Telnet and FTP (File Transfer Protocol) are two protocols that use TCP as a transport to initiate sessions on remote computers and both programs fall into the server-client model. Both protocols lack encryption, and process passwords and logins over the internet in the form of plain text. (Farrell) The principles of works of the protocols are similar, where the client machine sends the orders while the server receives them. The main difference is the usage of protocols, where FTP as its abbreviation implies establishes the connection to send files over then networks, while Telnet is used to work on remote terminals configured as servers by running commands from remote machines configured as clients. Ethereal Ethereal, the current name is Wireshark, is a program that analyzes packets and network traffic. The program allows looking through all the transient traffic that goes the network adapter in real time, capturing, decoding, and analyzing each packet. Although the program might have gained a popularity trough illegally intercepting valuable information, the program can be used as a diagnostic tool and also in education purposes. For example, Ethereal can be used when analyzing network clients and their behavior with different applications and drivers. Other examples include allocating problems of connectivity loss, graphing traffic patterns, and building statistics. (Combs) Network Sniffer Sniffers are programs that analyze traffic. In order to demonstrate the work of a sniffer to identify streams, the example of the program Ethereal will be used. Ethereal recognizes the structure of each protocol, and thus allows disassembling the network packet, showing every protocol field at any level, e.g. in Ethereal, there were currently 759 protocols that could be dissected. (“Ethereal: Features”) Thus, during browsing or any other internet activity, during which a login and a password were entered, the sniffer will capture all the packets that were sent and received during that session. The sniffer can translate each package according to the protocol used, e.g. HTTP and the stream that carried the login and the password can be revealed. PBX The simulation of PBX can be implemented through specific emulating software which emulates the hardware parts of the telephone exchange with software analogues. In this case the work of the PBX will be completely emulated on the computer, with no physical connections present. Additionally, other equipment, such as routers, can be configured to simulate the work of PBX and PSTN. In that regard, the simulation will involve physical connection with only the router simulating a PBX. VOIP There are many protocols available for Voice over Internet Protocol (VoIP), the most common of which are the following (Packetizer; Ixia): The Protocol  Advantage                                                                              Disadvantage                                                        * better interoperability with the PSTN                                                * no built-in methods for reporting user location H.323           * better support for video                                                             * far more complex                                                * excellent interop