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Network File System Protocol

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Network File System Protocol By Authentication Experts – PowerPoint PPT presentation

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Title: Network File System Protocol


1
Network File System Protocol
  • By Authentication Experts

2
Introduction
  • Provides transparent remote access to shared file
    across the network
  • Portable across different architecture and
    operating system

3
Introduction
  • Aim to provide the following logical view

4
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

5
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 servers 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

6
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 machines status
  • nlm
  • - Network Lock Manager
  • - Avoid simultaneous data modification by
    multiple clients

7
The NFS Protocol
8
How does RPC work?
9
Port Mapper Analogy
10
Port Mapper Analogy
11
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

12
The NFS Protocol
13
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

14
Sequence Diagram
15
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19
Statelessness
  • What is statelessness ?
  • - Server does not need to maintain protocol
    state about its 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

20
NFS Procedure
21
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

22
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

23
  • Thank
    you
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