Networking on z/OS
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TCP/IP Profile statements

Networking on z/OS

The primary configuration point for the TCP/IP stack on z/OS is the TCP/IP profile data set. It defines operating characteristics of everything that is under the umbrella of the TCP/IP stack.

Some of the more significant statements found in the TCP/IP profile are:

  • IP link and address configuration (DEVICE, LINK and HOME statements)
  • IP configuration (IPCONFIG statement)
  • TCP configuration (TCPCONFIG statement)
  • Static routing information (BEGINROUTES statement)
  • Automated IP application monitoring (AUTOLOG)

It is impractical to discuss all statements found within the TCP/IP profile. Further, it is not even practical to discuss all parameters within each of the chosen statements. Keep in mind that even the statements discussed have other parameters available that have been omitted in order to keep the discussion to a reasonable scope. All TCP/IP profile statements have default values that are used when they have not been explicitly coded.

  • Link configuration
    TCP/IP supports more than a dozen different types of device attachments to the network. The most significant one is the OSA-Express adapter. There are two statements involved in configuring any adapter for TCP/IP on a z/OS host: a DEVICE statement and a LINK statement.
  • IP configuration
    The IPCONFIG statement group can be used to control characteristics related to the IP layer function of the TCP/IP stack. Some of these parameters are related to sysplex functioning.
  • TCP configuration
    The configuration of TCP layer parameters is controlled with the TCPCONFIG parameter. The most significant parameters within this statement block are the parameters controlling the size of send and receive buffers. These parameters can have a significant impact on network performance, particularly when doing bulk data transfer.
  • Static routing information
    The big advantage of static routing is the simplicity. A static route identifies a destination and the appropriate link to take to reach that destination. Static routing usually takes advantage of default routes: when the destination is not explicitly coded, send the packet to the default router and let that router figure out how to get the packet to its destination.
  • Automated IP application monitoring
    All IP applications on z/OS require the TCP/IP stack to be running in order for IP communications to occur. It seems reasonable that when TCP/IP is started, the associated IP servers should be started at the same time. Better still, if TCP/IP can start these applications, why not have TCP/IP monitor them to make sure they continue to run correctly?
  • Generic servers and multiple TCP/IP instances
    Autologging has some limitations. For example, in an environment running more than one TCP/IP stack at the same time, an application like FTPD makes its services (listening port) available to all active TCP/IP stacks in the LPAR. In such a context, FTPD is referred to as a generic server. If FTPD is running with multiple TCP/IP stacks, then autologging could result in some confusion, as each TCP/IP stack attempts to stop and restart the FTPD server.
Parent topic: The TCP/IP profile

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