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Overview

Overview

This chapter provides a general description of the connection features supported on your server product (access server or router) to connect terminals, modems, microcomputers, and networks to local-area networks (LANs) or wide-area networks (WANs).

Supported Protocols

A user can dial in and use a line or interface for the following types of connections:

This range of functionality is possible because multiple roles can be assigned to each line. Each line can be a source of data for terminal-server communications (using Telnet, LAT, rlogin, and so forth), for remote-node services (using XRemote, ARA, and SLIP), or for terminal services or remote-node services using protocol translation.

Following are brief descriptions of the protocols and connection services supported by server products (access servers and routers).

Connection Services

Your server product supports three types of connection services (see Figure 1-1).


Figure 1-1: Connection Services



Terminal Services

Terminal services provide terminal-to-host connectivity with virtual terminal protocols, including Telnet, LAT, TN3270, and rlogin. Modems can be set up for rotary connections, so that you can connect to the next available modem. A host can also connect directly to a server product. In IBM environments, TN3270 enables a standard ASCII terminal to emulate a 3278 terminal and access an IBM host across an IP network. In Digital environments, LAT support provides a terminal with connections to VMS hosts. Using LPD, you can also connect a UNIX host to a UNIX printer through an access server. On LANs, terminal services support the following types of connections:

Figure 1-2 illustrates terminal-to-host connections.


Figure 1-2: Terminal-to-Host Connectivity



Remote-Node Services

Using SLIP, CSLIP, or PPP, you can run TCP/IP applications, including Telnet, Simple Mail Transfer Protocol (SMTP), and File Transfer Protocol (FTP), over serial lines. You can get remote connectivity with the same functionality as a PC attached to a local network. Using ARA, you can connect from a Macintosh computer in a remote office into an AppleTalk LAN and have access to all Apple-based resources on that LAN. You can also use the XRemote protocol over asynchronous lines, because an access server can provide network functionality to remote X display terminals.

Remote-node services support WAN connectivity with SLIP, PPP, and XRemote. Other WAN services include X.25, Switched Multimegabit Data Service (SMDS), and Frame Relay. Full IP and IPX routing services are also supported. Access servers are network-compatible with routers, and you can use either device to extend your local-area network to any size you need.

Figure 1-3 illustrates an XRemote connection using an access server. Refer to the Access and Communication Servers Configuration Guide for additional possible XRemote configurations.


Figure 1-3: XRemote Connection



Figure 1-4 illustrates remote-node connections where remote users dial into an access server and connect to network services.


Figure 1-4: Remote-Node Connection



Terminal or Remote-Node Services Using Protocol Translation

Protocol translation translates virtual terminal protocols so that devices running dissimilar protocols can communicate. Protocol translation on a server product supports Telnet, SLIP/PPP, ARA, LAT, and X.25.

There are two ways to make connections using a server product set up for protocol translation:

With the one-step method, you perform bidirectional translation between any of the following protocols:

  • X.25 and TCP

  • X.25 and LAT

  • LAT and TCP

  • LAT, X.25, and TCP (Telnet) to SLIP and PPP

For more information about using the one-step method, refer to the "Configuring Protocol Translation" chapter in the Access and Communication Servers Configuration Guide.
In general, you use the two-step method when you want temporary use of a server product supporting protocol translation as a general-purpose gateway between two types of networks (for example, X.25 PDN and TCP/IP). Instead of configuring the server product for every possible connection using the translate command, in the configuration file, the two-step method allows you greater flexibility in terms of connecting to network resources accessible via the server product supporting protocol translation. Figure 1-5 illustrates LAT-to-TCP protocol translation.

Figure 1-5: LAT-to-TCP Protocol Translation



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