Chapter 18 INTERNET TECHNOLOGY AND NETWORKS Lead author Avri Doria Introduction ing internet policy. This chapter is therefore most con- cerned to describe the logical constructs that make the This chapter briefly describes some of the most impor- network work. tant issues in internet technology and network manage- ment. It is concerned principally with how the internet The underlying logical structure comes in two variet- works, including how it differs from telecommunications ies: design principles and organisational constructs. networks, and with some of the technical issues that The chapter describes the constructs briefly, and also arise in discussions of internet services and governance. gives a basic overview of the roles of code, protocols The structure of the internet – i.e. the relationships and standards. Firstly, however, it describes the Inter- between different actors in the internet supply chain – net Protocol suite, commonly referred to as TCP/IP, and the services it offers to end-users are discussed in and the fundamental layered architecture of the internet Chapter 19. Issues of internet management and gover- (although this architecture is often followed more in the nance are discussed in Chapters 20 and 21. breach than in actuality). Two things crucially distinguish the internet from other communications media. Basic viewpoint • Firstly, it is a packet-based network. In a packet- based network, data for transmission are divided At a very high level, the mechanics of the internet are into a number of blocks, known as packets, which quite simple. Computer systems and other networking can be sent separately from one another and reas- entities (including telephones, Play Station 3 systems sembled by the recipients’ equipment. The way in and some household appliances, even refrigerators) can which a packet-based network transmits informa- all be connected to the internet. Each of these named tion between users is, therefore, focused on the entities can be found at an endpoint that sits at some data that are distributed rather than on the connec- location in the network. When they are connected, each tions between users. In particular, unlike traditional must have an identity (name/number) which is globally telephone connections, the links between internet unique. Specialised systems manage the movement of users do not require a dedicated channel between messages/data from one named entity to another by users to be set up before communication begins, following routes that are usually discovered and select- or to be continuously open while communication ed by the network itself. In short, there are things with continues. names that live at addresses and which send messages to one another along routes. • Secondly, the packet-based nature of the internet enables it to function as a network of more or less This works because the network is based on certain independent networks. The internet is defined by principles and uses code based on protocols that have the principles as well as the technology that hold been standardised. The fundamental protocols are in- these disparate networks together into a common cluded in a suite which is known as TCP/IP. Before de- global network. scribing them in more detail, it is useful to clarify the role of protocols, standards and codes within the internet. Technical descriptions of the internet often focus on the specifics of technology, such as its multilayer stacked architecture, the interfaces between these layers, techni- Protocols, standards and code cal protocols, and the bits and bytes that define how the protocols work at a detailed level. Some of these issues The rules which govern the organisation of the internet are discussed in this chapter and/or elsewhere in this are set out in protocols, standards and codes. handbook. • The term “standard” is used in a wide range of in- While detailed technical discussion is useful in an intro- dustries, to identify technical interfaces and speci- duction to network technology, it does not sufficiently ex- fications with which the designers of new products plain the entities that hold the various networks together and services must comply. Standardisation has in a single internet and which are crucial to understand- been particularly important in telecommunications The APC ICT Policy Handbook / 113 networks, especially in enabling the interoperability of the protocol must be created and tested against one of different networks, technologies and equipment. another to demonstrate that they can interoperate. If they It gives formal or de facto authority to agreed ap- can do so, this is taken to mean that the description of proaches to technology development. the protocol is sufficiently clear for unambiguous imple- mentation. If not, then further clarification is required • Within the internet, the details of addressing, nam- before the protocol proceeds towards standardisation. ing and routing are standardised in what are known as protocols. A protocol is the set of rules that Since standards are meant to indicate that code imple- determines the format and transmission of data. A mented in accordance with a standard will work with other protocol defines a generally loosely ordered set of code implemented in accordance with that standard, this instructions and defines the meaning and position step – the writing and testing of code – has become one of all of data within a message. of the most important in the IETF process. As a standard and its protocol mature through public use it can prog- • Code is the symbolic arrangement of data or in- ress from being a Proposed Standard to a Draft Standard structions in a computer programme, or the set of and finally to Internet Standard status. These stages of such instructions that constitutes instantiation of a standard reflect the degree of deployment and testing the protocol. In short it is code that gives substance to protocol receives in the internet. However, in practice, not a protocol and makes it a part of the internet; and it all standards that are in use within the internet go through is code that makes physical hardware interoperate. this full process; many of those which are widely used are There are many protocols used within the internet. Two still, formally, Proposed Standards. sets of protocols are most prominent: the TCP/IP suite of protocols which enable packet forwarding and data delivery and are maintained by the Internet Engineering TCP/IP Task Force (IETF); and the HTTP, HTML and other proto- The term often used to refer to the protocol suite used in cols which underpin the World Wide Web and which are the internet, TCP/IP protocols, is a historical reference maintained by the World Wide Web Consortium (W3C). as well as a reflection of current usage today. TCP, the There are many different ways in which protocols and Transmission Control Protocol (RFC 793, Std 007), and standards can be created. While there is no rule that IP, the Internet Protocol (RFC 791, Std 005), were two says that all internet protocols and standards are cre- of the first three protocols introduced as the new inter- ated in exactly the same way, a common process has net developed in 1980/1981. The third original proto- often been followed.1 Consensus – the achievement of col was the User Datagram Protocol (UDP, RFC 768, broad agreement with the absence of strong disagree- Std 006). IP, specifically IPv4 (IP version 4), and TCP ment – plays a major part in setting internet standards. still (at the time of writing, mid-2009) handle most of In the IETF process involved in the TCP/IP suite of pro- the network traffic. IPv4 effectively handles over 99.99% tocols, most often a need becomes apparent – whether of the traffic at the internet layer. While use of IPv6 (IP technical-, service- or business-related – for which there version 6) was still negligible in the internet at this time, is no existing protocol, or for which existing protocols it did figure in some research networks such as CER- are insufficient. Although this was not always so, a re- NET2, which is 100% IPv6. TCP handles somewhere quirements or framework document is often written between 90% and 95% of traffic in the transport layer, before a new protocol is developed to meet the need. depending on where it is measured, with UDP handling Often a specification for a protocol is written and distrib- somewhere between 6% and 9% of traffic. There are uted through a set of public documents, called Internet also other transport protocols, but these have little us- Drafts, to any other person who is interested in a new age proportionally. protocol. If there is widespread interest in it, especially IP provides the central datagram functionality of the in- in a commercial environment, a decision may be taken ternet. The basic principles involved are both simple and to form a working group to work on the protocol and highly flexible. This is generally felt to have contributed to move it in the direction of standardisation. Though a substantially to the internet’s ability to absorb new tech- working group is not necessary, one is often set up. nological opportunities and to innovate in the provision Once a protocol has been developed it is tested before of services. IP basically encapsulates the datagram, or it can begin moving towards standardisation. In this packet, with the source and destination addresses as case, testing means that several independent instances well as information such as type of service, which gives an indication of how a packet is to be treated in terms of priority and queuing, total length of the datagram, “time to 1 This is the model followed by the IETF, which is responsible for live” of the packet (i.e. how many hops it can take through most of the standards that make up the lower layers of the internet.