Expanded asynchronous capability can be added to the system unit with direct-attached adapters using Micro Channel (MC), Industry Standard Architecture (ISA), or Peripheral Component Interconnect (PCI) buses; distributed subsystems; or by local area network (LAN) attached communications servers. Several factors will influence the type of asynchronous connectivity you choose. The following table summarizes these products.
| Asynchronous Attachment | Bus Type | Feature Code or Machine Type (Model) | Maximum Data Rate per Port (KBits/sec) | Salient Features |
|---|---|---|---|---|
| Standard serial port | System planar | n/a | Selectable based on baud rate generator clock speed of universal asynchronous receiver and transmitter (UART). | Standard feature |
| 8-Port EIA 232 | Micro Channel | 2930 | 76.8 | Pervasive standard |
| 8-Port EIA 422A | Micro Channel | 2940 | 76.8 | Greater distance |
| 8-port MIL-STD 188 | Micro Channel | 2950 | Selectable based on baud rate generator clock speed of UART. | MIL-STD 188-114 for unbalanced voltage digital interface |
| 8-port EIA 232 | ISA | 2931 | 115.2 | Greater efficiency |
| 8-port EIA 232 | ISA | 2932 | 115.2 | Greater efficiency |
| 8-port EIA 422 | PCI | 2943 | 230 | Greater efficiency |
| 16-Port EIA 232 | Micro Channel | 2955 | 76.8 | Local connection focus |
| 16-Port EIA 422A | Micro Channel | 2957 | 76.8 | Greater distance |
| 232 RAN | 8130 | 57.6 | Remote capability | |
| Enhanced 232 RAN | 8137 | 230 | Remote capability | |
| 16-Port RAN EIA 422 | 8138 | 230 | Remote capability | |
| 128-Port Controller | Micro Channel | 8128 | 230 | Efficiency, higher device counts |
| ISA | 2933 | |||
| PCI | 2944 | |||
| Serial Communications Network Server (P10) | Network Attachment | 7318-P10 | 115.2 | Greater distance, multihost, two parallel ports |
| Serial Communications Network Server (S20) | Network Attachment | 7318-S20 | 115.2 | Greater distance, multihost, two parallel ports, Serial Line Interface Protocol (SLIP), complressed SLIP (CSLIP), Point-to-Point Protocol (PPP), Kerberos security, TN3270 |
| Network Terminal Accelerator | Micro Channel | 2402 2403 | n/a | Offload Telnet and rlogin processing, 256 or 2048 sessions |
| Note: 1. Rack Mount RAN FC is 8136 | ||||
The first feature in this table represents the standard-attached serial ports that are standard with every system unit. The next five features are the direct-attached adapters. The 128-port asynchronous subsystem includes the remote asynchronous nodes (RANs) that attach to it. The next two features, models of the machine type 7318, are the LAN-attached asynchronous products that are communications servers attached to Ethernet LANs for connectivity to the system units. The last feature is the Network Terminal Accelerator that offloads protocol processing for LAN-attached terminal sessions.
Most system unit models have two integrated (standard) EIA 232 asynchronous serial ports as shown in the following figure. The Model M20/M2A features a single integrated asynchronous serial connector that can be converted to support two serial devices using an optional fan-out cable. EIA 232 asynchronous serial devices can be attached directly to the standard serial ports using standard serial cables with 25-pin D-shell connectors. Some multiprocessor systems have a third serial port used for communication to the remote service center.
Each of the direct-attached adapters requires a bus slot and can only be used in systems that support the required bus type. The Micro Channel 8- and 16-port adapters are relatively simple, meaning that very little processing of asynchronous traffic is offloaded from the system processor. The 128-port, ISA 8-port adapters, and PCI 8-port adapters are intelligent adapters that provide significant offload of the main system processor. As shown in the following figure, the 8-port and 16-port adapters use fan-out cables to connect to devices and require no additional power supply.
EIA 232 is the most common communication standard, but the EIA 422A (used when a longer cable distance is needed) is also supported by each direct-attached adapter for the Micro Channel. The EIA 422A implementation does not include device status detection capability. A Micro Channel 8-port adapter complying with the military standard (MIL-STD) 188-114 is also available. All adapters are supported on AIX Version 3.2 and AIX Version 4 with the exception of the ISA and PCI bus adapters, which are not supported on Version 3.2.
The 128-port adapter, available for the Micro Channel, ISA, or PCI bus, allows attachments of one to eight remote asynchronous nodes (RANs). Each RAN has 16 asynchronous ports for connection to devices and are separately powered units. Up to four RANs can be daisy-chain connected from each of two connections on the 128-port adapter card (see figure). In AIX Versions 4.2 and later, RANs may support 16 EIA 232 devices or 16 EIA 422 devices. The 128-port controller is an intelligent adapter that increases the number of asynchronous sessions possible at a given CPU utilization level.
The following are additional characteristics of the 128-port feature:
LAN connectivity removes the physical connection limitations inherent with direct-attached or node-attached asynchronous ports. LAN connectivity also allows flexibility of connection to multiple system units on the network. There are two models of the 7318 LAN-attached communications server, Models P10 and S20. The two models have the same physical connectivity and appearance. The Model S20 supports a superset of Model P10 functionality. Each model offers asynchronous ports, two parallel ports, and the advantage of connection through Ethernet. This means that they can connect through the integrated Ethernet port available on some system units or through an Ethernet adapter card, thus requiring no additional Micro Channel slots dedicated to asynchronous I/O. The following figure depicts LAN-attached asynchronous ports.
The Model S20 also allows connection of its asynchronous ports to systems on the LAN. On each port, a user may have up to seven concurrent sessions to one or more systems and hot-key between sessions and systems.
All 16 asynchronous ports of the 7318 are RS-232D and EIA 423 compatible. Eight of the ports can support EIA 422A devices.
The 7318 has the capability to detect a problem and switch to its standby Ethernet port. In the event of a power outage, you can hot-key to a second system on the network and continue to be productive. This makes the 7318 an ideal choice for asynchronous connectivity in high availability cluster multi-processing (HACMP) installations.
The following are additional characteristics of the Models P10 and S20:
The Model P10 communication servers use Internet Packet Exchange/Sequence Packet Exchange (IPX/SPX) to transport asynchronous traffic to and from the system. The P10 also has the advantage of making its ports appear as AIX tty ports, thus simplifying configuration and system management tasks. P10 ports are configured using AIX's System Management Interface (SMIT) screens.
The P10 enhances system performance by offloading tty character processing from the system CPU. It provides more than 40% better system processor efficiency when compared to standard Telnet terminal servers for data entry intensive applications. This allows more users to utilize a system or provide faster application processing for a given number of users on a system.
The Model S20 ports may operate as P10-style ports, with the attributes described in the Model P10 section. As S20-style ports, they have the following capabilities.
The Model S20 ports provides connectivity to systems with Telnet protocols, rlogin protocols, and TCP/IP. With the S20, you can Telnet and rlogin to any similarly capable system on the network.
For large and mid-sized system connectivity (for example, S/390 and AS/400), the S20 supports 3270 data streams. This enables asynchronous terminals to emulate 3270 terminals. The S20 supports TN3270 on four user-configurable terminal types simultaneously, including support for color terminals. For AIX applications, the S20 offloads the TN3270 protocol processing from the system to improve system performance.
Serial Line Internet Protocol (SLIP) communications protocol is offered by AIX. In addition, the S20 has built-in support for SLIP as well as compressed SLIP (CSLIP) and point-to-point protocol (PPP). Each of these industry-standard protocols supports TCP/IP connections between AIX and other systems over asynchronous lines, enabling remote network access through modem connections.
The S20 supports reverse Telnet (rtelnet) protocol for modem and printer applications. Unlike terminals, printers cannot initiate Telnet or rlogin sessions to a system. Printers require the system to initiate the connection. rtelent is used by S20 to accept incoming connections from systems for printing or modem applications. With the modem or printer device pooling feature, systems can share modems or printers and use the first available device. Another useful feature is transparent printing. This allows the S20, using rtelnet, to support auxiliary printer ports, provided on most asynchronous terminals.
For printing applications requiring printer spooling, the S20 port can be configured as a P10-style port and use the AIX print queue capability.
The S20 supports standard Simple Network Management Protocol (SNMP) Management Information Base (MIB) II services with on-board SNMP agent. This enables the network administrator to query the S20 from any SNMP management node on the network.
The S20 comes with a default configuration file that enables terminals to be connected quickly and easily. This ASCII file may be customized to add additional sessions, configure SLIP options, or invoke applications, such as rlogin, to a specified host with a specific user name.
The S20 has a full range of security features. For minimal security protection, the S20 supports local password protection. This means that the user must first login to the S20 and enter the correct password before gaining access to the network. For remote network access, password authentication protocol (PAP) is supported with PPP.
The next higher level of security provided by the S20 is Kerberos V.5 password authentication. Kerberos V.5 is a protocol used to prevent passwords from being sent in clear text over the network. This is an important security feature for those networks that are not physically secure. Kerberos V.5 authentication utilities can be provided by the distributed computing environment (DCE). This allows the S20 to participate in the centralized security services provided by DCE.
The highest level of security provided by the S20 is full data encryption. With encrypted rlogin, all data sent and received by the S20 port is Data Encryption Standard (DES) encrypted. This protects data from unauthorized access on the network.
For more information on the 7318 Model S20, see the 7318 Model S20 Guide and Reference.
Note: The Network Terminal Accelerator is not supported in AIX Version 4.3 or later.
The Network Terminal Accelerator adapter is an Ethernet adapter that improves system performance in applications where user terminals connect to the host through a TCP/IP network. For host systems supporting large numbers of users, the Network Terminal Accelerator can significantly reduce host CPU usage by offloading the processing of Telnet and rlogin protocols from the host to the adapter. There are two models of the adapter which support up to 256 or 2048 maximum concurrent Telnet and rlogin user sessions.
Using the Network Terminal Accelerator in conjunction with the 7318 Model S20 terminal server maximizes system performance in addition to providing the flexibility of LAN-attached terminal connections.
