In an internetworked environment running the 5-layer TCP model, an application on one host sends a packet to a companion application on another host. They pass through four devices: a switch, two routers, and another switch.

1. Through how many communications links will packets?
2. Suppose the local LAN at the host is 100Mbps Ethernet from the switch to the host, and 10Mbps from the switch to the router. At the far end, all of the LAN connections from the switch are gigabit ethernet to everything that switch touches. The path between the routers is a radio microwave service. Because of our layered model, what extra code will the application developer be required to write for his packets to pass through these different communications mediums?
3. Switches are devices that operate only at the bottom two layers of the 5-layer stack. Routers operate at the bottom 3 layers. We know that the physical layer of two devices is what allows them to send bits back and forth to each other. Our host uses one of these connections to reach a switch. At what layer will they implement a protocol to manage the groups of bits they send back and forth
4. There is Layer 3 Network Layer protocol (IP protocol) implemented in each router. Is it also implemented in the hosts?
5. At that layer three, how many pairs of communications streams are present across the network? In other words, how many connections between pairs of devices that have a layer 3 module implemented are there?