Communication at application, transport, network, or data- link is logical; communication at the physical layer is physical. we have shown only ; host- to- router, router-to- router, and router- to- host, but the switches are also involved in the physical communication.
Although Alice and Bob need to exchange data, communication at the physical
layer means exchanging signals. Data need to be transmitted and received, but the media have to change data to signals. Both data and the signals that represent them can be either analog or digital in form.
Data can be analog or digital. The term analog data refers to information that is continuous; digital data refers to information that has discrete states. Analog data, such as the sounds made by a human voice, take on continuous values. When someone speaks, an analog wave is created in the air. This can be captured by a microphone and converted to an analog signal or sampled and converted to a digital signal. Digital data take on discrete values. For example, data are stored in computer memory in the form of Os and ls.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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