You can find some clues in the published service catalog of the NATO Communications and Information Agency (NCIA) here: https://www.ncia.nato.int/about-us/servi

You can find some clues in the published service catalog of the NATO Communications and Information Agency (NCIA) here: https://www.ncia.nato.int/about-us/service-portfolio/customer-area https://www.ncia.nato.int/about-us/service-portfolio/custome... It seems their "JChat" application is based on XMPP.