Telnet

Telnet was officially adopted as a widely accepted computer communications protocol in May 1983. It was created and implemented to allow servers and PCs to communicate through the creation of a widely deployed communication interface where commands that were issued by the host computer were sent across a link as simple, clear text. Communication links of the time were typically very slow. The servers receiving the telnet transmission would execute the commands, summarize the results, and transmit them back across the same slow link to the host.

In the early days of computer networking, bandwidth was afforded only at a premium. Its deployment was difficult, which required specialized skills. Telnet was able to minimize the impact and cost associated with this problem. Telnet allowed network managers to control devices remotely, and to run some simple applications across what could be hundreds or even thousands of miles without consuming all bandwidth on the network, or access points.

Even today, with the advent of broadband access , telnet has its place as a tool to be exploited in controlling one's digital assets. At the heart of all major and medium sized networks, one will likely find a router designed to join different networks together. These devices are provided an address so that all devices in the network for communication between the network and or the Internet can reach them. This address can also be reached via telnet. This simple fact makes telnet a very powerful protocol that can be used to troubleshoot, configure, and deploy new equipment on a network. In fact, telnet is the most widely used tool for the managing of all equipment in a given network.

Telnet Concerns

All switches, routers, and translational bridges built by such companies as Cisco, Marconi, Extreme Networks, and so on, come with a Command Line Interface (CLI). The CLI is a text-driven interface that is very obscure; it can be quite intimidating for first time users as they attempt to manage and configure a device. This is in stark contrast to a graphical user interface (GUI) that is intuitive and simple to use. The downside of a GUI is that it can often saturate a wide area link, and consume all available bandwidth, thus causing bottlenecks for users that can cost a great deal of money. The CLI is still widely used, however, and it is the perfect fit for managing a device or series of devices. Unfortunately for management, this method does not scale well as telnet can only access one device at a time. Thus, in a network of several hundred devices, the CLI with telnet access would not be a manageable condition, and would require a more robust management application to handle such a sizeable network.

There are other concerns about using the telnet protocol; for one, it is not secure. Text transferred to and from server devices and hosts is typically clear text. Even passwords for configuration of major devices are submitted across the wire unencrypted. This creates a serious management problem. When deploying the telnet protocol, a company's network manager must take care to secure unencrypted data from users outside the company network, as well as from internal employees, with whom the majority of all security violations originate. Typically, the best line of defense is to not allow the protocol to traverse the networks, thus making it impossible to breach the system with telnet. However, this results in the inability to utilize telnet for network configuration and management, which forces the purchase of expensive management applications. The decision to deploy or not to deploy telnet is a complicated management choice.

FTP

The File Transfer Protocol (FTP) was developed around the same time as telnet, and allowed for succinct transfer of files between servers and hosts and for the deployment of early remote storage solutions. This was particularly welcome in the early days of the Internet because bandwidth was at a premium. FTP would address this limitation and allow data to be transferred more efficiently.

Early implementers were also delighted with the option for remote storage of data because PC storage capabilities were still limited while user needs were growing. FTP and its usage are based on a simple command line utility. In addition, because FTP was a standard, it guaranteed that dissimilar systems and networks could interact with reasonable robustness and little variance in configuration.

FTP is still widely used today. Any user who gets an account with an ISP will likely be supplied space for a personal web site. To access this secured space, the user will typically utilize an FTP program for the downloading and uploading of HTML pages and graphical content for the web site. The application most commonly used is a GUI-based FTP application called Cute FTP. Cute FTP is a free shareware application that can be downloaded from many sites on the Internet.

FTP and telnet can be powerful tools for manipulating the web, in part because they require little networking knowledge to use them effectively and efficiently. From a technical perspective, telnet and FTP utilize a series of handshakes and negotiation parameters. The handshake is like the drone of a modem or fax machine as it attempts to connect with a compatible device somewhere in cyberspace. These handshakes and negotiation parameters are specified in Requests for Comments number 854 for telnet, and number 354 for FTP, respectively. The technical details of their implementation are extensive and beyond the scope of this text. Fortunately, understanding the technical aspects is not a prerequisite to using telnet or FTP because anyone who accesses the Internet will likely, at some time, make use of these protocols.

see also E-commerce; FTP; Internet; TCP/IP.

John Nau

Internet Resources

Cisco Connection Online. Cisco Systems, Inc. <http://www.cisco.com>

"STD/STD8." Telnet Protocol Specifications. Internet RFC/STD/FYI/BCP Archives. <http://www.faqs.org/rfcs/std/std8.html>

"Telnet and FTP." Heart of the Web. <http://www.heartoftheweb.net/ftp_&_telnet.htm>

TELNET Acronym for teletype network. The protocol developed for the ARPANET to allow users on one host computer to connect to the time-sharing resources of another host. The TELNET protocol specifies a standard terminal type, the network virtual terminal (NVT), including its character set (a modified form of ASCII) and standard control sequences for terminal functions such as “move to the next line”. Standard control sequences are also defined for host functions such as “interrupt process”. It is the responsibility of the programs at each end of the TELNET connection to perform a suitable mapping between the NVT's character set and control functions, and the conventions of the local system. Many of the parameters of the NVT can be modified through option negotiation, in which both ends of the TELNET connection must agree to a proposed change before it can take place.

The name TELNET is also used for similar protocols in networks other than the ARPANET.

TELNET (ˈtɛlnɛt) Computing teletype network