Dear liranc,
what you are asking as an answer is already there under the Networking section of firewall.cx. if you can go through all the chapters one by one following the sequence, then you will be able to understand the basics of networking, and also be able to refresh you memory on all that you might have learnt about networking but cannot recall right now.
i had a similar problem some years ago, and i used this to refresh my knowledge up. trust me, its a good way of learning. and if you have any questions, then you can post them in this same forum (i.e. Basic Concepts), and i'm sure there will be someone to help you out straightaway. incidentally i became known to firewall.cx through my subnetting forum in this section. people around here are really helpful, and you wont have any problems.
and about your english, don't worry mate, as long as someone can understand your query, and answer it, you should be fine. your so - called bad english should not be a obstacle to your path to becoming a networking expert!!!
so get cracking and enjoy it while you are here.
Picking pebbles on the shore of the networking ocean
