Protocol-control information explained

In telecommunication, the term protocol-control information or PCI has the following meanings:^{[1] [2] [3] [4]}

1. The queries and replies among communications equipment to determine the respective capabilities of each end of the communications link.
2. For layered systems, information exchanged between entities of a given layer, via the service provided by the next lower layer, to coordinate their joint operation.

Notes and References

1. Web site: CCITT X.200 – Information technology – Reference Model of Open Systems Interconnection for CCITT Applications. 1988. International Telecommunication Union (ITU).
2. Book: Boait. P.. Neville. G.. Norris. R.. Pickman. M.. Walmsley. J.. Tolhurst. M.. Definition of OSI Terms. https://link.springer.com/content/pdf/bbm%3A978-1-349-10306-5%2F1.pdf . https://ghostarchive.org/archive/20221009/https://link.springer.com/content/pdf/bbm%3A978-1-349-10306-5%2F1.pdf . 2022-10-09 . live. Open Systems Interconnection. 1988. Macmillan Computer Science Series. Palgrave. London. 978-0-333-46803-6. 10.1007/978-1-349-10306-5.
3. Web site: ITU-T X.260 ISO/IEC 14765 – Information technology – Framework for protocol identification and encapsulation. 1996. International Telecommunication Union (ITU).
4. Web site: Federal Standard 1037C – Telecommunications: Glossary of Telecommunication Terms. General Services Administration – Information Technology Service. 1996.