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documentation:setup_and_user_guide:services_tftp

6.3-Services TFTP

Using the Drop Down Navigation Menu on the top of the page, below the NAS4Free logo, click on “SERVICES”, then select “TFTP”. On this page you can enable or disable the TFTP service and create, delete and manage the TFTP server.

Trivial File Transfer Protocol

Trivial File Transfer Protocol (TFTP) is a simple protocol to transfer files. It has been implemented on top of the User Datagram Protocol (UDP) using port number 69. TFTP is designed to be small and easy to implement, therefore, lacks most of the features of a regular FTP. TFTP only reads and writes files (or mail) from/to a remote server. It cannot list directories, and currently has no provisions for user authentication.

In TFTP, any transfer begins with a request to read or write a file, which also serves to request a connection. If the server grants the request, the connection is opened and the file is sent in fixed length blocks of 512 bytes. Each data packet contains one block of data, and must be acknowledged by an acknowledgment packet before the next packet can be sent.

A data packet of less than 512 bytes signals termination of a transfer. If a packet gets lost in the network, the intended recipient will timeout and may retransmit his last packet (which may be data or an acknowledgment), thus causing the sender of the lost packet to retransmit that lost packet.

The sender has to keep just one packet on hand for retransmission, since the lock step acknowledgment guarantees that all older packets have been received. Notice that both machines involved in a transfer are considered senders and receivers. One sends data and receives acknowledgments, the other sends acknowledgments and receives data. Three modes of transfer are currently supported by TFTP: netascii, that it is 8 bit ascii; octet (This replaces the “binary” mode of previous versions of this document.) raw 8 bit bytes; mail, netascii characters sent to a user rather than a file. Additional modes can be defined by pairs of cooperating hosts.

Uses

  • TFTP is used by technicians to read files from, or write files to, a remote server, it is not used for file sharing or multi-user access to large libraries.
  • Due to the lack of security, it is dangerous over the open Internet. Thus, TFTP is generally only used on private, local networks, usually for maintenance purposes such as backing up configuration files, storing & distributing patches and updates, etc..

Additional Details

  • The original versions of TFTP, prior to RFC 1350, displayed a particularly bad protocol flaw, which was named Sorcerer's Apprentice Syndrome (after the “Sorcerer's Apprentice” segment of Fantasia) when it was discovered.
  • In the early days of work on the TCP/IP protocol suite, TFTP was often the first protocol implemented on a new host type, because it was so simple.
  • TFTP support appeared first as part of 4.3 BSD.

Disadvantages of TFTP

  • TFTP cannot list directory contents.
  • TFTP has no authentication or encryption mechanisms.
  • TFTP allows big data packets which may burst and cause delay in transmission.
  • TFTP cannot download files larger than 1 Terabyte.

Ref: Trivial File Transfer Protocol

Services|TFTP

Directory: This is the path to the directory ( folder ) that is to be shared using TFTP. The format of this is /mnt/storagename/folder where storagename is the mount point name. Click on to the right of the text box. This will bring up a simple file system browser. Click the desired mount point and click “OK”. The mount point will be added to the Path.

Allow New Files: If enabled, New files are allowed to be created. (Default is only already existing files can be uploaded.)

Advanced settings

Port: The port to listen to. Default port is defined in /etc/services (Usually 69).

Username: From the pulldown menu you can specify the user or username which the service will run as.

Umask: Sets the umask for newly created files to the specified value. (Default = Zero)

Timeout: Default timeout setting. (Default is 1000000)

Max Block Size: Specifies the maximum block size. (From 512 to 65464)

Extra Options: Please consult the TFTPD Man page for switches that can optionally be used here.

Save the Configuration Settings

  1. Make sure there is a check mark in the “ENABLE” box at the top right of the page.
  2. Click the “SAVE & RESTART” Button.

The TFTP service should now be running, you should test to make sure that everything is working properly. Brief test procedures are in SUG Section 2.6.3-Testing & Connecting.

documentation/setup_and_user_guide/services_tftp.txt · Last modified: 2018/10/05 17:23 by zoon01