Networking on z/OS
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Subarea networking

Networking on z/OS

The initial implementation by IBM was the SNA subarea network. This network is a hierarchical network implemented by the Virtual Telecommunications Access Method (VTAM) in the mainframe. VTAM is the software that controls communication and data flow in an IBM mainframe SNA network. VTAM resides in the mainframe and supports a wide variety of network protocols, like SDLC and LAN.

VTAM controls data transfer between channels and OSA LAN-attached devices and performs SNA routing functions.

VTAM provides an application programming interface (API) that enables the development of application programs that communicate using SNA with remote application programs or devices.

Currently, VTAM is part of Communications Server for z/OS and is called SNA services.

  • SNA nodes
    An SNA node is a set of hardware and associated software components that implement network functions.
  • System services control point (SSCP)
    A type 5 subarea node contains a system services control point (SSCP). An SSCP activates, controls, and deactivates network resources in a subarea network. In order to control and provide services for its subordinate nodes, an SSCP establishes sessions with components in the network.
  • Subareas and domains
    In a subarea network, every T5 and T4 node is assigned a subarea number. The subarea number has to be unique in the SNA network.
  • Connecting subarea nodes
    To establish a cross-domain session, that is, a session from a resource located in one domain to a resource connected in another domain, you have to have physical connections (channel, OSA, communication lines) in place to define the logical connection between the subarea nodes (T5 and T4 nodes).
Parent topic: Systems Network Architecture - basics and implementation

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