06-10-2012, 04:52 PM
Overview of Data Communication & Networking
Overview of Data Communication.ppt (Size: 881.5 KB / Downloads: 72)
Definitions
Telecommunication: Communication at a distance
Data: Information presented in whatever form is agreed upon by the parties creating and using the data
Data communications: Exchange of data between two devices via some form of transmission medium such as a wire cable.
The effectiveness of data communications depends upon three fundamental characteristics:
Delivery: Deliver data to the correct destination.
Accuracy: Deliver the data accurately.
Timeliness: Deliver data in a timely manner. Real-time transmission requires timely delivery [without significant delay].
Networks
Network: set of devices connected by communication links.
Distributed Processing: Task is divided among multiple computers.
Network Criteria
Performance: Transit and response time.
Transit time is the amount of time required for a message to travel from one device to another.
Response time is the elapsed time between an inquiry and a response.
Depends upon number of users, type of transmission medium, capabilities of hardware, efficiency of software.
Reliability: Measured by the frequency of failure, the time it takes a link to recover from a failure, and the network’s robustness in catastrophe.
Security: Protecting data from unauthorized access.
Star topology
Each device has a dedicated pt-to-pt link only to a central controller [Hub].
No direct connection or traffic.
Adv: less expensive, one link and one I/O port, easy to install and reconfigure, less cabling (but more than bus or ring), node failure will not affect others, fault identification is easier.
Disadv: Single point of failure.
Bus topology
Multipoint: One cable acts as a backbone to link all the devices in a network.
Drop line: a connection running between the device and main cable.
Tap: a connector that either splices into the main cable or punctures the sheathing of the cable to create a contact with the metallic core.
Signal degrades due to energy being transformed into heat. So, there is limitation on the number of taps allowed.
Adv: easy to install, less cabling.
Disadv: Limit on number of taps and the distance between taps, difficult to identify fault, signal degradation, modification is difficult.
Protocols and Standards
Protocols: set of rules that governs data communications.
A protocol defines what is communicated, how it is communicated and when it is communicated.
Syntax: it refers to the structure or format of data.
Semantics: it refers to the meaning of each section of bits
Timing: It refers to two characteristics; when and how much to send.
Standards: Provide guidelines.
de facto [by fact]
de jure [by law].
Standard Organizations
International Organization for Standardization (ISO)
International Telecommunication Union- Telecommunication Standards (ITU-T)
American National Standards Institute (ANSI)
Institute of Electrical and Electronics Engineers (IEEE)
Electronic Industries Association (EIA)
International Engineering Task Force (IETF)