Computer Networks: Homework 1 Chapter 15: –Problem 14 –Problem 16

Computer Networks: Homework 1 Chapter 15: –Problem 19

Computer Networks: Homework 1 Chapter 17: –Problem 11 Each STS-n frame carries (9  n  86) bytes of bytes. SONET sends 8000 frames in each second. We can then calculate the user data rate as follows: STS-3 →  8000  (9  3  86)  8 = Mbps STS-9 →  8000  (9  9  86)  8 = Mbps STS-12 →  8000  (9  12  86)  8 = Mbps –Problem 14 The user data rate of STS-1 is (8000 × 9 × 86 × 8) = Mbps. To carry a load with a data rate , we need 10 kbps worth of dummy data. This means that we need / 8 = 750 bytes of dummy data in 8000 frames. In other words, 750 out of every 8000 frames need to allow the next byte after H3 to be empty (dummy). For example, we can have sequences of 32 frames in which the first three frames are underloaded and the next 29 are normal.

Computer Networks: Homework 1 Chapter 18: –Problem 14 The address field in Frame Relay is 16 bits. The address given is only 15 bits. It is not valid. –Problem 18

Computer Networks: Homework 1 Chapter 19: –Problem 16 a. Class C (first byte is between 192 and 223) b. Class D (first byte is between 224 and 239) c. Class A (first byte is between 0 and 127) d. Class B (first byte is between 128 and 191) –Problem 18 a. netid: 114 hostid: b. netid: hostid: 8.6 c. netid: hostid: 12

Computer Networks: Homework 1 Chapter 19: –Problem 26 The total number of addresses in this block is = The ISP can divide this large block in several ways depending on the predicted needs of its customers in the future. We assume that the future needs follow the present pattern. In other words, we assume that the ISP will have customers that belong to one of the present groups. We design four ranges: group 1, group 2, group 3, and one reserved range of addresses as shown in Figure.

Computer Networks: Homework 1 Chapter 19: –Problem 26 (Cont’d) Group 1 In the first group, we have 200 businesses. We augment this number to 256 (the next number after 200 that is a power of 2) to let 56 more customers of this kind in the future. The total number of addresses is 256 × 128 = For this group, each customer needs 128 addresses. This means the suffix length is log = 7. The prefix length is then 32 − 7 = 25. The addresses are: 1st customer: /25 to /25 2nd customer: /25 to / th customer: /25 to /25 Unused addresses to Total Addresses in group 1 = 256 × 128 = Used = 200 × 128 = Reserved: 7168, which can be assigned to 56 businesses of this size. Group 2 In the second group, we have 400 business. We augment this number to 512 (the next number after 400 that is a power of 2) to let 112 more customer of this kind in the future. The total number of addresses is = 512 × 16 = For this group, each customer needs 16 addresses. This means the suffix length is 4 log 2 16 = 4. The prefix length is then 32 − 4 = 28. The addresses are: 1st customer: /28 to /28 2nd customer: /28 to / th customer: /28 to /28 Unused addresses to Total Addresses in group 2 = 512 × 16 = 8192 Used = 400 × 16 = 6400 Reserved: 1792, which can be assigned to 112 businesses of this size.

Computer Networks: Homework 1 Chapter 19: –Problem 26 (Cont’d) Group 3 In the third group, we have 2000 households. We augment this number to 2048 (the next number after 2000 that is a power of 2) to let 48 more customer of this kind in the future. The total number of addresses is = 2048 × 4 = For this group, each customer needs 4 addresses. This means the suffix length is 2 log 2 4 = 2. The prefix length is then 32 − 2 = 30. The addresses are: 1st customer: /30 to /30 2nd customer: /30 to / th customer: /30 to /30 Unused addresses to Total Addresses in group 3 = 2048 × 4 = 8192 Used = 2000 × 4 = 8000 Reserved: 192, which can be assigned to 48 households. Reserved Range In the reserved range, we have address that are totally unused. Note that we have unused addresses in each group and a large range of unused addresses in the reserved range. Summary: The following shows the summary of used and unused addresses:

Computer Networks: Homework 1 Chapter 19: –Problem 28 Each customer has only 1 address and, therefore, only one device. Since we defined a network as 2 or more connected devices, this is not a network