Introduction

The IBM® Z platforms provide the HiperSockets technology feature for high-speed communications among partitions. HiperSockets can provide in-memory TCP/IP¹ connections among LPARs running several different operating systems, including z/OS®, z/VM®, and Linux® on Z.

Although applications perceive no functional differences, HiperSockets require less processing overhead on either side of the connections, improving performance. Since they are memory-based, they operate at memory speeds, reducing network latency and improving end-user performance, especially for complex applications that would otherwise require multiple network hops to fulfill requests. HiperSockets also provide security benefits, especially on the memory key-protected mainframe, even without encryption, because there is no opportunity to intercept a network connection. Moreover, HiperSockets improve reliability and availability because there are no network hubs, routers, adapters, or wires to break.

KVM is a virtualization infrastructure that enables the Linux kernel to become a hypervisor with the ability to run a separate and distinct operating system in a virtual machine. Since 2015, IBM Z platforms have supported using KVM to create and run multiple virtual machines or guests in an LPAR.

KVM virtual machines currently use the Open System Interconnection (OSI)² Layer 2 (Data Link Layer)³ model to enable virtual network devices configured within the KVM guests to attach to and utilize network devices operating in the KVM host environment. The KVM host network devices and supporting software drivers then provide the means to allow the KVM virtual machine to communicate to other network resources located within or external to the KVM host environment. KVM guests require the KVM host interface being attached to also operate at Layer 2. This requirement limits KVM guests from directly attaching to interfaces configured to operate at Layer 3 (Network Layer)⁴. A Layer 3 interface is required to communicate with other LPARs installed with z/OS, z/VSE®, and potentially some z/VM guests.

The typical network cards used in IBM Z platforms are called Open Standards Adapters (OSA). OSA adapters have the ability to translate across OSA interfaces that are configured for Layer 2 and Layer 3 and are typically used to connect LPARs with different OSI model requirements. However, when using OSA interfaces, throughput and latency are limited to the capabilities of the OSA cards.

HiperSockets are capable of higher speeds and lower latency and can provide an excellent alternative for many KVM user scenarios.

This paper demonstrates how to set up, configure, and exploit the advantages that HiperSockets offer in an environment supporting KVM virtual machines.