NAS File Sharing Protocol

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

2.Following are common protocols for file sharing

a. NFS

b.CIFS

3.NFS is predominantly used in UNEX based operating environments; CIFS is used in window-based operating environments.

4.These file sharing protocols enable users to share file data across different operating environments & provide a means for users to migrate transparently from one operating system to another.

NFS:( Network File System)

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

2.NFS was originally based on the connection less User Datagram Protocol (UDP).

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

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

5.The NFS protocols provides a set of RPCs to access a remote file system for the following operations.

a.Searching files & directories

b.Opening, reading, writing to, & closing a file.

c.Changing file attributes.

d.Modifying file links & directories.

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

7.NFS (NFS v 3) is a stateless protocol, which means that it does not maintain any kind of table to store information about open files & associated pointless.

8.Currently three versions of NFS are in use:

a.NFS version 2 (NFS v 2)

b.NFS version 3 (NFS v 3)

c.NFS version 4 (NFS v 4)

NFSv2:-

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

Feature such as locking are handled outside the protocol.

NFSv3:-

The most commonly used version, it uses UPD ar ICP and 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)

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

2.It is a public or open, variation of server message block (SMB) protocol.

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

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

5.File names in CIFS are encoded using unicode characters.

6.CIFS provides following features to ensure data integrity.

7.It uses file & record locking to provide users from overwriting the work of another user on a file or a record.

8.It runs over TCP.

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

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