Basic Switch Configuration
53
boot.conf 256 1980-01-01 00:00:00 ----
nos.img 8,071,910 1980-01-01 00:00:00 ----
startup.cfg 1,590 1980-01-01 00:00:00 ----
2.5.3
FTP/TFTP Upgrade
2.5.3.1
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