Exercises

1. Looking at Figure , consider every instance of a failure by one processor that you can think of and determine if a problem will occur in executing the transaction. For example, if the client fails between issuing C-BEGIN and C-PREPARE, the transaction will not be executed by a server, since it was not completely specified and no C-COMMIT arrived.

2. In your system, find two examples of data delivery (transfer) facilities that perform the function offered by RTSE?

3. What dialog modes would you associate with use of a walkie-talkie? with calls answered by an answering machine?

4. Assume that you have available the services described in this chapter, plus one other: P-DATA. P-DATA takes data provided by a user process and delivers it to the user's peer at another open system. Using these services, sketch a solution to each of the following problems. For each show a time sequence diagram that displays the use of services on each participating open system. For each problem, describe the services required and the OSI Application Service Element that provides the service.
   1. Obtain a list of users currently logged in to System A.
   2. Query the inventory file on System A to find the quantity of widgets in stock. (Assume you know the necessary information to access the file.)
   3. Schedule a meeting at 2pm next Tuesday to involve Mary, Joe, and Chris by writing the meeting into their calendar files if everyone is available.
5. Using ASN.1 and the services of ROSE, specify a protocol to return the current time on a remote system.

6. You are developing applications using ROSE. What operations and errors would you define for each of the following protocols:
   1. Return the ratio of print queue length to number of users logged in.
   2. Return the process identifier of the longest running process on the system
   3. Return directory information about a specified file. (For example, the creation date, length, owner)

7. If you have access to a system with the TCP/IP protocols, use PING to discover the round trip time between your host and some other host known to you.

8. If you have access to a system with the TCP/IP protocols, use Traceroute to determine what machines participated in sending your message from your machine to a designated other host.