COE Data and Computer Communications Data Communications & Networking Overview

Term 042 COE 205 Dr.Talal AlKharobi 2 Communication Model

Term 042 COE 205 Dr.Talal AlKharobi 3 Communication Model  Fundamental purpose of communications system is exchange of data between two parties  The key elements of a communication model are  Source: Generates data to be transmitted  Transmitter: Converts data into transmittable signals (modulation, encoding, …)  Transmission System: Carries data  Receiver: Converts received signal into data (the opposite of the “Transmitter” role)  Destination: Takes incoming data

Term 042 COE 205 Dr.Talal AlKharobi 4 Communications Tasks  Transmission system utilization  Interfacing  Signal generation  Synchronization  Exchange management  Error detection and correction  Flow control  Addressing  Routing  Recovery  Message formatting  Security  Network management

Term 042 COE 205 Dr.Talal AlKharobi 5 Communications Tasks  Transmission system utilization  Making efficient use of transmission facilities  Multiplexing is used to allocate the total transmission medium among number of users  Congestion control is needed to assure that the transmission system is not overwhelmed  Interfacing: Interfacing here refers to how to interface communicating devices to the transmission system  Signal generation : Most forms of computer communication depend on the use of electromagnetic signals propagated over transmission media. Thus, we need to generate signals from the data to be transmitted.

Term 042 COE 205 Dr.Talal AlKharobi 6 Communications Tasks  Synchronization: The receiver needs to know when the signal start and ends. Also, it needs to know the duration of each signal  Exchange management: The communicating parties need to agree on a variety of requirements to communicate usefully. Such conventions include  Signal timing  How to start/end conversation  Simultaneous transmission or taking turns  Amount of data to be sent at one time  Data format  Dealing with errors

Term 042 COE 205 Dr.Talal AlKharobi 7 Communications Tasks Error detection and correction:  In all communication system there is a potential for error (signal d istortion, attenuation, interference)  In most cases, error in transmission is not accepted (tolerated)  We need to have a technique to detect errors in transmission and even better to have a technique to correct errors  Flow control: Flow control is required to assure that the source does not send information too fast  Addressing: When more than two devices share transmission facility:  Each system need to have unique address.  Source need to identify the destination by its address.

Term 042 COE 205 Dr.Talal AlKharobi 8 Communications Tasks  Routing: the transmission system must assure that the destination system receive the data  Recovery: Recovery is needed when the information exchange is interrupted or to restore the system to the point prior to the beginning of the exchange  Message formatting: Communicating parties need to agree on the form of data to be transmitted such as the binary code for characters  Security:  Data sender need to assure that only the intended destination receive the data.  Destination need to be sure that what he recived was sent actually by the purported sender.  Destination need to be sure that the data has not been altered

Term 042 COE 205 Dr.Talal AlKharobi 9 Communications Tasks  Network management: Network management is needed to  configure the system  Monitor the system status  React to failures and overload  Plan for future growth