[Laskey99] Section 5.3. MultiProtocol Interchange

5.3. MultiProtocol Interchange

Modern networkscan be extremely complex, supporting multiple network protocols in alarge, geographically dispersed network. In order to truly supportnetwork independence, SQL*Net must be able to communicate using morethan one protocol. For example, a truly independent and open systemwould allow a workstation running IPX/SPX in a Novell environment toaccess an Oracle server running TCP/IP in a Unix environment. Toprovide this capability, Oracle developed the MultiProtocolInterchange (MPI).

The MultiProtocol Interchange performs protocol conversions to allowSQL*Net data originating on a network utilizing one protocol to flowto a network utilizing a different protocol. Figure 5.4 shows a node on a network running IPX with theMPI in the center connecting to a network and server running TCP.

Figure 5.4. Using MultiProtocol Interchange

As can be seen from this figure, the MultiProtocol Interchangerequires:

• A host machine (which may be a PC)

• The MPI software

• Two or more network interface cards (NICs), one for each supported protocol

• Appropriate software to implement the supported network protocols

Because the MPI utilizes multiple NICs, it is able to convert datanot only from one protocol to another, but also from one physicalnetwork implementation to another. For example, a MultiProtocolInterchange may convert SQL*Net data from token ring to 10BaseT.

The MPI runs as a process on a host machine, which may be as simpleas a PC workstation. The MPI is configured using the Oracle NetworkManager, which specifies the location in the network of anyMultiProtocol Interchanges in use, as well as routing information(including cost data) and the protocols supported.

The MPI consists of alistener and a data pump.These components function in a manner similar to the SQL*NetMulti-Threaded Server, which provides a listenerand a server process. When the MPI listenerdetects a connection request, it allocates a data pump to handle theconnection. One or more data pumps may be available, and each datapump is able to handle a single protocol.

The MPI is controlled using the programintctl. This programis similar to the SQL*Net lsnrctl and OracleNames namesctl programs, and provides theability to start, stop, and obtain status information on theMultiProtocol Interchange.

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