Application of peer-to-peer network technology in IPTV

With the rapid development of embedded technology over the past few years, the streaming media technology, which shows strong market demand on the personal computer platform, has gradually shifted to the embedded platform. Media consumption demands for personal portability and household appliances provide a market opportunity for this platform transfer. IPTV is at the forefront of this consumption revolution. Most people in the industry think that IPTV contains huge commercial benefits, but few people are still involved, one of the reasons is the speed of the network. This article introduces the peer-to-peer (P2P) technology, which is applied to IPTV Network Transmission and can make full use of the upstream and downstream channels of each terminal, vrouters and other hardware are not required to support multicast, which can provide a solution to the IPTV Network Transmission bottleneck problem.

I. Peer-to-Peer Network Technology

1. Peer-to-peer network Introduction

Peer-to-peer network (P2P) is a new network technology that has emerged in recent years. It breaks the conventional network server/client (C/S) pattern in transmission mode and establishes a direct communication mechanism between the client and the client, this communication method also provides ideas for the future development of networks. In a peer-to-peer network, each node serves both as a client and a server of another person. In a sense, each node is in the same status. A peer-to-peer network is a successful expansion of the distributed concept. It distributes the server load in the traditional mode to each node in the network, and each node will undertake limited storage and computing tasks, the more nodes you add to the network, the more resources the node contributes, and the higher the service quality.

On the other hand, the C/S service model still dominates the network. Although the network bandwidth of end users has increased year by year in recent years, the user experience has not improved significantly, this is mainly because the servers are overwhelmed. When the number of users increases sharply, the servers may even be in the danger of crash. At this time, idle link bandwidth is being wasted. P2P network services can fully explore idle network resources and serve more users without additional investment. Therefore, we can see that the advantages of the peer-to-peer network technology are self-evident. It will create great value in future network applications.

2. Basic Structure of the peer-to-peer network

Peer-to-peer networks are generally divided into three types based on their organizational structures.

(1) centralized peer-to-peer network

A centralized peer-to-peer network is not a fully equivalent network. It is an extension of the traditional network mode based on the P2P concept between the C/S mode and the peer-to-peer network. The centralized peer-to-peer network is based on the central directory server. It provides directory query services for various programs in the network, and the transmitted content does not need to go through the central server. The structure of the network is relatively simple, and the burden on the central server is greatly reduced. However, due to the existence of central nodes, it is easy to form a transmission bottleneck and poor scalability, which is not suitable for large networks. However, due to centralized directory management, small network management and control is a feasible solution.

(2) unstructured Distributed Network

The most significant difference between a non-structured distributed network and a centralized network is that it does not have a central server. All nodes access the entire network through communication with adjacent nodes. In a non-structured network, nodes use a packet query mechanism to search for required resources. Specifically, a node sends a query package containing the query content to the adjacent node. The query package spreads across the network in a diffusion manner, if this method is not controlled, messages may flood. Therefore, an appropriate TTL is usually set to decrease in the query process, if the TTL value is 0, no sending will continue.

In this non-structured mode, the organization mode is loose, and the addition and departure of nodes are relatively free. It is easy to find popular content when querying, but if the content to be requested is relatively unpopular, the smaller TTL is not easy to find, and the larger TTL value is easy to cause large query traffic, especially when the network range is extended to a certain scale, even if the limited TTL value is small, the traffic will increase dramatically. However, when there are some so-called class server nodes with rich resources in the network, the query efficiency can be significantly improved.

(3) Structured Distributed Network

Structured Distributed Network is a research achievement Based on Distributed Hash table (DistributedHashTable) technology in recent years. The basic idea is to organize all the resources in the network into a huge table. The table contains the resource keywords and the address of the stored node, split the table and store it in each node of the network. When you search for resources on the network, you can find the nodes where the hash table content corresponding to the keywords is stored, the node contains the Node Address of the required resources, and then the node that initiates the search connects to the corresponding node and transmits the resource according to the address information. This is a technically advanced peer-to-peer network. It is highly structured, highly scalable, and freely joins and leaves nodes. This method is suitable for large networks.

II. Application of peer-to-peer network technology in IPTV

1. IPTV status quo

IPTV and P2P in China have been developing in two different directions. Because IPTV is similar to traditional TV watching modes, it is basically regarded as an upgrade of cable TV (CATV) or digital TV (DVB, therefore, the same central server model is used in the design concept. In the traditional method, the network is basically a one-way channel of broadcasting, that is, the client is unable to send upstream information or has little capacity to send upstream information. In this way, all the service content is sent by the central server, and all the processing work is completely completed by the central server, which cannot implement P2P connections.

To solve the server bottleneck problem in IPTV in the C/S mode, most of the current solutions are to adopt Multicast technology and work with the Content Delivery Policy (CDS) of a central server-Edge server).

Multicast technology is also very popular in recent years. It is superior to the one-to-one multi-point transmission service technology in broadcast networks. In traditional multi-point communication, the server must establish independent connections to each client that requests to connect. Generally, the maximum number of connections that a server can provide is quite limited, therefore, this method is not suitable for media services. In broadcast mode, you do not need to establish a connection for each user, but send a copy of the required content to each subnet in broadcast mode, this ensures that all users can receive the data. However, the disadvantage of this method is obvious. A large number of users who have not requested this content have also received this data, which will cause Network Data flooding and congestion. As a result, the multicast technology is generated. In the multicast mode, the concept of multicast group is added. When a user requests a service, the group is added, the server only sends a copy of the data to the multicast address of the desired subnet. When the data arrives at the subnet router, the router sends the data according to the current group members, in this way, only the current group members can receive the data, thus ensuring that the bandwidth is not wasted.

2. Application of peer-to-peer networks in IPTV

Multicast plays a significant role in reducing the burden on the server. However, multicast has high hardware requirements, and both the data source and the receiver's lower-Layer Networks must support the multicast protocol. In addition, the multicast mode still does not use the client's upstream channel, that is, the data received by the user cannot be forwarded to other users with the same requirements.

Comparison between the network structure of the traditional network mode and the peer-to-peer network mode 1. The IPTV system using peer-to-peer network technology has no requirements for the underlying hardware. You only need to modify it at the application layer. Because IPTV features real-time media, network nodes do not need to store Resource Information. Each node can only provide one resource service at a certain time, therefore, the search-based mechanism in peer-to-peer networks can be ignored. In addition, the IPTV system must have a sound user authentication billing management subsystem and provide relevant value-added services. Therefore, users cannot be allowed to join the network at will and a sound user management mechanism is required. In view of the characteristics of IPTV, peer-to-peer network technology is used in IPTV, and a centralized structure is suitable.

Figure 1 Structure comparison between traditional and peer networks in IPTV

A centralized structure is adopted in peer-to-peer IPTV systems. A small number of central servers should exist in the system. These servers not only store program content resources, you also need to save the current program list information and the client information of the program you are watching. When a user requests to watch a program, the server returns the user who is watching the program. Here, the server can view the route information of the request source, among all users watching the program, select the user information closest to the requesting user, that is, the user information with the Best Connectivity, to return. After receiving the address information returned by the server, the user starts to connect to the user who is watching to obtain the program content.

In this type of peer-to-peer network, the content server only needs to distribute a small amount of content, or even distribute some popular programs only one way, to meet the needs of a large number of users to watch. Compared with traditional program distribution methods, it does not require complex scheduling algorithms or thousands or even tens of thousands of media transmission connections. The pressure can be greatly reduced, the user's service quality will not be reduced as a result. On the contrary, some popular programs enjoy better service quality because of the large number of viewers and stable data sources.

In a traditional network, when a server fails, it may affect the watching of some users. users need to go to a server farther away to receive program content, which slows down the network speed, this also increases the burden on this server, that is, the risk of faults on the server is increased, which may cause the effect of chain failures. If users are restricted to a certain region to avoid this situation, these users cannot accept the service when the fault occurs.

However, when a peer-to-peer network is used, the probability of a server failure is greatly reduced because the vast majority of the server load is dispersed and transferred to all clients. Even if a server fails, as long as there are other servers that distribute content on the server on the network, that is, as long as the source of the content still exists in the network, the user can view the program, it is not affected by the faulty server. In a peer-to-peer network, all nodes are both end users and servers. The services of a program are provided by many users who watch the program at the same time. This makes the system have a soft capacity feature, that is, the maximum capacity of the IPTV system based on peer-to-peer networks is not fixed, which is different from the maximum number of users that traditional TV networks can serve, in addition, the higher the number of users, the better the service quality. The increased number of users does not require additional server investment.

Iii. Existing shortcomings and Solutions

Although the peer-to-peer IPTV system has many advantages, it still has some shortcomings. The biggest problem is the potential security risks of the network. In peer-to-peer networks, program sources are not limited to servers, and users are much less restricted by servers than in traditional methods. In this way, illegal users can bypass the step of applying for resources from servers, connect directly to the client. Because the user end must save a list of users who are currently watching the program to maintain connection with these users and add new connections in time according to the buffer status. After an illegal user accesses a legal user, the user can also obtain this list to initiate a connection, so that the user can view the program without communicating with the server.

As mentioned above, the IPTV system must have a sound billing management mechanism and have certain scalability to provide more value-added services. To solve the problem above, you can encrypt and save the current user list of the client, and prohibit users from exchanging the list information, that is, you can only obtain the user list from the server, however, this is only a solution to the standard. To provide higher security, you can use the digital rights management (DRM) technology to fundamentally encrypt the content. In this way, even if illegal users obtain the content without authorization, they still cannot watch the program.

The digital copyright management in IPTV can work in the following ways: an ID number is created on each user receiving terminal that is hardware-related and can uniquely identify the user identity, you can simply use the MAC address of the NIC, or use other digital-encrypted smart cards and other devices to improve system security. Before distributing content, use a key to encrypt the media. In this way, you must use the same key to decrypt the content and store the key separately from the program content. Create a separate user verification server in the system. In actual operations, the server can be merged with the resource request service, but it is best to separate the server from the content delivery server.

When a user makes a resource request, the server connects to the user verification server. The server identifies the validity of the request based on the unique ID of the user and encrypts the requested media key based on the ID to generate a license, issue the license to the user and return to the user list of the corresponding resources. After receiving the media, the user can use the license and hardware ID to decrypt the original key, and then use the key to decrypt the program content for viewing. Because the license is encrypted by the user's ID, even if it is obtained by another user illegally, the original key cannot be decrypted without the corresponding hardware support, and thus the program cannot be watched. The license for each program can be stored on the user end or deleted after use. A new license will be issued upon request.

Digital Copyright Management is flexible. It not only supports media programs, but also allows you to manage user permissions in various value-added services using DRM to implement complicated and efficient billing solutions to meet the needs of different users. Different algorithms can be used for digital encryption as needed. The encryption process is related to hardware, so the security is very high. To some extent, the security performance of peer-to-peer networks is insufficient, and provides more functions.

Iv. Conclusion

IPTV and peer-to-peer networks are currently quite popular technologies, but few have mentioned the combination of the two in the past and expand their application fields by taking advantage of their respective advantages. This article proposes a new idea for IPTV Network Structure, discusses the feasibility, and puts forward corresponding solutions to the possible problems. To sum up, as an emerging and booming network technology, peer-to-peer networks have obvious advantages and indicate the future direction of network development, the Application of peer-to-peer network technology in IPTV not only reduces the network cost, but also is of great significance as an exploration of the future network.

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