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 componentbased 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.
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