DISTRIBUTED APPLICATIONS

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DISTRIBUTED APPLICATIONS

• Session 5 1400 - 1500
• Dr Deepak B Phatak, IIT Bombay

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SESSION OVERVIEW

• Indian Banking Scenario
• Distributed Paradigms
• How to Construct the Distributed Infrastructure

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BANKING BUSINESS

• Requires Emphasis on
• Fast Movement of Funds
• Purposeful Expansion and Retention of Customer
  Base
• Non Repudiation of Valid Transactions. (TXNs)

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CONVENTIONAL RETAIL BANKING

• Low Value High Volume TXNs
• Attractive Deposit Products
• Speedy Customer Service
• Local TXNs, Within a Branch,
• Remote TXNs, Within A City,
• Anywhere Globally

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INDIAN BANKING SCENARIO

• Coexistence of Computerised, Semi-Automated and
  Manual Branch Operations
• Stronger Networks Emerging
• Any Banking Paradigm Must
• Work in Existing Situation
• Quickly Exploit Changes

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DISTRIBUTED PARADIGMS

• Hierarchies of Servers/Clients
• Use of Message Queues and/Or TP Monitors
• Multiple Delivery Mechanisms

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DELIVERY MECHANISMS

• Post, Telegrams, Fax
• Machine Readable Data On Media
• Data Transfer Through Networks

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MODERN NETWORKS

• Ethernet
• 10 Mbps, 75 Market, Over 40 Million nodes
• Token Ring
• 4/16 Mbps, 16
• Fast Ethernet
• 100 Mbps, 1, growing fast

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MODERN NETWORKS

• FDDI
• 100 Mbps, lt 1, Dying
• ATM
• 25 Mbps to 2.4 Gbps, Nascent

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MODERN NETWORKS (WAN BACKBONE)

• North American
• T1 or DS1 1.54 Mbps
• T3 or DS3 44.73 Mbps
• European (and Indian)
• E1 2.04 Mbps (CCITT standard)
• E2 8.44 Mbps
• E3 34.36Mbps

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MODERN NETWORKS (WAN BACKBONE)

• Sonet fibre Standards (ANSI, Synchronous optical
  Network)
• OC1 to OC3
• (51.84, 103.68, 155.52 Mbps)
• OC12 (622.08 Mbps)
• OC24 and OC48
• (1.244 Gbps, 2.488 Gbps)

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MODERN NETWORKS

• WAN Backbone
• IP Over Leased Circuits / Dial up Lines (Internet
  Is IP)
• X.25, Frame Relay, ATM (IP Can Run Over These)
• VSATS ( Delays, 400 ms Per Hop)

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TRANSACTIONS

• ACID Properties Revisited
• Atomicity All or None
• Consistency Stable Correct End State
• Isolation Unaffected by Other Happenings
• Durability Persistent Effect

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TRANSACTIONS

• A Single User Example
• Is It Simple to Handle?
• What Happens in a Crash?
• Simple If Things Work Correctly
• Difficult If Things Go Wrong.

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TRANSACTIONS

• Concurrent Distributed Transactions, More
  Problems
• Consistency and Isolation
• Roll Back Is Difficult
• Lock Step Synchronization Through Two Phase Commit

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TRANSACTIONS

• Flat Transactions
• Activities Are at Same Level
• SQL Implements Two Phase Commit Protocol
• Backbone of Most (Leaf-level) Applications

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FLAT TRANSACTIONS

• Limitations
• Complex Sub-activities With Partial Roll Back?
• Human in the Loop Locks Resources
• Temporally Long Transactions
• Bulk Update Transaction

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PAYMENT SETTLEMENT

• A Complex Transaction
• Jena of Jharsuguda gives a cheque to
  Kantheeswaran at Kandivali
• Kanthee Banks with Bank A at Kandiwali A(K)
• Jena With Bank B(J)

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PAYMENT SETTLEMENT

• Kanthee Presents Cheque to A(K) and demands money
• A(J) credits Kanthees account AFTER collecting
  from B(J)

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DISTRIBUTED PROCESSING SOLUTION
NCC
Bank A
Distributed Transaction
Bank B
Kandiwali
Jharsuguda
Local Data Base
Local Data Base
Jena
Kantheeswaran
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PAYMENT SETTLEMENT

• A presents the instrument to NCC
• NCC records information
• Sorts all Instruments for Bank B
• Asks B to pay A
• B sends Cheque to Jharsuguda (J)

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PAYMENT SETTLEMENT

• B(J) debits Jena
• Informs NCC and A(K)
• A(K) credits Kanthee
• Multiple Service Branches Are Actually Involved

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PAYMENT SETTLEMENT

• Transaction becomes funny if
• Jena has no funds
• Cheque is lost in transit
• B Debits Jena But Sits Tight
• A Receives Info, But Does Not Credit Kanthee

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PAYMENT SETTLEMENT

• More fun
• NCC Asks B to Pay A
• Later, B says give back my money
• Jena debited but Kanthee not credited (Someone
  Using Float)
• Kanthee sues A for delay

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DISTRIBUTED PROCESSING SOLUTION
NCC
Inter Bank Transaction Switch
B Switch
A Switch
Bank A
Distributed Transaction
Bank B
Kandiwali
Jharsuguda
Local Data Base
Local Data Base
Jena
Kantheeswaran
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TRANSACTIONS

• Emerging Transaction requirements
• Distributed Transaction
• Multiple Processing Nodes
• Not All Nodes Computerised
• Not All Links Electronic

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TRANSACTIONS

• ACID properties difficult to maintain for a
  Complex Transaction
• Human in the Loop is a MUST
• Carry Physical Instruments
• Multiple Data Capture
• Verify Signatures at B(J)

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TRANSACTIONS

• A Possible Solution is To Reduce Humans in the
  Loop
• Cheque Is a Message and Not a Physical Instrument
• NCC Is a Swithing System and Not a Physical
  Clearing House
• Electronic Transfer

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TRANSACTIONS

• Emerging Requirements
• Multi Location Transactions
• Incorporation of Work Flow
• Internet Transactions

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MIDDLEWARE

• A Vague Term
• All Distributed Software Components That Support
  Interactions Between Application Software
  Executing On Clients and Servers

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MIDDLEWARE

• General
• Communication stacks
• Distributed Directories
• Authentication Service
• Remote Procedure calls
• Queuing Services
• Message Oriented Middleware (MOM)

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MIDDLEWARE

• Service Specific
• Database related ODBC, DRDA, CLI
• OLTP Specific ATMI ( Tuxedo)
• Groupware Specific MAPI, LN calls
• Object Specific CORBA, OLE
• Internet Specific HTTP, SSL
• Management Specific SNMP, ORBs

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PEER TO PEER COMMUNICATION

• Connection Oriented
• Synchronous
• Connection Less
• Asynchronous, Store and Forward

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EXAMPLES OF DISTRIBUTED PARADIGM

• Bank Master and Branch Power
• Bancs 2000
• Micro Banker and Finware

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EXAMPLES OF DISTRIBUTED PARADIGM

• Provide Branch Functionality When Network Non
  Functional
• Provide Complete Customer Account and TXN Info
• Attempt to Provide Retail and Commercial
  Functionality

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EXAMPLES OF DISTRIBUTED PARADIGM

• SBI
• IDBI Bank
• ICICI Bank
• HDFC Bank
• A Malysian Bank Uses Four Servers For Many
  Branches

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DISTRIBUTED INFRASTRUCTURE

• Needs Indian Messaging Standards
• Needs Proper Application Software Development
• Needs Work Flow Changes

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BUILDING BLOCKS

• Client Systems
• Non-GUI
• ATMs, Barcode readers, cellular phones, fax
  machines
• Robots, Testers, Daemon Processes
• GUI Clients
• Graphics, Menus, Windows, dialogues

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BUILDING BLOCKS

• OOUI Clients
• Communicating objects
• Seamless access to information and action
• Compound Documents
• Live components
• NextStep, Mac OS

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BUILDING BLOCKS

• SHIPPABLE PLACES
• Place A visual ensemble of related components
• Shippable Place A mobile container
• can interact with collaborative environments
• Web, web form, Java enabled web pages, Compound
  Docs

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MORE ON SECURITY

• Kerberos from Athena (MIT)
• Encryption, Session Key
• Data Encryption Standard (DES-3)
• Shared Private key
• RSA, DH Algorithms
• Public/Private key

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PEER TO PEER COMMUNICATION

• Sockets
• BSD 4.2 UNIX, 1981
• Netid.Hostid.Portid (IP Port)
• Port (16 bit) entry point to service
• Transport Layer Interface (TLI)
• ATT, 1986

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PEER TO PEER COMMUNICATION

• Connection Oriented
• Session based
• Virtual Circuits
• Connectionless
• Datagrams

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PEER TO PEER COMMUNICATION

• Internet Package Exchange IPX
• Based on Xerox Network Services (XNS)
• Sequential Packet Exchange (SPX)
• NetBIOS, NetBEUI
• IBM, Sytec (1984), Microsoft

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PEER TO PEER COMMUNICATION

• Named Pipes
• Remote Procedure Calls
• Locate and start Server functions
• Define and pass parameters
• Handle Security and Failures
• Data representation

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PEER TO PEER COMMUNICATION

• Message Oriented Middleware (MOM)
• Distributed Application Development (DAD) needs
  MOM
• MOM consortium in 1993
• Queued Vs Call-return of RPC
• Provides Asynchronous Mechanism
• Ideal for Objets