IBM Communication Controller for Linux on z Systems considerations

With IBM® Communication Controller for Linux on z Systems™ (CCL), you can run your existing NCPs (possibly with minor configuration changes) on a Linux on z Systems (CCL). CCL provides an environment that mimics many of the functions provided by the 3745 Communication Controller hardware. The existing NCP product can run unchanged on a IBM z Systems Linux machine. See the CCL product documentation for more information about IBM Communication Controller for Linux on IBM z Systems.

When the CCL product first became available, only LAN (token-ring or Ethernet) connectivity was supported by CCL. As a result, the only way to attach one of these early CCL NCPs to VTAM® was through an External Communications Adapter (XCA) major node (the VTAM representation for LAN links). Because only XCA attachment was supported by CCL, VTAM provided support that enabled you to activate CCL NCPs over subarea XCA links. Before this support, you could configure VTAM to attach to NCPs over subarea XCA links and to use the virtual routes (VRs) and explicit routes (ERs) defined over these links for SSCP and LU sessions but you could not activate and own NCP resources over subarea XCA links. The new support enables you to activate (own) CCL NCPs that are directly attached to VTAM through an OSA port configured in LCS mode. The LAN attachment to VTAM is provided through an XCA-attached device (typically provided by another OSA port configured in SNA mode). In most cases, CCL NCPs attached to VTAM in this manner are treated as remote NCPs (rather than local NCPs, which implies that they are channel-attached).

Because CCL does not mimic all of the functions provided by the 3745 hardware, some functional limitations exist when running NCPs on the CCL engine when compared to running NCPs on real 3745 hardware. This information describes the operational differences and functional limitations of running NCP on the IBM Communication Controller for Linux on z Systems product (CCL NCP), compared to running NCP on real 3745 hardware (3745 NCP).

The IBM Communication Controller for Linux on z Systems V1R2 (and later) introduced additional connectivity options, including support for the new OSA OSN device, which appears to VTAM as an ESCON CDLC channel. The OSN support is fundamentally not apparent to VTAM. When the OSN CHPID and devices have been configured in your input/output configuration data set (IOCDS), modify your NCP definitions to specify one of the 3745 channel addresses configured for the OSN (3745) device on the CUADDR operand of the corresponding PCCU definition statement. CCL NCPs attached to VTAM using an OSN device provide the same functions and capabilities as channel-attached 3745 hardware; that is, they are not subject to the same operational differences as XCA-attached CCL NCPs.

Unless explicitly stated otherwise, the information presented in the following sections pertains only to CCL NCPs that are attached to VTAM using an XCA major node.