Internal queued direct communication (HiperSockets) support

HiperSockets provide a high speed internal TCP/IP connection between applications running on a CPC. These applications (for example, z/OS Communication Server or Linux for zSeries) can be in different z/VM images or different logical partitions. These "connections" are defined to the configuration with Internal Queued Direct (IQD) communication channel path types.

A CPC can support 4096 separate data queues. Typically each queue is represented by one data device and two control devices. IOCP ensures no more than 12288 (3*4096) valid subchannels are defined for all the IQD channel paths in the configuration. Valid subchannels are devices that are defined to a logical partition and permitted for use by the logical partition. Valid subchannels are calculated as follows:
  • For unshared channel paths, each IQD device defined in IOCP represents a single valid subchannel.
  • For shared channel paths, each IQD device defined in IOCP represents multiple valid subchannels based on the total number of logical partitions (LPs) in its device candidate list.

All devices defined on an IQD channel path should be defined with a device type (UNIT=) of IQD.

A CPC allows up to 16 or 32 (see Machine limits and rules for your processor) IQD channel paths. However, the only reason to define more than one is to ensure separation of applications or if IQD special functions are required. If you require all applications in the CPC to communicate with each other then only one IQD channel path is needed. If you require LPs in different CSSs to communicate, then the IQD channel path must be spanned. If you require one set of LPs to communicate with each other but not communicate with another set of LPs, then two channel paths need to be defined with each LP set defined in one of the CHPID candidate lists.

You can define up to 12288 valid subchannels or devices on a single IQD channel path. Use as many control unit (CNTLUNIT) definitions as needed to define the necessary number of devices.

You can define up to 256 devices per control unit. Each CNTLUNIT statement for the IQD channel path must contain a unique CUADD value. A maximum of 64 control units can be defined per IQD channel path.

The TCP/IP maximum transmission unit (MTU) and maximum frame size for internal queued direct communication is specified using the CHPARM keyword on the CHPID statement. The following CHPARM keyword values are supported:

  • 00 for 8 KB MTU and 16 KB frame size
  • 40 for 16 KB MTU and 24 KB frame size
  • 80 for 32 KB MTU and 40 KB frame size
  • C0 for 56 KB MTU and 64 KB frame size.

On 2828, 2827, 2817, and 2818 with enabling MCL applied or later processors, the following CHPARM values are provided:

  • 0x for 8 KB MTU and 16 KB frame size
  • 4x for 16 KB MTU and 24 KB frame size
  • 8x for 32 KB MTU and 40 KB frame size
  • Cx for 56 KB MTU and 64 KB frame size
  • x0 for a normal HiperSocket channel path
  • x2 for a HiperSocket for IEDN channel path
  • x4 for a HiperSocket capable to be externally bridged channel path.

Additional information about Internal Queued Direct Communication is in the z/OS® Communications Server IP Configuration Guide, SC31-8775.