# Link 1 > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Link_1 > Markdown URL: https://mediated.wiki/source/Link_1.md > Source: https://en.wikipedia.org/wiki/Link_1 > Source revision: 1355732302 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) **Link 1** is a [computer network](/source/Computer_network) standard developed by [NATO](/source/NATO) to provide information exchange for [air defence](/source/Air_defence). ## General description Link 1 is a [point-to-point](/source/Point-to-point_(telecommunications)), [duplex](/source/Duplex_(telecommunications)), [non-encrypted](/source/Encryption), [digital](/source/Digital_data) [NATO](/source/NATO) [Tactical Data Link](/source/Tactical_Data_Link) (TDL) Standard for the automatic exchange of Track and Strobe data, combined with link and data management messages between ground based ASACS-elements / e.g. [CRC](https://de.wikipedia.org/wiki/Control_and_Reporting_Centre) and [CAOC](/source/CAOC), specific units (TACCS / MC) and data link [buffers](/source/Data_buffer) (SSSB, CSI). In everyday language, the different meaning of the wording *Link 1 TDL Standard (format)* and *Link 1 information content (subject matter)* to be transmitted on this particular TDL Standard is mixed up in many cases. Remark: - TACCS / MC = [Tactical Air Command and Control Service](https://de.wikipedia.org/wiki/EinsF%C3%BCDstLw) / [(NATO) Major Command)](/source/Major_Command) - SSSB = Ship Shore Ship [Buffer](/source/Data_buffer) - CSI = CRC/SAM Interface - SAM = [Surface-to-air missile](/source/Surface-to-air_missile) ## History Link 1 is a NATO *first Generation's* TDL Standard. It was developed in the 1950s as pure *Air Surveillance* data link format in order to exchange radar track data between defined *Areas of Responsibility – AOR* (geographical areas) or *Track Continuity Areas (TCA)*. ### Data links first generation NATO first generation's TDL Standards were developed in line with the appropriate Standardization Agreement ([STANAG](/source/STANAG)) in the mid 1960s. These proprietary types of data formats do not support direct data and information exchange between different military [IT architectures](/source/IT_architecture) without specific conversion of data. NATO TDL Standards are being developed by the *Data Link Working Group (DLWG)* of the *Information Systems Sub-Committee (ISSC).* See also [TDL Synopsis)](/source/Tactical_Digital_Information_Link). ## Utilisation Today the Link 1 TDL Standard is not only used by NATO nations but also in [Partnership for Peace](/source/Partnership_for_Peace) (PfP) countries. Air Force internal it supports [NATO Air Defence Ground Environment (NADGE)](/source/Integrated_NATO_Air_Defense_System) and is used by the TACC Service, in CRC, CAOC and Air Defence. ## Types of tracks The following tracks are exchanged by Link 1 between different users of the [Recognized Air Picture](/source/Recognized_Air_Picture) (RAP). - Ground Environment Tracks (GE Tracks): tracks, which have received their last position-update by a ground site. These are either local or remote. - [Airborne Early Warning](/source/Airborne_Early_Warning) Tracks (AEW Tracks): Tracks, which have received their last position-update by an AEW-platforms. These are always remote. - GE / AEW Tracks: These Tracks are used as "Track Pairs" for registration purposes and are update by both the ground site and AEW. - [E-3A](/source/E-3A) Tracks: The Tracks of an active E-3A, usually correlated with the received P-1 Message on [IJMS](/source/JTIDS). ## Messages The following link messages are supported by Link 1 in the [NATO Air Defense Ground Environment](/source/Integrated_NATO_Air_Defense_System) (NADGE): - S0 – Test Message: Used to test the channel in order to exchange Link 1 data. The S0 is, on average, transmitted every 10 seconds. - S3 – [IFF](/source/Identification_friend_or_foe)/SIF Message: Use to transmit the IFF/SIF [Mode 1](/source/Aviation_transponder_interrogation_modes), 2 and 3 on a specific Track. This Message is always associated with a S4 Basic Track Data Messages. - S4 – Basic Track Data Message: Used to report the basic positional data of a track. The S4 is either associated with S3 or an S5 message. - S5 – Expanded Track Data Message: Used in conjunction with S4 (or S8) to report the additional data of a track. The initial transmission of an S4 / S5 message combination initiates a new Track at the receiving Link 1 site. - S6 – Weapon Assignment Message: Used to transmit weapon assignment S6 Messages. ## Specification The NATO Link 1 TDL Standard is characterised by the specification as: Link 1 Specification Term Reference STANAG 5501 (Ed. 4) Jan 2007 NCGX-101-IS Standardization level NATO Data Link Standard S-series-messages Configuration's controlling - ADSC (Implementation) - ADSIA (Standards) Services concerned and TACC Systems Air Force, Army NADGE, national weapon management systems Messages transmitted 1. surveillance (only air) 2. ECM-strobe-tell 3. Info-management Message- format 2 messages/frame - 128 bits/frame - 49 infobits/message fixed message format Message Series S-series Number of Messages 6 Speed of transmission 1200 bit/sec (basic speed) 600 or 2400 bit/sec (alternate speed) Communication FSK, point-to-point FOC, Wire, Radio relay IT-Security ECM Encryption NO NO Releasable to: - NATO - PfP nations - Internet Yes Yes Yes ## Conclusion Link 1, as a NATO 1st generation TDL Standard, is out of date and no longer meets operational requirements.[citation needed] Moreover, there is no [IT security](/source/IT_security) of information transmitted, as the result of no [Electronic countermeasure](/source/Electronic_countermeasure) (ECM) resistance and insufficient encryption. Although Link 1 became obsolete, it is still in operation.[when?] ## References - Allied Data Processing Publication 33 (ADatP-33) NHQC3S/ISEB (DLSS) ## External links - [US Department of Defense quick search for military standards](https://web.archive.org/web/20071006205659/http://assist.daps.dla.mil/quicksearch/) - [NATO STANAG Library (in English)](http://www.nato.int/docu/standard.htm) - [NATO STANAG search engine (in French)](https://web.archive.org/web/20060306082444/http://otan.w3sites.net/Serveur2.html) - [NATO Link 1 STANAG 5501](http://aero-defense.ihs.com/document/abstract/OWPYIBAAAAAAAAAA) --- Adapted from the Wikipedia article [Link 1](https://en.wikipedia.org/wiki/Link_1) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Link_1?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.