n tier Architecture issue involving net remoting

I have been asked to develop an n-tier application in .net such that the application has :
1. a database layer- makes calls to SQL server which could be anywhere in the network
2. a business layer
3 a presentation layer

database layer could be present on any n no of servers in our network and similarly business layer could be present on any no of servers in our network. Client making request from anywhere should be able to contact only the business layer and business layer should be able to contact database layer. There shouldn't be any direct contact of client and database layer.
Client could be a web site or windows application developed using .net



I can understand that I could make class libraries for business layer as well as database layer and I understand that I'll have to use net remoting for that. But, what I don't understand is/are

1. what objects(which layer) I should develop as remote objects using MashalObjByRef or Serializable attribute and
2. Which layer should be hosted in what host (e.g IIS or Windows service or web-serice) and why?


I've read and tried lot of examples and more I am trying, more I am getting confused. So, I need your help to really guide me especially on the hosting part. You can refer me to some link which discuss actuall design and implementation of remote object utilizing web service, windows service and IIS.


Will highly appreciate it.


Thanks