What would happen if wireless devices were not governed by the Wi-Fi Alliance and each vendor had its own standards and protocols? What impact would this have on your personal life or business communications? Personal information and business will slow down due to each vendor having its own standards/protocols. It will also be more vulnerable to attacks and make accessing more difficult.
Give another example of a model that is used to visualize something that is difficult to observe or perceive. How does the model make it easier to understand? Another way of displaying information for easier understanding is to use a flow chart. A flow chart can be used as a step by step guide.
Based on what you already know about networks, what are the different layers you think would be necessary for communication to be mapped to a model? Consider direct connections between host devices and connections that require other routing equipment, such as a hub, switch, or router.
1. Data link
The granularity of the reference model will often determine the usefulness of the model. What will happen if a model is too general? What will happen if a model is too granular (focused on individual detail)? If the data is too detailed, it may overlap with other information. However if the data is too general, then there may be crucial information missing.
1. Why would a three-layer model of communication that has the layers physical, network, and application be insufficient to adequately describe network communication? The model would be insufficient because it would not have the ability to transport data to any other network.
2. What is the history of the OSI reference model? How did it come about and why was it created? Use your textbook and internet research to support your answer. OSI was created in the late 1970s. It was created to define a unifying standard of architecture for networking systems. OSI was meant to be the foundation for what would later be known as the internet but when comparing to TCP/IP protocols, OSI just wasn’t enough to support the rapid growth of the internet. Now, the OSI model is used to explain networking in general terms. OSI is still used today by software/hardware designers to clarify roles in a networking system.
3. What is the history of TCP/IP model? Why was it created? Use your textbook and internet research to support your answer. TCP/IP was developed in the early 1970s, originally as part of a research network the United States Defense Advanced Research Projects Agency (ARPA) developed. However, due to the TCP/IP protocols limitations and flaws, ARPA developed a new network. In the mid-1970s, it was found that TCP was attempting to do too much. This is when they decided to split TCP and IP into two separate layers. In the 1980s, TCP/IP was used to run ARPAnet and also started to expand to other machines and networks, completely evolving ARPAnet. This is how the internet was born.
Using Figure 3-1, define each layer of the OSI model in your own words and state what each layer provides. Use your textbook or internet research to support your answer. Application – Quality of service is established, communication partners are identifies, user authentication and privacy is considered and established. Presentation – Changes data into a form that the application can accept. Session – Manages and terminates connections between applications. Transport – Transfers data between systems, maintains flow control and recovery. Network – Provides switches and routing technologies and creating logical paths. Data link – Data packet is encoded
Physical – provides the hardware necessary for sending and receiving data, bit stream
Using Figure 3-2 as a basis, complete the diagram to show the intermediate encapsulation provided by each layer. Use your textbook and internet research to support your answer. Transport – Segments
Network – Packets
Data link – Frame
Briefly explain the de-encapsulation steps in the communication of host B receiving a message and host A destined for an active application. Host A will use application for the OS while allowing the PC to still communicate to other devices. Transport will control the data sent and received. The network will place IP addresses to the packets allowing data to be added to the MAC addresses and physical link between host and lines.
Explain why routing devices do not need the upper layer of the OSI model to route traffic. What is the highest layer of the OSI model used by the router to decide where to forward traffic? The first three layers of the OSI is typically what a router needs to route traffic. The first three layer are physical, data link and network. The highest level the OSI decide where to forward traffic to is the transport layer which is located in the host layers.
Lab 3.2 Review
1. How does the abstraction of the physical layer facilitate interoperability across networks using different types of physical wires?
IP terminals might be located in different parts of the build making it complex. There are lines coming in and out of the build that might be different than that issued to a company. To try and replace one will be complex, confusing and time consuming if unsure.
2. The OSI model is not directly implemented in networking and often the distinction between the layers will blur in implementation. Why does it endure despite these issues? Use your textbook and internet research to justify your answer.
Technicians still use the OSI model because it gives a step by step guide on how the information is being transported and makes troubleshooting more precise.
3. Given the purpose of each, is it necessary to retain the top three layers of the OSI model as separate entities? Use your textbook and internet research to justify your answer.
It is not necessary to keep the top three layers of the OSI model when TCP/IP combines the top three layers of OSI into one layer that ultimately does the same functions.
Using your textbook and internet research, create a mapping between the TCP/IP model and the OSI reference model. What are the distinct differences between them?
One major difference between OSI and TCP/IP is the first three layers of OSI are combined into a single layer in TCP/IP known as the Application Layer. The other difference is the last two layers, Data link and Physical layer are combined into one layer known as Network Access or Link Layer.
Identify the layer in which each protocol resides according to the TCP/IP model. OSI #
OSI Layer Name
TCP/IP Layer Name
FTP, HTTP, POP3, IMAP, telnet, SMTP, DNS, TFTP
The most common protocols used from this suite are IP, TCP, and UDP. Briefly describe the purpose and function of each of these. Use your textbook and internet research to support your answer. UDP – User datagram protocol – this is a connectionless service the gives best-effort delivery but does not guarantee delivery. This is often used for point-to-point and point-to-multipoint communications such as video conference applications. IP – Internet protocol – Primarily a communications protocol within the internet protocol suite that relays datagrams across network boundaries. Ultimately it establishes the Internet. Delivers packets from the source host to destination hosts based on IP address in the packet header. TCP – Transmission Control Protocol – Core protocol of IP. Known for its reliability and error checking delivery between programs running on computers connected by common networks. Sends data in the form of message units between computers using the internet.
Lab 3.3 Review
1. UDP is a connectionless protocol, unlike TCP, so there is no feedback on whether a packet was received. When would this type of protocol be used and what is the benefit of using it? Use your textbook and internet research to draw your conclusions.
UDP is ideal for when you are managing a large amount of information and you don’t want to use TCP because the operating system won’t be able to support that many sessions at one time. This does not happen frequently as TCP has become more reliable but it still is one example of why you’d rather use UDP. UDP can also get a quick response from another server more quickly. However UDP has been viewed as unreliable because there is no feedback and information can get lost.
2. HTTP is the common protocol used to retrieve web resources in a web browser. This runs over TCP/IP networks using TCP. What characteristics of TCP make its use in this situation desirable? Use your textbook and internet research to draw your conclusion.
The feedback feature in TCP is ideal because you are guaranteed that messages will be sent and received successfully. One common application that is a prime example of TCP and its success is through e-mail.
The data link layer introduces physical addressing in the form of Media Access Control (MAC) addresses. Each frame header is Ethernet, for example, will contain a source and destination MAC address. Why is this sufficient to route traffic locally without invoking the higher-level logical addressing? Use your textbook and internet research to guide your conclusion. MAC addresses are sufficient enough to route traffic to other networks because the frame header of MAC addresses contains all that is required without having to access higher level logical addresses.
Choose one of the captured packets. Click the + sign next to the Ethernet entry. This should give you the data link layer information for the frame, including the source and destination MAC addresses. Record the frame number and the source and destination MAC addresses identified by the data link layer heading. You can identify a MAC address by its format; for example, 00: 26: 62: 65: 81: 07 00:26:62:65:81:07 is a MAC address. These are commonly written in hexadecimal shorthand.
Open a web browser and navigate to a site that you use frequently (or visit www.pearson.com) while the packet capture is active. This will record the individual frames involved in resolving the website and delivering its content to your PC. When you view this traffic in the life packet capture, what protocols do you see invoked? You can find these under the Protocol heading for each frame.
Exercise 3.4.4 and Exercise 3.4.5 cannot do because student doesn’t have access to data link layer connection (Omnipeek).
Lab 3.4 Review
1. Wireshark give you the ability to save captured traffic. This can be a great benefit to network administrators, but it can also pose a security risk. What kind of security risks does this present? Use your textbook and internet research to support your conclusion.
There are a few risks associated with Wireshark. There is a possibility of a back-door hack, and the security configuration of Wireshark enables it to run in the background after exiting. While running in the background, one can access your routing information, IP addresses, passwords and usernames. 2. The frame encapsulates all other information from the higher layers of the network communication. What kind of information on the network layer encapsulation is available in Wireshark?
Using Wireshark, you can track Wi-Fi access, IP addresses, network routings and encrypted packets.