TCP/IP layers

Figure 1 shows the TCP/IP layers that reside in the z/TPF host and those that reside in the 3745 or 3746 IP router.
Figure 1. TCP/IP layers
Figure 2 shows the TCP/IP layers that reside in the z/TPF host and those that reside in the 374x Internet Protocol (IP) routers and the Open Systems Adapter (OSA)-Express card.
Figure 2. TCP/IP layers with OSA-Express support
The following layers reside in the z/TPF system:
  • The socket layer
  • The protocol layers, which are Transmission Control Protocol (TCP) and User Datagram Protocol (UDP)
  • The IP layer
  • Two link layers:
    • IP over channel data link control (CDLC) protocol, which is used to communicate with the IBM® 374x routers.
    • The queued direct I/O (QDIO) protocol, which is used to communicate with the Open Systems Adapter (OSA)-Express card.
The following layers reside in the IP router:
  • The IP layer
  • Multiple link layers.

The IP router performs standard IP routing. The IP routers have no knowledge of sockets. Instead, the routers just forward packets based on the destination IP address of the packet.