• NAS devices support multiple file service protocol to handle file I/O requests to a remote file system.

  • Following are common protocol for file sharing: 1.NFS 2.CIFS

  • NFS is predominantly used in UNIX based operating environments;

  • CIFS is used in window-based operating environments.These file sharing protocols enable users to share file data across different operating environments & provide a means for users to migrate transparently from one operation system to another.

NFS: (Network file system)

• NFS is a client/server protocol for file sharing that is most commonly used on UNIX system.

• NFS was orignally based on the connectionless user datagram protocol (UDP).

• It uses a machine independent model to represent user data.

• It also uses RPC (Remote procedure call) as a method of interprocess communication between two computers.

• The NFS protocols provide a set of RPCs to access a remote file system for the following operations: 1.Searching files & directories 2.Opening, reading, writing to, & closing after. 3.Changing file attributes. 4. Modifying file links & directories.

• NFS uses the 'mount' protocol to create a connection between client & the remote system to transfer data.

• NFS (NFSV3) is a stateless protocol, which means that it does not maintain any kind of table to store information about open files & associated pointers.

• Currently three versions of NFS are in use: 1.NFS version 2 (NFSV2) 2.NFS version 3 (NFSV3) 3.NFS Version 4 (NFSV4)

NFSV2:

• Uses to provide a stateless network connection between a client & a server.

• Features such as loching are handled outside the protocol.

NFSV3:

• The most commonly used version, it uses UDP or ICP & is based on the stateless protocol design.

• It includes some new features, such as 64-bit file size, asynchronous writes & additional file attributes to reduce re-fetching.

NFSV4:

• This version uses TCP & is based on a stateful protocol design.

• It offers enhanced security.

CIFS: (Common Interface file System).

• CIFS is a client/server application protocol that enables client programs to make requests for file & services on remote computers over TCP/IP.

• It is a public or open variation of Server Message Block (SMB) protocol.

• CIFS protocol enables remote clients to gain access to files that are on a server.

• CIFS enables file sharing with other clients by using special locks.

• File names in CIFS are encoded using unicode characters.

• CIFS provides following features to ensure data integrity.

• It uses file & record loching to prevent users from overwriting the worth of another user on a file or a record.

• It runs over TCP.

• It supports fault tolerance & can automatically restore connections & reopen files that were open prior to interruption.

• The fault tolerance features of CIFS depend on whether an application is written to take advantage of these features.