.Net Remoting is the successor of Distributed component object Model(DCOM). Both these technology are introduced by Microsoft that enable inter-process communication across application domains. DCOM was very successful technology. But it is never treated as best technology for inter-process communication because of lack of its support for interoperability across platform.
.Net Remoting is a new technology that ship with .Net Framework. It has all those features which are missing in DCOM. There are other pain involve with DCOM such as difficult to control format or channels, message trace is painful, change in configuration setting such as channels or port is not easy. DCOM is hard to learn and complicated to deploy and to maintain.
Differences between these two technologies are as follows.
DCOM technology is based on the COM architecture whereas .NET Remoting is primarily based on .NET Frameworks.
DCOM is based on proprietary binary protocol which is not supported by all object model, thus has big drawbacks in the internet world.
DCOM is based on RPC protocol whereas .Net Remoting can use TCP or HTTP protocol which is stardard protocal in the market.
DCOM is not firewall friendly, can't choose port. .Net Remoting, on the other hand, works easily across firewalls.
.Net Remoting supports cross platform communication which is not possible with DCOM (only for windows platform).
Components created DCOM involves complex deployment in windows registries whereas .Net Remoting involves easy deployment using either xml based configuration file or programmatically in the code.
DCOM uses windows security features whereas .Net Remoting can use security features of IIS if hosted with ASP.NET. .Net Remoting, if hosted other than ASP worker process, allows to create own security mechanism for the application.
In DCOM, server is started by Service Control Manager (SCM) upon receiving the activation request from the client whereas in .Net Remoting, IIS is responsible to start server service. If not hosted with IIS then client request will fail if the Remoting server is not already started.
DCOM manages remote object lifetime by frequent pinging of clients whereas .Net Remoting has more efficient leasing mechanisms to maintain object lifetime.