Business Data Networks and Telecommunications, 7Th Edition

Chapter 8: TCP/IP Internetworking

Business Data Networks and Telecommunications, 7th Edition

Raymond R. Panko

Copyright Prentice-Hall, 2007

Homework

Chapter 8

TCP/IP Internetworking

Last Name: __________________

First Name: __________________

Due Date: ___________

Note: Figures 8-8 and 8-12 are at the back of this document.

Test Your Understanding

1. a) Compare TCP and IP along the dimensions in Figure 8-2.

b) Compare TCP and UDP along the dimensions in Figure 8-2.

2. a) What is routing?

b) What are the three parts of an IP address?

c) How long is each part?

d) What is the total length of an IP address?

e) Connecting different networks is the main job of what type of router?

f) What type of router only connects different subnets?

3. a) How many bits are there in a mask?

b) What do the bits in a network mask correspond to in IP addresses?

c) What do the bits in a subnet mask correspond to in IP addresses?

d) When a network mask is applied to any IP address on the network, what is the result?

4. a) List the bits in the mask 255.255.255.0.

b) What are the bits in the mask /14?

c) If /14 is the network mask, how many bits are there in the network part?

d) If /14 is the network mask, how many bits are there in the subnet and host parts?

e) If /14 is the subnet mask, how many bits are there in the network part?

f) If /14 is the subnet mask, how many bits are there in the subnet part?

g) If /14 is the subnet mask, how many bits are there in the host part?

5. Why are routing tables more complex than Ethernet switching tables? Be articulate.

6. a) In an Ethernet switching table, what does a row represent?

b) In a routing table, what does a row represent?

c) Do switches have a row for each individual Ethernet address?

d) Do routers have a row for each individual IP address?

e) What is the advantage of the answer to the previous subpart of this question?

7. a) In Row 3 of Figure 8-8, how will a router test if the row matches the IP address 60.168.6.7?

b) Why is the last row called the default row?

c) Why must a router look at all rows in a routing table?

d) Which rows match 128.171.17.13? (Don’t forget the default row.) Show your calculations for the matching rows.

e) What rows match 172.30.17.6?

f) Which rows match 172.30.12.47?

8. a) Distinguish between Step 1 and Step 2 in the routing process.

b) If any row other than the default row matches an IP address, why will the router never choose the default row?

c) Which rows match 128.171.17.13? (Don’t forget the default row.)

d) Which of these is the best-match row? Justify your answer.

e) What rows match 172.30.17.6?

f) Which of these is the best-match row? Justify your answer.

g) Which rows match 172.30.12.47?

h) Which of these is the best-match row? Justify your answer.

9. a) Distinguish between Step 2 and Step 3 in routing.

b) What are router ports called?

c) If the router selects Row 13 as the best match row, what interface will the router send the interface out?

d) To what device?

e) Why is this called the default router? (The answer is not in the text.)

f) If the router selects Row 2 as the best match row, what interface will the router send the interface out?

g) To what device? (Don’t say, “the local device.”)

h) What is the IP address of this device?

10. a) What is the main version of the Internet Protocol in use today?

b) What does a router do if it decrements a TTL value to 0?

c) What does the protocol field value tell the destination host?

d) Under what circumstances would the identification, flags, and fragment offset fields be used in IP?

e) Why is fragmentation suspicious?

f) Why are options suspicious?

11. a) How is IPv6 better than IPv4?

b) Why has IPv6 adoption been so slow?

c) What forces may drive IPv6’s adoption in the future?

d) Must IPv6 replace IPv4 all at once? Explain.

12. a) Why is TCP complex?

b) Why is it important for networking professionals to understand TCP?

c) What are TCP messages called?

13. a) Why are sequence numbers good?

b) What are 1-bit fields called?

c) If someone says that a flag field is set, what does this mean?

d) If the ACK bit is set, what other field must have a value?

e) What is a SYN segment?

f) Describe three-way openings in TCP.

g) Distinguish between four-way closes and abrupt resets.

h) Do SYN and FIN segments have data fields?

i) After a side sends a FIN segment, will it respond to further messages from the other side? Explain.

14. a) What type of port number do servers use?

b) What type of port number do clients use?

c) What is the port range for well-known port numbers?

d) What is the official range for ephemeral port numbers?

e) What is the range of Microsoft ephemeral port numbers?

15. A Windows host sends a TCP segment with source port number 25 and destination port number 2404. a) Is the source host a server or a client? Explain.

b) If the host is a server, what kind of server is it?

c) Is the destination host a server or a client? Explain.

16. a) What is a socket?

b) What specifies a particular application on a particular host in TCP/IP?

c) How is it written?

d) When the SMTP server in Figure 8-12 transmits to the client PC, what will the source socket be?

e) The destination socket?

17. a) What are the four fields in a UDP header?

b) Describe the third.

c) Describe the fourth.

d) Is UDP reliable? Explain.

18. a) What is the purpose of dynamic routing protocols?

b) In what two ways does TCP/IP use the term “routing?”

19. a) What is an autonomous system?

b) Within an autonomous system, can the organization choose its interior routing protocol?

c) What are the two TCP/IP interior dynamic routing protocols?

d) Which IETF dynamic routing protocol is good for small internets that do not have high security requirements?

e) Which IETF dynamic routing protocol is good for large businesses that have high security requirements?

f) What is the main benefit of EIGRP compared to OSPF as an internal dynamic routing protocol?

g) When might you use EIGRP as your interior dynamic routing protocol?

h) May a company select the routing protocol its border router uses to communicate with the outside world?

i) What is the main exterior dynamic routing protocol?

20. a) How is MPLS similar to the use of virtual circuits?

b) Which device adds the MPLS label?

c) On what does each label-switched router base routing decisions?

d) What is MPLS’s main attraction?

e) What are its other attractions?

f) How can MPLS provide quality of service?

g) What is traffic engineering?

h) Can MPLS provide traffic load balancing?

21. a) Is the Domain Name System only used to send back IP addresses for given host names?

b) What is a domain?

c) Which level of domain name do corporations most wish to have?

d) What are DNS root servers?

e) How many DNS root servers are there?

22. a) For what general class of messages is ICMP used?

b) How are ICMP messages encapsulated?

c) An Ethernet frame containing an ICMP message arrives at a host. List the frame’s headers, messages, and trailers at all layers. List them in the order in which they will be seen by the receiver. For each header or trailer, specify the standard used to create the header or message (for example, Ethernet 802.3 MAC layer header). Hint: remember how ICMP messages are encapsulated.

d) Explain error advisement in ICMP.

e) Explain the purpose of ICMP echo messages.

f) Sending an ICMP echo message is called __________ the target host.

23. What configuration information does a DHCP server send to a PC when the PC boots up and sends out a DHCP request?

24. a) Are Layer 3 switches really routers?

b) How are they better than traditional software-based routers?

c) How are they not as good? Give a full explanation.

d) When would you often use Layer 3 switches?

e) Where would you not use Layer 3 switches?

25. a) What are Layer 4 switches?

b) What field do Layer 4 switches examine?

c) Why are Layer 4 switches good?

d) What layer name is given to application switches?

Thought Questions

1. Give a non-network example of hierarchical addressing, and discuss how it reduces the amount of work needed in physical delivery.

2. A client PC has two simultaneous connections to the same webserver application program on a webserver. (Yes, this is possible, and in fact it is rather common.) What will be different between the TCP segments that the client sends on the two connections?

3. For security reasons, many organizations do not allow error reply messages to leave their internal internets. How, specifically, could hackers use information in echo reply messages to learn about the firm’s internal hosts?

4. Continuing from the previous question, how could a hacker use the TTL field to learn about the organization of the firm’s routers?

5. What was the most surprising thing you learned in this chapter?

6. What was the most difficult material for you in this chapter?

Troubleshooting Question

1. You suspect that the failure of a router or of a transmission line connecting routers has left some of your important servers unavailable to clients at your site. How could you narrow down the location of the problem using what you learned in this chapter?

Hands-On exercises

To get a second-level domain name, you need to go to an address registrar. Network Solutions is a well-known address registrar. Go to the Network Solutions website, www.netsol.com. Pick a second-level domain name for an imaginary business and see if it is available. If it is not, try other second-level domain names until you find one that is available.

Getting Current

Go to the book website’s New Information and Errors pages for this chapter to get new information since this book went to press and to correct any errors in the text.

Figures

Figure 8-8: Routing Table

Figure 8-12: Use of TCP (and UDP) Port Numbers

Chapter 8-1