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This chapter provides an overview of the Cisco Systems communication server product line. You will find the following information in this chapter:
Cisco communication servers connect terminals, modems, microcomputers, and networks over serial lines to local area networks (LANs) or wide area networks (WANs). They provide network access to terminals, printers, and computers that have no built-in network support.
Full network access control features help the network manager ensure secure and efficient system use. Remote configuration is also available through Telnet and MOP connections to virtual ports on the communication servers.
Security features allow restrictions to resources on the network. The network manager can specify access lists to establish which users have access to which computers. A username-and-password-pair authentication scheme is also supported.
The communication servers are network-compatible with the Cisco Systems routers, which you can use to extend your network to any size you need. Additionally, you can use the protocol translation capability of the communication server software, thereby providing connection service between different hosts and resources running different protocols.
Your communication server is designed to be an integral part of any distributed systems application. Communication servers can be used as a distributed data switch or PBX. They can also provide direct communication to hosts. On LANs, the communication server supports TCP/IP on UNIX machines by providing telnet and rlogin connections, IBM machines using TN3270 connections; DEC machines using LAT connections, and X.25 machines using X.25 PAD connections. WAN connectivity is provided using XRemote, NCD's X windows terminal protocol, Serial Line Internet Protocol (SLIP), and Point-to-Point Protocol.
Your communication server supports four types of server operation:
Figure 1-1 illustrates these four types of server functionality available on the communication server:
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A user can dial in and use a port for any of the following types of connections:
This range of functionality is possible because multiple roles can be assigned to each asynchronous interface. Each asynchronous line can be used as a network interface for IP routing some of the time, as a source of data for terminal-server communications (using Telnet, LAT, rlogin, and so forth), for protocol translation, and for telecommuting (using XRemote and SLIP).
The communication server provides terminal-to-host connectivity using virtual terminal protocols including Telnet, LAT, TN3270, rlogin, and X.25 PAD. Modems can be set up for rotary connections, allowing users to connect to the next available modem. A host can also connect directly to a communication server. In IBM environments, TN3270 allows a standard ASCII terminal to emulate a 3278 terminal and access an IBM host across an IP network. In DEC environments, LAT support provides a terminal with connections to VMS hosts. X.25 PAD allows terminals to connect directly to an X.25 host over an X.25 network through the communication server. X.25 PAD eliminates the need for a separate PAD device. This connection requires a synchronous serial interface.
Figure 1-2 illustrates terminal-to-host connections using a communication server.
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Using SLIP or PPP, PC users can run TCP/IP applications including Telnet, SMTP, and FTP over serial lines. The user gets remote connectivity with same functionally as a PC attached locally to a local network. Another option is to use the XRemote protocol over asynchronous lines. The communication server provides network functionality to remote
X display terminals.
Figure 1-3 illustrates an XRemote connection using a communication server. See the "XRemote Configuration and Management" chapter for additional possible XRemote configurations.
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The communication server translates virtual terminal protocols to allow devices running dissimilar protocols to communicate. Supports Telnet (TCP), LAT, and X.25. One-step protocol translation software performs bidirectional translation between any of the following protocols:
Figure 1-4 illustrates LAT-to-TCP protocol translation.
Routing is the process of determining the most efficient path for sending data packets to a destination address outside the local network. The communication server gathers and maintains routing information to enable the transmission and receipt of such data packets. Routing information takes the form of entries in a routing table, with one entry for each identified route. The communication server can create and maintain the routing table dynamically to accommodate network-configuration changes when they occur.
Communication servers allow you to route IP packets over an asynchronous line using Serial Line Internet Protocol (SLIP), Compressed SLIP (CSLIP), or Point-to-Point Protocol (PPP).
A key feature of asynchronous routing is its ability to provide low-cost operation over normal dial-up telephone networks. The communication server's routing capabilities provide remote home and sales offices with cost-effective access to a central site. For example, traffic from PCs and UNIX workstations can be routed through the communication server, eliminating multiple phone lines and modems. Routing over asynchronous lines also provides significant phone-line savings for small offices by allowing dial-up telephone lines to be used rather than more costly leased lines.
All of the IP routing protocols and special features that are implemented on Cisco routers (including the AGS+, MGS, CGS, and IGS) are available on your communication server. Routing protocols include OSPF, IGRP, RIP, EGP, and BGP. Special routing features include route filtering, priority queuing, access lists, and more.
Figure 1-5 illustrates an IP routing configuration using communication servers. In this configuration the host is connected to an Ethernet and is forming a routing connection with communication servers at remote sites.
Cisco Systems communication servers provide a flexible set of capabilities providing connection service using different media and (with the protocol translation option) between different hosts and resources running different protocols. The following descriptions summarize the protocols and connection services supported by the Cisco Systems communication servers.
The communication servers handle multiple device interfaces. They multiplex asynchronous RS-232 serial lines onto a high-speed network interface. ASCII terminals, modems, printers, and host serial ports are among the devices you can connect to the communication servers. You can use a number of methods to connect serial devices, including RJ-11,
RJ-45, and 50-pin Telco connectors. The 500-CS supports RJ-45 connectors only. The ASM-CS supports Telco and RJ-11 connectors.
The network interfaces for the communication servers provide easy connectivity. The network interface is typically to Ethernet, but can also be synchronous serial lines and Token Rings (ASM-CS only).
Using communication servers, any RS-232-compatible device--serial laser printer, film recorder, plotter, and the like--can become a shared resource to your organization over a local network.
Part of the power and flexibility of your communication server components is derived from their physical configuration options. Customers can choose from single-board systems, or card-based chassis configurations that offer processor, back panel connector mountings, and communications interfaces best suited to their network.
The following communication server models are available:
The protocol translation option for the communication server allows users of X.25
(ASM-CS only), DEC Local Area Transport (LAT), and TCP/IP networks to make virtual terminal connections between each of these environments. Access to IBM hosts via TN3270 terminal emulation is also available through the protocol translator. XRemote connections are also supported.
The ASM-CS offers a choice of an MC68020 microprocessor with 4 MB of memory or an MC 68040 microprocessor with 16 MB of memory. The 500-CS is based on the MC68331 processor, which comes with two MB of RAM and is expandable to 4 MB or 10 MB of RAM, and offers both RS-232 and RS-423 serial connectors, as well as hardware and software flow control. All Cisco System microprocessors contain onboard RAM, system ROM holding all operating system, bootstrap, and diagnostic software.
Cisco systems also include nonvolatile memory that retains configuration information despite power losses or system reboots. With the nonvolatile memory option, the terminal and network servers need not rely on other network servers for configuration and boot service information.
This section provides a roadmap for the Communication Server Configuration and Reference publication, as well as an overview of the tasks required to configure your communication server for the four server functions supported on this communication server.
Step 1: Attach an RS-232 ASCII terminal to the system console port located at the rear of the Cisco server ASM-CS, or to Port 1 on the 500-CS.
Step 2: Configure the terminal to operate at 9600 baud, 8 data bits, no parity, 2 stop bits.
Step 3: Power up the communication server (the setup program runs automatically for initial startup).
The configuration overview includes configuration guidelines and general steps for configuring all four server functions provided on the communication server:
Use the following process to configure your communication server. It lists general configuration tasks first, followed by specific telecommuting and protocol translation tasks. The last section lists the tasks required to configure your communication server for asynchronous IP routing.
The steps in this section are designed to guide you through the initial communication server configuration. When you have completed these steps, your communication server will be configured for terminal server functionality.
Step 1: Configure the desired global system parameters--see the "System Management" chapter.
Step 2: Configure communication server lines--see the "System Management" chapter.
Set up communication server lines for connection to asynchronous devices such as terminals and modems
Step 3: Define the interfaces: Ethernet, Token Ring, or synchronous serial--see the "Interface Configuration and Support" chapter.
Step 4: Define the interface encapsulation method--see the "Interface Configuration and Support" chapter.
Step 5: Enable the transmission protocol: LAT (see the "LAT Configuration and Management" chapter) or IP (the "IP Configuration and Management" chapter).
Step 6: Define other transmission features for that protocol as needed--see the chapters "LAT Configuration and Management" or "IP Configuration and Management".
Step 7: Configure line for packet switched software services such as X.25, frame relay, or SMDS (see the "X.25 Configuration and Management," "Frame Relay Configuration and Management," or "SMDS Configuration and Management" chapters respectively).
Step 8: Telecommuting
After you have completed steps 1 through 7, use the step in this section to configure your communication server for telecommuting functionality.
Step 9: Configure protocols for telecommuting applications--see the chapters "TN3270 Configuration and Management" or "XRemeote Configuration and Management."
Add the step in this section if you want to configure your communication server for protocol translation.
Step 10: Configure for protocol translation-- see the "Protocol Translation" chapter.
Complete the following tasks to configure your system for asynchronous IP routing:
Step 1: Enable IP routing, assign IP addresses--see the "Interface Configuration and Support" chapter.
Step 2: Configure IP address resolution, assign broadcast address (optional)--see the "Interface Configuration and Support" chapter.
Step 3: Configure interface for asynchronous communication--see the "Interface Configuration and Support" chapter.
Step 4: Configure asynchronous lines to run SLIP, CSLIP, or PPP encapsulation (optional)--see the "Interface Configuration and Support" chapter..
Step 5: Configure SLIP routing and default or dynamic SLIP addressing--see the "SLIP Configuration and Management" chapter.
Step 6: Configure CSLIP (optional)--see the "SLIP Configuration and Management" chapter.
Step 7: Configure IP routing protocol: OSPF, IGRP, RIP, EGP, or BGP--see the "IP Routing Protocols" chapter.
Step 8: Configure IP access control and security (optional)--see the "Interface Configuration and Support" chapter.
Step 9: Configure IP accounting (optional)--see the "Interface Configuration and Support" chapter.
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