Designing Home and SME Networks 4: More on Architectures
OK, so the recommended architecture for home and SME networks is a bit like a tree, but let's not push the analogy too far.
In fact, most Ethernet-based architectures in use nowadays are based on the hub-and-spoke architecture.
This may be complicated rather by having smaller hubs at the ends of some spokes, and even more layers of hubs on yet more spokes, but, essentially, the architecture consists of a central device (originally a 'hub' but more likely nowadays to be a 'switch') connected by radiating links to the connected devices.
These links may be wired or wireless, but, essentially, the hub/switch acts to allow traffic from one spoke to pass through to other spokes.
Your DSL connection is merely a rather specialist spoke that allows the hub/switch on your network to talk to the hub/switch that supports whatever Internet device you want to communicate with.
Of course, it's not quite that simple, but you don't need to know how the Internet works! Hubs (and switches) are relatively unintelligent devices which will do whatever the incoming traffic tells them to do.
If your network was connected directly through a hub to an Internet that only contained hubs, then all the traffic on your network would be completely accessible to anyone on the Internet, and all the traffic to and from anywhere else on the Internet, even stuff not addressed to you, would clog up your DSL connection and nothing would work.
If it did manage to work, then your devices would be 'hacked' pretty quickly.
So, for this and other equally good but more technical reasons, you normally place a 'router' between your network and the outside world.
This is a device that examines the traffic passing through it and decides, according to a set of rules, what to do with it.
It acts as a traffic director, sending traffic via the correct route to the destination (hence 'router'), and a filter, keeping out traffic that is not addressed to you and blocking anything you (or whoever sets the rules) don't want it to pass.
This filtering function is also known as a (packet filter) firewall.
Now you have a router to keep your stuff in and other peoples' stuff out while allowing you to communicate with those people if you want to.
Of course, it's not quite that simple...
In fact, most Ethernet-based architectures in use nowadays are based on the hub-and-spoke architecture.
This may be complicated rather by having smaller hubs at the ends of some spokes, and even more layers of hubs on yet more spokes, but, essentially, the architecture consists of a central device (originally a 'hub' but more likely nowadays to be a 'switch') connected by radiating links to the connected devices.
These links may be wired or wireless, but, essentially, the hub/switch acts to allow traffic from one spoke to pass through to other spokes.
Your DSL connection is merely a rather specialist spoke that allows the hub/switch on your network to talk to the hub/switch that supports whatever Internet device you want to communicate with.
Of course, it's not quite that simple, but you don't need to know how the Internet works! Hubs (and switches) are relatively unintelligent devices which will do whatever the incoming traffic tells them to do.
If your network was connected directly through a hub to an Internet that only contained hubs, then all the traffic on your network would be completely accessible to anyone on the Internet, and all the traffic to and from anywhere else on the Internet, even stuff not addressed to you, would clog up your DSL connection and nothing would work.
If it did manage to work, then your devices would be 'hacked' pretty quickly.
So, for this and other equally good but more technical reasons, you normally place a 'router' between your network and the outside world.
This is a device that examines the traffic passing through it and decides, according to a set of rules, what to do with it.
It acts as a traffic director, sending traffic via the correct route to the destination (hence 'router'), and a filter, keeping out traffic that is not addressed to you and blocking anything you (or whoever sets the rules) don't want it to pass.
This filtering function is also known as a (packet filter) firewall.
Now you have a router to keep your stuff in and other peoples' stuff out while allowing you to communicate with those people if you want to.
Of course, it's not quite that simple...
Source...