Basic objective of this lecture is to describe on Multiple Access Strategies for Sharing a Communication Medium. Most networks are shared medium, this means that a single medium (radio frequency) is shared by all of a network’s hosts. here also briefly describe on Carrier Sensing Hardware and Carrier Sensing (CSMA), to reduce the number of collisions, the medium is tested for a signal before each transmission. Finally discuss on Data Link Addressing, MAC Addresses, Data Link Flow Control, Sliding Window Techniques, Error Control etc.