Science

Lesson 5 Review: Networking Models, Traffic and Devices
The purpose of this activity is to reinforce what you have learned so far about local area networks technologies.

1. Describe the three modes of communication available on a network.
Simplex Data travels in only one direction, similar to a public address (PA) system. Half-duplex Data travels in two directions, but in only one direction at a time, similar to a walkie-talkie. Traditional shared Ethernet uses half-duplex transmissions. Full-duplex Data travels in two directions simultaneously, similar to a phone conversation. Full-duplex Ethernet (or switched Ethernet) supports full-duplex transmissions in a switched environment.
2. List the seven layers of the OSI model, including both layer number and name for each.
Layer 1 is the Physical Layer, Layer 2 is the Data link Layer, Layer 3 is the Network, Layer 4 is the Transport Layer, Layer 5 is the Session Layer, Layer 6 is the Presentation, and Layer 7 is the Application Layer.

3. Describe a protocol data unit (PDU).
Protocol Data Unit is a unit of data that is passed from one OSI layer another. Layer 7 takes a manageable piece of the data and adds its own information (called the header) to it. The piece of the original data is now referred to as payload. The entire unit (the payload plus the header) is referred to as a protocol data unit (PDU) and it is passed down to Layer 6.

4. List three practical functions of the OSI model.
1. It gives developers necessary, universal concepts so they can develop and perfect protocols that can work with operating systems and network products developed by other vendors. 2. It explains the framework used to connect different types of systems. That is, it allows clients and servers to communicate even if they are using different applications and operating systems; all they need is a common protocol, such as TCP/IP. 3. It describes the process of packet creation.

5. Describe a collision domain.
Collision domain — An area in a network where a group of network devices compete for access to the transmission medium. In traditional Ethernet networking, only one device can transmit at any time. When two devices attempt to transmit at the same time, their transmitted frames collide and are destroyed. The greater the number of collisions, the less efficient the network. For this reason, large networks are frequently divided into distinct collision domains through the use of a networking device such as a switch, bridge or router. Dividing a network into distinct collision domains reduces the number of collisions in the overall network, and keeps the network functioning efficiently.