Editing Packet Switch Stream (section)

==Research, development and implementation==

=== EPSS ===
[[Roger Scantlebury]] was seconded from the [[National Physical Laboratory (United Kingdom)|National Physical Laboratory]] to the British [[Post Office Telecommunications]] division (BPO-T) in 1969. He had worked with [[Donald Davies]] in the late 1960s pioneering the implementation of [[packet switching]] and the associated [[communication protocol]]s on the local-area [[NPL network]].<ref>{{Cite book |last=Naughton |first=John |url=https://books.google.com/books?id=bbonCgAAQBAJ&pg=PT290 |title=A Brief History of the Future |date=2015 |publisher=Orion |isbn=978-1-4746-0277-8 |language=en}}</ref><ref>{{Cite journal |last=Cambell-Kelly |first=Martin |date=1987 |title=Data Communications at the National Physical Laboratory (1965-1975) |url=https://archive.org/details/DataCommunicationsAtTheNationalPhysicalLaboratory |journal=Annals of the History of Computing |language=en |volume=9 |issue=3/4 |pages=[https://archive.org/details/DataCommunicationsAtTheNationalPhysicalLaboratory/page/n0 221]-247}}</ref><ref>{{Cite journal |last=Kirstein |first=Peter T. |date=2009 |title=The early history of packet switching in the UK |journal=IEEE Communications Magazine |volume=47 |issue=2 |pages=18–26 |doi=10.1109/MCOM.2009.4785372 |s2cid=34735326}}</ref><ref name="Early experiences with the Arpanet">{{cite journal |last1=Kirstein |first1=P.T. |date=1999 |title=Early experiences with the Arpanet and Internet in the United Kingdom |journal=IEEE Annals of the History of Computing |volume=21 |issue=1 |pages=38–44 |doi=10.1109/85.759368 |s2cid=1558618}}</ref> By 1973, BPO-T engineers had developed a packet-switching communication protocol from basic principles for an Experimental Packet Switched Service (EPSS) based on a [[virtual call capability]]. However, the protocols were complex and limited; Donald Davies described them as "esoteric".<ref name=":0">{{Cite web |last1=Smith |first1=Ed |last2=Miller |first2=Chris |last3=Norton |first3=Jim |date=2017 |title=Packet Switching: The first steps on the road to the information society |url=https://www.npl.co.uk/getattachment/about-us/History/Famous-faces/Donald-Davies/UK-role-in-Packet-Switching-(1).pdf.aspx?lang=en-GB |access-date= |website=National Physical Laboratory}}</ref><ref>{{Cite web |last=Pelkey |first=James L. |date=May 27, 1988 |title=Interview of Donald Davies |url=http://archive.computerhistory.org/resources/access/text/2017/11/102738594-05-01-acc.pdf |website=Computer History Museum}}</ref>

[[Ferranti]] supplied the hardware and software. The handling of link control messages (acknowledgements and flow control) was different from that of most other networks.<ref name=":0" /><ref>{{cite conference |last=Bright |first=Roy D. |author2=Smith, Michael A. |year=1973 |title=EXPERIMENTAL PACKET SWITCHING PROJECT OF THE UK POST OFFICE |url=http://rogerdmoore.ca/PS/EPSSB.html |conference= |location=Sussex, United Kingdom |publisher=Noordhoff International Publishing |pages=435–44 |archive-url=https://web.archive.org/web/20131020142503/http://rogerdmoore.ca/PS/EPSSB.html |archive-date=2013-10-20 |access-date=2013-08-30 |book-title=Proceedings of the NATO Advanced Study Institute on Computer Communication Networks |url-status=dead}}</ref><ref>{{cite conference |last=Pearson |first=DJ |author2=Wilkin, D |year=1974 |title=Some Design Aspects of a public packet switching network |url=http://rogerdmoore.ca/PS/EPSSFer/EF.html |conference= |pages=199–213 |archive-url=https://web.archive.org/web/20131020142152/http://rogerdmoore.ca/PS/EPSSFer/EF.html |archive-date=2013-10-20 |access-date=2013-08-30 |book-title=Proceedings of the 2nd ICCC 74 |url-status=dead}}</ref> The EPSS began operating in 1976, the first [[public data network]] in the UK.<ref>{{cite book |url=https://books.google.com/books?id=DN-t8MpZ0-wC&pg=PA2 |title=A history of international research networking: the people who made it happen |date=2010 |publisher=John Wiley & Sons |isbn=978-3527327102 |editor1-last=Davies |editor1-first=Howard |page=2 |editor2-last=Bressan |editor2-first=Beatrice}}</ref> EPSS was interconnected with [[SATNET]] and the [[NPL network]].<ref>{{Cite web |date=29 July 1977 |title=Issues in the interconnection of datagram networks |url=https://www.rfc-editor.org/ien/ien1.pdf}}</ref><ref>{{Cite web |last=Postel |first=Jon |date=August 18, 1977 |title=1.4.1 INTERNET Meeting Notes |url=https://www.rfc-editor.org/ien/ien3.txt}}</ref><ref name="Abbate00p125">{{harvnb|Abbate|2000|p=[https://books.google.com/books?id=E2BdY6WQo4AC&pg=PA125 125]}}</ref>

=== IPSS ===
{{Further|X.25#How the CCITT standardized virtual circuits}}

The [[International Packet Switch Stream]] (IPSS) was an international network service, based on the X.25 standard, launched by the international division of BT. This venture was driven by the high demand for affordable access to US-based database and other network services. A service was provided by IPSS to this market, which started operation in 1978. IPSS was later linked to PSS and other packet switched networks around the world using [[Gateway (telecommunications)|gateways]] based on the [[X.75]] standard.

IPSS was interconnected with SATNET.<ref>{{cite journal |last=Hauben |first=Ronda |year=2004 |title=The Internet: On its International Origins and Collaborative Vision |url=http://www.ais.org/~jrh/acn/ACn12-2.a03.txt |journal=Amateur Computerist |volume=12 |issue=2 |access-date=May 29, 2009}}</ref> [[JANET]] connections were available via IPSS.<ref>{{Cite book |last1=Earnshaw |first1=Rae |url=https://books.google.com/books?id=xy7LadoXUVYC&pg=PA46 |title=Digital Convergence - Libraries of the Future |last2=Vince |first2=John |date=2007-09-20 |publisher=Springer Science & Business Media |isbn=978-1-84628-903-3 |pages=46 |language=en}}</ref>

=== PSS ===
A period of pre-operational testing with customers, mainly [[UK universities]] and [[computer manufacturer]]s, began in 1980. Packet Switch Stream launched as a commercial service on 20 August 1981 based on X.25/X.75. The experimental predecessor network (EPSS) formally closed down on 31 July 1981 after all the existing connections had been moved to PSS.

The network was initially based upon a dedicated modular packet switch using DCC's TP 4000 communication processor hardware. The operating system and the packet switching software were developed by [[Telenet]] (later on [[GTE]] Telenet). BT bought Telenet's system via [[Plessey Controls]] of Poole, Dorset who also sold Telex and traffic light systems. PSS was launched before Telenet's own upgrade of its network and, at the time, most other networks still used general purpose mini-computers as packet switches.

For a brief time the EEC operated a packet switched network, [[Packet switching#Euronet|Euronet]], and a related project [[Diane (project)|Diane]] to encourage more database and network services to develop in Europe. These connections moved over to PSS and other European networks as commercial X.25 services launched.

Later on the InterStream gateway between the [[Telex]] network and PSS was introduced based on a low speed PAD interface.

In addition, BT used Telematics packet switches for the Vascom network to support the [[Prestel]] service.

The network management systems were based in [[London]] and [[Manchester]]. Packet switches were installed at major trunk exchanges in most major conurbations in the UK. Network management was run on a system of 24 [[Prime Computer|Prime]] 63xx and 48xx computers running a modified versions of Revisions 20 and 22 of the [[PRIMOS|Primos]] operating system.

The [[DDN NIC|DNICs]] used by IPSS and PSS were 2341 and 2342 respectively.

The last PSS node in the UK was finally switched off Wednesday, 28 June 2006.