mainframes ppt

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Mainframes • Contain about 70% of corporate data from operations (accounting, payroll, billing, etc.) • Often the “database server” in web-enabled database applications

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Page 1: Mainframes Ppt

Mainframes

• Contain about 70% of corporate data from operations (accounting, payroll, billing, etc.)

• Often the “database server” in web-enabled database applications

Page 2: Mainframes Ppt

Mainframes

• Dominated by IBM

• Mainframe competitors build clones– Called plug-compatible machines

Page 3: Mainframes Ppt

Terminal-Host Communication• Traditionally, Just a Terminal, Host, and

Transmission Line (Chapter 1)

– Poor response time

– Poor user interface: sending graphics over a distance is expensive (and lines usually are slow)

– Inadequate for production workers who use their terminals hours per day

Page 4: Mainframes Ppt

Mainframe Communication

• User site has multiple terminal users

• 3270 Terminals– High speeds, some color, some graphics

UserSite

3270 Terminal

Page 5: Mainframes Ppt

Mainframe Communication• Cluster Controller at User Site

– Supports a cluster of terminals and printers– Provides limited on-screen text editing power

to terminals• This elimination of text editing work allows the

mainframe to focus on high-value database chores

ClusterController

LimitedText Editing

Page 6: Mainframes Ppt

Mainframe Communication• Cluster Controller at User Site

– Supports a cluster of terminals and printers– Provides limited on-screen text editing power

to terminals• This also reduces response time because editing

is done locally

ClusterController

LimitedText Editing

Page 7: Mainframes Ppt

Mainframe Communication• Cluster Controller at User Site

– Multiplexes transmissions of multiple terminals and printers to the central site

• This reduces transmission costs, which are expensive for higher-speed long-distance links

CentralSite

CentralSite

Long-Distance

Line

A A A A AA A

BB

B B

Page 8: Mainframes Ppt

Mainframe Communication• Transmission Line

– Long-distance lines are expensive per bit sent– But 3270 terminals need high speeds– Multiplexes terminal communication onto 56

kbps, 1.544 Mbps or faster line to give high speed but keep cost reasonable

CentralSite

CentralSite

Long-Distance

Line

Page 9: Mainframes Ppt

Mainframe Communication• Central Site

• Communications Controller

– Handles multiplexing to reduce transmission cost

– Handles detailed interactions with cluster controllers, freeing mainframe to deal with database processing

CommunicationsController

Page 10: Mainframes Ppt

Mainframe Communication

• Mainframe– Handles high-value database work– Must be freed of low-value communications

processing work to be economically efficient

Mainframe

Page 11: Mainframes Ppt

Mainframe Communication

• Reducing Response Time– Text editing work is done locally

– Still delay for heavy database work on mainframe

• Reducing Transmission Costs

– Multiplexing, and

– Cluster controller provides limited local screen editing, so fewer bits need to be transmitted to and from the mainframe

Page 12: Mainframes Ppt

Mainframe Communication

• Reducing Work the Mainframe Needs to Do, so that it can Focus on High-Value Database Processing

– Cluster controller handles most text-editing chores freeing mainframe from having to support this work, and

– Communications controller handles details of communication with cluster controllers, freeing mainframe from having to support this work

Page 13: Mainframes Ppt

Application Servers• NOT Part of Mainframe Communications

– Can act as terminals or cluster controllers– Transparent to mainframe: no need to do

anything differently on mainframe system

App Server

App Server

Page 14: Mainframes Ppt

Mainframes• Use SNA Standards Architecture Instead

of TCP/IP– Not peer-to-peer control; Master-slave

control under a System Services Control Point program on a mainframe

– SSCP program governs all sessions among devices

SSCP

Page 15: Mainframes Ppt

Mainframes

• SNA Standards Architecture– Like TCP/IP and OSI, uses layering– Uses OSI standards at the physical and data

link layers

Page 16: Mainframes Ppt

Mainframes

• SNA Standards Architecture

– SNA Path Control layer is like TCP/IP internet layer and OSI network layer

– SNA Transmission Control layer is like the OSI and TCP/IP transport layer

– However, not peer to peer operation; master-slave operation under the control of the SSCP

Page 17: Mainframes Ppt

Mainframes

• SNA Standards Architecture– Highest layers are like OSI layers– Network Addressable Unit (NAU) Services layer is like

OSI session layer– Data Flow Control layer is like OSI presentation layer– However, applications are not standardized within SNA

• There is no SNA application layer

Page 18: Mainframes Ppt

Mainframes• SNA NAUs

– Communication takes place between network addressable units (NAUs)

– Unit is a general name for a communicating entity

– In networks, communicating entities must have addresses; So they are network addressable units

Page 19: Mainframes Ppt

Mainframes• Logical Units

– Deal directly with end users– Terminals are logical units!– Connection points on mainframe (not

mainframe itself) deal with application programs,which are considered to be end users

LU6Connection

Application

HumanUser

Page 20: Mainframes Ppt

Mainframes• Physical Units

– Do not deal directly with end users

– Mainframe, communications controller, cluster controller

– Path control network connects cluster controller and communication controller

PathControlNetwork

PathControlNetwork

Page 21: Mainframes Ppt

Mainframes

• SSCP

– Third type of NAU

– Program located on the mainframe

– In classic SNA, two other NAUs can only be connected under the control of the SSCP

Page 22: Mainframes Ppt

Mainframes

• Versions of SNA• Classic SNA

– All communication under the control of SSCP

• Advanced Peer-to-Peer Networking (APPN)– Newer; NAUs can connect directly

• High-Performance Routing– Classic SNA and APPN are difficult to route

– Newer still; HPR improves routing

Page 23: Mainframes Ppt

Mainframes

• SNA and Router Networks– To link cluster controllers to communications

controller over routed networks– Data Link Switching (DLSw) standard supports

SNA transmission through routers– High-Performance Routing (HPR) is better

Page 24: Mainframes Ppt

Mainframes

• Mainframes and TCP/IP Networks

• TN3270E– TN3270E servers communicate with

mainframe– Users have PCs with TN3270E client

software that emulates 3270 terminals

TCP/IPNetwork

TCP/IPNetwork

PC withTN3270E

Client

TN3270E Server