Networking on z/OS
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TCP/IP in a sysplex

Networking on z/OS

A sysplex is a cluster of tightly-coupled independent instances of the z/OS operating system. The internal communications within a sysplex are facilitated by the Coupling Facility. TCP/IP takes advantage of the Coupling Facility and Workload Manager to optimize availability and load balancing in a sysplex.

Availability is enhanced by the ability to dynamically move IP addresses using dynamic VIPA. Sysplex distributor combines dynamic VIPA, Workload Manager, and autonomic computing to create the highest possible availability of an IP host.

Within a sysplex environment, OSPF is used to handle routing changes dynamically.

  • Computer cluster
    A cluster of computers refers to a group of interconnected computers that are working together as one unit. It is a relatively simple concept and it has been around, arguably, for a very long time. Within a cluster, individual computers can be coupled either loosely or tightly.
  • The z/OS sysplex
    A sysplex refers to a tightly-coupled cluster of independent instances of the z/OS operating system.
  • Dynamic virtual addressing
    The sysplex has been identified as a tightly-coupled cluster of computers with some workload balancing capabilities added for good measure. But how does the IP network take advantage of all this technology? The first part of the answer is the dynamic virtual IP address, or DVIPA.
  • Dynamic cross-system coupling
    XCF links can carry IP traffic. With DVIPA, XCF was used to communicate signalling information such as when a new instance of an IP address has been dynamically activated on a TCP/IP stack within the sysplex. The next step in the progression of utilizing a sysplex's capabilities is to use XCF to carry IP traffic.
  • Sysplex distributor
    IP address availability in z/OS can be viewed as a progressive evolution. Static VIPA eliminates the problem of an IP address being associated with a single networking hardware point of failure. Dynamic VIPA allows us to move such IP addresses in event of an application, TCP/IP stack, or LPAR failure. Next, dynamic XCF provides automatic generation of links to provide an automated IP layer of connectivity within the sysplex. Finally, sysplex distributor takes advantage of workload balancing.
  • The routing function in a sysplex
    You might wonder how to keep on top of the routing requirements of these shifting IP addresses and shifting TCP/IP stacks.
Parent topic: TCP/IP implementation on the mainframe

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