DATA COMMUNICATION PRINCIPLES Synchronization Synchronization The DLC layer

DATA COMMUNICATION PRINCIPLES : Synchronization

Synchronization The DLC layer protocols have the job to deliver N-PDU to the network layer of a directly connected station. This service is provided through the following steps. A DLC protocol encapsulates the network layer PDU with its own header/trailer. This results in a D-PDU for transmission to the peer DLC layer. It then requests the PHY to transmit the D-PDU to the DLC on the other side of the link. The receiving DLC performs some procedures on the received D-PDU and then delivers it to the network layer above it. In order to perform the DLC functions properly, it needs to know how to interpret the received data. If it misses even a single bit of the received data, the whole packet could be interpreted incorrectly. Synchronization is therefore one of the first functions executed by the receiving DLC. The transmission of a D- PDU is sometimes classified as one of the two types with respect to synchronization mechanism, the synchronous transmission. The other type, asynchronous transmission, is mainly a physical layer mechanism. However, the two types of transmissions are do not imply certain protocol layers.

REFERENCES • Ahmad A. - Data Communication Principles. For Fixed and Wireless Networks • Cornelius T. Leondes - Database and Data Communication Network Systems, Three-Volume Set_. . -Academic Press