Application Interface to Protocols Chuan-Ming Liu Computer Science - - PowerPoint PPT Presentation

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Dec 26, 2022 128 likes •281 views

Mobile Computing & Software Engineering Lab Application Interface to Protocols Chuan-Ming Liu Computer Science and Information Engineering National Taipei University of Technology Taipei, TAIWAN MCSE Lab, NTUT, TAIWAN 1 Mobile Computing

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Application Interface to Protocols

Chuan-Ming Liu Computer Science and Information Engineering National Taipei University of Technology Taipei, TAIWAN

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Introduction

Graphical view Loosely specified protocol software interface Interface functionality Conceptual interface specification System calls Two basic approaches to network communication Basic I/O functions in Linux Using Linux I/O with TCP/IP

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Graphical View

applications TCP/UDP IP hardware sockets user process kernel

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Loosely Specified Protocol

TCP/IP protocol software resides in OS Routines in OS for the interface between the applications and protocol are known as Application Program Interface (API)

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Loosely Specified Protocol

TCP/IP designers

design to operate in a multi-vendor environment avoid choosing any vendor’s internal data representation avoid specifying the interface in terms of features available only on a single vendor’s OS

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Loosely Specified Protocol

The interface between TCP/IP and application is loosely specified Advantages

Flexibility Tolerance

Disadvantage

designer can make the interface details different for each OS

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Loosely Specified Protocol

Only a few APIs have been developed to use with TCP/IP

UNIX: socket API, socket interface, or sockets MS Window: window sockets AT&T: acronym TLI

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Interface Functionality

TCP/IP standards do suggest the functionality for the interface including:

Allocate local resources for communication Specify local and remote communication endpoints Initiate a connection (client) Wait for an incoming connection (server) Send or receive data Determine when data arrives Generate urgent data

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Interface Functionality

Handle incoming urgent data Terminate a connection gracefully Handle connection termination from the remote site Abort communication Handle error conditions or a connection abort Release local resource when communication finishes

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Conceptual Interface Specification

The conceptual interface defined by the TCP/IP standards does not specify data representations or programming details; it merely provides an example of one possible API that an operation system can offer to application programs that use TCP/IP OS designers are free to implement as long as the functionality holds

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System Calls

System calls

Mechanism that most OS’s use to transfer control between applications and OS procedures Like function calls (for a programmer)

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System Calls

System functions called by applications OS kernel containing TCP/IP protocol software

Applica- tion 1 Applica- tion 2 Applica- tion n

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Approaches to Network Communication

Designers must choose the exact set of procedures used to access TCP/IP protocols Two approaches

New implementation on all conceptual

perations

Using convention I/O primitives but overload them

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Basic I/O Functions

six system functions for I/O (on file or device)

close read write lseek ioctl

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Using LUNIX I/O with TCP/IP

when adding TCP/IP protocols to UNIX system, we extend the conventional I/O facilities

the set of file descriptor for application to use read and write system calls to with new network descriptor

Application Interface to Protocols

Introduction

Graphical View

Loosely Specified Protocol

TCP/IP protocol software resides in OS Routines in OS for the interface between the applications and protocol are known as Application Program Interface (API)

Loosely Specified Protocol

TCP/IP designers

Loosely Specified Protocol

The interface between TCP/IP and application is loosely specified Advantages

Disadvantage

Loosely Specified Protocol

Only a few APIs have been developed to use with TCP/IP

Interface Functionality

TCP/IP standards do suggest the functionality for the interface including:

Interface Functionality

Conceptual Interface Specification

System Calls

System calls

System Calls

Approaches to Network Communication

Designers must choose the exact set of procedures used to access TCP/IP protocols Two approaches

Basic I/O Functions

six system functions for I/O (on file or device)

Using LUNIX I/O with TCP/IP

when adding TCP/IP protocols to UNIX system, we extend the conventional I/O facilities

Not all network communication fit easily into UNIX open-read-write-close paradigm