Is589Week3

IS589

Rodger Strother

Keller Graduate School of Management

Chapter 4 Questions

Question 1

What does the data link layer do ? The Data Link layer performs a number of separate activities, including: Physical addressing Network topoloty Error notification Access to the physical medium Flow control . Different data link layer specifications define different network and protocol characteristics, including physical addressing, network topology, error notification, sequencing of frames, and flow control.

Physical addressing, is not to be confused with network or IP addresing. The physical address defines how devices are labeled in the data link layer. This physical address is most commonly called the Media Access Control (MAC) address. The MAC address is a unique number assigned by the manufacturer. This numbering system is actually administered by one of the networking governing bodies. Network topology consists of the data-link layer specifications that often define how devices are to be physically connected, such as in a bus or a ring topology. Error notification alerts upper layer protocols that a transmission error has occurred, and the sequencing of data frames reorders frames that are transmitted out of sequence. Finally, flow control moderates the transmission of data so that the receiving device is not overwhelmed with more traffic than it can handle at one time. Switches and bridges use MAC addressing to make networking decisions and therefore these types of equipment function on the data link layer. Logical Link Control (LLC) Conceptually, the LLC sublayer sits on top of the MAC sublayer. It's defined by the 802.2 standard to be topology independent. The LLC functions include:

Managing frames to upper and lower layers

Error Control

Flow control

The LLC works with the transport layer by providing connection-oriented and connectionless services. It manages and creates the communication link.

The LLC...