Tarea #2.

2.1 Describe and illustrate the client-server architecture of one or more major Internet applications (for example the Web, email or netnews).               

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2.2 For the applications discussed in Exercise 2.1 state how the servers cooperate in providing a service.            

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2.3 How do the applications discussed in Exercise 2.1 involve the partitioning and/or replication (or caching) of data amongst servers?              

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2.6 List the types of local resource that are vulnerable to an attack by an untrusted program that is downloaded from a remote site and run in a local computer.                

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2.7 Give  examples of applications where the use of mobile code is beneficial.                  

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2.14 Consider two communication services for use in asynchronous distributed systems. In service A, messages may be lost, duplicated or delayed and checksums apply only to headers. In service B, messages may be lost, delayed or delivered too fast for the recipient to handle them, but those that are delivered arrive with the correct contents.

Describe the classes of failure exhibited by each service. Classify their failures according to their effect on the properties of validity and integrity. Can service B be described as a reliable communication service?             

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