• Example: SQL*NET + TCP/IP
  • In a client/server session, SQL*NET on the client side takes the SQL requests from the application and packages them for transmission. Once the network package is received by the server machine, SQL*NET software on the server side assembles the SQL statements from the network packet, then passes them to the Oracle7 database. When the Oracle 7 Server replies, the data is sent back to the client machine via the same mechanism. This procedure is the same for all network operating systems
  • OSI Model in this context
    • application layer - represents the interface between applications - such as Oracle Financials on the client workstation and the network communication software
    • presentation layer - defines the processes that rely directly on the session layer for network services
    • session layer - responsible for creating, closing, and coordinatin process-to-process connections. This layer permits the user to invoke file transfers and virtual terminal services
    • transport layer - responsible for reliable transmission of data, making sure messages are buffered, causing retransmissions fro garbled messages. This layer packages user messages for transmission by lower layers
    • network layer - defines the routing layer, where communications software decides which network pathways to use for message traffic
    • data link layer - defines level at which operating system driver routines control the hardware, sending or receiving a single message or byte string
    • physical layer - defines the software that supports the actual physical medium used and the electronic signals transmitted, i.e., wire or cable. Software found here supports Ethernet, Token Ring, or other network media
  • SQL*NET software resides at the presentation layer
  • Oracle Protocol Adapters reside at the session layer (TCP protocol adapter)
  • The physical, data link, and network layers are invisible to Oracle Software
• Hardware