Chapter 1 Introduction

 

1. Introduction   简介

The Internet is a structured, organized system.  Before we discuss how it works and its relationship to TCP/IP, we first give a brief history of the Internet. We then define the concepts of protocols and standards and their relationships to each other. We discuss the various organizations that are involved in the development of Internet standards. These standards are not developed by any specific organization, but rather through a consensus of users. We discuss the mechanism through which these standards originated and matured. Also included in this introductory chapter is a section on Internet administrative groups.

 互联网是一个结构化、有组织的系统。在讨论互联网的工作原理和与TCP/IP的关系之前，我们首先介绍一下互联网的简史。然后，我们定义协议和标准的概念及其彼此之间的关系。我们讨论参与互联网标准发展的各种组织。这些标准不是由任何组织开发的，而是用户形成的共识。我们讨论这些标准的起源和成熟的机制。本入门课程还包括有关互联网管理小组的部分。 

 

OBJECTIVES    （章节目标）

The chapter has several objectives:　　(本章有几个目标)

• To give a brief history of the Internet.　　（简要介绍互联网历史）
• To give the definition of the two often-used terms in the discussion of the Internet: protocol and standard.    （在互联网讨论中给出两个经常使用的术语的定义: 协议和标准）
• To categorize standard organizations involved in the Internet and give a brief discussion of each.         （对参与互联网的标准组织进行分类，并对每个组织进行简要的讨论）
• To define Internet Standards and explain the mechanism through which these standards are developed.（定义互联网标准，并解释这些标准的机制）
• To discuss the Internet administration and give a brief description of each branch. （讨论互联网管理， 并简要说明每个分支机构。）

 

 

1.1 A BRIEF HISTORY

 一个简短的历史

A network is a group of connected, communicating devices such as computers and printers. An internet (note the lowercase i) is two or more networks that can communicate with each other. The most notable internet is called the Internet (uppercase I), composed of hundreds of thousands of interconnected networks. Private individuals as well as various organizations such as government agencies, schools, research facilities, corporations, and libraries in more than 100 countries use the Internet. Millions of people are users. Yet this extraordinary system only came into being in 1969.

 网络是一组连接的通讯设备，如计算机和打印机。 互联网（注意小写字母i）是两个或多个可以互相通信的网络。最著名的互联网叫做互联网（大写I）, 由数十万个互联网络组成。个人以及100多个国家的政府机构，学校，研究机构，公司和图书馆等各种组织使用互联网。

ARPANET  

 

In the mid-1960s,mainframe computers in research organizations were stand-alone devices. Computers from different manufacturers were unable to communicate with one another.The Advanced Research Projects Agency (ARPA) in the Department of Defense (DOD) was interested in finding a way to connect computers together so that the researchers they funded could share their findings, thereby reducing costs and eliminating duplication of effort. 

 

在20世纪60年代中期，研究机构的型计算机是独立设备。来自不同制造商的计算机无法相互通信。国防部（DOD）高级研究计划署有兴趣找到将计算机连接到一起的方法，使他们资助的研究人员可以分享他们的发现，从而降低成本，消除重复工作。

　　In 1967, at an Association for Computing Machinery (ACM) meeting, ARPA presented its ideas for ARPANET,a small network of connected computers. The idea was that each host computer (not necessarily from the same manufacturer) would be attached to a specialized computer, called an interface message processor (IMP). The IMPs, in turn, would be connected to each other. Each IMP had to be able to communicate with other IMPs as well as with its own attached host. 

 

　　在1976年，在计算机协会（ACM）会议上，ARPA向ARPANAET提出了一个小型网络连接计算机的想法。这个想法是每个主机（不一定来自同一制造商）将附加到称为接口消息处理器（IMP）的专用计算机。这些IMP又会相互联结。每个IMP必须能够与其它IMP以及自己

　　By 1969, ARPANET was a reality. Four nodes, at the University of California at Los Angeles (UCLA), the University of California at Santa Barbara (UCSB), stanford Research Institute (SRI) ,and the University of Utah, were connected via the IMPs to form a network. Software called the Network Control Protocol (NCP) provided communication between the hosts. 

 

Birth of the Internet

 

In 1972, Vint Cerf and Bob Kahn, both of whom were part of the core ARPANET group, collaborated on what they called the Internet Project. They wanted to link different networks together so that a host on one network could communicate with a host on a second, different network. There were many problems to overcome: diverse packet sizes, diverse interfaces, and diverse transmission rates, as well as differing reliability requirements. Cerf and Kahn devised the idea of a device called a gateway to serve as the intermediary hardware to transfer data from one network to another. 

 

Transmission Control Protocol/Internetworking Protocol (TCP/IP)

 

Cerf and Kahn's landmark 1973 paper outlined the protocols to achieve end-to-end delivery of data. This was a new version of NCP.  This paper on transmission control protocol(TCP) included concepts such as encapsulation, the datagram, and the funcions of a gatway. A radical idea was the transfer of responsibility for error correction from the IMP to the host machine. This ARPA Internet now became the focus of the communication effort. Around this time responsibility for the ARPANET was handed over the Defense Communication Agency (DCA).

　　In October 1977, an internet consisting of three different networks (ARPANET, packet radio, and packet satellite) was successfully demonstrated. Communication between networks was now possible. 

　　Shortly thereafter, authorities made a decision to split TCP into two protocol: Transmission Control Protocol (TCP) and Internet Protocol(IP). IP would handled datagram routing while TCP would be responsible for higher level functions such as segmentation, reassembly, and error detection. The new combination became known as TCP/IP.

　　In 1981, under a DARPA contract, UC Berkeley modified the UNIX operating system to include TCP/IP. This inclusion of network software along with a popular operating system did much for the popularity of networking. The open (non-manufacturer-specific) imp[lementation on Berkeley UNIX gave every manufacturer a working code base on which they could build their products.

　　In 1983, authorities abolished the original ARPANET protocols, and TCP/IP became the official protocol for the ARPANET. Those who wanted to use the Internet to access a computer on a different network had to be running TCP/IP. 

 

MILNET

In 1983, ARPANET split into two networks: MILNET for military users and ARPANET for nonmilitary users. 

 

CSNET

 

Another milestone in Internet history was the Creation of CSNET in 1981. CSNET was a network sponsored by the National Science Foundation (NSF). The network was conceived by universities that were ineligible to join ARPANET due to an absence of defense ties to DARPA. CSNET was a less expensive network; there were no redundant links and the transmission rate was slower. It featured connections to ARPANET and Telenet, the first commercial packet data service. 

　　By the middle 1980s, most U.S. universities with computer science departments were part of CSNET. Other institutions and companies were also forming their own networks and using TCP/IP to interconnect. The term Internet, originally associated with government-funded connected networks, now referred to the connected networks using TCP/IP protocols.

 

NSFNET

 

With the success of CSNET, the NSF, in 1986, sponsored NSFNET, a backbone that connected five supercomputer centers located throughout the United States. Community networks were allowed access to this backbone, a T-1 line with a 1.544-Mbps data rate, thus providing connectivity throughout the United States. 

　　In 1990, ARPANET was officially retired and replaced by NSFNET. In 1995, NSFNET reverted back to its concept of a research network. 

 

ANSNET

 

In 1991, the U.S. government decided that NSFNET was not capable of supporting the rapidly increasing Internet traffic. There companies, IBM, Merit, and MCI, filled the void by forming a nonprofit organization called Advanced Network and Services (ANS) to build a new, high-speed Internet backbone called ANSNET.

 

 

The Internet Today

 

The Internet today is not a simple hierarchical structure. It is made up of many wide and local area networks joined by connecting devices and switching stations. It is difficult to give an accurate representation of the Internet because it is continuously changing--new networks are being added, existing networks need more addresses, and networks of defunct companies need to be removed. Today most end users who want Internet connection use the service providers (ISPs). There are internet service providers, national service providers, regional service providers, and local service providers. The Internet today is run by private companies, not the government. Figure 1.1 shows a conceptual (not geographical) view of the Internet.

 

 

Backbone ISPs

 

Backbone ISPs are created and maintained by specialized companies. There are many backbone ISPs operating in North America; some of the most well-known are sprintLink, PSINet, UUNet Technology, AGIS, and internet MCI. To provide connectivity between the end users, these backbone networks are connected by a complex switching stations (normally run by a third party) called network access points (NAPs). Some regional ISP networks are also connected to each other by private switching stations called peering points. Backbone ISPs normally operate at a high data rate (10Gbps, for example).

 

Regional ISPs

 

Regional ISPs are small ISPs that are connected to oneor more backbone ISPs. They are at the second level of hierarachy with a lesser data rate.

 

 

Local ISPs

 

 

Local ISPs provide direct service to the end users. The local ISPs can be connected to regional ISPs or directly to backbone ISPs. Most end users are connected to the local ISPs. Note that this sense, a local ISP can be a company that just provides Internet services, a corporation with a network to supply services to its own employees, or a nonprofit organization, such as a collage or a university, that runs its own network. Each of these can be connected to a regional or backbone service provider.

 

 

 

World Wide Web

 

 

The 1990s saw the explosion of the Internet applications due to the emergence of the World Wide Web (WWW). The web was invented at CERN by Tim Berners-Lee. This invention has added the commercial applications to the Internet. 

 

 

Time Line 

 

The following is a list of important Internet events in chronological order:

• 1969. Four-node ARPANET established.
• 1970. ARPA hosts implement NCP.
• 1973. Development of TCP/IP suit begins.
• 1977. An internet tested using TCP/IP.
• 1978. UNIX distributed to academic/research sites.
• 1981. CSNET established. 
• 1983. TCP/IP becomes the official protocol for ARPANET.
• 1983. MILNET was born.
• 1986. NSFNET established.
• 1990. ARPANET decommissioned and replaced by NSFNET. 
• 1995. NSFNET goes back to being a research network.
• 1995. Companies known as Internet Service Providers(ISPSs) started.

Growth of the Internet

 

The Internet has growth tremendously.   In just a few decades, the number of networks has increased from tens to hundreds of thousands. Concurrently, the number of computers connected to the networks has grown from hundredsto hundreds of millions. The Internet is still growing. Factors that an impact on this growth include the following:

• • New Protocols　　New protocols need to be added and deprecated ones need to be removed. For example, a protocol superior in many respects to IPv4 has been approved as a standard but is not yet fully implemented (See IPv6, Chapter27)
  • New Technology　　New technologies are under development that will increase the capacity of networks and provide more bandwidth to the Internet's users.
  • Icreasing Use of Multimedia  It is predicted that the Internet, once just a vehicle to share data, will be used more and more for multimedia (audio and video).

1.2 PROTOCOLS AND STANDARDS   (协议和标准)

 

In this section, we define two widely used terms: protocols and standards. First, we define protocol, which is synonymous with "rule". Then we discuss standards, which are agreed-upon rules. 

在这节中，我们定义了两个广泛使用的词语：协议和标准。首先，我们定义协议， 这是规则的同义词。接着， 我们讨论标准，这是一致的规则。

 

 

Protocols

 协议

 

Communication between two people or two devices needs to follow some protocol. A protocol is a set of rules that governs communication. For example, in a face-to-face communication between two persons, there is a set of implicit rules in each culture that define how  two persons should start the communication, how to continue the communication, and how to end the communication. Similarly, in a telephone conversation, there are set of rules that we need to follow. There is a rule how to make connection (dialing the telephone number), how to respond to the call (picking up the receiver), how to greet, how to let the communication flow smoothly by listening when the other party is talking, and finally how to end the communication (hanging up).

　　In computer networks, communication occurs between entities in different systems. An entity is anything capable of sending or receiving information. However, two entities cannot simply send bit streams to each other and expect to be understaood. For communication to occur, the entities must agree on a protocol. A protocol defines what is communicated, how it is communicated, and when it is communicated. The key elements of a protocol are syntax, semantic, and timing.

1. Syntax. Syntax refers to the structure or format of the data, meaning the order in which they are presented. For example, a simple protocol might expect the first 8 bits of data to the address of the sender, the second 8 bits to be the address of the receiver, and the rest of stream to be the message itself. The data order is also applied to the order of bits when they are stored or transmitted. Different computers may store data in different bit orders. When these computers communicate, this difference needs to be resolved. 
2. Semantic.  Semantics refers to the meaning of each section of bits. How is a particular pattern to be interpreted, and what action is to be taken based on that interpretation? For example, does an address identify the route to be taken or the final destination of the message?
3. Timing. Timing refers to two characteristics: when data should be sent and how fast it can be sent. For example, if a sender produces data at 100 megabits per second (100 Mbps) but the receiver can process data at only 1 Mbps, the transmission will overload the receiver and data will be largely lost.

Standards 

Standards are essential  in creating and maintaining an open and competitive market for equipment manufacturers and also in guarateeing and international interoperability of data and telecommunications technology and processes. They provide guidelines to manufactures, verdors, government agencies, and other service providers to ensure the kind of inter connectivity necessary in today's marketplace and in international communications .

　　Data communication standards fall into two categories : de facto (meaning "by fact" or "by convention") and de jure (meaning "by law" or "by regulation").

　　1. De facto. Standards that have not been  approved by an organized body but have been adopted as standards through widespread use are de facto standards. Defacto standards are often established originally by manufacturers that seek to define the functionality of a new product or technology. Examples of de facto standards are MS office and various DVD standards. 

　　2. De jure. De jure standards are those that have been legislated by an officially recognized body. 

 

 

 

 

 

       两个人或者设备之间的通信需要遵循一些协义。协议是一组管理通信的规则。例如，在两个人面对面交流中，每个文化都有一套隐含的规则，定义两个人应该如何开始交流, 如何继续沟通，以及如何结束沟通。同样，在电话交谈中，我们需要遵循一系列的规则。 有一套规则， 如何进行连接（拨打电话号码），如何响应呼叫（接通接收器），如何打招呼，当对方正在说话的时候，通过听时，如何让通信流畅顺利，最后，如何结束通信（挂断）。

　　在计算机网络中，通信发生在不同系统之间的实体方间。一个实体是能够发送或者接收信息的任何东西。然而，两个实体之间不能将比特流相互直接发送，并且期望不太理想。为了发生通信，实体必须就协议达成一致。一个协议定义了所传达的内容，如保通信，以及何时通信。协议的关键要素是：语法，语义和时序。

　　1. 语法： 语法是指数据的结构和格式， 意思是表示数据的顺序。例如，一个简单的协议，可能会将第一个8位的比特数据预期定为发送方地址，另一个8位比特数据定为接收方地址，其余的数据流就是信息本身。数据顺序也适应于比特顺序，当他们被储存或传输时。不同的计算机可能用不同的位顺序储存。 当这些计算机通信时， 需要解决这些差异。

 

 

 

1.3 STANDARDS ORGANIZATIONS 

标准组织

 

Standards are developed through the cooperation of standards creation committees, forums, and government regulatory agencies. 

标准是通过标准制定委员会，论坛和政府监管机构合作制定的。

 

Standards Creation Committees

 标准创建委员会。

While many organizations are dedicated to be the establishment of standards, data communications in North America rely primarily on those published by the following: 

虽然许多组织致力于建立标准，但北美地区的数据通信主要依靠以下方式发布：

1. International Standards Organization (ISO).   The International Standards Organization (ISO; also referred to as the International Organization for Standardization) is a multinational body whose membership is drawn mainly from the standards creation committees of various governments throughout the world.  Created in 1947, the ISO is an entirely voluntary organization dedicated to worldwide agreement on international standards.  With a membership that currently includes representative bodies from many industrialized nations, it aims to facilitate the international exchange of goods and services by providing models for compatibility, improved quality, increased productivity, and decreased prices.The ISO is active in developing cooperation in the realms of scientific, technological, and economic activity. Of primary concern to this book are the ISO's efforts in the field of information technology, which have resulted in the creation of the Open Systems Interconnection(OSI) model for network communications. The United states is represented in the ISO by ANSI.   国际标准组织。 国际化标准组织（ISO,也被称为国际标准组织）是一个跨国机构，其成员主要来自各国政府的标准化制定组织。ISO 创建于1947年，是一个致立于全球国际标准协议的完全自愿组织。目前， 成员包括许多工业化国家的代表机构，目的在于通过提供兼容性，提高质量，提高生产力和降低价格的模式，促进货物和服务的国际交流。ISO 在积极开展科技、经济领域的合作。本书主要关注的是ISO 在信息技术领域的努力，从而为网络通信创建了开放系统互连（OSI）模型。美国在ISO由ANSI体现。
2. International Telecommunications Union-Telecommunications Standards Sector  (ITU-T).  By the early 1970s, a number of countries were defining national standards for telecommunications, but there was still little international compatibility. The United Nations responded by forming, as part of its International Telecommunication Union (ITU), a committee, the Consultative Committee for International Telegraphy and Telephony (CCITT).This committee was devoted to the research and establishment of standards for telecommunications in general and data systems in particular .On March 1 1993, the  name of this committee was changed to the International Telecommunications Union-Telecommunications Union-Telecommunications Standards Sector (ITU-I). 国际电信联盟--电信标准组织（ITUT）   到20世纪70年代，一些国家正在界定电信的国家标准，但国际上的兼容性依然很少。作为国际联盟（ITU）的一部分，联合国成立了一个委员会，即国际电报电话咨询委员会（CCITT）。 
3. American National Standards Institute (ANSI).  Despite its name, the American National Standards Institute (ANSI) is a completely private, nonprofit corporation not affiliated with the U.S. federal government. However, all ANSI activities are undertaken with the welfare of the United States and its citizens occupying primary importance. ANSI's expressed aims include serving as the national coordinating institution for voluntary standardization in the United States, furthering the adoption of standards as a way of advancing the U.S. economy, and ensuring the participation and protection of the public interests. ANSI members include professional societies, industry associations, governmental and regulatory bodies, and consumer groups.美国国家标准学会（ANSI）。 尽管如此，美国国家标准学会（ANSI）是一个完全非营利性的公司，不隶属于美国联邦政府。然而，所有ANSI的活动都是以美国及其公民的福利为重。ANSI的述求目标包括成为美国自愿标准化国家协调机构，推动标准化作为推动美国经济的途径，确保公众利益参与和保护。ANSI 成员包括专业协会，行业协会，政府和监管机构以及消费者团体。
4. Institute of Electrical and Electronics Engineers (IEEE)     The Institute of Electrical and Electronics Engineers (IEEE) is the largest professional engineering society in the world.  International in scope, it aims to advance theory, creativity, and product quality in the fields of electrical engineering, electronics, and radio as well as in all related branches of engineering. As one of its goals, the IEEE oversees the development and adoption of international standards for computing and communication. As one of its goals, the IEEE oversees the development and adoption of international standards for computing and communication.             电气与电子工程师学会（IEEE）   电气与电子工程师协会（IEEE） 是世界上最大的专业工程学会。 在国际范围内，旨在推进电气工程，电子，无线电以及相关工程部门的理论，创造力和产品质量。作为其目标之一，IEEE 监督制定和采用国际计算和通信的标准。
   
5. Electronic Industries Association (EIA)     Aligned with ANSI, the Electronic Industries Association (EIA) is a nonproft organization devoted to the promotion of electronics manufacturing concerns. Its activities include public awareness education and lobbying efforts in addition to standards development. In the field of information technology, the EIA has made significant contributions by defining physical connection interfaces and electronic signaling specifications for data communication. 电子工业协会     电子工业协会（EIA）和美国国家标准学会（ANSI) 签署，并且是一家致力于电子制造业关注的非营利组织。其活动除了标准制定外，还包括公众意识教育和游说工作。在信息技术领域，EIA通过定义物理连接接口和数据通讯的电子信号规范给出了重大规范。
6. World Wide Web Consortium (W3C)    Tim Berners-Lee founded this consortium at Massachusetts Institute of Technology Laboratory for Computer Science.  It was founded to provide computability in industry for new standards. W3C has created regional offices around the world.蒂姆.伯纳丝.李  在马萨诸塞理工学院计算机科学研究所创立了这个联盟。它的成立是为了在工业上为新标准提供可计算性。W3C在全球设立区域办事处。
   
7. Open Mobile Alliance (OMA). The standards organization OMA was created to gather different forums in computer networking and wireless technology under the umbrella of one single authority. Its mission is to provide unified standards for application protocols. 开放移动联盟（OMA） 创建标准组织（OMA)的目的是为了在一个权威的机构的保护伞下收集计算机网络和无线技术的论坛。其使命是为应用协议提供统一的标准。

 

 

Forums 

论坛

Telecommunications technology development is moving faster than the ability of standards committees to ratify standard. Standards committees are procedural bodies and by nature slow moving. To accommodate the need for working models and agreements and to facilitate the standardization process, many special-interest groups have developed forums made up of representation from interested corporation. The forums work with universities and users to test, evaluate, and standardize new technologies. By concentrating their efforts on a particular technology, the forums are able to speed acceptance and use of those technologies in the telecommunications community. The forums present their conclusions to the standards bodies. Some important forums for the telecommunications industry include the followwing:  

电信技术发展的速度比标准委员会批准标准的能力要快。标准委员会是程序性机构，本质上是缓慢的移动。为了适应工作模式和协议的需求，并促进标准化进程， 许多特殊利益集团已经开发了由感兴趣公司的代表组成的论坛。论坛与大学和用户合作，测试，评估和规范新技术。通过集中精力开展行定技术，论坛能够加速电信界对技术的接受和使用。这些论坛将其结论提交给标准组织。

　　1.  Frame Relay Forum.  The Frame Relay Forum was formed by Digital Equipment Corporation, Northern Telecom, Cisco, and StrataCom to promote the acceptance and implementation of Frame Relay. Today, it has around 40 members representing  North America, Europe, and Pacific Rim. Issues under review include flow control, encapsulation, translation, and multicasting. The forum's results are submitted to the ISO. 帧中继论坛     帧中继论坛，是由数字设备公司，北方电信，Cisco, 和 StrataCom 公司形成了帧中继和执行。今天，它具有代表北美、欧洲和太平洋沿岸各地的40名成员。正在审议的问题包括流量控制、封装、，翻译和流量控制。论坛的结果提交给ISO.

　　2. ATM Forum        The ATM forum promotes the acceptance and use of Asynchronous Transfer Mode (ATM) technology. The ATM Forum is made up of customer premises equipment (e.g. PBX systems) vendors and central office (e.g., telephone exchange) providers. It is concerned with the standardization of services to ensure interoperability.   ATM 论坛，促进了异步传输的模式（ATM）技术的接爱和使用。ATM 论坛由客户驻地设备（例如PBX系统）和中心局（例如电话交换）提供商组成。它关心的是服务的标准化， 以确保互操作性。

　　3. Universal Plug and play (UPnP) Forum.　　The UPnP forum is a computer network forum that supports and promotes simplifying the implementation of networks by creating zero-configuration networking devices. A UPnP-compatiable device can join a network without any configuration.   通用即插即用（UPnP）论坛。  UPnP 是一个计算机网络论坛，通过创建零配置网络设备来支持和促进简化网络的设施。

 

 

Regulatory Agencies

 监管机构

All  communication technology is subject to regulation by government agencies such as the Federal Communication Commission in the United States. The purpose of these agencies is to protect the public interest by regulating radio, television, and wire/cable communication. 

　　#  Federal Communication Commission (FCC). The Federal Communications Commission (FCC) has authority over interestate and international commrece as it relates to communication 

　　@The websites for the above organizations are given in Appendix G. 

 所有的通信技术都受到美国联邦通信委员会等政府机构的监管。

 

 

 

1.4 Internet Standards

互联网标准 

An Internet standard is a thoroughly tested specification that is useful to and adhered to by those who work with the Internet. It is a formalized that must be followed. There is a strict procedure by which a specification attains Internet standard status. A specification begins as an Internet draft. An Internet draft is a working document (a work in progress) with no official status and a six-month lifetime. Upon recommendation from the Internet authorities, a draft may be published as a Request for Comment (RFC). Each RFC is edited, assigned a number, and made available to all interested parties.

互联网标准是一个经过彻底测试的规范，对于使用互联网的人是有用的和遵守的。规范达到互联网标准的严格程序。规范以互联网草案开始。

　　RFCs go through maturity levels and categorized according to their requirement level. 

　Maturity Levels

　成熟度级别

　　An RFC， during its lifetime, falls into one of six maturity levels: proposed standard, draft standard, Internet standard, historic, experimental, and information (see Figure 1.2).

　　RFC，在其一生中属于六个成熟度级别之一：提出的标准、标准草案、互联网标准，历史，实验和信息（见图1.2）

　　Proposed Standard

　　拟议标准

  　  A proposed standard is a specification that is stable, well understood, and of sufficient interest to the Internet community. At this level, the specification is usually tested and implemented by several different groups.

　　一个拟议标准是一个稳定的、很好理理解的规范，以及对互联网社会足够的感兴趣。在这个级别，规范通常由几个不同的组进行测试和实现。

　　Draft Standard

　　标准草案

　　A proposed standard is elevated to draft standard status after at least two successful independent and interoperable implementations. Barring difficulties, a draft standard, with modifications if specific problems are 　　encountered, normally becomes an Internet standard.

　　在至少两次相互独立且交叉操作实现后，拟议标准才可提升为草案标准。除了困难，标准草案，如果遇到具体问题，修改通常会成为互联网标准。

 

　　Internet Standard

　　A draft standard reaches Internet standard status after demonstrations of successful implementation.

　　Historic 

　　The historic RFCs are significant from a historical perspective. They either have been superseded by later specifications or have never passed the necessary maturity levels to become an Internet standard.

　　Experimental 

　　An RFC classified as experimental describes work related to an experimental situation that does not affect the operation of the Internet. Such an RFC should not be implemented in functional Internet service. 

　　Informational

　　An RFC classified as informational contains general, historical, or tutorial information related to the Internet . It is usually written by someone in a non-Internet organization, such as a vendor.

　　Requirement Levels

　　RFCs are classified into five requirement levels: required, recommended, elective, limited use, and not recommended (see Figure 1.3)

　　Required

　　An RFC is labeled required if it must be implemented by all Internet systems to achieve minimum conformance. For example, IP (Chapter 7) and ICMP (Chapter 9) are required protocols. 

　　Recommended

　　An RFC labeled recommended is not required for minimum conformance; it is recommented because of its usefulness. For example, FTP (Chapter 21) and TELNET (Chapter 20) are recommended protocols.

　　Elective

　　An RFC labeled elective is not requiered and not recommended. However, a system can use it for its own benefit.

　　Limited Use

　　An RFC labeled limited use should be used only in limited situations. Most of the experimental RFCs fall under this category.

　　Not Recommended

　　An RFC labeled not recommended is inappropriate for general use. Normally a historic (deprecated) RFC may fall under this category.

1.5 INTERNET ADMINISTRATION    

　　互联网管理

　　The Internet, with its roots primarily in the research domain, has evolved and gained a broader user base with significant commercial activity. Various groups that coordinate Internet issues have guided this growth and development. Appendix G gives the addresses, e-mail addresses, and telephone numbers for some of these groups. Figure 1.4 shows the general organization of Internet administration. 

　　Internet Society (ISCO)

　　The Internet Society (ISOC) is an international, nonprofit organization formed in 1992 to provide support for the Internet standards process. ISOC accomplishes this through maintaining and supporting other administrative bodies such as IAB, IETF,and IANA (see the following sections). ISCO also promotes research and other scholarly activities relating to the Internet.

　　Internet Architecture Board(IAB)

　　The Internet Architecture Board (IAB) is the technical advisor to the ISOC. The main purposes of the IAB are to oversee the continuing development of the TCP/IP Protocol Suite and to serve in a technical advisory capacity to research members of the Internet community. IAB accomplishes this through its two primary components, the Internet Engineering Task Force (IETF) and the Internet Research Task Force (IRTF). Anther responsibility of the IAB is the editorial  management of the RFCs, described earlier in this chapter. IAB is also the external liasion between the Internet and other standards organizations and forums.

　　Internet Engineering Task Force(IETF)