CPTR.3700 Commun/Cptr Ntwrks 1 test2 ACTUAL UPDATED QUESTIONS AND CORRECT ANSWERS

CPTR.3700 Commun/Cptr Ntwrks 1 test2 ACTUAL UPDATED QUESTIONS AND CORRECT ANSWERS Distinguish between communication at the network layer and communication at the data-link layer. - CORRECT ANSWERSCommunication at the network layer is host-to-host; communication at the data-link layer is node-to-node. Can two hosts in two different networks have the same link-layer address? - CORRECT ANSWERSTwo hosts in two different networks can theoretically have the same link layer address because a link-layer address has only local jurisdiction. However, the tendency is to avoid this for the future development of the Internet. Even today, manufacturers of network interface cards (NIC) use different set of link-layer addresses to make them distinguished. What is the size of an ARP packet when the protocol is IPv4 and the hardware is Ethernet? - CORRECT ANSWERSARP Packet Size = 2 + 2 + 1 + 1 + 2 + 6 + 4 + 6 + 4 = 28 bytes Assume we have an isolated link (not connected to any other link) such as a private network in a company. Do we still need addresses in both the network layer and the data-link lay? Explain. - CORRECT ANSWERSEach hop (router or host) should know its own link layer address. The destination link-layer address is determined by using the Address Resolution Protocol When we talk about the broadcast address in a link, do we mean sending a message to all hosts and routers in the link or to all hosts and routers in the Internet? In other words, does a broadcast address have a local jurisdiction or a universal jurisdiction? Explain. - CORRECT ANSWERSA broadcast address is an address used to indicate that information being sent out should be delivered to every client on the local area network. Broadcasts on the Data Link Layer correspond to MAC addresses. When a MAC address broadcast is sent out, each network interface card on the local area network will see the broadcast address and automatically pass the information up to the upper layers of the OSI model. Why does a host or a router need to run the ARP program all of the time in the background? - CORRECT ANSWERSA host does not know when another host sends an ARP request; it needs to be ready all of the time to respond to an ARP request. Why does a router normally have more than one interface? - CORRECT ANSWERSThe purpose of a router is to connect two or more networks together. It will then route data between them. Therefore, a router has to have at least two interfaces. In Figure 9.5, assume Link 2 is broken. How can Alice communicate with Bob? - CORRECT ANSWERSThe communication is impossible unless router R1 can reach router R2 using another path (not shown in the figure) In Figure 9.5, show the process of frame change in routers R1 to R2. - CORR