The LDM-6 system is backward-compatible with LDM-5. LDM-6 supports the full complement of LDM-5 protocol messages:
Therefore, an LDM-6 system can both send and receive data products from an LDM-5 system.
LDM-6 is not backward-compatible with LDM-4. The only LDM-4 message supported by LDM-6 is NULLPROC, which is used by the ldmping(1) utility of LDM-5.