Editing X.25 (section)

=== How the CCITT standardized virtual circuits ===
{{anchor|How the CCITT standardized virtual circuits}}
{{See also|Protocol Wars}}
The CCITT appointed a special Rapporteur on packet switching, [[Halvor Bothner-By]], who held an initial meeting in January 1974. This resulted in a question, to be answered by study group (SG) VII for the next CCITT plenary in 1976, which was “Should the packet-node of operation be provided on public data networks and, if so, how should it be implemented?”. A list of packet switching networks “to be considered” was provided: [[ARPANET]] (of the [[Advanced Research Projects Agency|ARPA]] in the USA), [[Packet switching#EIN|EIN]] (of the European COST), [[Packet Switch Stream#EPSS|EPSS]] (of the British [[Post Office Telecommunications]]),[[Packet switching#RCP| RCP]] (of the [[Postes, Télégraphes et Téléphones|French PTT]]), [[CYCLADES]] (of [[French Institute for Research in Computer Science and Automation|IRIA]] in France), the [[NPL network]] (of the [[National Physical Laboratory (United Kingdom)|NPL]] in the UK), the SWIFT network (of the international [[SWIFT|SWIFT society]]), and the [[Packet switching#SITA Data Transport Network|SITA network]] (of the international [[SITA (business services company)|SITA company]]).<ref>{{cite web |last=Bothner-By |first=Halvor |date=July 1974 |title=REPORT OF THE RAPPORTEUR'S GROUP ON POINT C - |url=https://umedia.lib.umn.edu/item/p16022coll270:13778}}</ref>

The second Rapporteur meeting, hosted in Oslo by the Norwegian Telecommunications Administration in November 1974, gathered 24 participants, including representatives of other international organizations ([[International Organization for Standardization|ISO]], [[International Federation for Information Processing|IFIP]], [[Ecma International|ECMA]]).<ref name="ccitt1974-08">{{cite web |last=Rapporteur group on packet switching |title=Report of Meeting in Oslo (15 - 16 AUGUST 1974) |url=https://umedia.lib.umn.edu/item/p16022coll270:13778/p16022coll270:13739?child_index=116&query=&sidebar_page=39 |publisher=CCITT}}</ref> A document submitted by France “with the active support of a number of European administrations” served as “main basis for discussion in this meeting”. It was then “agreed that two types of services should be considered, a ‘datagram’ service and a ‘virtual call’ service”.{{r|ccitt1974-08|p=p3}}

At the third meeting, focus had moved from whether there should be packet-mode networks to whether there could be “a standard for the interface between the network and the computers”.{{r|Sirbu1985|p=p39}}

Starting in January 1975, several bilateral and multilateral meetings took place between network operators having commitments for a packet switching service, in view to draft a common interface specification. Meetings started between the Canadian [[DATAPAC]] and the French [[Transpac (data network)|TRANSPAC]], continued with the startup [[Telenet]] of the USA, and continued with the BPO of the UK.{{r|Sirbu1985|p=p39}}{{r|:20|p=p44}}

In March 1975, Halvor Bothner-By produced a list of recommendations to be created, or simply updated, for a packet switching standard to become possible. It was used as a framework at a drafting meeting in Ottawa between engineers of the four operators wishing to have a standard as soon as possible in the USA, Canada, France, UK and Japan. They prepared contributions to be submitted to SG VII in their name by administrations having voting right in CCITT. One contribution was a X.2x interface specification, the first version of  what will become X.25).<ref>{{cite web |last=CCITT Rapporteur on packet switching |date=March 26, 1975 |title=Proposals for Recommendations |url=https://www.dropbox.com/scl/fi/zc7pc47nfku3wytj3mqcs/1975-03-26-CCITT-Bothner-BY-Proposals-for-Recommendations.pdf?rlkey=g3e8o8a4y8wulel9lf3mh7qh2&dl=0 }}</ref><ref name=":4">{{cite journal |last1=Rybczynski |first1=Tony |date=December 2009 |title=Commercialization of packet switching (1975-1985): A Canadian perspective [History of Communications] |journal=IEEE Communications Magazine |volume=47 |issue=12 |pages=26–31 |doi=10.1109/MCOM.2009.5350364 |s2cid=23243636}}</ref>

The fourth Rapporteur meeting, in May 1975 in Geneva, had 45 participants and 27 new documents. The Rapporteur asked whether packet switching recommendations should be issued "with a view to making international interworking possible”, "the French administration answered in the affirmative and Canada strongly supported the French proposal". No firm conclusion was however obtained yet.<ref name="CcittMay1975">{{cite web |last=INWG#99 |title=Report of the Meeting in Geneva (28 May - 6 June 1975) (Extracts) |url=https://umedia.lib.umn.edu/item/p16022coll270:13610/p16022coll270:13465?child_index=90&query=&sidebar_page=31}}</ref>

The fifth Rapporteur meeting, in September 1975 in Geneva, had about 60 participants. After discussions on the proposed virtual circuit interface, numerous issues were left unresolved.{{r|Sirbu1985|p=p40}} Concerning datagrams, ‘It was proposed by Larry Roberts of the US delegation and supported by representatives from France and Canada respectively that the datagram classification be changed from “E” to “A”’, i.e., from essential "to be available internationally” to additional that "may be available in certain countries and internationally”.<ref>{{cite web |last=Pouzin |first=Louis |date=October 1975 |title=Meeting of the CCITT Rapporteur group on packet switching – (Geneva, 16 – 19 September 1975) |url=https://umedia.lib.umn.edu/item/p16022coll270:13610/p16022coll270:13486?child_index=111&query=&sidebar_page=38 |page=6 in Annex 4}}</ref> The Rapporteur's last report expressed doubts “that a standard would be ready for adoption by SG VII”.{{r|Sirbu1985|p=p40}}

At the last meeting of the full SG VII before the CCITT plenary of September 1976, the available draft X.25 raised numerous clarification questions and/or and technical objections. SG VII's chairman Vern MacDonald appointed an editor and provided a meeting facility for the weekend. After intense work during it, all issues had been dealt with. For an approval by the full study group, a challenge remained: copies of the updated X.25 draft had to be available in two languages. To get them in due time, Tony Rybczynski of DATAPAC and Paul Guinaudeau of TRANSPAC spent a full night to handwrite all negotiated amendments, and to assemble them with paste and scissors into clean documents. COM VII then reviewed distributed copies, and unanimously approved them for submission to the forthcoming CCITT plenary. <ref name=":20">{{Cite journal |last=Després |first=Rémi |date=2010 |editor-last=Schwartz |editor-first=Mischa |title=X.25 Virtual Circuits – TRANSPAC In France – Pre-Internet Data Networking |journal=IEEE Communications Magazine |volume=48 |issue=11 |pages=40–46 |doi=10.1109/MCOM.2010.5621965 |s2cid=23639680}}</ref> At this plenary of September 1976, the X.25 recommendation and the other 10 of SG VII were unanimously approved.{{r|Sirbu1985|p=p40}}

As requested by the USA, an optional datagram service was added to the revised X.25 of 1980, together with an alignment of its link layer, now called LAPB, with a recent evolution of HDLC in [[ISO]]. In absence of any public network operator implementing this option, datagrams were finally deleted from X.25 in its update of 1984.{{r|Sirbu1985|p=p41}}