after version 2.1 was established, specified that an SSH server supporting 2.0 as well as prior versions should identify its protocol version as 1.99. This version number does not reflect a historical software revision, but a method to identify backward compatibility. OpenSSH and OSSH In 1999, developers, desiring availability of a free software version, restarted software development from the 1.2.12 release of the original SSH program, which was the last released under an open source license. This served as a code base for Björn Grönvall's OSSH software. Shortly thereafter, OpenBSD developers forked Grönvall's code and created OpenSSH, which shipped with Release 2.6 of OpenBSD. From this version, a "portability" branch was formed to port OpenSSH to other operating systems. , OpenSSH was the single most popular SSH implementation, being the default version in a large number of operating system distributions. OSSH meanwhile has become obsolete. OpenSSH continues to be maintained and supports the SSH-2 protocol, having expunged SSH-1 support from the codebase in the OpenSSH 7.6 release. Uses SSH is a protocol that can be used for many applications across many platforms including most Unix variants (Linux, the BSDs including Apple's macOS, and Solaris), as well as Microsoft Windows. Some of the applications below may require features that are only available or compatible with specific SSH clients or servers. For example, using the SSH protocol to implement a VPN is possible, but presently only with the OpenSSH server and client implementation. For login to a shell on a remote host (replacing Telnet and rlogin) For executing a single command on a remote host (replacing rsh) For setting up automatic (passwordless) login to a remote server (for example, using OpenSSH) In combination with rsync to back up, copy and mirror files efficiently and securely For forwarding a port For tunneling (not to be confused with a VPN, which routes packets between different networks, or bridges two broadcast domains into one). For using as a full-fledged encrypted VPN. Note that only OpenSSH server and client supports this feature. For forwarding X from a remote host (possible through multiple intermediate hosts) For browsing the web through an encrypted proxy connection with SSH clients that support the SOCKS protocol. For securely mounting a directory on a remote server as a filesystem on a local computer using SSHFS. For automated remote monitoring and management of servers through one or more of the mechanisms discussed above.