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TCP/IP Tutorial and Technical Overview - IBM Redbooks

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Principle of operation<br />

REXECD is a server (or daemon). It h<strong>and</strong>les comm<strong>and</strong>s issued by foreign hosts<br />

<strong>and</strong> transfers orders to subordinate virtual machines for job execution. The<br />

daemon performs automatic login <strong>and</strong> user authentication when a user ID <strong>and</strong><br />

password are entered.<br />

The REXEC comm<strong>and</strong> is used to define the user ID, password, host address,<br />

<strong>and</strong> the process to be started on the remote host. However, RSH does not<br />

require you to send a user name <strong>and</strong> password; it uses a host access file<br />

instead. Both server <strong>and</strong> client are linked over the <strong>TCP</strong>/<strong>IP</strong> network. REXEC uses<br />

<strong>TCP</strong> port 512 <strong>and</strong> RSH uses <strong>TCP</strong> port 514. See Figure 13-5 for more details.<br />

Figure 13-5 REXEC: REXECD principle<br />

13.3 Introduction to the Distributed Computing<br />

Environment (DCE)<br />

Distributed Computing Environment (DCE) is an architecture, a set of open<br />

st<strong>and</strong>ard services <strong>and</strong> associated APIs, used to support the development <strong>and</strong><br />

administration of distributed applications in a multiplatform, multivendor<br />

environment.<br />

496 <strong>TCP</strong>/<strong>IP</strong> <strong>Tutorial</strong> <strong>and</strong> <strong>Technical</strong> <strong>Overview</strong>

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