Skip to main content

Message Delivery Protocol

 

Message Delivery Protocol

·         A protocol is a set of rules and conventions shared by communicating entities .

·         Message passing can be blocking or non blocking .

·         In blocking protocol, a sender process is blocked till the message selivered to the . in this case , sender process has guarantee that the message sent by it ie delivered before it continues its execution .

A blocking protocol normally includes:

1.       Blocking send : the sender process is blocked until the message is received by the receiving process or by the mailbox.

2.       Blocking receive : the receiver nlocks until a message is available thus when both sender as well as receiver is blocked ,it is known as rebdevezevous . this combination allows for tight sysnchronization between process.

·         In non blockeing protocol, asender continues the execution after performing a send operation irrespective of whether the message is delivered or not

·         A non blocking protocol has the advantage that a sender is free to continue its execution immediately after sending a message

·         However , sender has no means of knoiwing when(and wheather )its message  is delivered to the receiver.

     

·         A non blocking send : the sending process sends the message and resumes operation.

·         Non blocking receive: the receiver retrieves either a valid message or a null.

 

Buffering

Wheather the communication is direct or indirect , message exchanged by communicating processes reside in a temporary queue.

There are  three different  ways of implementing such queue.

 

Zero capacity

·         Zero capacity queue cannot keep and message waiting in it , thus it has maximum length 0

·         For this , sending process must be blocked until the receiving process receives the message .

·         System with zero capacity queue is known as message system with no buffering.

 

Bounded capacity

·         Bounded capacity queue has finite length n. thus it can have n message.

waiting in it .

·         If the queue is not full , new message can be placed in the queue and the sending process is not blocked , it not blocked , it can continue execution without waiting.

·         If the link or queue is full , then the sender must be blocked until space is available in the queue.

·         This system is also known as automatic buffering .

 Unbounded capacity

·         Unbounded capacity queue has infinite length . thus any number of messages can wait in it .

In such a system , sending process is never blocked , can continue execution without waiting

Shared memory model

·         Normally , process use memory areas within the scope of virtual memory space . also memory management systems ensure that every process has a  well-defined and separate data and separate data and code area.

·         In shared memory model parts of private address space of two or more rae processes are mapped to same physical memory.

·         Such a memory areas are called shared memory regions.


Comments

Post a Comment

Popular posts from this blog

Multi processing system

  Multi processing system ·           Multi processesor system is the sytem that contain two or more processors or CPUS and has ability to simultaneously execute     several programs. Hence the name multi-processor In such a system, multiple processor share the clock, bus, memory and peripheral devices. ·           A multi processor system is also known as parallel system ·           Multi processor system are categorized into two different types:                single user operating system    2.        Multi user operating system   3.         Batch processing operating system 4.        Multi programming operating system   5.       Multi tasking operating sy...
Post a Comment
Read more

Real-time system

  R eal-time system ·           In a real time operating system, a job is to be completed within the    rigid time constraints otherwise job loses its meaning. ·           A real time system function correctly only if it returns the correct result within its time constraints ·           Thus, in a    real-time system, the correctness of the    computation not only depends upon the logical correctness of the computation but also upon the time at which the result is produced. R eal-time system In a real time system various functions like process scheduling, memory management, I/O management and file  management are performed as follows : 1.         Process scheduling  . the real time system uses priority based pre-emptive scheduling. each process is assigned a certain level of ...
Post a Comment
Read more

Virtual Machine Architecture

  Virtual Machine Architecture A virtual machine can exist as a standalone machine or it can exist within a vApp. A virtual machine is a software computer that, like a physical computer, runs an operating system and applications. The virtual machine consists of a set of specification and configuration files and is backed by the physical resources of a host. Every virtual machine has virtual devices that provide the same functionality as physical hardware are more portable, more secure, and easier to manage. Virtual machines can be standalone, or they can exist within a vApp. A vApp is compound object composed of one or more virtual machines as well as one or more networks. 1.    Monolithic architecture 2.     Layerd archtecture . 3.     Virtual machine architecture 4.       Exokernel architecture 5.      Client server architecture   6.       Micro kernel architecture The following figure ...
Post a Comment
Read more

Defination of OS(operating system) and its concepts

    What do you mean by operating system?     Definition :  An operating system is a program that act as an interface between the user of a computer and the                                      Computer hardware. Operating system is a first program that gets loaded into the memory through a process called booting. Concepts of operating system : ·                       The purpose of operating system is to provide an environment in which a user can execute program in a convenient and efficient manner. ·                       Operating system is an integrated set of program that ma...
3 comments
Read more

Multitasking System

  Multitasking system ·           Technically , multitasking is same as multi programming ·           In a multitasking operating system, s single user can execute multiple programs at the same time ·           We can also say, multitasking is the system capability to work on more than one job or process at the same time. ·           It means that whenever a job needs to perform I/O operation, the cpu can be used for execting some other job                                                        diagram of multi tasking     ·           There are two type of multitasking : 1.       ...
Post a Comment
Read more