Device Servers:
Network-Enabling Nearly Any Device
Terminal and Print Servers -- Traditional
Applications
Despite many of the advancements of the computer industry,
there still exist a great many applications where serial
I/O devices are the best or only solution. Terminal/print/serial
servers have long been the best method for networking
simple terminals, bar code readers, scanners or printers.
Input devices attached to a serial port on a server
can reach any host supporting the same protocols as
that server. Printers can be shared over the network
in the same manner, with a job from one protocol following
a job from another. In the case of the print server
that has multiple ports, jobs coming from hosts supporting
different protocols can even print simultaneously.
Traditionally, terminal/print servers have been larger,
multiport devices. But as the marketplace demands that
singular devices in remote locations are networked and
as technology has developed to allow for single-port
device servers to be economically feasible, these smaller
servers now provide this remote connectivity. Single
port device servers are now being used to provide network
connectivity for devices such as bar code readers, factory
automation devices, security/monitoring devices and
medical devices. This type of technology has been labeled
device server technology by industry analysts. For nearly
10 years, Lantronix has been a leader in terminal/print
server technology and has been an innovator in the area
of micro print server and single-port device server
technology. Lantronix is now on the forefront of device
server technology for the purpose of networking devices
previously not on the network.
Management via Serial Communications
Over a Network
In the 1980's and 1990's, terminal servers became a
popular way to connect serial devices to a network for
accessing multi-user host systems. In a terminal server
design, serial devices were physically connected to
terminal server ports. The terminal server itself governed
protocol use, and the availability of added features
such as multiple connection support from a single port
or dedicated connections to a single system on powerup.
TCP/IP was the protocol suite of choice for this type
of configuration, for it allowed more efficient communications
over both the local network (Intranet) and the Internet.
The primary function of terminal servers was to give
terminal users access to network devices. Connecting
network devices to remote serial ports became another
popular use. Printers, modems, converters and other
task-specific devices could be attached to server ports,
and these ports could then be accessed from network
hosts. In this configuration, monitoring devices could
be polled at regular intervals, serial console ports
on computers could be accessed from remote locations
for important boot-time parameter configuration and
the server itself could be accessed to examine performance
data collected on the various ports themselves. While
some users simply used IP's Telnet for management connections,
other management-specific suites, such as SNMP, were
developed to further enhance status and configuration
management of these remote device ports.
Whereas earlier terminal server products were somewhat
large, requiring substantial processing resources, newer
integrated circuit designs have made it possible shrink
the size of a terminal server. As we begin the new millennium,
new single-port device servers can be built which are
cost-effective and small in size. The availability of
single-port Device Servers created the potential for
isolated single-port serial devices to be networked
in a cost-effective manner.
One can see very quickly how a network manager can
now attach the serial port of a device to a single-port
server and immediately have network access to that device.
No long cable runs, dedicated modem or multiplexor ports
are now required - simply install the Device Server
on the nearby network, attach it to the serial port
of the device and manage the device from anywhere within
the corporate or campus network (Intranet) or from the
Internet.
Some devices require a dedicated PC to not only present
the management and configuration information, but also
to process it before the user views it. Can this type
of device also benefit from the availability of a Device
Server? The answer is yes.
By using a redirector software package, a PC running
software specifically to process information from a
serial device can become a networked PC. The redirector
takes the PC's output destined for it's communications
port and redirects it to a network port--specifically,
the network port on the Device Server. Thus, the PC
"believes" it is talking to a local device
on the COM port, when it is really talking to a device
located remotely on the network.
Even without a redirector, a remote PC can be connected
via a process called "tunneling." Here, each
Device Server passes the serial data from one end of
the connection to the other. This configuration can
be utilized if the data between the serial device and
the PC is encoded or proprietary.
The Benefits of Networked Management
Device Server technology allows an isolated device
to be networked into the campus or corporate network.
Why network these devices? Several reasons come to mind:
- Easy Installation and Maintenance
Network connections tend to populate every location
of a campus or corporate site. Wherever one goes,
a network access port is usually nearby. This means
a device in any location can be put onto the network
and accessed from anywhere else on the local network
or even over the Internet. As networks are extended
to great lengths using switches, hubs and converters,
connectivity becomes available to areas that previously
required long dedicated serial cable runs.
- Management From Anywhere
Network managers now have a great many tools at their
disposal for ensuring that the network performs efficiently.
SNMP (including MIBs) is a standardized management
protocol providing pro-active management information
arising from continuous process monitoring. Many vendors,
such as HP (HPOpenview) and SUN (SunNetmanager), have
well-developed software packages for network management,
while most vendors support simple telnet or menu-based
management interfaces. These protocols are supported
over the Internet, allowing a network manager to roam
at will, literally around the world, and still have
access to a device.
- Reliable Management Access
Corporate and campus networks have become very highly
scrutinized. In most larger networks, 24-hour-a-day
maintenance and monitoring takes place to ensure the
network is running properly. Networking protocols
designed for data delivery ensure that information
arrives from node to node. Routed networks provide
multiple pathways for data deliver. New software capable
of measuring quality of service helps the network
manager to tune the network topology to allow data
to flow freely between devices virtually all the time.
All of these reasons combine to make management over
the network one of the most reliable ways to manage
a remote device.
- Lower Management Costs
With a reliable remote management tool available,
network managers can streamline their staffing and
troubleshooting requirements to a centralized or even
automated system. Standards-based management features
such as SNMP maximize the investment in software and
analysis devices based upon that protocol. Even a
simple management technique such as a ping or a telnet
login to validate that a node is alive can be run
from a script. With a management scheme based upon
established standards, network managers can train
internal staff better and more easily hire new staff
with known levels of skill regarding the management
suite. Better management technology and better staff
results in lower costs for the network manager.
The availability of smaller, more tightly integrated
circuits makes it possible to build a single-port Device
Server on a circuit board no larger than a matchbook.
As a board-level product, a Device Server can be integrated
into a device's design to allow a number of options:
(1) for devices able to preprocess in full the status
and configuration information, the Device Server can
be used to allow that device to be offered with a network
port which can accept or generate connections to any
network node; (2) for those devices requiring processing
elsewhere, a Device Server can allow that device to
be located anywhere on the network with the serial data
being "piped" from the sending device to the
processing device.
Lantronix MSS and UDS/CoBox® Device
Server Product Families
The MSS and CoBox/UDS Device Server product families
have paved the way for remote serial-only devices to
be managed over a network. These products provide serial-to-Ethernet
connectivity in a compact and cost-effective design.
Both families provide external and embedded solutions,
and support a variety of serial and Ethernet interfaces.
Serial-to-Ethernet Service
For many devices, the only access available to a network
manager or programmer is via a serial port. The reason
for this is partly historical and partly evolutionary.
Historically, Ethernet interfacing has usually been
a lengthy development process involving multiple vendor
protocols (some of which have been proprietary) and
the interpretation of many RFCs. Some vendors felt Ethernet
was not necessary for their product which was destined
for a centralized computer center - others felt that
the development time and expense required to have an
Ethernet interface on the product was not justified.
From the evolutionary standpoint, the networking infrastructure
of many sites has only recently been developed to the
point that consistent and perceived stability has been
obtained - as users and management have become comfortable
with the performance of the network, they now focus
on how they can maximize corporate productivity in non-IS
capacities.
The key to network enabling any device is in a server's
ability to handle two separate areas: (1) the connection
between the serial device and the server and (2) the
connection between the server and the network (including
other network devices). Terminal, print and serial servers
have been developed over the years specifically for
the tasks of connecting terminals, printers and modems
to the network and making those devices available as
networked devices. As current demands for networking
other devices increases, these servers need to become
more generic in their handling of the attached devices.
Additionally, they will have to become even more flexible
in the manner in which they provide network connectivity.
Device Server Technology
Dataquest has described a device server to be "a
specialized network-based hardware device designed to
perform a single or specialized set of functions with
client access independent of any operating system or
proprietary protocol." Terminal, print and recently
one-port terminal servers have come to embody
this notion of independence from proprietary protocols
and the ability to meet a number of different functions.
The RAID controller application discussed above is just
one of many applications where these Device Servers
can be used to put any device or "thing" on
the network. The recent development of the single port
Device Server now makes it economically possible to
connect even single devices with serial ports to network
- prior to this development, users had only multiport
solutions which were sometimes too expensive when the
serial devices were very far apart.
Someone might ask the question, "But haven't dedicated
PCs been used to network some serial devices with success?"
The answer to this would be a somewhat qualified yes
- qualified because it required the designer of the
product with the serial port to have software able to
run on the PC and then have that application software
allow the PC's networking software to access the application.
This task would be somewhat akin to the problems of
putting Ethernet on the serial device itself! To be
successful, a device server must provide a simple solution
for networking a device and allow access to that device
as if it were locally available through its serial port.
Additionally, the device server should provide for the
multitude of connection possibilities that a device
may require on both the serial and network sides of
a connection. Should the device be connected all the
time to a specific host or PC? Are there multiple hosts
or network devices that may want or need to connect
to the newly-networked serial device? Are there specific
requirements for an application which requires the serial
device to reject a connection from the network under
certain circumstances? The bottom line is a server must
have both the flexibility to service a multitude of
applications requirements and be able to meet in depth
the demands of those applications.
*Some information contained
in this article was provided by Lantronix Corp.
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