Foreword
Mobile Internet is the product of the integration of mobile communication network and (fixed) Internet. Mobile communication networks and the Internet have each achieved great success in their fields, but there are many differences from business models to technical architectures, from terminals, networks to applications. The different cultural backgrounds and resource advantages of the two have led to the mobile communication industry represented by mobile phone companies, with mobile voice as the main business, and the Internet industry represented by the Internet and computer manufacturers, with data communication as the center. The understanding of the Internet differs in many ways. In addition, in the past two years, with the great success of Apple's terminal-centric innovation in business and technology such as iPhone, iTouch, App Store, etc., the understanding of mobile Internet has emerged as a "three-legged" situation.
1) Mobile-centric definition
Use smart phones / handheld digital assistants, notebook computers, netbooks and other mobile terminals to access open Internet, wireless access protocol (WAP), IP multimedia protocol (IMS) and other Internet services through the mobile network. This understanding mainly comes from the mobile communication industry. It is considered that the mobile Internet is the development of the "mobile network", but the services provided have evolved from traditional mobile communication services to "Internet services", and terminals have developed from mobile phones to a variety of smart terminals. This definition attempts to distinguish it from the "mobile packet network" proposed by 3GPP and so on, and introduces two ambiguous concepts: "mobile network" and "Internet service". Broadly speaking, the mobile network can be the link layer or the network layer, or even the application layer and the content layer, and it seems to refer only to the cellular mobile network here. In addition, IMS is also included in the "Internet service", and IMS is a technical description of the implementation of the application, and "Internet service" is not a matter of the same level.
2) WEB-centric definition
Connect to the public network through mobile devices (such as PDAs, mobile phones) or other portable devices (such as netbooks, etc.) to access the World Wide Web (WWW). This understanding comes from the Internet community, who believes that mobile Internet is the development of the Internet, and only highlights the differences brought by handheld terminals at the WEB level. Of course, the difference here can be restrictive (such as slow access rate, small terminal screen, etc.), or it can be advantageous (better portability, with location information, etc.). Although the vast majority of application types on the Internet are currently in WEB mode, some applications are not (such as the need to download client software), so this definition cannot cover some non-WEB mobile Internet applications (such as some short messages, maps, etc.) Mobile Applications). In addition, the impact of handheld terminals and wireless access links on the transmission and network layers of the mobile Internet has not been taken into account.
3) Terminal-centric definition
With mobile terminals as the center (note that it is not mobile phones as the center), through the user interface, development tools, hardware, distributed processing and 3G + WLAN and other wireless access capabilities, the Internet and mobile industry ecosystem are optimized to provide a new User experience and pricing. In 1990, Microsoft introduced Windows 3.0 innovations for personal computers, which completely changed the PC era. In 1995, Netscape browser (and its initial public offering) innovations for the Internet led to (fixed) Internet explosion. Apple Innovation based on mobile terminals since 2007
(IPhone, iTouch and App Store), leading a new era of mobile Internet.
This article starts with the fixed Internet, introduces the Internet's system architecture and the challenges of mobility support, and explains some of the work and problems that the Internet currently does to address the challenges of mobility. The article concludes that from the outside of the Internet, the mobile Internet still uses the Internet architecture, but only adds some mobility support functions at the network layer, transport layer, and application layer. From the inside of the Internet, although these functions added to the mobile Internet are evolutionary changes to the Internet architecture, these changes will have a "revolutionary" impact on upper-layer applications because of the portability of the terminal and the wide coverage of the network. After transmission, it will have a major impact on the entire human society.
1 Internet architecture
Unlike the architecture of centralized control and hierarchical routing of mobile communication networks, the Internet advocates an “opennessâ€, “equality†and “innovation†based on “self-disciplineâ€, allowing everyone to participate in the construction and The spiritual concept of development. Under the guidance of this spiritual concept, the Internet engineering community put forward the core design concept of "end-to-end transparency". The "end-to-end transparency" described in RFC3439 and others is the core design principle of the architecture that is rarely seen on the Internet and has always adhered to. The so-called "end-to-end transparency" means that in the design of the Internet Protocol (TCP / IP), the communication-related part (IP network) of the Internet system is separated from the high-level applications (endpoints) to simplify the design of the network to the greatest extent. , Put as much complexity and control as possible on the user terminal. Some documents also call it the "hourglass" model, as shown in Figure 1. All the characteristics of the Internet seen today (including the external and internal advantages and problems of mobile) are almost related to the core design concept of "end-to-end transparency".
This core design concept was later extended with the development of the Internet, and was extended to: TCP / IP protocol design should maintain state information on the endpoint as much as possible, and no state information related to specific applications is maintained within the network. Because only in this way, it is possible that the communication will not be interrupted when a part of the network fails, unless the communication endpoint itself fails. According to this expanded concept, the following well-known inferences emerge:
1) (connectionless) packet switching technology is superior to the traditional circuit-switched network, because the status information is not maintained in the packet-switched network, so the communication will only be interrupted when the communication terminal fails;
2) Separation of services and bearers, information related to services and applications is not saved in the IP network, the terminal is intelligent and the network is fool-proof.
This core design idea of ​​the Internet is obviously based on fixed networks:
1) "End-to-end transparency" means that the Internet believes that whether it is wired or wireless, no matter how huge the link layer attributes are, the network layer will provide services "best effort", that is, the service capability of end-to-end communication It is likely that the wireless link is limited to the worst performance segment;
2) Hope to put complexity on the terminal, which means that the terminal must have strong computing and storage capabilities, and the network's ability to transmit such computing tasks must be relatively strong;
3) The state information is not retained to the greatest extent in the network, which means that the network believes that mobility support is not a necessary function and is not an issue to be considered by the architecture, but a "value-added" service.
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