Variable Message Formats

The Variable Message Format (VMF) Tactical Data Link (TDL) providing exchange of tactical data in the ground and air environment.  It is one of the J-Series family of Tactical Data Links (TDLs) whose major roles include Fire Support, Close Air Support (CAS) and Situational Awareness (SA).

JCSys are highly experienced in VMF having supported the UK MoD for the majority of the last decade.  We provide technical expertise to the UK MoD in their support to platforms including provision of standards and assistance with User Requirements Documents (URDs) and Systems Requirements Documents (SRDs).  We also maintain the UK VMF Documentation Set and assist the US in the development of their VMF MIL STDs.  JCSys regularly attends the Bold Quest test events assisting UK JALO, JDLMO and Engineering support organisations.  Advising on VMF implementation issues and VDS interpretations.


VMF use is controlled by 3 documents:

  • MIL-STD-6017 (VMF) - General rules and K Series message list.
  • MIL-STD-2045-47001 - Message Header (mandatory for use with VMF K Series messages)
  • MIL-STD-188-220 - Combat Net Radio (CNR) protocols. 

The VMF message standard (MIL-STD-6017) is fully maintained by the USA.  However, JCSys has supported the UK MoD with questions, discussions, implementation, reviews, change proposals and impact reporting through UK/US TDL Bilateral meetings and the ABCANZ Armies VMF Subgroup.  JCSys supports the UK MoD at the Combat Net Radio (CNR) Working Group (CNRWG) that is responsible for the Header and Bearer Standards.  For MIL-STD-2045-47001 that describes the header, JCSys were heavily involved in the creation of version E (released 2021) and are currently assisting with modifications that will form version F.  For MIL-STD-188-220 that describes the CNR protocols, JCSys are currently assisting with the rewrite to version E.

UK VMF Standards (VMF Documentation Set)

  • VMF SLIRS - Message implementation requirements specifications for DaCAS and SA.
  • HIRS - Header Implementation Requirements Specifications.
  • BDD - Bearer Definition Documents.
  • SMOPS - UK VMF System Management and Operating Procedures.
  • VUG – VMF User Guide.

VMF Single Link IRS (SLIRS)) provides the VMF message processing requirements for UK platforms. The Header IRS (HIRS)) provides the header processing requirements for UK platforms intending to implement VMF. The CNR Bearer Definition Document (BDD)) provides the bearer processing requirements for UK platforms intending to implement VMF on a CNR bearer. The VMF SLIRS, HIRS and BDD improves IO by reducing the potential for misunderstanding in the MIL-STDs.  JCSys is responsible for the maintenance and configuration management of these documents and recently undertook a major rewrite.

Standards Management