Can anyone explain how an ISP network works?

I mean when I dial up to my ISP,I connect to their network.

so this means that whatever security rules they have setup on their network apply to me,OK

Now if they block ports,I can't use them.Even if they are enabled on my PC and the remote.
So all illegal packets sent from my PC go straight to their router where they are dropped?

I'm confused ,help....

Babaton.

Correct... I presume you've got problems with netbios too.
If you isp blocks port 135 nomatter if you have it enabled you will not receive any traffic on it. You're on your isps network and as you say you're subject to their rules

OK,if thats the cse then does anyone know of any ISPs which are a bit more liberal.

BTW i'm in the UK,I don't want to dial internationally for my connection.

Cheers.