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The main function of this Case Study was to introduce the basic concepts of internetworking and have the group engineer the network layout for the assigned building. We did this according to the drawing found on the Other Materials page.

The main learning objectives of the TCS were the following:

1. Identify the seven different layers of the OSI Reference Model and describe what each of them does.

Physical - Comprised of all the physical cabling and devices in a network. Data Link - Responsible for flow control and physical addressing (MAC.) Network - Main purposes are path determination and switching. Transport - Mostly used for data segmentation and error correction. Session - Creates and maintains sessions between applications. Presentation - Converts from computer language to human language. Application - Provides network services to applications. I.E. E-Mail and Telnet.

2. Explain how IP addressing works, the different parts of network addressing (IP and MAC), and the different classes of IP addresses that are available from InterNIC.

IP Address - 32 bit address that has four octets. Logical addressing, can be easily be changed at any time.
MAC Address - 48 bit hexadecimal address contained on a chip located on the NIC. Permanent address.

Class A - (NNN.HHH.HHH.HHH) First octet must be 0-127. "A" licenses have the most available hosts.
Class B - (NNN.NNN.HHH.HHH) First octet must be 128-191. "B" licenses have the 2nd most hosts.
Class C - (NNN.NNN.NNN.HHH) First octet must be 192-223. "C" licenses have the fewest hosts.

3. Describe how data encapsulation works.

When a user sends out information its alphanumeric characters are converted to use the network. This is the actual data. Second, one change packages the message "data" for network transport. This is accomplished by using segments and the transports layer makes sure both ends of the transfer can reliably communicate. Third, the next change puts the data into packets that contain the source and destination logical addresses. fourth, each network device must put the packet into a frame. The frame allows connection to the next directly connected network device on the link. finally the frame must be converted into a pattern or 1's and 0's for transmission on the medium.

4. Explain the pros and cons of using a certain network device over another within your LAN.

The three main devices used within a LAN:

Bridges - Key benefit is filtering traffic based on MAC address. If a bridge receives a packet and notices the destination MAC address is located on the segment that the packet came from, it will not forward it. If the destination MAC address is on the next segment, the bridge will forward the packet and send it on its way. Switch - Provides dedicated bandwidth. This is a good feature because each port on a switch has the same amount of bandwidth. That way each device that is plugged into a switch port has just as much bandwidth as another. This keeps your network from being bogged down by hubs. Routers - A router is the most intelligent device that can be used on a network. Routers are the devices that make all the real decisions. They decide where to forward a packet based on IP address and they also separate networks. Each port on a router is capable of being its own network.

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