Communications Server for z/OS V1R7 TCP/IP Implementation, Volume 1: Base Functions, Connectivity, and Routing

Chapter 1. Introduction 9

can execute in TSO, online, or batch. The REXX sockets programming interface supports

AF_INET and AF_INET6.

Refer to z/OS Communications Server: IP Sockets Application Programming Interface Guide

and Reference: z/OS Communications Server: IP Sockets Application Programming Interface

Guide and Reference Version 1 Release 7, SC31-8788-05, for complete documentation of

the TCP/IP Services APIs.

1.3.6 z/OS Communications Server applications

z/OS Communications Server TCP/IP support provides a number of standard client and

server applications, including:

򐂰 SNA 3270 Logon Services (TN3270)

򐂰 z/OS UNIX logging services (syslogd)

򐂰 File Transfer Services (FTP)

򐂰 Network Management Services (SNMP Agents, Subagents, Trap forwarding)

򐂰 IP Printing (LPR, LPD, Infoprint Server)

򐂰 Internet Daemon Listener (INETD)

򐂰 Mail Services (SMTP and sendmail)

򐂰 z/OS UNIX logon services (otelnetd)

򐂰 Remote Execution (REXECD, RSHD, REXEC, RSH, orexecd, orshd, orexec, orsh)

򐂰 Domain Name Services (Caching DNS BIND9 server)

These applications are discussed in detail in Communications Server for z/OS V1R7 TCP/IP

Implementation, Volume 2 - Standard Applications, SG24-7170, and the z/OS V1R7.0

Communications Server: IP Configuration Reference, SC31-8776.

1.3.7 UNIX Systems Services

UNIX System Services is the z/OS Communications Server implementation of UNIX as

defined by X/Open in the XPG 4.2. UNIX System Services coexists with traditional MVS

functions and traditional MVS file types (partitioned data sets, sequential files, and so on). It

concurrently allows access to z/OS UNIX file system files and to UNIX utilities and commands

by means of application programming interfaces and the interactive shell environment. CS for

z/OS IP offers two variants of the UNIX shell environment: The z/OS shell (the default shell)

and the tcsh shell (or Ishell) (an enhanced version of the Berkeley UNIX C shell). The

Communications Server for z/OS IP requires that UNIX System Services be customized in

full-function mode before the TCP/IP stack will successfully initialize. We will therefore

conduct an overview of UNIX System Services to provide an appreciation for the coding and

security considerations involved with UNIX System Services.

Customization levels of UNIX System Services

There are two levels of z/OS UNIX services:

򐂰

Minimum mode, indicating that although OMVS initializes, it provides few z/OS UNIX

services, and there is no support for TCP/IP and the z/OS shell. In this mode there is no

need for DFSMS or for a security product such as RACF.

򐂰

Full-function mode, indicating that the complete array of z/OS UNIX services is available.

In this mode DFSMS, RACF, and the z/OS UNIX file system are required. TCP/IP and

z/OS UNIX file system interaction with UNIX System Services is defined within the

BPXPRMxx member of SYS1.PARMLIB.

z/OS V1R7.0 UNIX System Services Planning, SA22-7800, provides a good description of

the UNIX System Services customization process. It also includes a chapter devoted to

TCP/IP.