Telnet
Telnet, short for teletype network, is a computer networking protocol developed in the 1960s to enable communication between different computer systems. Before Telnet, computers required custom terminals for operation, making it costly and inefficient for organizations to share resources and data across machines. Telnet allows for the transmission of data between computers regardless of their manufacturer-specific coding, which was crucial in fostering interoperability at a time when computers were large and expensive. The protocol operates using concepts such as the Network Virtual Terminal (NVT), symmetric operation, and option negotiation, enabling different systems to communicate effectively.
Despite its historical significance, Telnet has largely been supplanted by Secure Shell (SSH), which offers encrypted connections, enhancing security against cyber threats. SSH is now recognized as the industry standard due to its ability to protect sensitive data, such as usernames and financial information. Although Telnet is still present in some devices today, its use is generally discouraged in favor of more secure alternatives like SSH. Understanding the evolution from Telnet to SSH provides insight into the ongoing development of network security practices.
Telnet
Telnet¸ short for teletype network, is a method for computer networking. It was designed in the 1960s as a means for early computer components to communicate with one another. Prior to the invention of Telnet, computers needed individually customized terminals to function properly. They were unable to share data easily between machines. This forced companies to purchase multiple, expensive computer systems. Telnet allowed computer engineers to open a connection between computers, allowing them to send data back and forth. It also allowed computer technicians to transmit data between computers and terminals from different manufacturers. It accomplished this by stripping manufacturer specific coding from data before sending it between computers. To compensate for the disadvantages of stripping complex coding, Telnet offered users the option to send unstripped data between machines. Telnet is used in some devices into the twenty-first century; however, Secure Shell (SSH) has mostly replaced Telnet. SSH allows for data encryption, which creates a more secure connection to protect against hackers and other malicious digital attacks.
Background
In the era before the advent of Telnet, most computers were extremely large and very expensive to build and maintain. They were difficult to move from place to place and required special training to use. Large corporations and governments primarily built them to use for complex calculations.
Many individuals within an organization had to share computers. To work on the machine, computer technicians and researchers were required to access the physical machine itself. In most cases, this included utilizing a single, customized terminal attached to the computer.
To most computer users, this was an inefficient situation. Because each terminal was customized to the machine or project, each computer user required his or her own terminal to work on a particular assignment. The terminals could not easily be switched to other machines. If a business or corporation wanted several individuals to work on a specific project or wanted multiple projects carried out at the same time, they had to purchase multiple computers. This was not an easy or inexpensive solution, as the computers and terminals were costly. Another problem associated with this system was the inability of computers to communicate with one another. Data could not be shared between computers.
Computer engineers began to theorize solutions. They determined that the first step would be developing a means for computers to communicate with one another. In the late 1960s, they experimented with early networking protocols, which are ways to allow computers to transfer information between one other.
The first version of Telnet premiered on the ARPANET, one of the earliest forms of the Internet, in 1969. Telnet continued to be developed in the years that followed, with the final version of the protocol released in 1983.
Overview
Because early computer manufacturers did not use uniform methods of data representation, Telnet had to allow computers using different languages, coding, and hardware to communicate with one another. This made the process of creating Telnet more difficult than designing a method for exchanging the same type of information between machines.
The Telnet protocol is built on three primary concepts: the Network Virtual Terminal (NVT), symmetric operation, and option negotiation. The NVT was a digital terminal standardized across any machine that utilized Telnet. Input devices, such as physical terminals, took information provided by computer users and turned it into digital information. That information was sent to a Telnet server, which was connected to multiple machines. The Telnet server found the destination machine, which also had to be connected to the Telnet network. It checked the language required by the recipient machine, then it translated the information into that language. Finally, the translated information was sent to the destination. When the recipient machine wanted to send data back to the sender, the process was reversed.
To avoid incompatibilities between systems, most system-specific or brand-specific language was stripped. This helped to remove most of the difficulties that could be encountered by trading information directly between computers of differing manufacturers. However, certain specialized machines had the ability to send more complex information. To accommodate for these circumstances, computers using Telnet were given the ability to negotiate various options for their connection.
Telnet utilized symmetric operation when a connection was established. This means that all computers on a Telnet network are equal. All are granted the ability to negotiate options with other computers on the network, and all can send and receive information.
Some modern computers and devices utilize Telnet into the twenty-first century. It allows for a simple means of transferring information between two devices. Many other information transfer services utilize variations of the NVT pioneered by Telnet. However, computer engineers recommend that Telnet connections be replaced with SSH. SSH is considered the industry standard replacement for Telnet. Unlike Telnet, SSH connections utilize encryption. Encryption is a method of modifying data to make it readable only by its intended recipient. Without encryption, hackers can intercept valuable information such as usernames, passwords, and credit card numbers. They can then sell this information, use it for identity theft, or use it to steal money and other valuable commodities.
SSH is more secure than the traditional Telnet connection, allowing for security certificates, encryption, and digital signature algorithms (DSA), which are used for digital signatures. These features help protect information from malware, spoofing, and other forms of digital attack. SSH was eventually upgraded to SSH2. SSH2 utilizes different forms of digital encryption. These include the Data Encryption Standard (DES), Blowfish, and Triple DES (3DES).
Bibliography
"Linux Telnet Command." Computer Hope, 29 Dec. 2017, www.computerhope.com/unix/utelnet.htm. Accessed 27 Feb. 2018.
Mullins, Michael. "Replace Telnet with SSH to Shore Up Secure Connections." TechRepublic, 13 Oct. 2005, www.techrepublic.com/article/replace-telnet-with-ssh-to-shore-up-secure-connections. Accessed 27 Feb. 2018.
Neagu, Codrut. "Simple Questions: What Is Telnet & What Can It Still Be Used for?" Digital Citizen, 5 Aug. 2014, www.digitalcitizen.life/simple-questions-what-telnet-what-can-it-still-be-used. Accessed 27 Feb. 2018.
"Telnet—and SSH as a Secure Alternative." SSH Communications Security, www.ssh.com/ssh/telnet. Accessed 27 Feb. 2018.
"Telnet Commands." Microsoft Docs, 11 Sept. 2009, docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-xp/bb491013(v=technet.10). Accessed 27 Feb. 2018.
"Telnet Overview, History, and Standards." TC/IP Guide, www.tcpipguide.com/free/t‗TelnetOverviewHistoryandStandards.htm. Accessed 27 Feb. 2018.
"Using Telnet." Media Temple, mediatemple.net/community/products/grid/204644790/using-telnet. Accessed 27 Feb. 2018.
"What Is Telnet?" Indiana University, 24 Jan. 2018, kb.iu.edu/d/aayd. Accessed 27 Feb. 2018.