Spring 2020 CPET 281 Local Area Networks And Management ✓ Solved

Spring 2020cpet 281local Area Networks And Managementtap5 Quiz 3 15

Identify the core assignment question: Explain the differences between forwarding and routing, discuss switching techniques used by routers and identify the fastest one, analyze data overhead versus application data in network segments, describe packet loss and its mitigation, explain IP address assignment and NAT in a home network, evaluate true/false statements about networking and encryption, discuss the impossibility of decrypting hashes, encode and decode messages using monoalphabetic cipher, and analyze the number of interfaces and forwarding tables involved in data transmission across routers.

Sample Paper For Above instruction

Understanding Forwarding vs. Routing and Switching Techniques

In computer networks, forwarding and routing are fundamental operations that determine how data packets travel from source to destination. Forwarding is the process performed by routers and switches that involves moving packets from an input interface to an appropriate output interface based on the destination address. Routing, on the other hand, determines the entire path that data packets take across multiple networks, typically through the use of routing algorithms and routing tables (Kurose & Ross, 2017).

Switching techniques employed by routers include store-and-forward, cut-through, and fragment-free switching (Tanenbaum & Wetherall, 2011). Store-and-forward switching reads the entire packet before forwarding, ensuring error checking but introducing delay. Cut-through switching begins forwarding once the destination MAC address is read, reducing latency but risking forwarding erroneous packets. Fragment-free switching forwards packets after reading the first 64 bytes, balancing error detection and low latency. Fasting switching is achieved through cut-through switching, which minimizes delay by forwarding packets as soon as the destination address is available (Comer, 2018).

Overhead and Data Analysis in Network Segments

When data is transmitted over networks, overhead includes protocol headers added at various layers, which do not constitute user data. Assuming an application generates 40-byte chunks every 20ms encapsulated in TCP segments and IP datagrams, overhead consists of TCP and IP headers totaling approximately 40 bytes per segment. The total datagram size would be roughly 80 bytes, with about 40 bytes overhead, making overhead approximately 50% and data 50%. Increasing the chunk size to 80 bytes doubles the data portion, reducing overhead percentage to about 33.3%, as the data makes up most of the total datagram (Forouzan, 2013).

Packet Drop Causes and Prevention

Packets may be dropped at a router's input port due to congestion, buffer overflow, or queue overloads (Kurose & Ross, 2017). To prevent packet loss, routers can implement congestion avoidance algorithms such as Random Early Detection (RED), increase buffer sizes, or utilize Quality of Service (QoS) policies to prioritize critical traffic (Tanenbaum & Wetherall, 2011). Proper network design with adequate bandwidth and traffic management also reduces the risk of packet loss.

IP Addressing and NAT in Home Networks

In typical home networks connected via a wireless router, external IP addresses are assigned dynamically by the ISP, often via DHCP (Dynamic Host Configuration Protocol). The seven PCs at home receive private IP addresses assigned by the router through NAT (Network Address Translation), which translates internal local addresses to the single external public IP address. The router uses NAT to enable multiple devices to share a single public IP and offers security by hiding internal IP addresses from external entities (Comer, 2018).

True or False Network and Security Statements

a. False. VPNs commonly ensure data encryption through application-layer protocols like TLS rather than at the datalink or physical layers.

b. False. IP datagrams are encapsulated within TCP segments, not the other way around.

c. False. Packets can be dropped at output ports due to congestion, buffer overflow, or hardware errors.

d. True. Monoalphabetic ciphers are vulnerable to frequency analysis, making them easy to decrypt.

e. False. Stateless packet filters do not track TCP connection states; stateful filters do.

Decrypting Hashes

Hashes are designed as one-way functions, meaning they are not reversible. Attempting to decrypt a hash to recover the original message is infeasible because hashes do not contain the original data but rather a fixed-size digest representing it (Stallings, 2017). Therefore, it is impossible to decrypt a hash directly to obtain the original message.

Monoalphabetic Cipher Encoding and Decoding

The cipher maps each letter to a unique substitute based on a key. To encode "this is the last tap in the online course" using a specific monoalphabetic cipher, each letter is replaced accordingly; the exact process depends on the key. Decoding the message "vk jku bklw mjv lmiuc" involves reversing the substitution. Due to the absence of the key in the prompt, the specific cipher cannot be demonstrated here, but the general approach is substitution based on the cipher alphabet.

Drawbacks of monoalphabetic ciphers include vulnerability to frequency analysis, which allows attackers to crack the cipher easily. Enhancing security involves using polyalphabetic ciphers like the Vigenère cipher or adding more complex encryption layers (Stallings, 2017).

Routing Interfaces and Forwarding Tables in Multi-router Paths

The data packet from PC1 to PC2 traverses four routers, each with at least two interfaces—one in and one out—resulting in a total of eight interfaces involved. The datagram's path involves each interface for forwarding, and each router maintains a forwarding table to decide the appropriate outgoing interface. Since each router uses its own forwarding table, four tables are ultimately indexed to progress the datagram through the network (Kurose & Ross, 2017).

References

• Comer, D. (2018). Computer Networks and Internets. 6th Edition. Pearson.
• Forouzan, B. A. (2013). Data Communications and Networking. 5th Edition. McGraw-Hill Education.
• Kurose, J. F., & Ross, K. W. (2017). Computer Networks: A Systems Approach. 7th Edition. Pearson.
• Stallings, W. (2017). Cryptography and Network Security: Principles and Practice. 7th Edition. Pearson.
• Tanenbaum, A. S., & Wetherall, D. J. (2011). Computer Networks. 5th Edition. Pearson.