# Protocol Requirements

A TIBCO messaging client for z/OS must be installed and operated within a previously existing, fully functional, and integrated network.

At a minimum, this requirement includes the following conditions:

- The Transmission Control Protocol (TCP) and Internet Protocol (IP) stack, called the TCP/IP stack, within z/OS Communications Server.
- A Domain Name System (DNS) server that provides the host name and host address of the z/OS client, and the TIBCO EMS server.
- Unrestricted network connectivity among the DNS server, TIBCO EMS Client for z/OS (MVS), and the TIBCO EMS server.

Be sure to run a properly configured and customized z/OS `RESOLVER` address space. Also, ensure that your TCPCONFIG parameters meet the following installation requirements:

- To run the TIBCO messaging client non-APF authorized, use the RESTRICTLOWPORTS parameter.
- To control TCP buffering, limit storage usage, or support large bandwidth devices, you might have to use the TCPSENDBFRSIZE, TCPRCVBUFRSIZE, and TCPMAXRCVBUFRSIZE parameters. TIBCO typically recommends that you override the IBM default value of 16 KB by setting the TCPRCVBUFRSIZE and TCPSENDBFRSIZE parameters to a minimum value of 48 KB.

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