VI - How to Communicate Across Network Boundaries? Shortly after the successful ICCC'72 conference, Bob Kahn left his job at Bolt Beranek and Newman (BBN) and went to work at IPTO. Joining IPTO as a program manager, Kahn initiated certain projects and also took over responsibility for one that had already been funded. A new initiative was to create a ground based packet radio network. An existing initiative was to create a satellite-based packet switching network. (Ronda Hauben, "The Birth of the Internet", 7)
The ground packet radio network would be of particular interest to the US Department of Defense(DOD), as it would make packet switching computer networks possible in otherwise difficult to reach areas or conditions. Kahn's objective was to create a multinode ground packet radio network (PRNET) where each node could be mobile. In parallel, he sought to create a packet satellite network (SATNET) utilizing INTELSAT satellites.(14) The goal of the packet satellite network research was to make resource sharing computer communications networking possible with different European sites. Two of the networks (PRNET and SATNET) would use radio transmission and the third network which already existed (ARPANET) used shared point to point leased lines from the telephone company. Though Kahn originally considered the possibility of seeking changes to each of the constituent networks to solve the multiple network problem, he soon recognized the advantage of an architecture that would directly accommodate a diversity of networks. While existing networks like the ARPANET would require that another network become a component of it, there was a need for an architectural conception that would allow the communicating networks to function as peers of each other, rather than requiring that any one become a component of another. There was a need to design an architecture that would be open to all networks, an architecture that Kahn called "open architecture".(15)
VII - Designing Protocols and Specifications for an Internet
Once at IPTO, Kahn invited Vinton (Vint) Cerf to collaborate with him. Kahn wanted to design an open architecture protocol and needed Cerf's knowledge of computer operating systems to do it. Other researchers were also interested. For example, at an INWG meeting in June, 1973, in New York City, Kahn and Cerf were joined by E Aupperle, R Metcalfe, R Scantlebury, D Walden and H Zimmerman. Scantlebury was from the UK and Zimmerman, from France. Others listed were members of the US network research community. The document also credits G Grossman and G LeLann for contributing after the meeting. LeLann is French. (INWG note #39 NIC # 18764, dated 9-13-73). Cerf explains that LeLann worked with Louis Pouzin at IRIA (now INRIA) and “spent 6 months
working with me and others on the design of the Internet's TCP protocol."
(Cerf, Email, April 13, 2003) Pouzin also remembers a June 1973 INWG meeting, noting that it was quite hot in NYC. (Pouzin, Email, April 28, 2003)
The INWG note #39 is a draft paper that Kahn and Cerf prepared for presentation at the September 16, 1973 INWG meeting in Brighton, England. A revised draft of the paper was published in May, 1974, titled "A Protocol for Packet Network Intercommunication" in the IEEE Transactions on Communications. The paper describes the philosophy and design for the TCP/IP protocol, though the original paper called the protocol TCP, as the IP function was originally embedded in TCP.(16)
After designing a protocol, there is a need to write specifications to implement the design.(16a) Cerf refers to the development of two versions of the specifications for TCP developed at Stanford University, one in December 1974 and a second in March 1977. Subsequently two further specifications were developed with other groups.(Cerf) Among the names of those working on the initial specifications for TCP, Cerf lists US researchers or graduate students including Y Dalal, C Sunshine, R Karp, J Estrin, and J Mathis, at Stanford, R Tomlinson and W Plummer, at BBN, R Metcalfe, D Boggs, and John Schoch, at Xerox PARC. He also lists several researchers from the UK, from UCL, F. Deignan, C J Bennett, A J Hinchley and M Gallard. Cerf also thanks G LeLann from the University of Rennes, France. Cerf writes that Dag Belsnes, from the University of Oslo, Norway provided "additional philosophical leavening which influenced the design of the protocol."(Cerf, The Final Report, IEN 151, 2)
When asked what he thought the term "philosophical leavening referred to," Belsnes responded, "I also wonder what 'philosophical leavening' is referring to. Perhaps that I always like to discuss and establish some understanding of problems."(17)
In 1973, Belsnes received a one year grant from the Norwegian Research Council. After meeting Vint Cerf at a conference in England in 1973, Belsnes contacted Cerf and was accepted to be part of the research effort at the Digital System Laboratory at Stanford University. "I got the opportunity," Belsnes writes, "to participate in his Protocol Design Group that worked on creating a specification for the Internet Transmission Control Program." Belsnes explains that among his main interests were "protocol correctness and flow congestion control." (Belsnes, Email, June 17,2002)
Creating a design and then specifications for the development of a protocol for an Internet is a significant step. It is, however, part of a larger research process. Elaborating on the value of the experimental work, Paal Spilling, another of the Norwegian Internet pioneers, writes:
"A group at Stanford University (SU) specified in detail a control
program ... the Transmission Control Program (TCP) allowing computers
in different inter-connected networks to communicate.... Although the
TCP was specified in detail, it had to be considered as a first
approach towards making a reliable process-to-process communication
tool in an internetwork environment. Experience showed that this was
first version of the TCP, and uncovered some deficiencies in its design.
Some of these could be taken care of rather easily, while others were
subjects for further investigations."(Spilling, Proposal to Nato)
Kahn had recognized the need to include at least three different kinds of packet switching networks to test if the protocol created for intercommunication among dissimilar networks would be adequate.
NATO, Shimoliy Atlantika alyansi (ingl. North Atlantic Treaty Organization, NATO; frans. Organisation du traité de l'Atlantique Nord , OTAN; oʻzb. Shimoliy Atlantika shartnomasi tashkiloti) - Yevropa, AQSh hamda Kanada kabi koʻpchilik mamlakatlar birlashgan jahondagi eng yirik harbiy va siyosiy jamlanma, yaʼni, „Yevropani tashqi taʼsirlardan himoya qilish“ uchun ushbu tashkilotga 4-aprel 1949-yil AQShda asos solingan. Tashkilot yaratilgan paytda 12 ta mamlakat aʼzo boʻlgan, hozirgi kunda esa aʼzolar soni 28 taga yetgan.
If a prototype has only two different entities, it is difficult to tell what is particular about each and what is general about the two. With three or more dissimilar networks as part of a prototype, it is possible to identify what is general to them all despite the dissimilar nature of each.
In June 1973, a TIP was installed at Kjeller, Norway for the NDRE researchers. By the end of July 1973, the UCL TIP in the UK was also passing packets between the US and UK. These packets went from the US via satellite to the Tanum Earth Station in Sweden, via land and underwater lines to NORSAR in Kjeller, Norway, and then to London in the UK. Kirstein and Kenny provide a diagram of the relation between the
UK TIP, the Norwegian TIP and the US ARPANET.(18)
Kirstein writes that one of the significant activities in the early work to develop the Internet was "an early protocol experiment in late 1974 between a junior assistant professor at Stanford (Vint Cerf) and a visiting scholar from Norway at UCL (Paal Spilling) of the Proposed Transmission Control Protocol." Spilling visiting UCL from NDRE, worked with Kirstein's research group. Judy Estrin was a graduate student working with Vint Cerf at Stanford. Estrin and Spilling "did what was probably the first TCP tests with each other. They were independent implementations," Kirstein explains. (Kirstein, Email, May 20, 2002.) Describing this research, Spilling elaborates, "As I remember the fellows at the Stanford side may have been Judy Estrin and Jim Mathis. At the UCL side were Frank Deignan, Andrew Hinchley and me. Frank was the implementer. It was extremely exciting to observe packets coming from Stanford and after an initial debugging being accepted and processed by Frank's implementation of TCP. One critical problem I can remember was that the TCP checksum was applied slightly differently at Stanford and at UCL." (Spilling, Email, August 1, 2002)
Kirstein describes how the British government became more supportive of his research by 1975. He writes:
"The British authorities became increasingly positive from 1975. I had
set up a management committee to oversee the use of the Arpanet link.
This included representatives from the British Post Office, the Ministry
of Defence, the Science Research Council and the Department of Industry.
They had to approve all requests for usage. From 1976, there was increasing
pressure for using the emerging X.25 infrastructure (International Packet
Switched Service - IPSS) as an alternative to SATNET. First this involved a
commercial 9.6 Kbps line from about 1978 between UCL and BBN; here it was
BBN and DARPA. Later, I think it was around 1980, a 64 Kbps IPSS link was
provided also free of charge by the British Post Office. This link existed
until around 1984, and allowed much fuller research into multiple routes
with different capacity, charging and access control considerations. The
IPSS link was always using IP; for this reason the multiple use of the
commercial use and SATNET was an important landmark into the use of
interconnected networks. It was their existence which allowed UCL to adopt
a phased approach to the adoption of the Internet Protocol. We first proved
it on the IPSS link without affecting NCP traffic on SATNET; this needed
NCP-TCP relays at UCL and BBN. We could then move it onto SATNET, without
impacting too drastically our service traffic -- which could use the IPSS
route in an emergency. Finally, when the ARPANET had moved to Internet
Protocols, we could abandon our relays in BBN and also leave SATNET; all
the traffic could use IP/X.25 over IPSS. It is the phased nature of this
transition which explains why UCL finally left SATNET (see below) after the
Norwegians -- though they used IP for service traffic much earlier.
By the time we got to around 1983, complete alternate mail nets, like
UUCP and Bitnet started coming into being. The various gateways these
provided gave a much richer topology. When the DNS was added, its
impact on the international infrastructure was not realised at first.
When we introduced blocking on some of our IPSS routes, we suddenly
realised the magnitude of international traffic that was passing
over the UK-US routes originating from these other networks. It was
then that the work on peering and service agreements took on a new
urgency for these data networks." (Kirstein, Email, October 8, 2002)
VIII - Early Norwegian Internet Research Challenges During its earliest stage, Lundh's research group consisted of his 2 graduate students and himself. By 1974 he was able to get Paal Spilling assigned to his group, Spilling had a PhD in nuclear physics and was interested in the networking project. Subsequently other qualified engineers were assigned by NDRE to the research group. Lundh describes the change Spilling's participation made in the NDRE research group. He writes (Lundh, Email, June 12, 2002)(19):
"Paal Spilling came to my group in 1994....I recruited him from
one of my colleague's group(s) at NDRE where he had become superfluous.
At that time I had good contact with people in PSP and INWG. I
participated in their meetings and knew Peter Kirstein. They were all
delighted that I finally got someone beside me. And - as I recall -
Peter offered to have him at UCL for a couple of months to give a
flying start, which was very good and useful indeed. Paal soon
got the whole networking business 'under his skin' and after that
participated together with me in all the meetings. He soon became
the main contributor to the networking effort at NDRE, for some time
being the only one who spent full time in it."
Lundh emphasizes that the continual invitation to the Norwegian
Telecommunications Administration Research Establishment (NTA-RE) to participate in the research led to "the free loan for experimental purposes of a spare channel in the INTELSAT IV satellite and a spare line between NDRE and the existing Scandinavian Satellite Earth Station at Tanum, Sweden. This permission was obtained in 1975 permitting the SIMP - Satellite IMP - to be installed at the Tanum Station in mid 1975. From then on SATNET had three ground stations permitting experiments involving contentious traffic situations. Mario Gerla in Leonard Kleinrock's group at UCLA was very active in the SATNET studies which eventually resulted in the CPODA-protocol for Contention Priority Oriented Demand Access."(Lundh) According to Lundh, other researchers in Norway were not eager to use the NORSAR TIP during the 1970s. But interest was expressed by the staff at NORSAR in utilizing the ARPANET as an alternative to the channel they had for exchanging seismic data with the US. Lundh notes that "Commercial traffic was prohibited in the Arpanet from the outset and that was still the rule as the network changed into the Internet. The network was an experimental facility supported for research purposes."(Lundh, 18)(20)
IX - Creating an Internet The protocol suite that makes the Internet possible is known as the TCP/IP protocol suite (Transmission Control Protocol/Internet Protocol). Lundh explains the extensive effort needed to transform the design into functioning protocol specifications. He describes the years of experiments, analysis of the results, and the design of new experiments to test the theory developed from the experimental
process. Failures or surprises from the actual experience of the researchers helped them to make the needed changes in the implementation efforts. Lundh writes:
"Those protocols resulted from an extremely thorough analysis and design.
'No stone was left unturned' during the development which took several
years. Theoretical analyses were complemented by experiments. Combinations
of traffic types and requirements, network topologies and application types
were imagined, tried, failed, changed and tried again. The 'final' TCP and
IP were not easily postulated and approved. Nobody can ever reproduce in a
network and even less the diverse demands of information exchange. The
growing active dynamic traffic situation in the ARPANET prevailed during
onwards development of its own underlying technology. That may be one reason
for the robustness, elegance and survivability of the result." (Lundh, 12)
Lundh emphasizes the importance of a functional network with actual users and traffic as a laboratory for the researchers. He describes how theory grew out of experimental research and then was used to guide the experimental process. In this way, the theory was verified or modified.
Recalling his experience, Lundh writes, "During a period of intensively active development, methods were conceived and perfected until functioning well in an environment which was closer to reality than anyone might have dreamt up in a 'sterile' laboratory." This experimental process was closely intertwined with theoretical development. He adds:
"At the same time a profound theoretical understanding was developed.
It kept its scrutiny on experimental results and was both guiding and
following up the work in an admirable teamwork."(Lundh, 12)
Describing the political conditions that had to be accommodated to create a protocol that would function for the international community, Spilling explains the rationale of the TCP design:
"In order to allow Host computers, connected to different networks to
communicate, these networks have to be interconnected. This is not a
trivial matter, since different networks, in general, are supported by
organizations with different requirements and therefore will develop
differently. Any changes in existing networks in order to interconnect
these, will be costly and impeded by political factors. The obvious
approach therefore, would be to leave the local nets undisturbed and
to perform the interconnections outside them. This is one of the main
ideas behind the TCP." (Spilling, Proposal to Nato, 5)
The protocol requirements were such that the networks participating in the Internet would not be limited in their internal development or activities.(21) The use of gateway computers helped in this process. Gateway computers would reformat the packets of data from the form needed by one network into the form to meet the requirements of the next network on their journey to their final destination. The gateway software would also determine the best next path for the packets of data to take to get to their destination.
Spilling explains that when Host 1 (on Net 1) wants to exchange data with Host 2 (on Net 2), it forms the data into Internet packets according to the TCP format and encloses them in the format required by Net 1. This action, he says, is called "wrapping."(Spilling, Proposal to Nato, 6) Spilling attributes the term "wrapping" to an article by Louis Pouzin and H. Zimmerman. Internet packets are then transported to the gateway where they are unwrapped from the Net 1 format and rewrapped in the format for Net 2 for transmission to Host 2 (on Net 2).
X - 1970s Networking Collaboration to Develop Internet Technology Critical to the scientific process of the development of the TCP protocol was the international collaboration of researchers working together on its development. Describing the role of this collaboration, Lundh writes:
"(T)he network technology was further refined and developed in an
intimate co-operation of ten research groups during the 1970s. That
co-operation resulted in the technology underlying today's Internet."
The results were documented as standards and made openly available to anyone around the world, particularly to academic researchers. The period from 1973 to 1980 was a significant period in the research to develop the Internet. For Lundh, the Internet is the networking of interconnected nets. "From the initial ARPANET," he writes, "the technology was developed into a basically new computer cooperating technology -- Internetworking technology. Its main constituents were defined as proposed standards around 1980."(Lundh, 10) Further important technical refinements and geographical expansion occurred in the 1980s.
This development was done on a non-commercial research basis. The earliest ARPANET development was done on the basis of leased telephone lines. The research in the mid to late 1970s and into the 1980s, however, included research on Ethernet, packet radio and packet satellite forms of communication. Lundh points out that not only was the ARPANET a laboratory, it was at the same time "an active telecom network, a resource sharing network and a forum of creative and critical people."(Lundh, 12)(22)
Lundh cites an experiment where three people were located in different geographical locations, Boston, MA in the US, London, England, and Kjeller, Norway. They held a demonstration conference using speech, which was observed by other researchers in a meeting at another ARPANET-TIP international site, at University College London (UCL). Lundh writes:
"Each of the three sites ... communicated through local area nets
interconnected through gateways via Arpanet and SATNET. The packet
traffic in that Internet situation (new then!) was a combination of
that speech traffic together with 'natural' traffic in the Arpanet at
the time."(Lundh, 13)
Lundh calls this experiment in 1978, "one of the several major milestones during development of Internet technology." He also emphasizes that not only did the Internet research result in important and robust standards, but it also influenced and actually pioneered a new methodology for developing telecommunication standards.(Lundh, 13)
According to Lundh, ten groups collaborated on developing the TCP/IP protocols. The whole team, he explains, referred to itself as the "Packet Switching Protocols Working Group - PSPWG." Eight of the groups were in the USA, one in England and a small group in Norway. "The development comprised investigation of a variety of suggested methods. They were thoroughly studied theoretically and experimentally."
(Lundh, 13)(23) Kirstein adds that in phases of the SATNET research, there were researchers from Germany and Italy involved and there were also meetings at their sites. (24)
Communication via email helped the research, along with in person meetings held every three months that some people from each group attended. Lundh credits DARPA/IPTO with providing the leadership and much of the funding for the work. The research, he emphasizes, "had the main purpose to study and develop resource-sharing networks." (Lundh, 14)
The resources to be shared were the 'power' of the computers, programs and data of various types. The human users were also seen as a significant resource. "Further, and not least," writes Lundh, "it was important to create an environment where human resources could co-operate and strengthen creativity and knowledge." (Lundh, 14)
Lundh lists ten of the research groups that collaborated on Internet research in the 1970s. (Lundh, 16)
1. ARPA in Washington, DC, USA
Advanced Research Projects Agency - Information Processing
"The tone," Lundh writes, "was open and could be heated although always friendly. A certain amount of social occasions usually took place and stimulated the smooth co-operative spirit. ... The assembled group," he explains, "constituted a strong and inspiring research team." (Lundh, 17) When not assembled, "from day to day the researchers exchanged e-mail. It comprised of discussions, experimental results, comments and programs." (Lundh, 17) From 1977, the usual 2 day PSPWG was "supplemented," reports Lundh, by a third day "Internet meeting dedicated to techniques for internet-working of different nets." (Lundh, 17) Also see Appendix.
Following is a list Lundh provides of some of the rotation of meetings. These were meetings between August 1974 and February 1978. (Lundh, 17):
10-11 Aug 74 On the ferry between Stockholm, Sweden and Abo, Finland
4-5 Sep 75 Linkabit Co, San Diego, California
Host: Irwin Jacobs
12-13 Nov 75 UCL, London, England
Host: Peter Kirstein
12-14 Feb 76 DCA and ARPA, Washington, DC.
Host: Bob Kahn
29-30 Apr 76 BBN, Cambridge, Massachusetts
Host: David Walden
29-30 Jun 76 NDRE, Kjeller, Norway
Host: Yngvar Lundh
23-24 Sep 76 UCLA, Los Angeles, California
Host: Leonard Kleinrock
9-10 Dec 76 UCL, London, England
Host: Peter Kirstein
10-11 Mar 77 Comsat, Washington, DC
Host: Estil Hoversten
8-10 Jun 77 NDRE, Kjeller, Norway
Host: Yngvar Lundh
17-19 Aug 77 Linkabit, San Diego, California
Host: Irwin Jacobs
31 Oct-2 Nov 77 BBN, Cambridge, MA
Host: Bob Bressler
1-3 Feb 78 UCLA, Los Angeles, California
Host: Wesley Chu
Dave Mills, who worked at COMSAT, as chief architect for the Internet
from 1977–1982, adds that there were several meetings after the ones Lundh lists, at least until January 1, 1983 when ARPANET computers were officially to change to the TCP/IP protocol. The actual Internet coming out party, Mills writes was at the NCC in 1979. (Mills, Email, April 28, 2003)
The original vision of resource sharing networking was an important source of inspiration for Internet development. Included in this resource sharing were technical resources, and even more significantly, the sharing of human resources, ideas and suggestions.(Lundh, 10)