TCP IP Illustrated

13 newer implementations are providing newer versions

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Unformatted text preview: /09/2001 14.47.56] Chapter 29. NFS: Network File System that performs a single system call and remains inside the kernel as a kernel process. Most Unix hosts can operate as either an NFS client, an NFS server, or both. Most PC implementations (MS-DOS) only provide NFS client implementations. Most IBM mainframe implementations only provide NFS server functions. NFS really consists of more than just the NFS protocol. Figure 29.4 shows the various RPC programs normally used with NFS. Application port mapper NFS mount lock manager status monitor Program number 100000 100003 100005 100021 100024 Version numbers 2 2 1 1,2,3 1 Number of procedures 4 15 5 19 6 Figure 29.4 Various RPC programs used with NFS. The versions we show in this figure are the ones found on systems such as SunOS 4.1.3. Newer implementations are providing newer versions of some of the programs. Solaris 2.2, for example, also supports versions 3 and 4 of the port mapper, and version 2 of the mount daemon. SVR4 also supports version 3 of the port mapper. The mount daemon is called by the NFS client host before the client can access a filesystem on the server. We discuss this below. The lock manager and status monitor allow clients to lock portions of files that reside on an NFS server. These two programs are independent of the NFS protocol because locking requires state on both the client and server, and NFS itself is stateless on the server. (We say more about NFS's statelessness later.) Chapters 9, 10, and 11 of [X/Open 1991] document the procedures used by the lock manager and status monitor for file locking with NFS. File Handles A fundamental concept in NFS is the file handle. It is an opaque object used to reference a file or directory on the server. The term opaque denotes that the server creates the file handle, passes it back to the client, and then the client uses the file handle when accessing the file. The client never looks at the contents of the file handle-its contents only make sense to the server. Each time a client process opens a file that is really a file on an NFS server, the NFS client file:///D|/Documents%20and%20Settings/bigini/Docu...homenet2run/tcpip/tcp-ip-illustrated/nfs_netw.htm (9 of 23) [12/09/2001 14.47.56] Chapter 29. NFS: Ne...
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This test prep was uploaded on 04/04/2014 for the course ECE EL5373 taught by Professor Guoyang during the Spring '12 term at NYU Poly.

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