LINK LAYER (AND NETWORK LAYER) ADDRESSING AND FORWARDINGConsider the figure below. The IP and MAC addresses are shown for nodes A, B, C and D, as well as for the router's interfaces.1F-2C-5D-67-62-8E128.119.134.90AQUESTION 3 OF 5AnswerConsider an IP datagram being sent from node D to node C.What is the source IP address at point 5?6A-A4-2E-AB-94-D3128.119.81.211BFA-7C-90-45-8C-1D128.119.134.23972-F0-35-56-CA-42128,119.81.191(4)47-FF-04-D4-B3-27128.119.20.251CC-CF-5A-C7-02-03128.119.20.755E-C8-B0-3D-5D-DE128,119,20,91

Link Layer Addressing and Forwarding: The link layer, also known as the data link layer, is responsible for the node-to-node communication over the physical link, typically involving devices on the same local network. Link layer addressing involves assigning unique Media Access Control (MAC) addresses to network interface cards (NICs) of devices. These addresses facilitate the identification of devices on a local network, enabling the framing of data packets for reliable transmission. Forwarding at the link layer involves the local delivery of packets between directly connected nodes, using MAC addresses to navigate the network. Switches operate at this layer, making forwarding decisions based on MAC addresses to optimize local traffic.Network Layer Addressing and Forwarding: The network layer operates above the link layer and is concerned with end-to-end communication across multiple networks. Internet Protocol (IP) addresses are assigned at the network layer, uniquely identifying devices globally. Forwarding at the network layer involves routing packets between different networks, and routers play a crucial role in this process. Routers make forwarding decisions based on destination IP addresses, determining the most efficient path for data packets to reach their intended destination. Network layer addressing allows for the establishment of logical connections between devices across diverse physical networks.Let's break down the details of the source and destination IP addresses at point 5 in the given scenario:1. Source IP Address at Point 5:The source IP address at point 5 is the IP address of the node or device that initially sent the IP datagram. In the provided scenario, the source IP address is 128.119.167.204.2. Destination IP Address at Point 5:The destination IP address at point 5 is the IP address of the node or device to which the IP datagram is intended. In this case, as the datagram is being sent from node D to node C, the destination IP address remains the same as the initial destination, which is 128.119.167.204.Conclusion:In the journey of an IP datagram from the source (node D) to the destination (node C), the source and destination IP addresses do not change at point 5. This consistency is a fundamental characteristic of IP addressing, where the source and destination IP addresses remain constant throughout the path of the datagram within a network. The source IP address represents the origin, and the destination IP address signifies the final destination of the data packet. In the given context, both IP addresses are identified as 128.119.167.204 at point 5.