PC Plus HelpDesk - issue 231
|This month, Paul Grosse gives you more insight into
some of the topics dealt with in HelpDesk and HelpDesk
From the pages of HelpDesk, we look at:
- Configuring Network Devices; and,
- Which Server Operating System?
From HelpDesk Extra, we look at Network-based
- IP v USB;
- Retrieving images; and,
- Example Web Page.
Configuring Network Devices
One problem with new network devices is that they
often come with a factory settings IP address that is not
on your network. In order to communicate with that device
- at least until you give it an IP address that is on
your network - you need to reconfigure a machine so that
it has a compatible network address.
Windows XP, right-click on the 'My Network
Places' icon and select 'Properties' from the
menu. This should open up the Network connections
Right-click on the network interface
icon and select 'Properties' from the menu.
the 'General' tab, select the 'Internet Protocol
(TCP/IP) line and click on the 'Properties'
the next dialogue box, you enter the IP address
you want to change the computer's IP address to
and then click on 'OK'.
After a few seconds (or
so), the new IP address will be in place and you
can configure the device.
When you have given your new device its new IP
address so that it is on your LAN, you will have to
change the computer's IP address back again just by
repeating the process.
Which Server Operating System?
Servers for small- to medium-sized enterprises (SMEs)
tend to be based upon PC architecture and therefore will
run many different operating systems. Usually, this means
that you end up running Windows on the server as this is
what servers tend to have on them when you buy them but
you are not necessarily stuck with Windows as this is not
the best choice. Here's why...
Unlike a desktop PC, a configured server only needs to
communicate with the outside world through its network
connection. Like things such as software firewalls and so
on, anything that is running that is of no use just gets
in the way as far as memory and other resources go; and
also, extra processes that are not part of the server or
its supporting processes only serve to weaken the
security (including reliability) of the server - things
such as buffer overruns, resource conflicts which both
allow malicious users to gain a foothold and genuine
user's experiences being degraded.
So, what do we actually need to run on a server? The
following is not an exclusive list but it gives an
- Operating system kernel so that other things can
- Server software such as a web server or smtp/pop3
server and so on;
- A firewall - just a basic one if you have another
dedicated firewall as all you need to do is to
make sure that anything that has broken through
the outer layer of perimeter security has yet
another obstacle in its way.
You certainly don't need to run a GUI. It is possible
to set up a server completely without using a GUI but
today, a GUI makes things so much easier. However, once
you have your server configured, you need to shed the GUI
as it becomes nothing more than a parasite - stealing
your resources and giving nothing in return.
So how can this be done with Windows? Unfortunately,
the GUI is designed to be a part of Windows so the
Windows Operating System is not suitable.
It seems a little like wishful thinking so, can it
really be done with anything else? The answer is yes. If
you are running one of the Unices such as Linux, the
operating system on boot up goes through a number of
levels of operation call 'Runlevels':
- Runlevel 2 gives you a standalone system;
- Runlevel 3 gives you a networked system;
- Runlevel 5 gives you a networked system with a
- Runlevel 6 reboots the system.
You get a Runlevel (in increasing order) by typing
as 'root' at the command prompt - in this case to
start run level 5.
to set up your server, you boot up into Runlevel
5 and once you have everything running the way
you want it - so that everything runs on boot up
- you go and set the default Runlevel to 3. This
can be done in SuSE Linux using the Runlevel
next time you boot your server, it will only go
as far as Runlevel 3 which means that you have
everything running except the GUI. You can still
log on and edit files and so on as long as you
are familiar with a command line text editor or,
if you want, you can copy files to another
machine, edit them there and then copy them back
you want to use your GUI, all you do is log in as
root and then type
edit the configuration files, install drives
or whatever you need to do and then reboot into
run level 3.
IP v USB
USB cameras are limited in so far as they have to be
within 5 metres of a computer which in effect ties up a
computer. In addition to this, computers consume quite a
bit of power so if you are thinking about having one with
a UPS, it will not be able to keep taking images for such
a long time.
With an IP camera, they only take around 15 Watts so a
UPS that would give life to a medium-sized computer for
15 minutes will last considerably longer. In addition to
this, you are not tying up a computer and, you can have
the IP camera up to 100 metres from any other piece of
hardware such as a switch although you do need a mains
supply nearby (some of the more expensive ones can have
power over Ethernet which means that your power supply
can be as far away as the other end of the Ethernet cable
ie, up to 100 metres).
Clearly IP cameras have a definite advantage but
another thing to consider is that some IP cameras can be
Wireless. With regard to wireless, I would avoid it if
you are using the cameras for security work as wireless
generally is far more vulnerable to attack.
If you log into one of these cameras and then sniff
the traffic, you will probably find that the browser is
looking for an image called something like ...
... or some similar superficially meaningless string
after the JPG part of the URI. Rather than try to
second-guess this (it is often the time), you can usually
get the latest image just by typing in ...
So, if you have a local web page that reloads itself
every few seconds or so (depending upon how much network
capacity you can afford) then, each time it loads, it
will load a new image from the camera.
You can, of course,
use these cameras for anything you like so, if you look
at the image on the right, you can see that it is
possible to work and keep an eye on the Guinea Pigs in
their pen on the front lawn at the same time.
If you want to cut down on the web page content or
have a number of them on the same page, you can put them
in iframes so that each reloading page has its own little
bit of the browser window.
As far as logging into a number of cameras at the same
time is concerned, (most) browsers (certainly all of them
that display images that I have come across) will
maintain many current realm/userid/password combinations
so that you don't have to log in repeatedly.
Example Web Page
Although this is
not a real IP camera web page, it does demonstrate some
of the potential of the system. Click on the image on the
right to load it in another browser window.
The difference is that instead of having four cameras
with different IP addresses - of which each needs logging
into the first time - we have a common directory with a
series of images in it that represent four cameras. Each
of these images is called by a self-loading page that
sits within an iframe in the main page.
It is fairly easy to modify this so that each image
page loads itself so that a fresh image is loaded and
also, instead of waiting 10 seconds (as in this example)
to put a self-referencing link on each image so that if
you click on the image, it refreshes instantly (in this
example, it just loads the next one in the sequence).
In the real situation, you could have a set of these
pages as indicated by the mock menu down the left hand
side of the example page.
Back to PC Plus Archive Index Page