gtpc1m0a | Transmission Control Protocol/Internet Protocol |
Transmission Control Protocol/Internet Protocol (TCP/IP) supports an interconnection of computer networks that provides universal communication services.
A computer network is a group of connected nodes used for data communication. A computer network configuration contains:
Figure 1 shows how the TPF system, running on a host processor and using an IBM 3172 Model 3 Interconnect Controller has access to local area networks (LANs), a wide area network (WAN), and remote applications.
A local area network (LAN) is a computer network that connects computer systems that are in a limited geographical area. A LAN has distance limitations.
A wide area network (WAN) is a computer network that is usually in different cities or even different countries and, therefore, provides communication services to a geographic area larger than that served by a local area network (LAN).
Figure 1. TCP/IP Sample Computer Network
The original TCP/IP support required an offload device (IBM 3172). That support enabled TPF applications to use the socket application programming interface (API) to talk to remote socket applications. The socket calls were passed to the 3172 by using the Common Link Access to Workstation (CLAW) protocol. The offload server code in the 3172 would then run the socket call. In this environment, a thin socket layer existed in the TPF system. The full socket layer TCP, UDP, and IP layers existed in the 3172. Later, support was added to allow TPF to connect to another offload device, specifically the Cisco 7500 router.
With TCP/IP native stack support, the stack is incorporated in the TPF system itself. The IP over channel data link control (CDLC) link layer is included with this support, enabling TPF to connect to more IP router boxes in addition to continuing to support offload devices (see Figure 2).
Figure 2. TCP/IP Native Stack Support Sample Computer Network Using Channel Data Link Control (CDLC)
With the introduction of an integrated hardware feature called the Open Systems Adapter (OSA) card, direct connectivity between IBM System/390 applications and remote TCP/IP applications is provided. Now, with the third generation OSA-Express card, OSA-Express support is enabled on the TPF system, allowing you to connect to high-bandwidth networks such as the Gigabit Ethernet (GbE or GENET) or Fast Ethernet (FENET). Queued direct I/O (QDIO) protocol is used to communicate between the TPF system and the OSA-Express card, enabling memory to be shared and reducing I/O. See Figure 3 for an example of TCP/IP native stack support and the OSA-Express interface. See Figure 4 for an example of TCP/IP native stack support combining both CDLC and OSA-Express interfaces.
Figure 3. TCP/IP Native Stack Support Sample Computer Network Using the OSA-Express Interface
Figure 4. TCP/IP Native Stack Support Sample Computer Network Using Combined CDLC and OSA-Express Interfaces