OSA (Open Systems Adapter)

In the past network connections used the normal CSS (Channel SubSystem)together with external network controllers.

Today the channel subsystem can still be used for VTAM and TCP/IP network connections, either connecting a network device to the mainframe with a FICON CCW channel or directly between mainframe operating systems using coupling channels, HOWEVER

Normally a different technology is used to connect mainframe directly to external networks
It is called Open Systems Adapter (OSA), it is a hardware card that plugs into the mainframe and allows it to connect to standard Ethernet network infrastructure for TCP/IP connections.

The first OSA adapters were effectively network controllers that communicated with the mainframe using internal connections to the normal channel system
Standard networking configurations including Ethernet, FDDi and Token Ring were supported.

The current OSA cards, called OSA Express are faster and bypass the channel subsystem completely. They only support Ethernet, including Gigabit Ethernet and 1000Base-T

Hardware Management Console (HMC)

Hardware Management Console can be used to create and manage a configuration source file for the Open Systems Adapter - Integrated Console Controller (OSA-ICC) which is used to provide operating systems with z/OS consoles.

Shared Memory Communication (SMC)

SMC is a protocol that can improve throughput by accessing data faster with less latency by allowing two peers to transfer data using system memory buffers that each peer allocates for its partner to use. System-system communication can be done via two methods

• SMC-Direct Memory Access (SMC-D)
  • Data is transferred between systems that are within the same CPC using internal shared memory (ISH) (or ISM I guess) technology, providing virtual adaptors to allow intranet-system communication between each TCP socket endpoint within the same system. This means that no additional hardware is required.
• SMC-Remote Directory Access (SMC-R)
  • This allows data to be transferred between two separate systems in different CPCs using remote direct memory access (RDMA) over Converged Ethernet (RoCE) technology. This will need an RDMA-enabled network card (RNIC)such as 25 GbE RoCE Express 2.1 and 10 GbE RoCE Express 2.1

Hipersockets Can also be used to achieve connection like OSA, just without the hardware, within the same CPC