (such as computing, storage, communication, and information, it corresponds to the dominant Client Server (Client/Server, C/S) architecture in the current network. P2P can be used for streaming media communication (such as voice, video, or instant messaging), or transmission of control signals, management information, and other data files, specific applications include Napster MP3 music file search and sharing, BitTorrent Multi-Point file download, and Skype VOIP voice communication. In the beginning, the basic protocol TCP/IP of the Internet addresses the interconnection of computers of different machines. The communication between all devices (email, FTP, and BBS) is equivalent, they are of the same direction as the upper, lower, and lower sides. Based on Web applications, the C/S structure has achieved great success. People operate or access the server on a distant website through a browser on the client, the data and Application Processing Software processed by the user are stored on the server. With the popularization of Internet applications, the functional defects of centralized computing and storage and its C/S network architecture are gradually exposed. The centralized computing and Storage Architecture makes every website supported by the central server a digital island. Browsers on the client can easily jump from one isolated island to another, but it is difficult for the client to integrate data between them. Network capabilities and resources (storage resources, computing resources, communication resources, information resources and expert resources) are all concentrated on the central server. In this architecture, it is difficult for central servers to integrate transparent communication and capabilities according to user requirements. They become the bottleneck of network openness and capability expansion. In contrast to the C/S network architecture, the P2P network architecture does not have a central node for media communication, and the peer nodes are equal, that is, each node can communicate with each other, each node can receive, store, send, and integrate media content and search for and be searched for media metadata (metadata. The advantage of this network architecture is that the capabilities and resources of each node in the P2P network can be shared. Theoretically, the capabilities and resources of the network are the sum of the P2P sections. Content is no longer concentrated on the central server of the network, but distributed on P2P nodes close to the user's network edge. The Application of P2P technology makes the business system evolve from centralized to distributed, especially the publishing of servers, and overcomes the bottleneck caused by centralized business nodes, this greatly reduces system construction and usage costs and increases the utilization of networks and system equipment.

Ii. P2P technical architecture and Classification

P2P technology has three architecture modes: centralized directory structure represented by Napster, pure P2P network structure represented by Gnutella, and hybrid P2P network structure. From the perspective of P2P technology, P2P technology has been divided into four generations: First Generation P2P (Central Control Network Architecture) and second generation P2P (Distributed Network Architecture ), third-generation P2P (hybrid network architecture) and fourth-generation P2P (currently developing P2P technology ).

2.1 first-generation P2P (Central Control Network Architecture-centralized directory structure)

Centralized directory structure uses a central server to manage P2P nodes. P2P nodes register information about themselves (names, addresses, resources, and metadata) with the central Directory Server ), however, all content is stored on each node rather than on the server, the query node selects and locates other peer points based on the information query in the directory server and network traffic and latency, without going through the central Directory Server. The advantage of a centralized directory structure is that it improves the manageability of the network and makes searching and updating shared resources very convenient; the disadvantage is the Network Stability (if the server fails, all the peer nodes under the server will fail ).

2.2 Second Generation P2P (Distributed Network Architecture-pure P2P Network Architecture)

The pure P2P network structure is also called the broadcast P2P model. It does not have a centralized central directory server, and each user randomly accesses the network, A group of neighboring nodes establish a logical Coverage Network through end-to-end connections. Content Query and content sharing between peer nodes are directly transmitted through broadcast relays of adjacent nodes. At the same time, each node also records the search track to prevent the generation of the search loop. The pure P2P network structure solves the problem of centralized network structure, and provides better scalability and fault tolerance. Because no peer node knows the structure of the entire network, search in the NetworkAlgorithmIn flood mode, the flood of control information consumes a large amount of bandwidth and quickly causes network congestion or even network instability, resulting in poor availability of the entire network, in addition, such systems are more vulnerable to spam or even virus attacks.

 

2.3 Third-generation P2P (hybrid network architecture-hybrid network architecture)

The hybrid network structure combines the advantages of pure P2P decentralization and centralized P2P quick search. Different Node capacities (computing capacity, memory size, connection bandwidth, and network retention time) are classified into common nodes and search nodes. A self-governing cluster is formed between a search node and several neighboring common nodes. The cluster adopts a centralized directory-Based P2P mode, different clusters in the P2P network are connected to the search nodes through the pure P2P mode. You can select the node with the best performance among each search node again, or introduce a new node with the best performance as the index node to save the information of the search nodes that can be used throughout the network, maintains the entire network structure. Because file search on common nodes is performed in the cluster to which the local node belongs, only when the query results are insufficient can a limited pan-flood be performed between search nodes. In this way, it is extremely effective to eliminate the adverse effects of network congestion and search latency caused by the use of flood algorithms in a pure P2P structure. At the same time, because the search nodes in each cluster monitor the behavior of all common nodes, it can ensure that some malicious attack behaviors can be controlled locally on the network, to a certain extent, the load balancing of the entire network is improved.

2.4 fourth-generation P2P (P2P technology in development)

It should be said that the fourth generation of P2P did not form a real generation, but made improvements based on the original technology, and proposed and applied some new technical measures. Typical examples include:

(1) select one of the dynamic ports. Currently, P2P applications generally use fixed ports, but some companies have begun to introduce protocols to dynamically select transmission ports. Generally, the number of ports is between 1024 and ~ In the range of 4000. Even P2P streams can be transmitted using the port 80 (25) originally used for HTTP (SMTP) for hiding. This makes it more difficult to identify P2P streams across carrier networks and master their traffic.

(2) Two-way download. Companies such as Ed and Bt are further developing and introducing two-way stream downloads. This technology allows multiple parallel downloads and uploads of one file and/or multiple parallel downloads of a part of a file. At present, the traditional architecture requires that the object be uploaded only after full download. This will greatly speed up file delivery.

(3) intelligent node auto-overlapping networks. Smart node auto-overlapping network is a new technology in which the system uses P2P technology to schedule existing IP addresses to carry network resources. In the Router network layer, smart nodes are configured with various link peering connections, an elastic overlapping network at the network application layer. Network security, QoS, and management can be improved while maintaining the Internet Distributed Autonomous system structure. Smart nodes can exchange data between routers and ensure data classification (virus identification and spam. By observing the Internet through multiple geometric distribution nodes, sharing information can help you understand the scope and nature of Internet worm infections. Provides high-performance, scalable, and location-independent message routing to locate the nearest local resource location. Improve content delivery. Use smart nodes to detect Internet path traces and send back trace data. This solves the existing cross-Autonomous Region path selection problems on the Internet. Implement QoS routing, reduce packet loss and latency, and quickly and automatically restore data.

Iii. P2P applications in broadband audio and video services

In future broadband services, especially audio and video services, P2P technology is expected to be widely used. At present, a major reason why broadband audio and video services cannot develop is that the service network system is too expensive, whether it is a video-on-demand business system, a video conferencing system, or a remote teaching system, the cost of building a system is very high. Because most of the system construction costs need to be passed on to users, and the business cannot be opened up because users cannot afford to consume the system, it is critical to greatly reduce the construction cost of the business system, the rational application of P2P technology may be an order of magnitude reduction in construction investment, which may greatly promote the commercialization of broadband services.

A carrier-level audio/video business system can be designed using P2P technology. The following is an instance that uses a centralized directory structure or a hybrid network structure. Each P2P business node is composed of highly reliable operating servers, the topology of the network is known to operators in advance, and the network topology can be planned and optimized based on the distribution of users, content and business traffic. The audio/video business platform is a private network-Based P2P system architecture that does not contain user (or content provider) clients, the end user terminal may be a set-top box with relatively weak processing capabilities (no longer a PC with powerful processing capabilities ). For audio and video services, if user terminals are directly used as p2p service nodes, problems such as manageability, service quality, and security will occur. The user terminal is equivalent to the client of the P2P network, and the P2P network is equivalent to a large server, meeting the management, service quality and security requirements. The system consists of three basic business modules: Business convergence business module, content delivery business module, and streaming media playback business module.

3.1 P2P-based business convergence Module

The audio and video industry chain to be formed in the future includes content providers (CP), operators and users. P2P-based audio and video business platforms are constructed, operated, and managed by operators (including content operators and network operators. As a P2P network client, the content provider's terminal (such as a PC) must provide program content to the business platform. The provided content is first authenticated by the carrier's content. All authenticated program content must be aggregated to the Central Business node in the P2P network for relevant content processing, including: copyright License, content encoding conversion, content encryption, content slicing, and content distribution between content providers and carriers. The process of transmitting program content from a content provider to a P2P network's central business node is called business convergence. Business convergence may produce many applications, including the production of connected advertisements and resident advertisements, virtual home storage environments, online games, and provision of audio and video-based content. Figure 1 shows how to use P2P to achieve business convergence.

Figure 1 P2P-based business convergence