I am not sure where else to ask this, so here goes:
I have got a small office network (15 Computers) which is sharing a (supposedly) 20 Mbit Internet Connection. The ISP provides us with a single DHCP IP address, which is used by (the one and only) router, to share it amongst other computers on the network. The router has got NAT (Network Address Translation) and a DHCP server enabled, to provide each computer with an individual local IP address per computer. Oh, and all the connections are multiplexed via a switch. This is shown diagrammatically as follows
A very crude dig. but it helps to illustrate the network setup I currently have. The problem is this, it's fine when around 5 ppl are using the network, but the moment it goes beyond that, the network capacity "fluctuates". What I mean by this is, that if somebody starts using the network to say e.g. download a file, everybody else feels the strain and everyone's network speed falls. That is not really surprising given that we are sharing a network and I am assuming we just tend to reach the limiting point in network. My question is this, how can I modify the network so that I can gaurantee everybody atleast a min. amount of bandwidth - or cap everybody's speed to 1 Mbit so that in that way at least the network will be more homogenous to access?
Any suggestions appreciated, I have been hacking on this problem for ages but I can't seem to find any solution, or even a way to go about doing this. The router's own management console is "primitive" and doesn't allow much conifguration. For reference, in case it helps anybody, it's a