Transcript 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.

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