Manav Goyal

Interprocess Communication - Distributed Systems

Message passing interface
- Supports point to point and collective communication
- Goals are High performance, Scalability, Portability
- Dominant in HPC (High performance computing)
Middleware Services
- Software layer situated between software and operating system
- Provides services that help in communication between components in DS
Types of communication
- Synchronous communication
  - Client sends request to server and waits for response
  - Types
    - RPC (Remote Procedure Call)
      - Protocol that a program can use to request a service from a program from a program located in another computer on a network without having to understand the network detail
      - Steps
        
        Client procedure calls client stub in a normal way
        
        Client stub builds message, calls local OS
        
        Client OS sends message to local OS
        
        Remote OS gives message to Server stub
        
        Server stub unpacks parameters, calls server
        
        Server does work, returns result to the stub
        
        Server stub packs it in message, calls local OS
        
        Server OS sends message to client OS
        
        Client OS gives message to client stub
        
        Stub unpacks result, returns to client
      - Components
        
        Client
        
        Client stub
        
        RPC Routine
        
        Handle transmission of message between client and server
        
        Server stub
    - RMI (Remote Method Invocation)
      - Set of protocols being developed that enables java objects to communicate remotely with other java objects
      - All objects must be written in Java
      - Characteristics of Java objects
        
        Simple protocol as compared to COBRA & DCOM
        
        Works only with java objects as compared to COBRA & DCOM
        
        Based on RPC
      - Goals
        
        Seamless object remote invocation
        
        Callbacks from server to client
        
        Distributed garbage collection
- Asynchronous communication
  - Client sends request to server but doesn't waits for response and keeps doing other tasks
- Transient communication
  - Both client and server needs to be active for communication
- Persistent communication
  - Both client and server doesn't needs to be active for communication
Classification
- Message Oriented Communication
  - Way of communication between the processes on the sender and receiver machine
  - Classification
  - Types of Message Oriented
    - Persistent Asynchronous communication
    - Persistent Synchronous communication
    - Transient Asynchronous communication (One way RPC)
    - Transient Synchronous communication
      - Receipt-based transient Synchronous communication
      - Delivery-based transient Synchronous communication at message delivery (Asynchronous RPC)
      - Response-based transient Synchronous communication (RPC)
- Stream Oriented Communication
  - Form of communication in which timing plays a crucial role
  - Transmission Modes
    - Synchronous
      - Specifies max end to end delay variance between teo packets is ok
    - Asynchronous
      - End to end delay can be maximum (no effect of time)
    - Isochronous
      - Max end to end delay is specified and variance to 0
  - Algorithm
    - Leaky bucket
    - Open bucket
- Difference
  - Trick: Sexy Senorita Ranawaywith CAR OF Police Department
Group Communication
- Modes
  - Unicast
    - Point to Point (1 to 1)
  - Anycast
    - 1 to nearest 1 of several identical nodes
  - Netcast
    - 1 to many (1 at a time)
  - Multicast
    - 1 to many
  - Broadcast
    - 1 to all
- Types
  - One to Many (Single sender and Multiple receivers)
    - Receiver processes messages from group
    - Closed group vs Open group
    - Peer group vs Hierarchical group
  - Many to One (Multiple senders and Single receiver)
    - Many senders send the message to selective receiver
    - Uses buffer to control incoming messages
    - Receiver can be selective or non selective
      - Selective
        
        Specifies a unique sender, the message exchange takes place only if that sender sends the message
      - Non Selective
        
        Specifies a set of sender and if any one sender in the set sends a message to this receiver message exchange takes place
  - Many to Many (Multiple senders and Multiple receivers)
    - Many senders sends messages to many receivers
    - Semantics ordered message delivery are
      - Absolute ordering
        
        All messages delivered to all receivers exactly in the way that they are sent
      - Consistent ordering
        
        The message is delivered to all receivers possessing the same order
      - Casual ordering
        
        Events of sending messages are linked, messages are received in same order as sent