View source for Link 1

'''Link 1''' is  a [[computer network]] standard developed by [[NATO]] to provide information exchange for [[air defence]].
== General description ==
Link 1 is a [[point-to-point (telecommunications)|point-to-point]], [[duplex (telecommunications)|duplex]], [[Encryption|non-encrypted]], [[Digital data|digital]] [[NATO]] [[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. [[:de:Control and Reporting Centre|CRC]] and [[CAOC]], specific units (TACCS / MC) and data link [[Data buffer|buffer]]s (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 = [[:de: EinsFüDstLw|Tactical Air Command and Control Service]] / [[Major Command|(NATO) Major Command)]]
* SSSB = Ship Shore Ship [[Data buffer|Buffer]]
* CSI = CRC/SAM Interface
: SAM = [[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]]) in the mid 1960s. These proprietary types of data formats do not support direct data and information exchange between different military [[IT architecture]]s 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 [[Tactical Digital Information Link|TDL Synopsis)]].
==Utilisation==
Today the Link 1 TDL Standard is not only used by NATO nations but also in [[Partnership for Peace]] (PfP) countries. Air Force internal it supports [[Integrated NATO Air Defense System|NATO Air Defence Ground Environment (NADGE)]] 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]] (RAP).
* <u>  Ground Environment Tracks (GE Tracks): </u> <br /> tracks, which have received their last position-update by a ground site. These are either local or remote.
* <u>  [[Airborne Early Warning]] Tracks (AEW Tracks): </u> <br /> Tracks, which have received their last position-update by an AEW-platforms. These are always remote.
* <u>  GE / AEW Tracks: </u> <br /> These Tracks are used as "Track Pairs" for registration purposes and are update by both the ground site and AEW.
* <u>  [[E-3A]] Tracks: </u> <br /> The Tracks of an active E-3A, usually correlated with the received P-1 Message on [[JTIDS|IJMS]].
== Messages ==
The following link messages are supported by Link 1 in the [[Integrated NATO Air Defense System|NATO Air Defense Ground Environment]]  (NADGE):
* <u>  S0 – Test Message: </u> Used to test the channel in order to exchange Link 1 data. The S0 is, on average, transmitted every 10 seconds.
* <u>  S3 – [[Identification friend or foe|IFF]]/SIF Message:</u> Use to transmit the IFF/SIF [[Aviation transponder interrogation modes|Mode 1]], 2 and 3 on a specific Track. This Message is always associated with a S4 Basic Track Data Messages.
* <u>  S4 – Basic Track Data Message: </u> Used to report the basic positional data of a track. The S4 is either associated with S3 or an S5 message.
* <u>  S5 – Expanded Track Data Message: </u> 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.
* <u>  S6 – Weapon Assignment Message: </u> Used to transmit weapon assignment S6 Messages.
== Specification ==
The NATO Link 1 TDL Standard is characterised by the specification as:
{| class="wikitable"
|-
! Link 1 !! Specification !! Term
|-
|| '''Reference'''
||
|| STANAG 5501 (Ed. 4) Jan 2007<br /> NCGX-101-IS
|-
|| '''Standardization level'''
|| NATO Data Link Standard
|| S-series-messages
|-
|| ''' Configuration's <br />controlling '''
||
|| - ADSC (Implementation) <br /> - ADSIA (Standards)
|-
|| ''' Services concerned <br /> and TACC Systems '''
||
|| Air Force, Army <br /> NADGE, national weapon management systems
|-
|| ''' Messages <br />transmitted '''
|| 1. surveillance (only air) <br /> 2. ECM-strobe-tell <br /> 3. Info-management
||
|-
|| ''' Message- <br />format '''
||  2 messages/frame <br />- 128 bits/frame <br /> - 49 infobits/message
|| fixed message format
|-
|| ''' Message Series '''
||
|| S-series
|-
|| ''' Number of Messages '''
|| 6
||
|-
|| ''' Speed <br />of transmission '''
|| 1200 bit/sec (basic speed) <br /> 600 or 2400 bit/sec (alternate speed)
||
|-
|| ''' Communication '''
|| FSK, point-to-point
|| FOC, Wire, Radio relay
|-
|| ''' IT-Security '''
|| ECM <br /> Encryption
|| NO <br /> NO
|-
|| ''' Releasable to: '''
|| - NATO <br /> - PfP nations <br /> - Internet
|| Yes <br /> Yes <br /> Yes
|-
|}
== Conclusion ==
Link 1, as a NATO 1st generation TDL Standard, is out of date and no longer  meets operational requirements.{{citation needed|date=November 2011}} Moreover, there is no [[IT security]] of information transmitted, as the result of no [[Electronic countermeasure]] (ECM) resistance and insufficient encryption. Although Link 1 became obsolete, it is still in operation.{{when |date=November 2018}}
==References==
* Allied Data Processing Publication 33 (ADatP-33) NHQC3S/ISEB (DLSS)
==External links==
* [https://web.archive.org/web/20071006205659/http://assist.daps.dla.mil/quicksearch/ US Department of Defense quick search for military standards]
* [http://www.nato.int/docu/standard.htm NATO STANAG Library (in English)]
* [https://web.archive.org/web/20060306082444/http://otan.w3sites.net/Serveur2.html NATO STANAG search engine (in French)]
* [http://aero-defense.ihs.com/document/abstract/OWPYIBAAAAAAAAAA NATO Link 1 STANAG 5501]
[[Category:Military communications of the United States]]
[[Category:NATO standardisation]]