a. What is the network layer used for? What is interior routing and what is exterior routing? In the Open Systems Interconnection model (OSI model), the network layer is at the third level, and for network communication, it provides paths for data routing. It is considered the backbone of the OSI model because for the purpose of data transfer between nodes, the network layer performs the selection and management of the best logical path. Switches, firewalls, bridges, and routers are hardware devices that this layer contains. From the transport layer, it responds to requests and sends requests to the data link layer. The process of moving data from one network to another is called routing. Interior Gateway Protocols (IGPs) manage routing within a single autonomous system. They keep track of the paths used to move data from one system to another within a network. All networks communicate with each other via IGPs. On the Internet, if we need to move from one place to another outside of a network, the use of EGP (Exterior Gateway Protocol) comes into play or for communication purposes between several autonomous systems. use EGP.b. What is Quality of Service Routing and why is it useful? The standards and mechanisms established to enable high-quality performance for applications are known as Quality of Service routing. Its main purpose is to provide a special service to applications that need it by ensuring that the required bandwidth is provided, controlling latency and reducing data loss. Some of its useful features are: User experience is improved. Utilizes already existing resources and reduces costs, reducing the need for upgrades and growth. Administrators are allowed to control the network. .... middle of paper .... ....triple IP addresses and VLANs due to its connection with different VLANs and three subnets. Upon receiving the message, the router being a layer 3 device drops the Ethernet frame and reads the IP packet. The router looks at the routing table and notices that the destination IP address (179.58.10.101) is in a subnet that it controls (179.58.10.1). The new Ethernet frame is now created by the router and sets the destination Ethernet address on the destination computer2. It uses ARP if necessary and sends the frame to switch 3. Switch 3 reads the Ethernet address and looks it up in its forwarding table. It discovers that the frame should be forwarded to Switch 1. The VLAN tag field is now set and forwards the frame over the trunk to Switch 1. Switch 1 removes the VLAN tag information and sends the frame to the correct computer (Computer2 ). In our case