Networking Self-Teaching Guide: OSI, TCP/IP, LANs, MANs, WANs, Implementation, Management, and Maintenance

Chapter 11. The Data Link Layer

	Power consists in one's capacity to link his will with the purpose of others, to lead by reason and a gift of cooperation.
	--Woodrow Wilson

The Data Link layer is Layer 2 of the OSI reference model. This layer allows for direct communication between nodes over the physical channel provided at the lower layer. The communication can be point-to-point (one-to-one communication between two nodes) or point-to-multipoint (one-to-many communication, from one node to many nodes), depending on the nature and configuration of the network.

LAN technology exists primarily at the Data Link and Physical layers of the architecture. The functions performed by a network bridge or switch occur mainly at the Data Link layer. Network switches are able to tremendously enhance the capabilities provided by the Data Link layer. This is true to the point where you have to be careful that the implementation of the features doesn't affect the operations of some protocols within the upper layers.

The generic operation performed at the Data Link layer is the movement of data between nodes within a network over a physical connection. Once the Data Link layer has ensured that a connection is set up, the layer divides data into frames and transmits them to other nodes within a network. The receiving node sends acknowledgments and ensures that the data is received by keeping track of bit patterns in the received frames.

In this chapter, we discuss the Data Link layer. We cover concerns ...