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Factors to consider when selecting a transmission medium (TRANSMISSION IMPAIRMENTS)

There are many transmission media available and each media type has certain characteristics, so it’s necessary to aware about all the benefits and shortcomings of each one.
•Cost & Ease of installation •Attenuation •Delay Distortion •Capacity (Bandwidth and throughput) •Transmission delay •Propagation delay •Interference •Noise •Thermal/White Noise •Intermodulation Noise •Crosstalk •Impulse Noise
•Cost & Ease of installation : Costing is an important factors , when we select a media. Because absolute cost and ease of installation data are difficult to provide without referring to specific implementations, one can make relative judgments by comparing each medium to the others. •Attenuation : Attenuation refers to the tendency of electromagnetic waves to weaken or become distorted during transmission. It is loss of energy as the signals propagates outwards. Attenuation increases with distance, as a wave passes through a medium, some of its energy is absorbed or scattered by the medium’s ph…

Signed and Unsigned Numbers

Service primitives of Network Software

Service primitivesA service is formally by a set of primitives or operations a user or other entities can invoke to access the service. That is what materializes an interface. We commonly classify service primitives into 4 classes:
primitivemeaningrequest an entity is requesting a service (we are requesting a connection to a remote computer) indication an entity is informed of an event (the receiver has just received a connection request) response an entity is responding to an event (the receiver is sending the permission to connect) confirm an entity acknowledges the response to its request (the sender acknoledge the permission to connect to the remote host) Most primitives need parameters. For instance, parameters of a CONNECT.request (used to query a connection) are the machine you want to connect to, the service you want to use (FTP, telnet...) and the maximum size of exchanged packets.
A acknowledged service is a service that requires a request, an indicatio…