|  | 6.1 |
| Ethernet Fundamentals
|  | 6.1.3 |
| Ethernet and the OSI model
Ethernet operates in two areas of the OSI model, the lower half of the data link layer, known as the MAC sublayer and the physical layer. To move data between one Ethernet station and another, the data often passes through a repeater. All other stations in the same collision domain see traffic that passes through a repeater. A collision domain is then a shared resource. Problems originating in one part of the collision domain will usually impact the entire collision domain. A repeater is responsible for forwarding all traffic to all other ports. Traffic received by a repeater is never sent out the originating port. Any signal detected by a repeater will be forwarded. If the signal is degraded through attenuation or noise, the repeater will attempt to reconstruct and regenerate the signal. Standards guarantee minimum bandwidth and operability by specifying the maximum number of stations per segment, maximum segment length, maximum number of repeaters between stations, etc. Stations separated by repeaters are within the same collision domain. Stations separated by bridges or routers are in different collision domains. Figure maps a variety of Ethernet technologies to the lower half of OSI Layer 2 and all of Layer 1. Ethernet at Layer 1 involves interfacing with media, signals, bit streams that travel on the media, components that put signals on media, and various topologies. Ethernet Layer 1 performs a key role in the communication that takes place between devices, but each of its functions has limitations. Layer 2 addresses these limitations. Data link sublayers contribute significantly to technology compatibility and computer communication. The MAC sublayer is concerned with the physical components that will be used to communicate the information. The Logical Link Control (LLC) sublayer remains relatively independent of the physical equipment that will be used for the communication process. Figure maps a variety of Ethernet technologies to the lower half of OSI Layer 2 and all of Layer 1. While there are other varieties of Ethernet, the ones shown are the most widely used.
|  | Interactive Media Activity
Drag and Drop: The OSI Model After completing this activity, the student will be able to identify the 7 layers of the OSI model including the two data link sublayers. Interactive Media Activity 6.1.3 is located in the CCNA 3.0 Bridge 1 Activities and Quizzes file. The Activities and Quizzes file can be downloaded in the Course Material section of your class homepage.
Web Links
The OSI Model http://www.usyd.edu.au/is/comms/ networkcourse/ USydNet_mod1_ introduction&amp;osimodel.html#tocOSIModel