IBM i series Handbook page 585

TCP/IP Connectivity Utilities (5722-TC1)
Internet, e-business, and other
network server applications utilizing
Asynchronous I/O Completion Ports
design models and APIs should allow
a much smaller pool of threads to
process work from clients when
compared to other design models and
APIs. In the typical threaded server
application design model, there is
usually one thread per client
connection. Each thread, especially in
applications where there is
intermittent data flow being
exchanged, such as an interactive
application like TELNET, spends
much of its time waiting for data. This
means each thread expends CPU
cycles going to sleep when no data is
available or waking up when data finally becomes available.
Applications using Async IOCP designs and APIs should allow any of the applications
threads to service any client. This means fewer threads are needed per server application,
and each thread is constantly kept busy. Therefore, little or no system resource is consumed
by the server application's threads either waiting for data, going to sleep, or waking up. This
means that for many Internet or e-business applications designed and written to use Async
IOCP APIs, there can be a drastic and dramatic reduction in CPU utilization rates. In general,
less system CPU resource, less paging resource, less system memory, and less system
storage is needed by Async IOPCP-enabled applications.
Sockets on the system are based on and are compatible with Berkeley Software Distributions
(BSD) 4.3 sockets. Application programs written in the Integrated Language Environment
(ILE) C/400 language can use the sockets API.
Secure Sockets Layer (SSL) is a security protocol that provides privacy over an open
communications network (for example, the Internet). SSL protocol allows client/server
applications to communicate in a way that is designed to prevent eavesdropping, tampering,
and message forgery. Many applications on the iSeries servers are SSL enabled in V4R4,
including TELNET, HTTP server, CA/400 host servers, systems management, and LDAP.
Also, OS/400 SSL support includes a set of APIs, which, when used in addition to the existing
OS/400 sockets APIs, provide the functions required for applications to establish secure
communications.
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TCP/IP Connectivity Utilities (5722-TC1)