The Historical Role of TCP, IP

Introduction

The internet has been developed through the untiring efforts of various computer scientists, engineers, and other experts. Various have been the innovations that have made the internet what it is today. The first thing that happened was way back in the later 1960s. During the 1950s, a new concept for communicating data across different networks had been examined. This was the packet switching concept which was unlike the circuits through which data used to be communicated. Kleinrock in 1961 first proposed that the packet switching technology be examined as an alternative to the circuits in use. He proved the packet switching as effective through his queuing theory. Bran in 1964 even successfully applied the innovative concept in the defense environment which formed the basis for adapting the same by the US ARPA in later years. The ARPA set up the ARPANET, which was thus the first internet, which worked on a protocol known as Network Control Protocol or NCP. The innovation of the internet is thus technologically synonymous with the development of computer network protocols like the NCP. This NCP later gave way to another protocol called the UDP. Over the years, other innovations were introduced in related fields. Such innovations included the email, HTML, World Wide Web, and other concepts that substantially influenced the direction in which data communications developed and grew. One of the most significant developments was the designing of a suite of protocols called TCP/Cerf and Kahn in 1974. Originally, these computer specialists designed the Transfer Control Protocol or TCP. This protocol ensured reliable but connection-oriented data communications across discrete networks located physically apart across the world. However, the Internet Protocol or IP was developed in order to provide a mechanism for transmitting data over heterogeneous networks and could provide for connectionless data communications. Hence, Cerf and Kahn converted their TCP into a TCP/IP suite of over 100 protocols. Thus, the design and development of the TCP/IP lead to the present-day advanced internet technology that we see around us and in which the TCP/IP serves as the backbone of the network architecture.

The Internet and TCP/IP

The internet is defined by various people in different ways. However, the definitions by experts and those who have influenced the development of the internet as we know it today are the best definitions available. Thus, Dr. Vinton Cerf, who along with jointly created the TCP/IP, defines the Internet as the largest network of networks in the world that uses the TCP/IP protocols and packet switching and runs on any communication substrate. Previously, Slater defined the Internet also as a network of networks, that joined the various government, universities as also private computers for providing an infrastructure for computer activities like E-mail, bulletin boards, file archiving, hypertext documents, creating and managing databases, etc. He also viewed the Internet as a huge network of computers that comprised a mechanism for transporting data and messages across the world. Many authors like Stevens (1993: p. 28) consider the ‘internet’ (the ‘i’ in small case) as interconnected networks utilizing common protocols while they term the ‘Internet’ (the ‘I’ in capital letter) as numerous ‘hosts’ across the world that communicate among one another by the use of TCP/IP suite of protocols. The American Federal Networking Council or FNC defines the internet as a global information system comprising of computers linked by the TCP/IP protocol and providing services over the same (FNC 1995).

The Origin of the Internet: From the ARPANET to the NSFNET

The earliest form of the internet was the ARPANET which was the brainchild of the Advanced Research Project Agency or the ARPA which was formed by the US government. During the late 1960s, the ARPA tried to influence the development of a common network of computers shared by multiple users and sponsored some studies on the same. Around the same time, various studies on developing data communications through packet switching technology were also conducted. Among such studies, that due to Kleinrock proposed the use of packets in lieu of circuits normally used in data communications deserves special mention since the development and use of the packet switching technology basically ushered on the internet. The designs of the ARPANET, which was the precursor of the Internet, evolved in 1967 and this earliest form of the internet primarily deployed and utilized distributed packet networks. By late 1969, the structure of this ARPANET was finalized and it became operational with an initial four nodes. The ARPANET essentially comprised a distributed packet switching network based on a single software networking protocol. Also, around the same time as the ARPANET was being designed in the US, the National Physical Laboratory (NPL) in England was experimenting with a network using packet switching technology for data communications. This was termed the NPL Network. The launch of the ARPANET or the earliest form of the internet was followed by the development of host-to-host protocols, and the first such protocol was the Network Control Protocol or NCP, which is the precursor of the modern day TCP/IP. The introduction and expansion of the ARPANET using these protocols continued through the early part of the 1970s. It was only following this development of the first protocols that the first internet applications that we commonly use nowadays like email, HTML, etc were innovated one by one. And these innovations further lead to the rapid development of internet technology.

Subsequent developments occurred, one after the other, and these molded the development of data communications mechanisms. The first commercial version of ARPANET was the Telenet introduced by BBN in 1978. The same year saw the splitting of the original protocol by Cerf and Kahn into TCP and IP. In 1983, the name server was introduced, which later evolved into the DNS. This was also the year in which the ARPANET was divided into the ARPANET and the MILNET. In 1985 the NSFNET was created with a backbone of 56 kbps with an initial connection of 5 supercomputers. With the birth of the NSFNET, a period of rapid growth in internet usage and technology truly started, to which, the present-day commercial internet as it exists today owes its existence.

The Evolution of the Transmission Control Protocol or TCP

One of the most significant developments as discussed earlier and which also occurred in the 1970s was the innovation in internet protocols due to Dr. Vinton Cerf and Bob Kahn in 1974. This was the TCP or the Transmission Control Protocol. This was a significant advancement in that the original protocol i.e. the NCP adopted by the ARPANET could only function as a device driver whereas the TCP was designed more as a communications protocol by its designers. Coffman and Odlyzko (2001: pp. 13-15) rightly observe that the innovation of the TCP by Cerf and Kahn constitutes one of the most significant developments in the entire history of the internet. It definitely paved the way for the future advanced form of commercial Internet that we see in existence today. The late 1970s and the 1980s thus also saw further developments in protocols in use. The NCP used by the ARPANET came to be perceived as insufficient as it could not connect to computers outside the ARPANET system and could only work on the ARPANET hardware configuration. Communication between heterogeneous networks was hence sought to be achieved by developing a software protocol whose functioning would be independent of the technology underlying the networks. Such a protocol was developed by Cerf and Kahn (1974) who designed the TCP as the answer, and this was actually envisaged by them as an end-to-end model where the ‘intelligence’ was placed at the terminals while the protocol for effecting data transfer between networks was ‘dumb’ and only designed towards reliable data transmission (Tarkowski, 2003: p. 12).

Further Advances: The Internet Protocol or IP

The TCP was later transformed into a suite of protocols-the TCP/IP since the TCP essentially comprised a reliable data communications system that was connection-oriented while the Internet Protocol or IP could provide the connectionless datagram service for effective data transmission across heterogeneous networks. Essentially, a stream of 8-bit bytes gets exchanged across a TCP connection between two applications. The application data is then broken into segments of data and the process of such data communication by TCP/IP is entirely different from that by UDP. The TCP does not interpret the bytes’ contents, ensures flow control, and actually transmits segments as IP Datagrams. While the IP is thus a workhorse protocol within the TCP/IP protocol suite, it only provides an unreliable and connectionless datagram delivery mechanism. Basically, the UDP (User Datagram Protocol) was created so that users could use the features of the IP, which provided for unreliable and connectionless transmission of data.

The TCP/IP – Its Emergence as the Modern Internet Standard

The TCP/IP protocol simplified routing, did away with the need for an IMP, and permitted physically distinct heterogeneous computer networks to connect with one another as “peers” for exchanging data via a gateway or special hardware between networks. Essentially this consisted of transmitting packets between the diverse networks. The open architecture allowed network-to-network connectivity. But the original TCP was later remodeled as TCP/IP and the suite of protocols numbering over 100 separate protocols has now come to be regarded as the present-day open and accepted standard protocol which was gradually accommodated with the developing computing standards, particularly the IBM or DEC hardware running on UNIX operating system. In the words of Slater (2002: p. 28), “While the TCP had powerful error and retransmission capabilities, and provided extremely reliable communications, it was subsequently layered into two protocols, TCP/IP, where TCP handles high-level services like retransmission of lost packets, and IP handles packet addressing and transmission”. The TCP/IP was designed in order to support multiple, packet-switched pathways across different networks and such transmission was essentially required to be optimally reliable and able to survive all types of failures. It could also enable safe and strong data exchange between heterogeneous computer systems, and effectively bridge vast physical distances joining the various computer networks located across the globe. Mowery and Simcoe (2001: p. 10) rightfully observe that TCP/IP has emerged as the leading protocol for various networking applications, and also regard the protocol as almost technically synonymous with the Internet.

Significant Developments in the History of the Internet: Chronology of Events

Major events in the development of data communications and hence the internet are primarily those relating to the birth of novel concepts contributed by some enterprising researchers, scientists, and engineers. These include Kleinrock (1961) who first proposed and tested the application of packet switching instead of the commonly used data circuits for communicating information, Cerf and Kahn (1974) for their path-breaking concept of TCP/IP, Metcalfe who proposed the Ethernet, Berners-Lee, T., who first invented the HTML and then the World Wide Web in 1989, Baran (1964) who developed the concept of packet switching networks, Licklider (1960) who first developed the idea of a universal computer network, among many others. A chronological sequence of the major events relating to the evolution of the TCP/IP and the internet and the various concepts introduced by the various experts, as derived from Conron (pp. 27-29) is mentioned below to throw light on the significant developments over the years.

• 1961: Kleinrock’s queuing theory proves the efficacy of packet switching
• 1964: Baran’s work helps usher in packet switching to military networks
• 1967: ARPANET planned under the Advanced Research Projects Agency (ARPA)
• 1969: The first ARPANET node becomes operational
• 1970: The ALOHANET satellite network set up in Hawaii
• 1972: ARPANET is publicly demonstrated, the first email program introduced and
• Also the first machine-to-machine protocol, the NCP set up.
• 1973: Metcalfe brings out his doctoral thesis proposing an Ethernet
• 1974: Cerf and Kahn introduce their significant innovation, the TCP (later on the TCP/IP), a suite of protocols that subsequently revolutionize the internet
• 1982: The e-mail protocol SMTP is defined
• 1983: The first application of the TCP/IP protocols occurs and also DNS defined to Translate a name into an IP address
• 1985-86: The FTP protocol is defined. This year also sees the set up of the NSFNET
• 1987: Number of hosts on the Internet breaks the 10,000 mark
• 1989: Number of hosts on the Internet breaks the 100,000 mark
• 1990: McGill University releases the Archie protocol which is based on TCP/IP. The ARPANET ceases doing business under its name. Work begins on HTTP protocol and the idea of the Worldwide Web is Born at the CERN
• 1991: The Commercial Internet Exchange (CIX) is formed and the University of Minnesota releases Gopher, a unique TCP/IP-based protocol
• 1992: The Internet Society (ISOC) is chartered
• 1993: The Internet Network Information Center (Inter NIC) is chartered to manage Domain names
• 1994: U.S. Senate & House of Representatives set up Web information servers
• 1995: Netscape launches Netscape Navigator and begins commercializing the Web
• 1996: Microsoft launches Internet Explorer Web browser

The TCP/IP-Some Technical Considerations

While the internet is a vast area of knowledge and is still evolving in various aspects, the features of the TCP and IP that required their adoption as the modern internet backbone as also a comparison of their distinctive characteristics, merits, and demerits, can explain the way the internet has developed over the years. This paper now presents some essential features of the TCP/IP features, in concise terms and as applicable for understanding why they have been adopted as standard. This would also provide some idea of the direction that the internet can take in the future.

In those earlier years, the US Department of Defense was seized of the need to ensure that their computer systems survived and stayed operational during wartime. The system of communication between computers on the network was by point-to-point linkages. Thus, even when a single computer on the network broke down, the rest of the system became inoperable. While the formation of the ARPANET was a step in this direction, it was only in the late 1960s that the design and development of a new protocol took shape. The result was first the TCP, followed by the evolution of the TCP/IP.

The TCP/IP is a suite of different protocols. These protocols are located in various layers of the protocol stack. An understanding of the TCP/IP thus requires the knowledge of the interactions of the various layers of the protocol stack among one another as also as those layers outside the protocol stack. Also, there are the routers and gateways, which also need to be understood to grasp the data communication process better. Routers receive packets of data and transmit these to another network or to another part within the same network through a port. The gateway is similar in function but it basically provides access to another network and can hence be termed as either an exit or an entry point from a network to the next. The TCP is connection-oriented located in the Transport Layer and is considered a service protocol. The IP is located in the network layer. It facilitates end-to-end data transfer via the internet and uses connectionless services. The IP does not provide reliable data transfers but the TCP does. The TCP does not need the IP for the delivery of data over the internet networks. It can make do with any network layer protocol so long as such protocol can effectively provide routing and also support inter-layer interfaces. Basically, the IP provides information on the routing of data through the internet. It does not provide error control and the system depends on error control and reliable transmission facilitated by the upper layer protocols like the TCP (Russell, 2000: pp. 155-164).

The TCP/IP is generally a four-layer system (Figure 1). The network layer is also termed the internet layer and contains the protocols like the IP and ICMP. This layer handles packet movement across the network. The transport layer ensures the flow of data between hosts and in the case of the TCP/IP consists of protocols TCP and UDP. TCP-enabled data flow is reliable and connection-oriented. The TCP essentially breaks down data that it receives from an application into small chunks or segments and then passes these on to the network layer below it. TCP also acknowledges the packets received by it and also sets timeouts to denote that sent packets are acknowledged on receipt. The UDP functions more simply and only sends Datagrams or data packets from a host to another host. However, the UDP does not ensure reliability. An important thing is also that while the topmost layer is the application layer that only concerns itself with the applications, the other three lower layers only ensure communication success (Stevens, 2002).

One thing that is evident is that the TCP is a transport layer protocol that utilizes the IP as the network layer protocol. But while TCP is reliable, IP is not. All data packets that the TCP passes through going through the IP i.e. all TCP (also other protocols in transport layer) data are transmitted as IP Datagrams. The IP transmission is connectionless and unreliable, which means that IP does not maintain any status information on following Datagrams or relate successive Datagrams (connectionless) and also does not guarantee that the transmitted Datagrams will successfully reach the destination (unreliable) (Stevens, 2002).

Generally, the IP can receive a datagram from the TCP which it then sends, or a datagram from a network interface which it then forwards. The IP searches within its Routing Table memory when sending Datagrams that it receives for sending whereas in the case of a datagram that it receives for forwarding (when it receives from a network interface), it first checks the destination IP address to see if that address is one of its own IP addresses or if an IP broadcast address. The delivery of the datagram is finally as an outgoing data packet (when the IP acts as the router) or else gets discarded (Stevens, 2002).

Both TCP and IP have some inherent advantages which have made them indispensable as the modern internet standard protocol. For one, the TCP provides a sequence of services called fragmentation and reassembly whereby it effectively fragments data that are too large to fit one data unit and then again reassembles these same data fragments which reach back to the transport layer from the network layer. Incidentally, both the IP and the TCP manage fragmented data packets at both the transport layer and the network layer. Also, a timer mechanism ensures that when some parts of data are lost, an error message is generated and sent to the source of the data which then provides for retransmission of the data. Another advantage is that in the combination of protocols that make up the TCP/IP suite, different routing methods are available although this does not affect the transmission outcomes in any case i.e. it does not affect the delivery of data. Actually, the TCP/IP were designed so that data could be successfully transmitted through heterogeneous computer networks without affecting delivery reliability even though the network could fail on the way (Russell, 2000, pp. 155-164)

However, there are some disadvantages that computer engineers are trying to overcome. For instance, IP cannot support very many addresses. Also, IP does not provide error control at all. It can only report errors to the hosts originating the data packets (Russell, 2000, pp. 155-164).

Conclusion

Thus the TCP handles and delivers data information reliably across physically distinct and heterogeneous computer networks. The Internet Protocol, or IP, performs the task of routing the network transmissions from the sender to the receiver and handles all issues relating to addresses of computers and networks, among others. The development of the TCP/IP suite of network protocols is thus nearly synonymous with the development of the modern internet network systems as we know it. The advancements made in so developing a suitable protocol, which is essentially software, which primarily communicates data over physical distances across heterogeneous computer hardware architecture has contributed substantially in bringing the concept of internet and data communications to the present day technologically advanced state.

References

Baran, P., “On Distributed Communications”, Rand Corporation, 1964

Cerf, V. and Kahn, B., “A protocol for packet network interconnection”, Transactions of Communications Technology, IEEE, 1974

Coffman, K.G., and Odlyzko, A.M., “Growth of the internet”, AT&T Labs, 2001: pp. 13-15

Conron, J., Data Communication and Networks, Computer Science Department, New York University, 2004: pp. 27-29

Cyborg Computers, “Introducing TCP/IP”, Thomson Learning

Kleinrock, L., “Information Flow in Large Communication Nets”, RLE Quarterly Progress Report, 1961

Licklider, J.C.R., “Man-Computer Symbiosis,” 1960

Mowery, D.C., and Simcoe, T., “Is the Internet a U.S. Invention? – An Economic and Technological History of Computer Networking”, Haas School of Business, University of California, Berkeley, USA, 2001: p. 10

Olavly, ”Introduction to Data Communication”, University of Oslo, Edited by Bringsrud, Kjell Åge, 2001

Russell, T., Telecommunications Protocols, McGraw Hill, Second Edition, ISBN: 0071349154, 2000: pp. 155 -156

Slater-III, W.F., “Internet History and Growth”, Chicago Chapter of the Internet Society, Chicago, Illinois, USA, and 2002: p. 28

Stevens, W.R., “The Protocols Accessed”, TCP/IP Illustrated, Volume 1, 1993: p. 28.

Tarkowski, A., “Heterogeneous Engineers of the Internet: How Inventors Weaved Together Internet Technologies, Social Values and Blueprints for New Social Institutions” Central European University, Warsaw, Poland, 2003: p. 12. Web.

Appendix

Figure 1: The four layers of the TCP/IP protocol suite