Changes

<td>'''21'''</td><td>'''FTP'''<td> '''File Transfer (Control)''' - Traditionally FTP has two ports assigned (port 20 and port 21). Port 20 was originally conisidered considered the data transfer port, while port 21 was assigned to communicate control information. In modern implementations port 20 is now rarely used, with all communication taking place on port 21.</td>

<td>'''22'''</td><td>'''SSH'''<td>'''Secure Shell''' - The Secure Shell is used to provide a secure, encyptedencrypted, remote logon session to a remote host over a TCP/IP network. The original mechanism for remote access was the Telnet protocol. Because Telnet transmits data in plain text its use is now strongly discouraged in favor of the secure shell, which encrypts all communications, including log-in and password credentials. SSH also provides the mechanism by which files can be securely trandferred transferred using the Secure Copy Protocol (''SCP''), and is also the basis for the Secure File Transfer Protocol (''SFTP''). SSH also replaces both the ''rsh'' and ''rlogin'' clients.</td>

<td>'''23'''</td><td>'''Telnet'''<td>'''Telnet''' - Telnet is a terminal emulation protocol that provides the ability to log into a remote system over a TCP/IP connection. The access is text based allowing the user to type into a command prompt on the remote host and text displayed by the remote host is displayed on the local Telnet client. Telnet encrypts neither the password nor the text communicated between the client and server. As such, the use of telnet is strongly discouragaeddiscouraged. Most modern systems will have port 23 closed and the telnet service disabled to prevent its use. SSH should be used in place of Telnet.

<td>'''69'''<td>'''TFTP'''<td>'''Trivial File Transfer Protocol''' - TFTP is a strpped stripped down version of the File Transfer Protocol (FTP). It has a reduced command-set and lacks authentication. The most significant feature of TFTP is that it uses UDP to transfer data. This results in extremely fast transfer speeds but, consequently, lacks data reliability. TFTP is typically used in network based booting for diskless workstations.</td>

<td>'''119'''<td>'''NNTP'''<td>'''Network News Transfer Protocol''' - The protocol responsible for posting and retrieving messages to and from Usenet News Servers (i.e . newsgroups and discussion forums hosted on remote servers). NNTP operates at the Application layer of the OSI stack and uses TCP to ensure error free message retrieval and transmission.</td>

<td>'''161'''<td>'''SNMP'''<td>'''Simple Network Management Protocol''' - Provides a mechanism whereby network administrators are able to collect information about the devices (such as hubs, bridges, routers and switches) on a network. The SNMP protocol enables ''agents'' running on network devices to communicate their status to a central ''manager'' and, in turn, enables the ''manager'' to send new configuration parameters to the device ''agent''. The ''agents'' can further be configured to notify the ''manager'' when certains certain events, known as ''traps'', occur. SNMP uses UDP to send and receive data.</td>

<td>'''443'''<td>'''HTTPS'''<td>'''Hypertext Transfer Protocol Secure''' - The standard HTTP (non-secure) protocol transfers data in clear text (i.e . with no encryption and visible to anyone who might intercept the traffic). Whilst this is acceptable for most web browsing purposes it poses a serious security risk when confidential information such as credit card details need to be transmitted from the browser to the web server. HTTPS addresses this by using the Secure Sockets Layer (SSL) to send encypted data between the client and server.</td>