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Chapter 5: Twenty-first century transport:SNG over IP - Pg. 220

5 Twenty-first century transport: SNG over IP 5.1 Introduction In this chapter, we are going to cover a subject that will strike a chord with everyone who uses a com- puter and the Internet ­ and it is highly doubtful if that excludes any reader. In the last few years, we have seen the emergence of a new method of transporting video and audio signals across networks through the use of Transmission Control Protocol (TCP) and Internet Protocol (IP) ­ together referred to as TCP/IP ­ and the Ethernet Networking Protocol. In networking, a `protocol' is the term for a set of rules that allows the orderly exchange of informa- tion over a network, and many of them are defined by a body called the Internet Engineering Task Force (IETF). Protocols are to computers what language is to humans. Since this book is in English, to under- stand it you must be able to read English. Similarly, for two devices on a network to successfully com- municate, they must both understand and use the same language ­ or protocols. Interestingly, the birth of the Internet can be traced back to the launch of SPUTNIK in 1957, which we mentioned in Chapter 1. In 1958, US President Eisenhower was lobbied by the military and political establishment to initiate and fund the Advanced Research Projects Agency (ARPA) to draw together all the research being undertaken by the myriad of US military agencies at the time. Over the following years as ARPA developed, it encompassed a wider range of interests which included computing and con- trol. By the early 1970s, ARPA had a comparatively small Intranet of 15 nodes across the US connected; and by the early 1980s, in association with a number of manufacturers and research laboratories, finally had a TCP/IP network interconnecting a significant part of US academic and military research facilities. From this, the Internet gradually emerged as a public network through the late 1980s and early 1990s. This use of computer transmission technology has now extended to the world of SNG. The move toward compact SNG units has also seen a shift to the use of IP for providing connectivity for both MPEG-2 and MPEG-4 streams (or whichever other type of compression is used), as well as providing ancillary services on site at major news events, and thus an understanding of IP is now critical. In simple terms, Internet Protocol (IP) works by sending packets of data across the Internet and Local Area Network (LAN) in a series of hops in a discontinuous stream, which are assembled at the destination. Data is sliced into packets which have addresses on the front for the destination. The packets are sent through a series of nodes (switches, routers, etc.) on a hop-by-hop basis. At each node, every packet is analyzed to decide which hop it should take next. This is decided on parameters com- pletely unrelated to any importance that may be attached to this packet as part of the whole stream (a complete anathema to newsgatherers, who naturally regard their traffic packets as more important than anyone else's).