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Console Server Technology.

Solving the critical problems of remote network management

With organizations relying more and more on the network infrastructure as the primary conduit for all information, the demand upon network managers to provide a network that is free from downtime and performance constraints is greater than ever. Couple this demand with the fact that many organizations are using wide area networks which span many remote sites or campuses, have multitudes of remote users dialing in from various locations worldwide, and are supporting connections to the Internet for advertising, e-commerce, or for data gathering. Increasing sales in network infrastructure equipment indicates this trend towards expansion. In fact, the Dell 'Oro Group, analysts of the switch and hub marketplace, has reported that sales of network switches will grow to an excess of $23 billion by year 2004 (an annual growth rate of 20% per year over the next five years).

Organizations with multiple sites will have a myriad of switches, routers, hubs, access servers, and networked computers such as PCs, workstations, file servers, and even some mainframes. The key fact here is that these devices are in a number of locations and, depending upon the size of the organization, could be located across the country or even continental boundaries.

Today, network managers are on the hot seat to maintain both availability and performance of the organization's network regardless of how widely dispersed the network infrastructure might be. Generally hindered by small staffs or by a lack of seasoned personnel, time is a network manager's most valuable resource.

The stakes are high: Infonetics Research recently reported in a study of Fortune 100 and Fortune 500 companies that network downtime totaling only 5.5 hours for the average company could cause a loss of up to $3.9 million in revenue and productivity. The problem is how to expand the capabilities of network management personnel within an organization to better maintain the variety of network infrastructure devices and networked systems presently being used to minimize and possibly avoid network downtime or performance loss.

In-band Management--An Incomplete Solution

At first glance, when analyzing the problem of how to better manage a widely-dispersed network infrastructure and networked systems, a network manager might decide to purchase only those network switches or routers that support in-band management via SNMP, telnet connections, or proprietary management software. The idea of having the entire network mapped onto one or more monitoring servers sounds appealing and potentially simple. However, this strategy has a number of flaws:

In-band management as a solution is limited. It relies on the existence of the very network which one is intent upon managing. So if your only means of management is through network connections and then the network goes down, you are left without management capabilities.

SNMP (Simple Network Management Protocol)

SNMP provides limited abilities to manage devices using a standard developed to run on the IP protocol. The advantage of SNMP is that it can be used to manage devices supporting the protocol from any number of hosts or PCs running SNMP software. The limitation is the same as any other in-band management tool: what to do if the network itself has failed?


Telnet is of course one of the great features of the IP protocol stack in that it allows connections just about anywhere but sometimes users are limited to a subset of features by certain devices. Many vendors want to protect users from themselves by not allowing them to change the IP address or reboot a device that they are connected to.

Vendor-specific software

While some vendor-specific packages provide a wealth of information beyond that of ordinary telnet or even SNMP, the cost/benefit decision remains. The specific features a software package provides may not be fully realized in the hands of a relatively untrained staff.

Devices without network ports

When one considers all of the devices which might show up in a computer rack, there are a number of devices which might be critical and yet have no network port at all (PBXs, UPSs, cooling systems). For these devices, the only access is via a console port connection.

So a simple strategy based on in-band management will provide some assistance in certain circumstances but will have minimum benefit if a key router goes down or if there are a number of critical devices which do not have network ports. A simplistic solution to this problem is to connect those devices which are "really critical" to modems for out-of-band connectivity. But will this strategy make sense in rapidly expanding networks? If there are 50 "really critical" devices, then this could entail the installation of 50 modems and 50 phone lines-a very expensive and potentially difficult-to-maintain configuration.

Console Access--The "Proximity" Issue

In the 1970s and 1980s, when many organizational networks were LANs rather than WANs, the central computer room was the focal point of all information processing. Various mainframe or mini computers supplied most of the computing power and much of the storage devices were either large disk systems or magnetic tape drives.

A key component of these types of devices was the console--a serial interface which allowed communication to the mainframe, mini, or the peripheral, and presented to the network manager access to those commands that could completely control that device. From the console of a Unix workstation, for instance, a network manager could partition portions of the system disk, reconfigure the system kernel, or simply reset that system to take advantage of changed settings. The fundamental assumption of console management was that key systems would be located in a secure place where only authorized persons would have access. For an organization where all the computing resources were contained to one or even a few rooms, this presented the simple challenge of arranging staffing 24 hours a day for those few locations.

The console port has remained a staple of many devices--guaranteeing a means to manage the device under any circumstances but requiring proximity to that device. Access to a device's console port by an out-of-band dial-up connection ensures that the network manager can manage that device remotely under any condition. This fact is very important when one considers the impact of a router or switch losing connectivity, as such a failure can result in whole network segments failing. In this case, without an out-of-band alternative, the only solution is to physically go to the failing router or switch and gain access to the console port to ascertain the nature of the failure. One shudders to think of the consequences should this router or switch be in a location requiring several hours or even a day's travel to reach.

A Total Management Solution: The Console Server

The solution to the limitations of in-band management and to the requirement of direct access to remote system or device consoles can be found in the use of a hybrid server called a console server. A console server is a device which provides a multitude of connectivity options to device and systems consoles. When in-band connectivity is possible, a console server will allow simple connections via telnet direct to a device's console, providing the network manager with direct interfacing to that device. When in-band management connections are not possible, then the console server provides dial-in connectivity to a system's consoles providing for reconfiguring or simply rebooting devices to return them to operation. With the console server, any condition which occurs can be potentially resolved from a remote connection be it via a network or via dial-in.

Let us take as an example a backbone switch controlling several Ethernet segments in a large corporation. Failure of the switch could lead to failure of each of those segments, leading to a complete loss of connectivity for those departments and making them completely inaccessible for a network manager. If the network manager has the console port of the switch connected to a port on a console server, however, it would be possible to connect to the console via a dial-up connection even if network connectivity is impossible.

The console server provides multiple connectivity options to the network manager, allowing them to reach the console port of any device from anywhere they have a network connection or dialup connection. This situation leads to a number of benefits for network managers employing console servers:

In-band or Out-of-Band management.

When managing networking infrastructure devices, such as routers or switches, failure of those devices could prevent management connectivity through the network itself; if a console server is used, then connectivity through a dialup connection could alternatively be made, allowing the network manager access to the router/switch console that might allow them to fix the problem from a remote location.

Simplified management.

By connecting through the console server to a device console using simple telnet, the network manager is able to do so without the need for vendor-specific or other specialized software. A well-designed console server will offer features such as custom menus and multiple sessions which will allow the network manager or their staff to make easy connections to device consoles by name and allows multiple sessions so that multiple devices can be monitored from a single connection to the server.

Cost-effective management.

A console server with a modem attached can support a number of system consoles through a single dial-in connection. This means that individual modems and phone lines do not need to be installed in order to provide out-of-band management support to every device or system in the network infrastructure. Additionally, there is no need to purchase vendor-specific software for managing your devices; more money can be spent on "best-of-breed" solutions rather than being locked into one vendor's technology. Finally, by supporting a simple management tool, the console server allows the network manager to avoid the need for long, complex and expensive training programs for networking: personnel.

Secure management.

Console servers can also provide a wide variety of sophisticated authentication and security features which go far beyond simple passwords. Dial-in connections can be required to exercise PAP and/or CHAP authentication or they can be forced to be validated using authentication servers supporting such methods as Radius, Kerberos, or SecurID. Incoming network connections can be restricted to a set of specific IP addresses using features such as SSH or IPsecurity.

All of the above factors serve to make console servers the ideal solution for modern distributed networks.

A Simple Yet Effective Solution To The Demands Of Remote Management

As organizational networks continue to expand, the demand for management of those networks will become ever more critical to the success of those organizations. For many organizations this will include expansion of facilities and personnel to include more remote users and offices. The question will be how to manage these expanded networks.

By using console servers to manage their critical system and device consoles, network managers can achieve a simple, flexible solution to the problem of remote management. With console servers, access can be established through the network or it can be outside the network--this makes the console server more flexible than vendor-specific or even generic solutions that only use the network itself for connectivity. The other advantage of console servers is that there is no major learning curve for new personnel to understand the technology--connection to a device console port via a console server brings the user directly to the device itself and requires only the specific knowledge required to manipulate the device.

Mark Prowten is a product manager in charge of the Multiport Device Server product line at Lantronix (Irvine, CA).
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Title Annotation:Industry Trend or Event
Author:Prowten, Mark
Publication:Computer Technology Review
Geographic Code:1USA
Date:Dec 1, 2000
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