Distributed Computing
Second Edition
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Chapter 3
Interprocess
Communication
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OUTLINE
• Message passing
• Group communication
• API for Internet protocol
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Message Passing vs Shared Memory
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Desirable Features of Message
Passing Systems
• Hardware approach
• Functionality
• Performance
• Uniform semantics
• Efficiency
• Reliability
• Correctness
• Flexibility
• Portability
• Security
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Message Passing Process
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IPC Message Format
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IPC Message
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IPC Synchronization
• Ensure message is received in the buffer:
– Polling
– Interrupt
• Message communication techniques
– Synchronous communication
– Asynchronous communication
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IPC: Synchronous Communication
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IPC: Asynchronous Communication
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IPC Primitives
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Message Buffering Strategies
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Null Buffering
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Null Buffering with Blocked Receiver
Null buffering with blocking
mechanism
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Null Buffering with Non-blocked Receiver
Null buffering with non-blocking mechanism
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Message Buffering: Single Buffer
Single-message buffering
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Message Buffering: Multiple
Message Buffer
• Receiver overflow handled using
– Unsuccessful communication indication
– Flow control mechanism
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Multidatagram Messaging
• Concept of MTU
• Message sequencing and reassembly
• Message contents
• Message representation: tagged, untagged
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Message Data Transmission
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Process Addressing Techniques
• Explicit addressing :send (process_id, message) and receive
(process_id, message)
• Implicit addressing:send_any (service_id, message) and
receive_any (service_id, message)
– Two level addressing : machine_id@local_id (receiver
machine name)
– Three level addressing:
machine_id@local_id@machine_id (node where the
process was created @ generated by the first machine@
last known location of the machine)
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Link-based Process Addressing
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Failure Handling Mechanism
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IPC Protocols
• 4-message reliable IPC protocol
• 3-message reliable IPC protocol
• 2-message reliable IPC protocol
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IPC 4 Message Protocol
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IPC 3 Message Protocol
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IPC 2 Message Protocol
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IPC Failure
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Group Communication
• Unicast –one to one communication
• Many-to-one group communication
• One-to-many or multicast group communication
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Unicast Group Communication
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Many-to-One Communication
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Multicast Communication
Broadcast Communication
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Types of Groups
• Closed group
• Open group
• Peer group
• Hierarchical group
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Group Management
• Centralized approach
• Distributed approach
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Group Addressing Message Delivery
• High level naming • Send to all semantics
• For large LANs/ • Bulletin board
MANs: send message semantics
to individual group
members
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Reliability Mechanism
• Classified based on number of receivers from which sender
expects a response
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Message Ordering
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Message Ordering: Absolute Ordering
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Message Ordering: Consistent Ordering
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Message Ordering: Causal Ordering
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https://www.geeksforgeeks.org/difference-between-synchronous-and-
asynchronous-transmission/
API for Internet Protocol
• Synchronous Communication
Both the sending and receiving processes synchronize at every
message so that both send and receive primitives are blocking
operations. When a send is issued, the sending process is blocked
until the receive command is issued, and the other process is
blocked until the message is received.
• Asynchronous Communication
The send is a non-blocking command. The issuing process is allowed to
continue when the message is stored in a local buffer and then both
the transmission of the message and the sender process continues
simultaneously. The receive operation works both in blocking and
non-blocking modes.
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https://www.geeksforgeeks.org/differences-between-tcp-and-udp/
UDP Datagram Communication
• A datagram is transmitted from the client process and sent to
the server process, which receives it.
• To communicate messages to and fro, a process must first
create a process and bind it to a local port and to an Internet
address of the local host.
• The receive method includes the Internet address and the
port number so that the receiver can send a reply.
• UDP protocol may be used for some services where
sometimes the messages may be dropped.
• The main advantage lies in the fact that datagrams do not
require overheads for correct delivery.
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TCP Datagram Communication
• TCP is a connection-oriented protocol
• Sequencing: A data stream is divided into a sequence of data
segments with a sequence number attached to each and
transmitted as IP packets. It gives the byte number within the
stream for the first byte of the segment.
• Flow control: When a segment is received, its sequence number is
noted and periodically, the receiver sends the highest number of
received segments and also the window size to the sender. This is
sent in a special acknowledgement segment.
• Retransmission and buffering: The sender keeps track of the
sequence number of sent segments and retransmits them in case
any segment does not receive acknowledgement from the receiver.
The incoming buffer at the receiver’s site stores the incoming data
packets.
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Services Using TCP Protocol
• HTTP Hypertext transfer protocol is used to communicate
between Web browsers and Web server.
• FTP File transfer protocol allows files to be transferred
between the remote computer and the host computer. It also
allows directories from a remote computer to be accessed.
• Telnet It allows a user to log on to the remote computer
system and start a terminal session.
• SMTP Simple mail transfer protocol is used to send mail from
one computer to another.
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