a. Frame| a. Two or more devices connected to a common medium| b. Node| d. A layer of the Open Systems Interconnection (OSI) model that frames upper-layer data and controls how data is placed on a medium| c. Media| b. A device on a network|
d. Network| e. The physical means used to carry data signals| e. Data Link| c. The protocol data unit (PDU) used in Layer 2 of the OSI model|
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 the next link in the network.
1. Compare and contrast controlled media access control and contention-based media access control. Although controlled media access is well ordered and provides predictable throughput, these methods can be inefficient because a device has to wait for its turn before it can use the medium. Contention-based media access allows any device to try to access the medium whenever it has data to send. 2. List the steps in the carrier sense multiple access collision detect (CSMA/CD) process. At this point, you can keep the list simple. You will learn more about CSMA/CD in Chapter 9. In CSMA/CD, the device monitors the media for the presence of data signal. 3. What is the difference between full-duplex communication and half-duplex communication? Half-duplex communication means that the devices can both transmit and receive on the media but cannot do so simultaneously. In full-duplex communication, both devices can transmit and receive on the media at the same time. Vocabulary Exercise: Completion
1. A logical multiaccess topology enables a number of nodes to communicate by using the same shared media. 2. Having many nodes share access to the medium requires a data link MAC layer media access control method to regulate the transmission of data. 3. Three media access control methods used by logical multi-access topologies include Header, Data, and Trailer. 4. Data link layer rules (also called protocols) specify the media access control method that is used for a particular Frame Check Sequence (FCS). For example, Ethernet uses 802.3 Standards.
Vocabulary Exercise: Matching
a. Start Frame| g. Used to indicate overloading on the medium| b. Address| f. Used to start and stop traffic when overloading occurs| c. Type| d. Specifies the number of bytes in the data part of the frame| d. Length| c. Indicates the upper-layer service contained in the frame| e. Priority| a. Tells other...