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Network File System Protocol. By Authentication Experts. Introduction. Provides transparent remote access to shared file across the network Portable across different architecture and operating system. Introduction. Aim: to provide the following logical view. Introduction.

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network file system protocol
Network File System Protocol

By Authentication Experts

  • Provides transparent remote access to shared file across the network
  • Portable across different architecture and operating system
  • Aim: to provide the following logical view
  • First version developed by Sun Microsystems for internal research
  • Version 2 introduced in March, 1989 defined in RFC 1094
  • Version 3 introduced in June, 1995 defined in RFC 1813
  • Version 4 introduced in December, 2000 defined in RFC 3031; revised in RFC 3530, April 2003
introduction to file system
Introduction to File System
  • A file system is a way of storing data on a medium: the way it is organized and managed
  • Every file is represented by an “inode”

A file descriptor holding, among other things, file access permissions, physical block addresses holding data, etc.

  • The NFS server’s task is to give clients the inodes they want to access
  • An NFS server gives an additional net layer allowing remote machines to handle the inodes
the nfs protocol
The NFS Protocol

NFS is built from 4 distinct protocols:

  • nfs

- File creation, searching, reading, writing

Authentication and statistics

  • mountd

- Mounting of “exported” systems for access via nfs

  • nsm

- Network Status Monitor

- Monitors a client or server machine’s status

  • nlm

- Network Lock Manager

- Avoid simultaneous data modification by multiple clients

file handling in nfs
File Handling in NFS
  • The protocol revolves around the filehandle

-A data structure allow unique identification of a file system object

-Contains the file inode and an entry representing the device where the file resides

  • How does a server know which file/directory the client needs to access?

- At first, client obtains a file handle for root of the file system

- File handle is opaque to the client

- Client sends file handle to server when referencing a file/directory

- No need to use the full path names

  • The file handle contains whatever information the server needs to distinguish an individual file
the nfs protocol3
The NFS Protocol
  • Each relies on Remote Procedure Calls(RPC) andPortmap(also calledrpc.portmap).
  • An RPC server tells portmap which port will be used and the managed RPC number
  • A client contacts portmap to get port number of desired server program
  • RPC packets are addressed to the corresponding port
  • What is statelessness ?

- Server does not need to maintain protocol state about it’s client

- Server does not keep previous request information

- Client keeps track of all information required to send requests to the server

  • Advantage :

- If server crashes, no state information lost

- Client needs only retransmit a request until the server responds

nfs version 3
NFS Version 3
  • Introduced in June,1995, described in RFC 1813
  • Support for 64-bit file sizes and offsets, to handle files larger than 4 GB
  • Support for asynchronous writes on the server, to improve write performance
  • Using TCP as a transport made using NFS over a WAN more feasible
nfs version 4
NFS Version 4
  • Introduced in December,2000(RFC 3010) and revised in April,2003, described in RFC 3530
  • Introduces a stateful protocol
  • Mandates strong security
  • Performance improvements