Internet and Distributed Application Services

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Internet and Distributed Application Services

• Chapter 13

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Objectives

• Describe client-server and multi-tier application
  architecture and discuss their advantages
  compared to centralized applications
• Explain how operating systems and network
  protocol stacks cooperate so users and programs
  can access remote resources
• Describe low-level protocols for interprocess
  communication across networks, including sockets,
  named pipes, RPC, and DCE
• List and describe standard Internet protocols
  used to access distributed resources
• Discuss component-based application development
  and describe the protocols and standards that
  support component-based applications
• Explain the role and function of directory
  services and the LDAP standard

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Chapter Topics
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Distributed Computing

• Client-server architecture is the current
  dominate architecture for distributed computing.

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Distributed Computing

• Client-server architecture is the current
  dominate architecture for distributed computing.

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Distributed Computing

• Client-Server Architecture
• A server manages one or more system resources and
  provides access to those resources through a
  well-defined communication interface.
• A client uses the communication interface to
  request resources from the server.

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Distributed Computing

• 3-Layer Client-Server Architecture
• Data layer manages stored data, usually in one
  or more databases
• Business logic layer implements the rules and
  procedures of business processing
• View layer accepts user input and formats and
  displays processing results

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Distributed Computing
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Network Resource Access

• Protocol Stacks
• Software that implements the lowest five
  levels of the OSI model.

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Network Resource Access

• Advantages of Protocol Stacks
• divide the task of network interaction into
  several well-defined pieces that can be
  separately implemented and installed
• provide the flexibility needed to keep up with
  rapid protocol standard evolution
• insulate application programs and many portions
  of the operating system from details of low-level
  network communication protocols.

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Network Resource Access
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Network Resource Access

• Accessing Remote Resources
• A static connection is initialized by the user or
  system administrator prior to accessing a remote
  resource.
• A dynamic connection is created by the
  interaction between a resource locator and a
  primary resource registration repository.

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Network Resource Access
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Network Resource Access
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Interprocess Communication
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Interprocess Communication

• Peer-to-peer protocol
• Socket
• Named Pipe
• Remote Procedure Call

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Interprocess Communication

• Socket
• A socket is a unique combination of an IP number
  and a port number.
• A port number is an unsigned 16-bit integer.
  (65,536 possible port numbers)

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Interprocess Communication
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Interprocess Communication

• Named Pipe
• A named pipe has a name that is permanently
  placed within a file system directory and the
  ability to communicate among processes on
  different computers.

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Interprocess Communication
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Interprocess Communication

• Remote Procedure Call
• With a remote procedure call protocol, a process
  on one machine can call a process on another
  machine.

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Interprocess Communication

• Remote Procedure Call
• The calling process
• Passes parameters to the called process.
• Waits for the called process to complete its
  task.
• Accepts parameters back from the called process.
• Resumes execution with the instruction following
  the call.

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Technology Focus
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The Internet

• Internet a global collection of networks that
  are interconnected using TCP/IP.
• World Wide Web a collection of resources that
  can be accessed over the Internet.
• Intranet a private network that uses Internet
  protocols but is accessible only by a limited set
  of internal users.

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The Internet

• Standard Web Protocols and Services
• All resources are identifies by a unique Uniform
  Resource Locator (URL).
• The URL has four parts protocol, host, port and
  resource.

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The Internet

• Uniform Resource Locator
• Protocol an optional header specifying the
  resource access protocol.
• Host the IP number or registered name of an
  Internet host computer or device.
• Port an optional port number that specifies the
  socket.
• Resource the complete path name of a resource
  on the host.

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The Internet
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Interprocess Communication
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Interprocess Communication
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Interprocess Communication

• In later versions of HTML, program code or
  scripts can be embedded within HTML documents.

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Interprocess Communication
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Interprocess Communication
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Components and Distributed Objects

• Component-Based Software
• A component is a standardized and
  interchangeable software module that
• Is executable
• Has a unique identifier
• Has a well-known interface
• Similar to objects within an OO program

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Components and Distributed Objects

• CORBA - Industry-wide component specifies the
  middleware used by objects to interact across the
  network.
• Two components
• Object Request Broker (ORB)
• Internet Inter-ORB Protocol (IIOP)
• COM - a Microsoft specification for component
  interoperability.

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Components and Distributed Objects

• Differences between CORBA and COM
• Components are not assigned a permanent
  identifier.
• Components are registered in the Windows Registry
  of the client machine.

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Components and Distributed Objects
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Components and Distributed Objects

• Simple Object Access Protocol (SOAP)
• SOAP is a standard for distributed object
  interaction that attempts the shortcomings of
  both CORBA and COM.

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Components and Distributed Objects
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Directory Services

• Lightweight Directory Access Protocol (LDAP)
• An LDAP directory stores information about LDAP
  objects.
• Each object is an instance of an objectclass.
• An objectclass defines the attributes common to
  all member objects.
• LDAP objects are organized in a hierarchy.

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Directory Services
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Technology Focus
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Technology Focus
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Summary

• Modern information systems typically are
  distributed across many computer systems and
  geographic locations.
• A network protocol enables user and applications
  to interact with resources and applications on
  remote computer systems.
• Distributed processes must communicate with one
  another to exchange data and synchronize their
  activities.

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Summary

• The Internet is a global network based on TCP/IP
  and many other protocols.
• Component-based applications divide an
  application into many different cooperating
  processes or distributed objects.
• With directory services, users, resources, and
  components can find one another on the Internet.