No description about networking has been found in [1] , [2], and [3]. Taking the social and technology backgrounds into consideration, it seems to be natural to think that no networking facility was supported in the original Unix. Over the fifteen years, Unix has gained a lot of networking capabilities. We can login to other machines ( rlogin, telnet), transfer files ( ftp, rcp), execute commands on other machines ( rsh), opening windows ( X-Windows) over the network. Socket mentioned in the section 1.2 is network transparent, that is, it can also communicate over the network.
As an extension of the mounted file system (in the section 1.5), Solaris 2 (and earlier versions of SunOS) supports Network Files System (NFS). It is an implemented in the client-server model. A system can mount a disk which is on another computer on its directory hierarchy over the network. A processes (client) sends file access requests to the machine having the file (file server) over the network. From user's view point, there is no distinction between the local disk and the remote disk, that is, NFS is transparent to the users. On NFS, information of open file (such as read/write point) is maintained at the client, and each request from the client contains such informations. A server that does not maintain such information is called to be stateless. The advantage of the stateless system is that the server need not keep the informations of the open files. Hence if the server crashes and then re-booted, the informations will not be lost. In Unix System V, the Remote File System. RFS, the server keeps track of open files. In NFS, locking files is not possible, because the server does not know which files are opened and locked. RFS has an advantage over NFS on this point. Since Solaris 2 is a version of SunOS, and has acquired the features of SVR4, it provides both NFS and RFS.