What Is A Link Layer Frame And Network Layer Data?

Question 1what Is A Link Layer Frame A Network Layer Datagram A Tran

Question 1 what is a link-layer frame? A network layer datagram? A transport-layer segment? an application-layer message? Question 2 Is it possible for an application to enjoy reliable data transfer even when the application runs over UDP? If so, how? Question 3 Consider a router that interconnects three subnets: Subnet 1, Subnet 2, and Subnet 3. Suppose all of the interfaces in each of these three subnets are required to have the prefix 223.1.17/24. Also, suppose that Subnet 1 is required to support at least 60 interfaces, Subnet 2 is to support at least 90 interfaces, and Subnet 3 is to support at least 12 interfaces. Provide three network addresses (of the form a.b.c.d/x such as 223.1.17/24) that satisfy these constraints, and how the steps of how to obtain your answers. Question 4 Case study In this problem, you need to put together what you have learned about Internet protocols. Suppose you walk into a room outside CSU campuses, connect to Ethernet, and want to download Slides published in a Web page of the ITC 542 site in Interact 2. What are all the protocol steps that take place, starting from powering on your PC to getting the CSU Web page? Assume there is nothing in our DNS or browser caches when you power on your PC. (Hint: the steps include the use of Ethernet, DHCP, ARP, DNS, TCP, and HTTP protocols.) Explicitly indicate in your steps how you obtain the IP and MAC addresses of a gateway router. Answers with APA format and with references.

Paper For Above instruction

The communication process across computer networks involves various layers, each serving specific functions and passing data units called Protocol Data Units (PDUs). Understanding the distinctions among these units—link-layer frames, network-layer datagrams, transport-layer segments, and application-layer messages—is fundamental to network communications. Additionally, recognizing how applications achieve reliability over unreliable protocols and the process of network address assignment are crucial topics in networking. This paper discusses each aspect in detail, exemplified through a practical case study involving accessing a web page within a campus network.

Understanding the Basic Data Units in Network Layers

At the link layer, data is encapsulated into frames, which include not only the payload but also header and trailer information necessary for data transmission over a physical medium. A link-layer frame commonly comprises source and destination MAC addresses, along with error detection codes such as CRC. These frames traverse from a network device’s physical interface to neighboring devices and are essential for local network communication (Tanenbaum & Wetherall, 2011).

The network layer distinguishes itself by encapsulating the data into datagrams. A network layer datagram contains source and destination IP addresses, enabling routing across multiple networks. It is a self-contained packet that can be independently routed from source to destination through various hops (Comer, 2018).

Transport layer segments are units of data provided to facilitate end-to-end communication between processes running on hosts. For TCP, a segment includes flow control, error detection, and sequence numbering, offering reliable data transfer. UDP, by contrast, provides a minimal service, encapsulating data into segments without reliability guarantees (Stevens, 1994).

An application-layer message is the data generated by user applications, such as web page requests or emails. This message is encapsulated beneath various protocol headers as it moves down the layers, ultimately transmitted over the physical medium as frames (Kurose & Ross, 2017).

Reliability Over UDP

While UDP (User Datagram Protocol) is inherently unreliable, applications can implement mechanisms to achieve reliable data transfer, such as acknowledgments, retransmissions, sequencing, and timeout management. For instance, streaming media applications or file transfer services may incorporate application-layer protocols like RTP (Real-time Transport Protocol) or custom reliability schemes atop UDP (Perkins et al., 2003). This layered approach allows the application to control data integrity despite UDP's minimal overhead, providing flexibility and efficiency for specific use cases.

Addressing Subnet Design Constraints

Designing network addresses for multiple subnets with specific host requirements involves subnetting techniques. Given the requirement for three subnets with prefixes 223.1.17/24 and varying host counts—subnet 1 with at least 60 hosts, subnet 2 with 90 hosts, and subnet 3 with 12 hosts—the subnet masks must be chosen accordingly.

For subnetting, we first determine the number of bits needed to support the hosts:

• Subnet 1 (≥60 hosts): 6 bits (2^6 - 2 = 62 usable addresses)
• Subnet 2 (≥90 hosts): 7 bits (2^7 - 2 = 126 usable addresses)
• Subnet 3 (≥12 hosts): 4 bits (2^4 - 2 = 14 usable addresses)

Adjusting for CIDR notation:

• Subnet 1: 223.1.17/26 (supports 62 hosts)
• Subnet 2: 223.1.17/25 (supports 126 hosts)
• Subnet 3: 223.1.17/28 (supports 14 hosts)

Given that all subnets include the prefix 223.1.17, the network addresses can be assigned as follows:

• Subnet 1: 223.1.17.0/26
• Subnet 2: 223.1.17.128/25
• Subnet 3: 223.1.17.144/28

These assignments satisfy the host requirements and adhere to the common prefix.

Case Study: From Powering On to Web Page Retrieval

When a user powers on their PC outside the CSU campus, several protocol steps take place to retrieve a web page hosted within the campus network, specifically the ITC 542 site in Interact 2. Assuming no cached information, the process involves activating hardware, acquiring network configurations dynamically, resolving addresses, establishing connections, and retrieving data.

Initially, powering on the PC initiates the POST process, followed by the network interface card (NIC) initializing. The PC then uses the Dynamic Host Configuration Protocol (DHCP) to obtain an IP address and network parameters. The DHCP process involves broadcasting DHCPDISCOVER messages to locate DHCP servers, which respond with DHCPOFFER. The client then requests an IP address via DHCPREQUEST, and the server confirms with DHCPACK, providing IP, subnet mask, default gateway, and DNS server addresses (Reilly, 2017).

To communicate with the default gateway, the PC must resolve the MAC address of the router. It sends an Address Resolution Protocol (ARP) request broadcast to find the MAC address associated with the default gateway’s IP address. Upon receiving the ARP reply, the PC records the MAC address corresponding to the gateway.

Next, the PC initiates a DNS query to resolve the domain name of the CSU website to an IP address. It first checks its cache; since the cache is empty, it sends a DNS query to the configured DNS server. The server responds with the IP address of the web server hosting the CSU page.

To establish a connection, the PC initiates a TCP handshake with the web server. It sends a SYN packet, receives SYN-ACK, and completes the handshake with an ACK. Following this, an HTTP GET request is sent to retrieve the web page content. The server responds with the HTML, which is then rendered by the browser. Throughout this process, Ethernet frames encapsulate all Protocol Data Units, with MAC addresses obtained via ARP and IP addresses through DHCP and DNS (Kurose & Ross, 2017).

Conclusion

The layered approach in network communications ensures reliable and efficient data transfer. From the initial hardware activation, configuration via DHCP, address resolution through ARP, address resolution via DNS, and data transfer over TCP, each protocol plays a vital role in successfully downloading web content. Recognizing the interaction among these protocols enhances our understanding of internet operations and network design principles.

References

• Comer, D. E. (2018). Computer Networks and Internets (6th ed.). Pearson.
• Kurose, J. F., & Ross, K. W. (2017). Computer Networking: A Top-Down Approach (7th ed.). Pearson.
• Perkins, C., Royer, E., & Egan, R. (2003). RTP: A transport protocol for real-time applications. IETF RFC 3550.
• Reilly, S. (2017). DHCP essentials: How DHCP works and why it matters. Network World.
• Stevens, W. R. (1994). TCP/IP Illustrated, Volume 1: The Protocols. Addison-Wesley.
• Tanenbaum, A. S., & Wetherall, D. J. (2011). Computer Networks (5th ed.). Pearson.