What are the advantages of using dedicated hardware devices forrouters and gateways?

Why would it be a bad idea for gateways to pass broadcast packets between networks? What would be the advantages of doing so?

Discuss the advantages and disadvantages of caching name translations for computers located in remote domains.

What are the advantages and disadvantages of using circuit switching? For what kinds of applications is circuit switching a viable strategy?

What are two formidable problems that designers must solve to implement a network system that has the quality of transparency?

Process migration within a heterogeneous network is usually impossible, given the differences in architectures and operating systems. Describe a method for process migration across different architectures running: a. The same operating system b. Different operating systems

To build a robust distributed system, you must know what kinds of failures can occur. a. List three possible types of failure in a distributed system. b. Specify which of the entries in your list also are applicable to a centralized system.

Is it always crucial to know that the message you have sent has arrived at its destination safely? If your answer is yes, explain why. If your answer is no, give appropriate examples.

A distributed system has two sites, A and B. Consider whether site A can distinguish among the following: a. B goes down. b. The link between A and B goes down. c. B is extremely overloaded, and its response time is 100 times longer than normal. What implications does your answer have for recovery in distributed systems?

What is the difference between computation migration and process migration? Which is easier to implement, and why?

Even though the OSI model of networking specifies seven layers of functionality, most computer systems use fewer layers to implement a network. Why do they use fewer layers? What problems could the use of fewer layers cause?

Explain why doubling the speed of the systems on an Ethernet segment may result in decreased network performance. What changes could help solve this problem?

What are the advantages of using dedicated hardware devices for routers and gateways? What are the disadvantages of using these devices compared with using general-purpose computers?

In what ways is using a name server better than using static host tables? What problems or complications are associated with name servers? What methods could you use to decrease the amount of traffic name servers generate to satisfy translation requests?

Name servers are organized in a hierarchical manner. What is the purpose of using a hierarchical organization?

The lower layers of the OSI network model provide datagram service, with no delivery guarantees for messages. A transport-layer protocol such as TCP is used to provide reliability. Discuss the advantages and disadvantages of supporting reliable message delivery at the lowest possible layer.

How does using a dynamic routing strategy affect application behavior? For what type of applications is it beneficial to use virtual routing instead of dynamic routing?

Run the program shown in Figure 17.4 and determine the IP addresses of the following host names: www.wiley.com www.cs.yale.edu www.apple.com www.westminstercollege.edu www.ietf.org

The original HTTP protocol used TCP/IP as the underlying network protocol. For each page, graphic, or applet, a separate TCP session was constructed, used, and torn down. Because of the overhead of building and destroying TCP/IP connections, performance problems resulted from this implementation method. Would using UDP rather than TCP be a good alternative? What other changes could you make to improve HTTP performance?

What are the advantages and the disadvantages of making the computer network transparent to the user?

What are the benefits of a DFS compared with a file system in a centralized system?

Which of the example DFSs discussed in this chapter would handle a large, multiclient database application most efficiently? Explain your answer.

Discuss whether OpenAFS and NFS provide the following: (a) location transparency and (b) location independence.

Under what circumstances would a client prefer a locationtransparent DFS? Under what circumstances would she prefer a location-independent DFS? Discuss the reasons for these preferences.

What aspects of a distributed system would you select for a system running on a totally reliable network?

Consider OpenAFS, which is a stateful distributed file system. What actions need to be performed to recover from a server crash in order to preserve the consistency guaranteed by the system?

Compare and contrast the techniques of caching disk blocks locally, on a client system, and remotely, on a server.

OpenAFS is designed to support a large number of clients. Discuss three techniques used to make OpenAFS a scalable system.

What are the benefits of mapping objects into virtual memory, as Apollo Domain does? What are the drawbacks?

Describe some of the fundamental differences between OpenAFS and NFS (see Chapter 12).