Loid

• The term telecommunication, which includes telephony, telegraphy, and television, means communication at a distance (tele is Greek for “far”).
• Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable.
•  Delivery. The system must deliver data to the correct destination.
•  Accuracy. The system must deliver the data accurately.
•  Timeliness. The system must deliver data in a timely manner.
• Jitter refers to the variation in the packet arrival time.
• Message. is the information (data) to be communicated.
• Sender. is the device that sends the data message.
• Receiver. is the device that receives the message
• Transmission medium. is the physical path by which a message travels from sender to receiver.
• Protocol. is a set of rules that govern data communications.
• Today, the prevalent coding system is called Unicode
• the first 127 characters in Unicode and is also referred to as Basic Latin
• In simplex mode, the communication is unidirectional, as on a one-way street
• ASCII: American Standard Code for Information Interchange
• The full duplex mode is like a two-way street with traffic flowing in both directions at the same time.
• The half duplex mode is like a one-lane road with traffic allowed in both directions.
• mesh topology, every device has a dedicated point-to-point link to every other device
• star topology, each device has a dedicated point-to-point link only to a central controller, usually called a hub.
• A bus topology, on the other hand, is multipoint.
• ring topology, each device has a dedicated point-to-point connection with only the two devices on either side of it.
• LAN is usually privately owned and connects some hosts in a single office, building, or campus.
• WAN is also an interconnection of devices capable of communication
• Physical layer: Bits
• Data link: frame
• Network: datagram
• Transport layer: Segment
• Application: Message
• Established in 1947, the International Organization for Standardization (ISO) is a multinational body dedicated to worldwide agreement on international standards
• An ISO standard that covers all aspects of network communications is the Open Systems Interconnection model.
• The OSI model: Application, Presentation, Session, Transport, Network, Data link, Physical
• The most common twisted-pair cable used in communications is referred to as unshielded twisted pair.
• IBM has also produced a version of twisted-pair cable for its use, called shielded twisted pair
• The most common UTP connector is RJ45
• Coaxial cable carries signals of higher frequency ranges than those in twisted pair cable, in part because the two media are constructed quite differently
• To connect coaxial cable to devices, we need coaxial connectors. The most common type of connector used today is the BNC connector.