Networks Analyzed @ Netralized

Every ip address belongs to a specific class.
The ip address classes are:

But how is an Ip address related to a class?

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Nowadays a lot of people talk about DSL but what exactly is the DSL technology?

In this article I will try to give you a very brief overview about DSL and how it works.

DSL (Digital Subscriber Line) is an OSI layer 1 technology that allows you to deliver extra bandwidth and high speed data connections over a copper wire pair that is typically used for phone connections. This technological breakthrough is based on the research of Bell Labs that several years ago identified that a typical conversation on the telephone only uses a small frequency range of the available frequency spectrum (from 300HZ up to 3KHZ). That leaves all the other frequencies range up to 1MHZ, free to be used for other services.
Therefore, DSL uses our existing phone lines with very few changes from the phone company side, giving us extra services.

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Many of us have a DSL connection at home. Most of us can configure the DSL router by our selves and most of us can even port forward the ports that are needed. But do we really know why and when it is needed to be done?

Let’s say we have a DSL connection installed at our house or our business. We have three computers, all getting Internet from the same router with Ethernet or wireless connections. Let’s also suppose that we have a web server installed on one of the three computers listening to TCP port 80.

When someone from the Internet tries to access our web server, his browser sends a request at port 80, but our router doesn’t know to which computer the request should be forwarded, since all three of them have the same Internet IP address. As a result, the host (our web server) becomes unreachable.

When we do port forwarding, we assign to the router instructions that when someone from the internet requests information from a specific port (80 in our case), the request should be forwarded to a specific computer identified by its local IP address, 192.168.xxx.xxx for example. The local IP, that the computer hosting the web server has, is usually assigned from the DHCP of the router. Therefore, when someone asks information on that port, router forwards the traffic automatically to the specified computer based on the information we’ve entered to the router.

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