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The Coloured Book protocols were a set computer network protocols used on the SERCnet and JANET X.25 packet-switched academic networks in the United Kingdommarker between 1980 and 1992. The name originated with each protocol being identified by the colour of the cover of its specification document.

After 1992, Internet protocols were adopted on JANET instead; they were operated simultaneously for a while, but X.25 support was phased out entirely by August 1997.


The standards were:

  • The Pink Book defined protocols for transport over Ethernet. The protocol was basically X.25 level 3 running over LLC2.
  • The Orange Book defined protocols for transport over local networks using the Cambridge Ring.
  • The Yellow Book defined the Yellow Book Transport Service (YBTS) protocol, which was mainly run over X.25. It was developed by the Data Communications Protocols Unit of the Department of Industry in the late 1970s.
  • The Green Book defined two protocols to connect terminals across a network: an early version of what became Triple-X PAD running over X.25, and the TS29 protocol modelled on Triple-X PAD, but running over YBTS. It was developed by the GPO. These protocols are similar in functionality to TELNET.
  • The Fawn Book defined the Simple Screen Management Protocol (SSMP)
  • The Blue Book defined the Network-Independent File Transfer Protocol (NIFTP), analogous to Internet FTP, running over YBTS. Unlike Internet FTP, NIFTP was intended for batch mode rather than interactive usage.
  • The Grey Book defined protocols for e-mail transfer (not file transfer as is sometimes claimed), running over Blue Book FTP.
  • The Red Book defined the Job Transfer and Manipulation Protocol (JTMP), a mechanism for jobs to be transferred from one computer to another, and for the output to be returned to the originating (or another) computer, running over Blue Book FTP.

One famous quirk of Coloured Book was that components of hostnames were backwards compared to the Internet standard. For example, an address might be acc@UK.AC.HATFIELD.STAR instead of For more information, see JANET NRS.

It should be noted that the Yellow Book Transport Service was somewhat misnamed, as it does not fulfill the Transport role in the OSI 7-layer model. It really occupies the top of the Network layer, making up for X.25's lack of NSAP addressing at the time (which didn't appear until the X.25(1980) revision, and wasn't available in implementations for some years afterwards). YBTS used Source routing addressing between YBTS nodes—there was no global addressing scheme at that time.



  • A Dictionary of Computing. Oxford University Press, 2004, s.v. "coloured book"

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