1. CGS 3763 Operating Systems Concepts Spring 2013
Dan C. Marinescu
Office: HEC 304
Office hours: M-Wd 11: :30 AM

2. Lecture 13 – Wednesday, February 6, 2013
Last time:
Process creation and termination
Interprocess communication
Message passing
Today:
Networking concepts
Next time
Client-server systems
Remote procedure call
Reading assignments
Chapters 3 and 4 of the textbook
Chapters 3 and 4 textbook slides
Lecture 13

3. Asynchronicity
Asynchronous events occur independently of the main program flow.
Asynchronous actions  executed in a non-blocking scheme, allowing the main program flow to continue processing.
Asynchronous I/O   input/output processing that permits a processing to continue before the I/O operations has finished.
Asynchronous processes do not share a clock
Asynchronous communication  the sender does not wait to receive an acknowledgment from the receiver.
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4. Message passing Processes must have a way to refer to each other.
Direct communication  a process must explicitly name the recipient or sender of the communication:
send(P, message) -Send a message to process P.
receive (Q, message)-Receive a message from process Q.
Indirect communication  messages are sent to and received from mailboxes, or ports.
send (A, message) -Send a message to mailbox A.
receive (A, message)-Receive a message from mailbox A.
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5. Blocking and non-blocking send & receive
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6. Message queues
Processes communicating through message passing implement sending and receiving queues.
The queues/buffers:
Bounded capacity –
Unbounded capacity –
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7. If a message is sent to a mailbox
If the mailbox is not full, the message is copied to the mailbox, and the sending thread continues.
If the mailbox is full, the sending thread has four options:
Wait indefinitely until there is room in the mailbox.
Wait at most n milliseconds.
Do not wait at all but rather return immediately.
Temporarily cache a message. One message can be given to the operating system to keep, even though the mailbox to which that message is being sent is full. When the message can be put in the mailbox, a message is sent back to the sender; only one such message to a full mailbox can be pending at any time for a given sending thread.
9/19/2018

8. Networking concepts
Protocol – a communication discipline; a set of rules obeyed by two entities to communicate with one another.
Internet core and periphery.
Internet layered architecture.
Peer-to-peer communication; each layer running on one host communicates with its peer running on another host.
Multiplexing and de-multiplexing of messages.
Message delivery to processes.
Lecture 13

9. Lecture 13

10. Internet layered architecture
Lecture 13

11. Peer-to-peer communication
Lecture 13

12. Local and wide area networks
Lecture 13

13. Multiplexing, de-multiplexing
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14. Multiplexing and de-multiplexing
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15. Ports and socket
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16. Lecture 13

17. Communications in Client-Server Systems
Sockets
Remote Procedure Calls
Remote Method Invocation (Java)
Lecture 13

18. Sockets A socket is defined as an endpoint for communication
Concatenation of IP address and port
The socket :1625 refers to port 1625 on host
Communication takes place between a pair of sockets
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19. Socket Communication
Lecture 13