420 CHAPTER 4 • THE NETWORK LAYERPrefix Match Interface1010 1111 2otherwise 3For each of the four interfaces, give the associated range of destination hostaddresses and the number of addresses in the range.P13. Consider a router that interconnects three subnets: Subnet 1, Subnet 2, andSubnet 3. Suppose all of the interfaces in each of these three subnets arerequired to have the prefix 223.1.17/24. Also suppose that Subnet 1 isrequired to support at least 60 interfaces, Subnet 2 is to support at least 90interfaces, and Subnet 3 is to support at least 12 interfaces. Provide three net-work addresses (of the form a.b.c.d/x) that satisfy these constraints.P14. In Section 4.2.2 an example forwarding table (using longest prefix matching)is given. Rewrite this forwarding table using the a.b.c.d/x notation instead ofthe binary string notation.P15. In Problem P10 you are asked to provide a forwarding table (using longestprefix matching). Rewrite this forwarding table using the a.b.c.d/x notationinstead of the binary string notation.P11. Consider a datagram network using 8-bit host addresses. Suppose a routeruses longest prefix matching and has the following forwarding table:Prefix Match Interface00 0010 1011 210 211 3For each of the four interfaces, give the associated range of destination hostaddresses and the number of addresses in the range.P12. Consider a datagram network using 8-bit host addresses. Suppose arouter uses longest prefix matching and has the following forwardingtable:P16. Consider a subnet with prefix 128.119.40.128/26. Give an example of oneIP address (of form xxx.xxx.xxx.xxx) that can be assigned to this network.Suppose an ISP owns the block of addresses of the form 128.119.40.64/26.Suppose it wants to create four subnets from this block, with each block having the same number of IP addresses. What are the prefixes (of forma.b.c.d/x) for the four subnets?P17. Consider the topology shown in Figure 4.17. Denote the three subnets withhosts (starting clockwise at 12:00) as Networks A, B, and C. Denote the sub-nets without hosts as Networks D, E, and F.a. Assign network addresses to each of these six subnets, with the follow-ing constraints: All addresses must be allocated from 214.97.254/23;Subnet A should have enough addresses to support 250 interfaces; Sub-net B should have enough addresses to support 120 interfaces; and Subnet C should have enough addresses to support 120 interfaces. Ofcourse, subnets D, E and F should each be able to support two interfaces.For each subnet, the assignment should take the form a.b.c.d/x ora.b.c.d/x – e.f.g.h/y.b. Using your answer to part (a), provide the forwarding tables (using longestprefix matching) for each of the three routers.P18. Use the whois service at the American Registry for Internet Numbers(http://www.arin.net/whois) to determine the IP address blocks for three universities. Can the whois services be used to determine with certainty thegeographical location of a specific IP address? Use www.maxmind.com todetermine the locations of the Web servers at each of these universities. P19. Consider sending a 2400-byte datagram into a link that has an MTU of 700 bytes. Suppose the original datagram is stamped with the identifica-tion number 422. How many fragments are generated? What are the values in the various fields in the IP datagram(s) generated related tofragmentation?P20. Suppose datagrams are limited to 1,500 bytes (including header) betweensource Host A and destination Host B. Assuming a 20-byte IP header, howmany datagrams would be required to send an MP3 consisting of 5 millionbytes? Explain how you computed your answer.P21. Consider the network setup in Figure 4.22. Suppose that the ISP insteadassigns the router the address 24.34.112.235 and that the network address ofthe home network is 192.168.1/24.a. Assign addresses to all interfaces in the home network.b. Suppose each host has two ongoing TCP connections, all to port 80 at host 128.119.40.86. Provide the six corresponding entries in the NATtranslation table.PROBLEMS 421Subnet 3EFCSubnet 2DABSubnet 1Figure 5.33 ! Three subnets, interconnected by routersP13. Consider a broadcast channel with N nodes and a transmission rate of R bps.Suppose the broadcast channel uses polling (with an additional polling node)for multiple access. Suppose the amount of time from when a node completestransmission until the subsequent node is permitted to transmit (that is, thepolling delay) is dpoll. Suppose that within a polling round, a given node isallowed to transmit at most Q bits. What is the maximum throughput of thebroadcast channel?P14. Consider three LANs interconnected by two routers, as shown in Figure 5.33.a. Assign IP addresses to all of the interfaces. For Subnet 1 use addresses ofthe form 192.168.1.xxx; for Subnet 2 uses addresses of the form192.168.2.xxx; and for Subnet 3 use addresses of the form 192.168.3.xxx.b. Assign MAC addresses to all of the adapters.c. Consider sending an IP datagram from Host E to Host B. Suppose all ofthe ARP tables are up to date. Enumerate all the steps, as done for the single-router example in Section 5.4.1.d. Repeat (c), now assuming that the ARP table in the sending host is empty(and the other tables are up to date).P15. Consider Figure 5.33. Now we replace the router between subnets 1 and 2with a switch S1, and label the router between subnets 2 and 3 as R1. PROBLEMS 505a. Consider sending an IP datagram from Host E to Host F. Will Host E askrouter R1 to help forward the datagram? Why? In the Ethernet frame con-taining the IP datagram, what are the source and destination IP and MACaddresses?b. Suppose E would like to send an IP datagram to B, and assume that E’sARP cache does not contain B’s MAC address. Will E perform an ARPquery to find B’s MAC address? Why? In the Ethernet frame (containingthe IP datagram destined to B) that is delivered to router R1, what are thesource and destination IP and MAC addresses? c. Suppose Host A would like to send an IP datagram to Host B, and neither A’sARP cache contains B’s MAC address nor does B’s ARP cache contain A’sMAC address. Further suppose that the switch S1’s forwarding table containsentries for Host B and router R1 only. Thus, A will broadcast an ARP requestmessage. What actions will switch S1 perform once it receives the ARPrequest message? Will router R1 also receive this ARP request message? If so,will R1 forward the message to Subnet 3? Once Host B receives this