420 CHAPTER 4 THE NETWORK LAYER P11 Consider a datagram network using 8 bit host addresses Suppose a router uses longest prefix matching and has the following forwarding table Prefix Match Interface 00 010 011 10 11 0 1 2 2 3 For each of the four interfaces give the associated range of destination host addresses and the number of addresses in the range P12 Consider a datagram network using 8 bit host addresses Suppose a router uses longest prefix matching and has the following forwarding table Prefix Match Interface 1 10 111 otherwise 0 1 2 3 For each of the four interfaces give the associated range of destination host addresses and the number of addresses in the range P13 Consider a router that interconnects three subnets Subnet 1 Subnet 2 and Subnet 3 Suppose all of the interfaces in each of these three subnets are required to have the prefix 223 1 17 24 Also suppose that Subnet 1 is required to support at least 60 interfaces Subnet 2 is to support at least 90 interfaces and Subnet 3 is to support at least 12 interfaces Provide three network 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 of the binary string notation P15 In Problem P10 you are asked to provide a forwarding table using longest prefix matching Rewrite this forwarding table using the a b c d x notation instead of the binary string notation PROBLEMS P16 Consider a subnet with prefix 128 119 40 128 26 Give an example of one IP 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 form a b c d x for the four subnets P17 Consider the topology shown in Figure 4 17 Denote the three subnets with hosts starting clockwise at 12 00 as Networks A B and C Denote the subnets without hosts as Networks D E and F P18 P19 P20 P21 a Assign network addresses to each of these six subnets with the following constraints All addresses must be allocated from 214 97 254 23 Subnet A should have enough addresses to support 250 interfaces Subnet B should have enough addresses to support 120 interfaces and Subnet C should have enough addresses to support 120 interfaces Of course 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 or a b c d x e f g h y b Using your answer to part a provide the forwarding tables using longest prefix matching for each of the three routers 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 the geographical location of a specific IP address Use www maxmind com to determine the locations of the Web servers at each of these universities Consider sending a 2400 byte datagram into a link that has an MTU of 700 bytes Suppose the original datagram is stamped with the identification number 422 How many fragments are generated What are the values in the various fields in the IP datagram s generated related to fragmentation Suppose datagrams are limited to 1 500 bytes including header between source Host A and destination Host B Assuming a 20 byte IP header how many datagrams would be required to send an MP3 consisting of 5 million bytes Explain how you computed your answer Consider the network setup in Figure 4 22 Suppose that the ISP instead assigns the router the address 24 34 112 235 and that the network address of the 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 NAT translation table 421 PROBLEMS P13 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 completes transmission until the subsequent node is permitted to transmit that is the polling delay is dpoll Suppose that within a polling round a given node is allowed to transmit at most Q bits What is the maximum throughput of the broadcast 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 of the form 192 168 1 xxx for Subnet 2 uses addresses of the form 192 168 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 of the 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 2 with a switch S1 and label the router between subnets 2 and 3 as R1 C A E B F D Subnet 1 Subnet 3 Subnet 2 Figure 5 33 Three subnets interconnected by routers 505 506 CHAPTER 5 VideoNote Sending a datagram between subnets linklayer and network layer addressing THE LINK LAYER LINKS ACCESS NETWORKS AND LANS a Consider sending an IP datagram from Host E to Host F Will Host E ask router R1 to help forward the datagram Why In the Ethernet frame containing the IP datagram what are the source and destination IP and MAC addresses b Suppose E would like to send an IP datagram to B and assume that E s ARP cache does not contain B s MAC address Will E perform an ARP query to find B s MAC address Why In the Ethernet frame containing the IP datagram destined to B that is delivered to router R1 what are the source and destination IP and MAC addresses c Suppose Host A would like to send an IP datagram to Host B and neither A s ARP cache contains B s MAC address nor does B s ARP cache contain A s MAC address Further suppose that the switch S1 s forwarding table contains entries for Host B and router R1 only Thus A will broadcast an ARP request message What actions will …