The fundamental communications model implies both discovery (i.e. what data should be sent) and delivery (i.e. when and where to send the data). This design mirrors time-critical information delivery systems in everyday life (e.g. television, radio, magazines and newspapers).

Naming and name resolution - How do two processes locate each other to communicate? Routing strategies - How are messages sent through the network? Connection strategies - How do two processes send a sequence of messages? Contention - The network is a shared resource, so how do we resolve conflicting demands for its use?

What is a Distributed System? • “You know you have one when the crash of a computer you’ve never heard of stops you from getting any work done.”-- Leslie Lamport • “A system in which components located at networked computers communicate and coordinate their actions by passing messages”

Communication between processes and objects in a distributed system is performed by message passing. In a typical scenario (e.g. client-server model), such a communication is through request and reply messages.

Communication among distributed processes can be categorized into: 1. Unstructured communication - uses shared memory or shared data structures; Update a distributed

Communication in distributed systems is always based on low-level message passing. Communication through message passing is harder than using primitives based on shared memory. √ How many volts should be used to signal a 0-bit, and how many for a 1-bit? √ How does the receiver know which is the last bit of the message? √

Inter process Communication, Desirable Features of Good Message-Passing Systems, Issues in IPC by Message, Synchronization, Buffering, Multidatagram Messages, Encoding and Decoding of Message Data, Process Addressing, Failure Handling, Group Communication.

Connection-oriented communication pattern using sockets.

Provide a high-level overview of the networks that interconnect distributed systems. configuration. WiFi defined by standard IEEE 802.11 with speeds typically varying from 11Mbps to over 400Mbps. The TCP/IP protocol stack has fewer layers than the OSI model.

Communication is an important issue in distributed computing systems. This chapter addresses the communication paradigm of distributed network systems, i.e., issues about how to build the communication model for these systems.