PLANET XGS3-24040 - Manual (Page 66)

Chapter 4 Basic Switch Configuration
4-17
2. CONFIG RUN command
Used to set the IMAGE file to run upon system start-up, and the configuration file to run upon configuration
recovery.
[Boot]: config run
Boot File: [nos.img] nos.img
Config File: [boot.conf]
4.5.3 FTP/TFTP Upgrade
4.5.3.1 Introduction to FTP/TFTP
FTP(File Transfer Protocol)/TFTP(Trivial File Transfer Protocol) are both file transfer protocols that belonging
to fourth layer(application layer) of the TCP/IP protocol stack, used for transferring files between hosts, hosts
and switches. Both of them transfer files in a client-server model. Their differences are listed below.
FTP builds upon TCP to provide reliable connection-oriented data stream transfer service. However, it does
not provide file access authorization and uses simple authentication mechanism (transfers username and
password in plain text for authentication). When using FTP to transfer files, two connections need to be
established between the client and the server: a management connection and a data connection. A transfer
request should be sent by the FTP client to establish management connection on port 21 in the server, and
negotiate a data connection through the management connection.
There are two types of data connections: active connection and passive connection.
In active connection, the client transmits its address and port number for data transmission to the server, the
management connection maintains until data transfer is complete. Then, using the address and port number
provided by the client, the server establishes data connection on port 20 (if not engaged) to transfer data; if
port 20 is engaged, the server automatically generates some other port number to establish data connection.
In passive connection, the client, through management connection, notify the server to establish a passive
connection. The server then creates its own data listening port and informs the client about the port, and the
client establishes data connection to the specified port.
As data connection is established through the specified address and port, there is a third party to provide data
connection service.
TFTP builds upon UDP, providing unreliable data stream transfer service with no user authentication or
permission-based file access authorization. It ensures correct data transmission by sending and
acknowledging mechanism and retransmission of time-out packets. The advantage of TFTP over FTP is that
it is a simple and low overhead file transfer service.
Switch can operate as either FTP/TFTP client or server. When switch operates as a FTP/TFTP client,
configuration files or system files can be downloaded from the remote FTP/TFTP servers (can be hosts or
other switches) without affecting its normal operation. And file list can also be retrieved from the server in ftp
client mode. Of course, switch can also upload current configuration files or system files to the remote
FTP/TFTP servers (can be hosts or other switches). When switch operates as a FTP/TFTP server, it can
provide file upload and download service for authorized FTP/TFTP clients, as file list service as FTP server.