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AIX Versions 3.2 and 4 Asynchronous Communications Guide

Software Features

The Network Terminal Accelerator adapter provides unique integration of standard networking protocols with a host interface similar to a multiplexer. While networked communications servers such as the IBM 7318 Model P10 and S20 view the adapter as a host that offers standard Telnet or rlogin terminal services, the host computer views the adapter as a simple, efficient, serial multiplexer and a standard Ethernet interface. The adapter supports both 802.3 Ethernet thin (BNC) and thick (DIX) wiring.

The adapter's serial multiplexer capability makes the intervening network and its protocols invisible to the host. The host appears to communicate directly with the serial ports of the networked communication server devices. The multiplexer capability completely removes time-consuming network interface tasks from the host, including all network packet interrupt and TCP/IP protocol processing and, more importantly, the telnetd daemon, which runs as a user-level process. In addition, this capability eliminates the high overhead of processing context switches normally associated with network-connected terminal I/O.

While the adapter insulates the host from networked terminal I/O processing, it provides most of the communication capability of a standard Ethernet interface. This capability is provided by two unique IP addresses for the adapter's single Ethernet interface. The serial multiplexing software is addressed with its own IP address. The standard Ethernet software is addressed with a different IP address. Users must use the IP address appropriate for their application.

POSIX Functions

The serial multiplexing software provides additional tty processing beyond the protocol processing already mentioned. It handles special character recognition, line buffering and editing, echoing, character translation, and tab expansion. These functions are compliant with the POSIX 1003.1 standard, as applicable to network-attached terminal devices.

Network Terminal Accelerator Devices

The Network Terminal Accelerator subsystem maps to several AIX logical devices. Each adapter in a system must have a corresponding "raw" device named in the /dev directory. Any of the commands that configure or report status on an adapter use this raw device interface. For example, the ntx_load command opens a raw device to load the microcode onto each adapter. All Network Terminal Accelerator commands that open a raw interface to an adapter default to /dev/rhp0. If you have more than one Network Terminal Accelerator adapter installed in your system, you can use the ntx_load -d command to override the default and select another raw device name.

For each adapter installed in a system, there can be up to 256 child devices (2048 on some systems). Each of these corresponds to one channel on the associated adapter. Once the adapter is downloaded and configured, the child devices implement standard interfaces to I/O ports on terminal servers on the network.

Network Terminal Accelerator supports three child device types: hty, tty, and lp. Support for the "generic" tty and lp devices allows for the configuration of channels with these familiar interfaces.

Both hty and tty devices provide the same termio interface. The only difference between them is the name used for the device node in the /dev directory and the SMIT panels used to add, delete, and configure them. The tty child devices can be configured through SMIT using the smit tty fast path. The hty child devices can be configured through SMIT using the smit htyDevice_menu fast path.

Printer devices (/dev/lp*) provide a standard AIX line-printer interface and are configured using the smit pdp fast path.

Simple Network Management Protocol (SNMP)

The adapter provides an SNMP agent on the adapter for managing the adapter and its associated software. This agent does not manage the host or host software. Once configured, this agent responds to protocol data units (PDUs) received from the network. The adapter's SNMP agent complies with Management Information Base (MIB) II (request for comment 1213).

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