5 Conclusions

In this report we have examined five distributed communication mechanisms. Table 5 presents our conclusions in tabular form. Each of the transport methods have different advantages and are best suited for different situations. Some are very specialized and are only good for certain tasks. SQL/RDA is an example of this type of method. It was designed to allow queries of remote databases. It does this task well but it does not support general communication. OLE does support communication between application, but best support is only provided in the Microsoft Windows environment. By limiting the environment this way, OLE can provide integration at the level of the user interface. Distributed COM will most likely be at the same level as CORBA.

The three general mechanisms trade efficiency for ease of use. The lowest level is the socket interface, which is very fast and efficient, but must be programmed at the lowest level. RPC is a higher level transport that also supplies a programming language independent IDL. The highest support is supplied by CORBA. A CORBA user can ask for an object and let the CORBA implementation worry about where the object can be found. The tradeoff is that communication using CORBA is inefficient.

In the demonstration viewers we attempted to show a way to use the various mechanisms to their best advantage. By combining the transport methods, we were able to get support when needed and efficiency when that was needed. Using each of the distributed transport mechanisms where it was most effective allowed us to achieve the best overall performance for the entire system. This is more complicated in terms of program development, but the payoffs can be quite high.

CORBAOLE SQL/RDAsocketsRPC
ease of usehigher level Object Oriented API; Interface Definition Language low level API

encapsulating Object Oriented frameworks exist; Interface Definition Language

only requires knowledge of SQLlow level API

large amount of work to use, but very flexible

higher level

Interface Definition Language

language bindingsC, C++, Smalltalk, Ada C, C++, Visual Basic, various product control languages ASCII text using SQLC C
class of applicationdistributed object systems Microsoft Windows application integration distributed database operationshigh performance bulk transport distributed

client/server

securityunder development based on security available at the file level Access Control Lists at item level;

authentication strings

none (some research efforts)kerebos

secure RPC

protocols supportedTCP/IP; work on Interoperability not yet distributedTCP/IP TCP/IPTCP/IP
performance of transport serviceslow, still under development N/Afastfastest slow

Table 5. Project Conclusions

Up Previous Next