CHAPTER Mainframe/Mini Related Communication Equipment Chapter Objectives • Present mainframe and minicomputer related communication hardware that has not been presented elsewhere – Front-end processors, concentrators, protocol converters etc. • Describe the different types of terminals such as the ASCII and EBCDIC terminals, smart terminals etc. • Present examples of the use of the Chapter Modules • Mainframe Data Communication Equipment: Front End Processor and Concentrator • Minicomputer Data Communication Equipment: Communication Controllers • Protocol Converters • Data Terminal Equipment END OF CHAPTER INTRODUCTION MODULE Mainframe Communication Equipment: Front End Processor and Concentrator Definition of DCE and DTE • DCE – Data Communication Equipment • DTE – Data Terminal Equipment DCE and DTE in the Real World DCE DTE Printers, Terminal etc. Mainframe Computer DCE Front End Processors, Concentrators, Protocol Converters etc. DTE Some Mainframe Communication Equipment • Front End Processors – Manages the network traffic in a mainframe environment • Multiplexers – Discussed in an earlier chapter in detail • Communication controllers – Controllers, concentrators etc. Mainframe Communication Equipment (Cont.) • Protocol converters – Used for linking devices that operate under a different protocol - different from the mainframe protocol Overview of Communication Controllers • Used extensively in mainframes – 3270 controllers for IBM mainframes • Level of sophistication – On one end of the spectrum is the front end processor – On the other end is the communication controller – There are also the other intermediate communication controllers and devices that are grouped under the 3270 family of communication equipment Front End Processors (FEPs) • Computers by themselves • Connected to a mainframe for the purpose of managing the network traffic • FEPs reduce the load on the CPU – Enable the CPU to perform its primary task of running applications • FEP is a comprehensive DCE – Minicomputers, modems, LANs etc. can be attached to the mainframe through the FEP A Front End Processor Connection External Lines Ter. Mainframe Ter. MiniComputer Front End Processor Gateway Concentrator Term. Term. Modem Server PC LAN PC END OF MODULE MODULE Minicomputer Data Communication Equipment: The Communication Controller Communication Controllers for Minicomputers • In the case of the minicomputer, the controllers can be of the internal or external type • If they are internal controllers, they are installed in the expansion slot of the minicomputers • Manages the network traffic among the host, DTE and DCE Controllers for AS 400 • Known as the 5250 controllers – Fall under the 5250 family of DCE • Compare this with the mainframe’s 3270 family of DCE Connecting DTE to a Communication Controller ASCII Printer 5250 Communication Controller ASCII Terminal AS 400 HP Plotter Modem AS/400 Connection to Terminal Equipment AS/400 with Built-in Communication Controller Source: Black Box AS/400 Terminal Equipment AS/400 LAN Connection OS/400 Server PC Plotter AS 400 OS/2 PC Modem Pool Printer AS 400 LAN Connection Practical Example LAN Remote AS 400 Central Unit Source: Black Box In Summary • Two different ways by which a minicomputer can be connected to other devices including the DTE • Connect the terminal equipment directly to the minicomputer through its communication controller • Link the mini to its terminal equipment over a LAN END OF MODULE MODULE Protocol Converter Definition and Use • A protocol converter can be defined as an equipment used for interfacing systems working under different protocols • Protocol converters are most widely used for connecting peripheral devices to hosts – An example is the connection of ASCII terminals to IBM mainframes ASCII and EBCDIC Terminals • EBCDIC terminals – Standard terminals used with the IBM mainframe • Code conversion difference is present between the EBCDIC and ASCII terminals • A protocol converter is required when an ASCII terminal is to be linked to an IBM mainframe ASCII Terminal Link to an IBM Mainframe Modem IBM 3274 Controller To IBM Mainframe (FEP) Protocol Converter PSTN ASCII Terminal Use of Protocol Converter to Connect ASCII Equipment to IBM Mainframe Protocol Converter ASCII Printer Source: Black Box PC (ASCII) Terminal Mainframe Modem Connection To IBM Mainframe Remote PC Source: Black Box Unix Computer Protocol Converter Used in Mini Computer Connection ASCII Printer ASCII Terminal AS 400 Twinax Multi-port Protocol Converter HP Plotter Modem Protocol Converters:AS/400 to ASCII Connection Source: Black Box Protocol Converter: AS400 to LAN and Printer Connection Source: Black Box Preferred AS 400 Connection to a LAN AS 400 Network Interface Card LAN PC In Summary • Frequent Usage – Connecting ASCII equipment to computers that operate under a different protocol • Utilized for connecting DTE to the mini and mainframe computers END OF MODULE MODULE Data Terminal Equipment (DTE) EBCDIC and ASCII Terminals • EBCDIC – IBM mainframes • ES 9000 series – IBM minis • AS 400 series • ASCII – Popular in the Unix environment • IBM RS 6000 Unix computer • DEC computers running the Unix OS – Most recognizable ASCII terminal is the VT 100 terminal Initial (Dumb) Terminals Mainframe Dumb Terminals Only involved in conveying the information between the mainframe and the terminal. Smart Terminals • Smart terminals are likely to incorporate reasonably powerful processors within themselves • They are able to perform local processing such as the local editing of information on the screen Dumb Terminals • Do not have processors for local processing • They rely on the host to perform most operations • Overloading the CPU is not a desirable course of action • The use of dumb terminals is on the decline Microcomputer as a Terminal • There are two methods by which a microcomputer can be connected to a mainframe to act as a terminal • One involves a direct connection to a concentrator – Terminal emulation hardware and software are required for terminal emulation • The alternative method is to connect a LAN consisting of microcomputers to the mainframe Micro as a Terminal: Direct Connection Terminal Emulation Software IBM Cluster Controller. To IBM Mainframe (FEP) Micro Terminal Emulation Board IBM Terminal Emulation Source: Black Box LAN Based Connection PC Terminal Emulation Software PC PC Gateway or similar device Main Frame FEP PC RS 6000: Native ASCII Connection Terminals AIX (Unix) Computer Source: Black Box In Summary • Two major types – ASCII and EBCDIC • Smart and Dumb terminals • Smart terminals engage in local processing • Microcomputers are increasingly being used to emulate the terminals END OF MODULE END OF MODULE END OF CHAPTER