DISTRIBUTED COMPONENT OBJECT MODEL - A STUDY OF ITS ARCHITECTURE AND WHY IT IS CONSIDERED A FAILURE BY EXPERTS.

DISTRIBUTED COMPUTING PROTOCOLS CORBA Java’s RMI DCOM

ADVANTAGES OF DISTRIBUTED COMPUTING Speeding up development processes Improving deployment flexibility Lowering maintenance costs Improving scalability Load balancing

REGISTRIES AND KEYS A Registry is the place where the components installed in a machine store their settings. The ‘registry’ contains many sections called keys. The keys contain value data such as Class ID and Application ID.

ARCHITECTURE OF DCOM

THE FIVE COMPONENTS OF DCOM Object Instantiation Process Data transferring between clients and components Security in DCOM The DCE RPC component The low-level protocol stack

OBJECT INSTANTIATION PROCESS Clients use COM’s "create instance" functions such as CoCreateInstanceEx, CoGetClassObject, etc. to create a new instance of a component. To specify the server on which a component resides, DCOM employs the notion of RemoteServerName

Data transferring between clients and components Marshaling : is the process of reading parameters from the stack into a flat memory buffer (that will be transferred across "the wire" later.) Unmarshaling :it reads the memory buffer and re-creates the stack that is the same as the caller’s stack.

Security in DCOM Access Security Launch Security Identity Security Connection Policy

IS DCOM AN UNQUALIFIED SUCCESS? Initially, DCOM was a major competitor to CORBA. There were difficulties in getting them to work over internet firewalls. DCOM and CORBA lost out to web browsers combined with http requests.

THE MS-BLASTER WORM DCOM RPC Interface Buffer Overrun Vulnerability TCP port 135 is overrun by a large amount of data This allows the remote system to gain local system privileges on tcp port In essence it causes a ‘DENIAL OF SERVICE’ error for microsoftupdate.com. Microsoft did come up with a patch to rectify the ‘buffer overrun in msrpc’. The patch is available at S mspx. S mspx

DCOM SUPPORTERS All said and done DCOM is not without its supporters. SAP DUNN and BRADSTREET SYBASE