Week 2 notes
4.1 Ethernet As you study this section, answer the following questions:
What logical topologies are supported on an Ethernet network? What is the purpose of the backoff on Ethernet networks? How can you eliminate collisions on an Ethernet network? What device is used to enable full-duplex communications with Ethernet?
The key terms for this section include:
Term
Definition
UTP stands for unshielded twisted pair. UTP cables are easy to work with and less expensive than shielded cables.
UTP
MAC Address
A Media Access Control (MAC) address is a unique identifier burned into the ROM of every Ethernet NIC.
The cyclic redundancy check (CRC) is the result of a mathematical calculation performed on the frame. The CRC helps verify that the frame contents have arrived uncorrupted.
CRC
This section helps you prepare for the following certification exam objectives:
Exam
Objective
CompTIA Network+
1.3 Explain the concepts and characteristics of routing and switching.
Properties of network traffic CSMA/CD
2.1 Given a scenario, deploy the appropriate cabling solution.
Transceivers
Characteristics of fiber transceivers
Duplex
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4.1.1 Ethernet Architecture l>>0:01 / 8:201. Ethernet Architecture
IL Interactive Script
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0 Ethernet Architecture 0:00-0:11
Ethernet is the most popular local area networking standard. In this video, we're going to talk about what makes Ethernet architecture unique.
Topology 0:12-1:04
Ethernet can use two physical topologies. Older Ethernet standards use a physical bus topology, where you have a single common trunk that all network devices connect to.
Newer Ethernet standards use a physical star topology, where you have a central device, such as a hub or a switch, connected to all the devices.
Ethernet architectures that use a physical star topology use one of two logical topologies:
Hub-based networks use a logical bus topology, where a signal coming into a hub is
is forwarded only to that device and not to any other.
Ethernet supports both copper unshielded twisted pair cables and fiber optic cables.
Ethernet uses a unique media access method, which refers to the set of rules that determine how devices can access the network medium and transmit data.
Carrier Sense Multiple Access Collision Detection (CSMA/CD) 1:05-2:38
Ethernet uses Carrier Sense Multiple Access Collision Detection, or CSMA/CD. Let's look at the media access method in the context of a bus topology.
In this scenario, a linear physical bus topology also uses a logical bus topology. Computers A, B, and C are connected to the network medium.
Suppose computer A needs to send a message to computer B. According to the CSMA/CD media access method, the first thing computer A must do is listen to the transmission medium to see if data is already being transmitted. This is called carrier sense. It's like using a two-way radio. Before you talk, you briefly listen to see if anybody else is already talking.
Let's say that computer A listens to the medium, determines that it's clear, and transmits its message to computer B. When the message is sent to