Network file system protocol
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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


Introduction
Introduction

  • Provides transparent remote access to shared file across the network

  • Portable across different architecture and operating system


Introduction1
Introduction

  • Aim: to provide the following logical view


Introduction2
Introduction

  • 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



Statelessness
Statelessness

  • 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



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