Concept Questions
1. What are the two main jobs of the data link layer? * Allows the upper layers to access the media using techniques such as framing. * Controls how data is placed onto the media and is received from the media using techniques such as media access control (MAC) and error detection.
2. What is the difference between a logical network and a physical network? * Logical network refers a group of devices that associated by the arrangement of a hierarchical addressing scheme. * Physical network refers the connection of devices on a common media.
3. If the data link layer didn’t exist, what changes would be required of a network layer protocol such as Internet Protocol (IP)?
Without the data link layer, a network layer protocol, like IP, would require provisions for connecting to every type of media that could exist along a delivery path.
Vocabulary Exercise: Completion
1. The technique for getting a frame on and off a medium is called the MAC method.
2. To connect to a network, an end device uses an adapter, such as a Network Interface Card (NIC) on a Local Area Network (LAN). The adapter manages the framing and media access method.
3. An intermediary device, such as routers, has physical interfaces that can encapsulate a packet into the appropriate frame and handle the MAC method to access each link.
4. A router uses data link layer services to receive a frame from one medium, decapsulate the frame to the Layer 3 PDU, encapsulate the Layer 3 PDU into a new frame, and place the frame on the medium of