On the other hand ip is a connectionless protocol in

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Unformatted text preview: ayer in library subroutines in the user's address space, and the application layer in the user's address space, and the application layer in the user’s program. Physical Layer The physical layer is responsible for transmitting raw bit streams between two nodes. That is, it may convert the sequence of binary digits into electric signals, light signals, or electromagnetic signals depending on whether t two nodes are on a cable circuit, fiber-optic circuit, or microwave/radio circuit, respectively. Electrical details such as how many volts to use for 0 and 1, how many bits can be sent per second, and whether transmission can take place only in one direction or in both directions simultaneously are also decided by the physical layer take place only in one direction or in both directions simultaneously are also decided by the physical layer protocols. In addition, the physical layer protocols also deal with the mechanical details such as the size and shape of the connecting plugs, the number of pins in the plugs, and the function of each pin. In short, the physical layer protocols deal with the mechanical, electrical, procedural, and functional characteristics of transmission of raw bit streams between two sites. RS232-C is a popular physical layer standard for serial communication lines. Data-Link Layer The physical layer simply transmits the data from the sender's node to the receiver's node as raw bits. It is the responsibility of the data-link layer to detect and correct any errors in the transmitted data. Since the physical layer is only concerned with a raw bit stream, the data-link layer partitions it into frames so that error detection and correction can be performed independently for each frame. The data-link layer also performs flow control of frames between two sites to ensure that a sender does not overwhelm a receiver by sending frames at a rate faster than the receiver can process. Therefore, the error control and flow control mechanisms of a network form the data-link layer protocols in the OSI model. Notice that th...
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