Because the NFS version 2 protocol as well as the NFS version 3 protocol is stateless, an additional Network Lock Manager (NLM) protocol is required to support locking of NFS-mounted files. The NLM version 3 protocol, which is used with the NFS version 2 protocol, is documented in [X/OpenNFS].
Some of the changes in the NFS version 3 protocol require a new version of the NLM protocol. This new protocol is the NLM version 4 protocol. The following table summarizes the correspondence between versions of the NFS protocol and NLM protocol.
NFS and NLM protocol compatibility +---------+---------+ | NFS | NLM | | Version | Version | +===================+ | 2 | 1,3 | +---------+---------+ | 3 | 4 | +---------+---------+
This appendix only discusses the differences between the NLM version 3 protocol and the NLM version 4 protocol. As in the NFS version 3 protocol, almost all the names in the NLM version 4 protocol have been changed to include a version number. This appendix does not discuss changes that consist solely of a name change.