Cisco Networking Academy Program CCNA 1 and 2 Companion Guide, Revised part 54 is the Cisco approved textbook to use alongside version of the Cisco Networking Academy Program CCNA 1 and CCNA 2 web-based courses. The topics covered provide you with the necessary knowledge to begin your preparation for the CCNA certification exam (640-801, or 640-821 and 640-811) and to enter the field of network administration. | Page 499 Tuesday May 20 2003 2 53 PM TCP IP Application Layer 499 Telnet Terminal emulation Telnet software provides the capability to remotely access another computer. It enables you to log in to an Internet host and execute commands. Telnet commonly is used for remote administration of servers and network equipment such as routers and switches. A Telnet client is referred to as a local host and a Telnet server which uses special software called a daemon is referred to as a remote host as shown in Figure 9-14. Figure 9-14 Telnet Client Telnet Server To make a connection from a Telnet client you must select a connection option. The host name and terminal type will need to be entered on the command-line prompt. The host name is the IP address DNS of the remote computer to which you connect. The terminal type describes the type of terminal emulation that you want the computer to perform. The Telnet operation uses none of the transmitting computer s processing power. Instead it transmits the keystrokes to the remote host and sends the resulting screen output back to the local monitor. All processing and storage takes place on the remote computer. When a DNS name for a Telnet location is entered the name must be translated into its associated IP address before a connection can be established. The Telnet application works mainly at the top three layers of the OSI model the application layer commands the presentation layer formats usually ASCII and the session layer transmits . The data then passes to the transport layer where it is segmented and the port address and error checking are added. The data then passes to the network layer where the IP header containing the source and destination IP addresses is added. Next the packet travels to the data link layer which encapsulates the packet in a data frame adds the source and destination MAC address and adds a frame trailer. If the source computer doesn t have the MAC address of the destination computer it .
