CS601 Midterm Notes Lectures 1-22

CS601 Mid-term Notes

Lec 1 to 113

LECTURE #1 Introductions to Data Communications Communication: Sharing of Information (Local or remote) Telecommunications: Communication at a Distance (includes telephony, telegraph, and television etc.) Data communications: “Data Communication is the exchange of data (in the form of 0’s and 1’s) between two devices (computers) via some form of the transmission medium.” A Simple Communication Model In a simple model, often referred to as the transmission model or standard view of communication, information or content is sent in some form (as spoken language) from an transmitter/emisor/sender/encoder to a receiver/decoder. A transmitter, which encodes the message into signals.

LOCAL and REMOTE Data Communication LOCAL Data communication is considered to be local if the communicating devices are present in the same building or a similarly restricted geographical area. REMOTE Data Communication is considered remote, if the devices are farther apart. Effectiveness of a Data Communication System: The effectiveness of a data communications system depends on four fundamental characteristics: delivery, accuracy, timeliness, and jitter. Components of a Data Communication system A data communications system has five components.

•  Message
•  Sender
•  Receiver
•  Medium
•  Protocol

Message A message (verbal or nonverbal, or both) is the content of the communication process. The originator of the message in the communication process is the sender. In short anything that can be represented using binary bits.

•  Files (meaningful collections of records)
•  Data/information requests (database queries, Web page requests, etc.)
•  Responses to requests and commands or error messages
•  Status messages (about the network’s functional status)
•  Control messages transmitted between network devices to control network traffic
•  Correspondence among network users

SENDER A source or sender is one of the basic concepts of communication and information processing. Sources are objects which encode message data and transmit the information, via a channel, to one or more observers. RECEIVER In the communication process, the "receiver" is the listener, reader, or observer—that is, the individual (or the group of individuals) to whom a message is directed. The receiver is also called the "audience" or decoder. Medium In the communication process, a medium is a channel or system of communication— the means by which information (the message) is transmitted between a speaker or writer (the sender) and an audience (the receiver). The plural form is media, and the term is also known as a channel. PROTOCOL A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchronization of communication and possible error recovery methods. An Actual Digital Data Communication System Key Data Communication Terminology

•  Session: communication dialog between network users or applications Different Types of this session for Info Exchange. ™
•  Network: interconnected group of computers and communication devices we will look into it in a little bit.™
•  Node: a network-attached device Node can be any device in the network.

LECTURE #2 KEY DATA COMMUNICATION TERMINOLOGY

•  Link: connects adjacent nodes Wires, Cables, Anything that physically connects two nodes ™ Path: end-to-end route within a network ™
•  Circuit: the conduit over which data travels ™
•  Packetizing: dividing messages into fixed-length packets prior to transmission over a network’s communication media ™
•  Routing: determining a message’s path from sending to receiving nodes The transmission medium may itself be a network, so route needs to be specified

Network “A NETWORK is a set of devices (Nodes) connected by Communication Links”

•  Node: Can be a Computer, Printer or any other device capable of sending or receiving.

Two Main Classifications of the Networks

•  LANS
•  WANS

DISTRIBUTED PROCESSING Instead of a single large machine being responsible for all aspects of a process, each separate computer handles a subset of the task. Example – Office Work Advantages of Distributed Processing

•  Security A system designer can limit the kind of interaction that a given user can have with the entire system. For example : Bank’s ATM ™