The data link layer is organized in two ways:
1)Logical Link Control(LLC): The LLC sublayer provides multiplexing mechanisms that make it possible for several network protocols (e.g. IP, IPX, Decnet and Appletalk) to coexist within a multipoint network and to be transported over the same network medium.
2)Media Access Control(MAC):The MAC sublayer provides addressing and channel access control mechanisms that make it possible for several terminals or network nodes to communicate within a multiple access network that incorporates a shared medium, e.g. an Ethernet network. The hardware that implements the MAC is referred to as a media access controller.
The Design issues are as under:
1)Framing 2)Providing Interface to d Network Layer Services 3)Flow Control 4)Error Control 5)Synchronization 6)Link Configuration on Control. I hope d descp helps u. :)