Illustrated TCP/IP by Matthew G. Naugle Wiley Computer Publishing, John Wiley & Sons, Inc. ISBN: 0471196568   Pub Date: 11/01/98

Chapter 3
The Origins of TCP/IP

A TCP/IP network is generally a heterogeneous network, meaning there are many different types of network computing devices attached. The suite of protocols that encompass TCP/IP were originally designed to allow different types of computer systems to communicate as if they were the same system. It was developed by a project underwritten by an agency of the Department of Defense known as the Advanced Research Projects Agency (DARPA).

There are many reasons why the early TCP/IP became popular, three of which are paramount. First, DARPA provided a grant to allow the protocol suite to become part of Berkeley’s Unix system. When TCP/IP was introduced to the commercial marketplace, Unix was always mentioned in every story about it. Berkeley Unix and TCP/IP became the standard operating system and protocol of choice for many major universities, where it was used with workstations in engineering and research environments. Second, in 1983, all U.S. government proposals that included networks mandated the TCP/IP protocol. (This was also the year that the ARPAnet was converted to the TCP/IP protocol. Conversions in those days happened within days. That was when the Internet was small.)

And third, a graphical user interface was developed to allow easy access with the system. TCP/IP or its applications can be a difficult protocol to use if you have not had experience with it. Finding information on the Internet was a formidable task. Before the browser, TCP/IP applications were accessed from a command line interface with a few basic applications that allowed you to call a remote system and act as a remote terminal, transfer files, and send and receive mail. Some companies of these applications built graphical interfaces to the applications, but they were still rough and would not have gained commercial success. The browser hid all the complexities of the TCP/IP protocol and its applications and allowed for graphics to appear as well as text, and by clicking on either the graphics or text, we could place ourselves anywhere on the Internet (within security reasons!). It also allowed for easier access to information on the Internet.

Based on those points, it was not very long before everyone knew of the capability of the protocol to allow dissimilar systems to communicate through the network—all this without a forklift upgrade to mainframes, minis, and personal computers. It simply bolted on to existing computer devices. TCP/IP became a very popular network operating system that continues today.

TCP/IP originated when DARPA was tasked to bring about a solution to a difficult problem: allowing different computers to communicate with one another as if they were the same computer. This was difficult, considering that all computer architectures in those days (the early 1970s) were highly guarded secrets. Computer manufacturers would not disclose either their hardware or software architectures to anyone. This is known as a closed or proprietary system.

The architecture behind TCP/IP takes an alternative approach. TCP/IP developed into an architecture that would allow the computers to communicate without grossly modifying the operating system or the hardware architecture of the machine. TCP/IP runs as an application on those systems.

However, before TCP/IP, the original result was known as the Network Control Program (NCP). The protocol was developed to run on multiple hosts in geographically dispersed areas through a packet switching internet known as the Advanced Research Project Agency network—ARPAnet. This protocol was primarily used to support application–oriented functions and process–to–process communications between two hosts. Specific applications, such as file transfer, were written to this network operating system. The ARPAnet was taken down in 1993. The Internet that we run today was built during the ARPAnet time, but as a parallel network.

In order to perpetuate the task of allowing dissimilar government computers to communicate, DARPA gave research grants to the University of California at Los Angeles (UCLA), the University of California at San Bernadino (UCSB), the Stanford Research Institute (SRI), and the University of Utah. A company called BBN provided the Honeywell 316 Interface Message Processors (IMPs, which have evolved into today’s routers), which provided the internet communications links. In 1971, the ARPAnet Networking Group dissolved, and DARPA took over all the research work. The first few years of this design proved to be an effective test, but had some serious design flaws, so a research project was developed to overcome these problems. The outcome of this project was a recommendation to replace the original program known as NCP with another called Transmission Control Program (TCP). Between the years of 1975–1979, DARPA had begun the work on the Internet technology, which resulted in the TCP/IP protocols as we know them today. The protocol responsible for routing the packets through an internet was termed the Internet Protocol. Today, the common term for this standard is TCP/IP.

Origins (continued)

With TCP/IP replacing NCP, the NCP application–specific programs were converted to run over the new protocol. The protocol became mandated in 1983, when ARPA demanded that all computers attached to the ARPAnet use the TCP/IP protocol.

In 1983, the ARPAnet was split into two networks: the Defense Data Network (DDN), also known as the MILNET (military network), and the DARPA Internet, a new name for the old ARPAnet network.

Outside of the ARPAnet, many networks were being formed, such as CSNET (Computer Science Network); BITNET (Because It’s Time Network) used between IBM systems; UUCP (User to User Copy), which became the protocol used on USENET (a network used for distributing news); and many others. All of these networks were based on the TCP/IP protocol, and all were interconnected using the ARPAnet as a backbone. Many other advances were also taking place with Local Area Networks using Ethernet, and companies began making equipment that enabled any host or terminal to attach to the Ethernet. The original route messengers, known as IMPs (Interface Message Processors), were now being made commercially and were called routers. These routers were smaller, cheaper, and faster than the ARPAnet’s IMPs, and they were more easily maintained. With these devices, regional networks were built and could now hook up to the Internet. However, commercial access to the Internet was still very limited.

One experiment that was successful, CSNET (computer science network), provided the foundation for the NSF to build another network that interconnected five supercomputer sites. The five sites were interconnected via 56–kbps lines. This was known as NSFnet. However, the NSF also stated that if an academic institution built a community network, the NSF would give it access to the NSFnet. This would allow both regional access to the NSFnet and the regional networks (based on the TCP/IP protocol) to communicate with one another. The NSFnet was formally established in 1986. It built a large backbone network using 56–kbps links, which were later upgraded to T1 links (July 1988). Anyone who could establish a physical link to the NSFnet backbone could gain access to it. In 1990, the NSFnet was upgraded to 45–Mbps links.

Once the word of NSFnet spread, many regional networks sprang up, such as NYSERnet (New York State Educational Research Network), CERFnet (named for California Educational Research Network and not Vint Cerf), and others. The regional networks were supported at their level and not by the NSF.

The NSFnet was found to be very useful beyond its conception of linking supercomputers to academic institutions. In 1987, NSF awarded a contract to MERIT Network (along with IBM and MCI) to upgrade the NSFnet to T1 and to link six regional networks, the existing five supercomputer centers, MERIT, and the National Center for Atmospheric Research into one backbone. This was completed in July 1988. In 1989, a nonprofit organization known as ANS (Advanced Network and Services, Inc.) was spun off from the MERIT team. Its goal was to upgrade the NSFnet to a 45–Mbps backbone and link together 16 regional sites. This was completed in November 1991.

More commercial entities were springing up building regional networks via TCP/IP as well. To allow these entities access to the backbone, a concept known as the Commercial Internet eXchange (CIX) was built. This was a point on the backbone that allowed commercial regional networks access to the academic NSFnet backbone.

The original ARPAnet was expensive to run and interest inside DARPA began to wane. Major promoters of the ARPAnet had left DARPA to take positions elsewhere. It was taken completely out of service in 1989, and what emerged in its place is what we know as the Internet. The term Internet was coined as an abbreviation to the Internet Protocol (IP).

The NSFnet was basically a mirror image of the ARPAnet, and they were running in parallel. Regional networks based on the TCP/IP protocol were interconnected via NSFnet, which had connections to the ARPAnet. More connections were being made through NSFnet because it was higher speed, easier to hook into, and less expensive.

It was determined that the original network, the ARPAnet, should be shut down. Sites on the ARPAnet found new homes within the regional networks or as regional networks. NSFnet provided the backbone for interconnection of these regional networks.

Word quickly spread about the Internet and around 1993, and NSF decided it could not continue supporting the rapid expansion directly and produced contracts for outsourcing the continuation of the Internet. Many companies responded to the call, and the functional responsibilities of running the Internet were given to many different companies. In place of the NSFnet would be a concept called Network Access Points, points located throughout the United States through which companies that built their own backbones could interconnect and exchange route paths. Also with this came the concept of peering. NAPs provided access to other backbones, and by peering with another backbone provider, a provider allowed their backbone to be used by another provider to move their customers’ traffic. There was a lot of controversy with this concept: Who should a backbone provider peer with or not peer with? Why should a provider let another provider use its backbone as a transit for its customers for free? The answer: because NSF stated this and the issue was tabled.

NAPs are basically the highest point in the Internet. In this way, many backbones would be privately built, and all would be interconnected through the NAPs. Initially, there were four official NAPs, but this number has grown by an additional 13 (with more being added) as of this writing. Even with the commercialization of the Internet, no one company owned any part of the Internet, and everyone associated with the Internet had to abide by the rules in place. External companies simply provided a specific service required to run the Internet. For example, Network Solutions, Inc. was granted the right to control the domain name registration. However, it does not own this capability. Network Solutions is still under the authority of the Internet Assigned Numbers Authority run by Jon Postel (as of this writing) at the University of Southern California. AT&T was granted the right to host many document databases required by the Internet user community. Eventually, all the functions of running the Internet were contracted out by NSF. Any company (with lots of money) can build a backbone. To provide access to others, its backbone must be connected to others at the NAP. Individual backbone providers then interconnect multiple connections known as Points of Presence, or POPs, which are where the individual user or business connects to the Internet. In April of 1995, the NSFnet backbone was shut down, and the Internet was up and running as we know it today.

One last distinction of TCP/IP: Running the protocol on any network does not require a connection to the Internet. TCP/IP may be installed on as few as two network stations or on as many as can be addressed (possibly millions). When a network requires access to the Internet, the network administrator must call his or her local registry (or Internet Service Provider [ISP]) to place a request for access and be assigned an official IP address.