One Minute Evaluations for 11-13 February

CS 537 - Client-Server Interfaces

1. Topic: We dealt with state vs. stateless, concurrent vs. iterative servers, client and server architecture.

   Unclear: Did not understand TCP client and TCP server.

   Explanation: The best way to understand is to implement; as you're reading along in Comer and Stevens, you should be implementing the code they show. There's also Chapter 2 of Donahoo and Calvert.

2. Topic: We talked about connection/connectionless servers, iterative servers, concurrent servers, and statefull vs. stateless servers.

   Unclear: How to select the server being a concurrent server or iterative server.

   Explanation: Iterative servers are useful until proven otherwise; concurrent servers are not useful until proven otherwise.

3. Topic: We talked about iterative and concurrent servers.

   Unclear: Confusion between connection and request in state/stateless server.

   Explanation: Requests (and replies) travel over connections. Neither connections nor requests (and replies) are state, although they can cause a server (or client) to create state.

4. Topic: State vs. stateless; Iterative server (bit); server architecture.

   Unclear: Still some confusion between state vs stateless.

   Explanation: A statefull wallet contains lots and lots of information about you: in addition to money, your driver's license, your blood type, your credit-card numbers. A stateless wallet contains nothing about you; it just has money. Which would you rather lose?

5. Topic: Iterative and concurrent servers.

   Unclear: The choice to make is difficult, even though there are lots of points discussed.

   Explanation: In the abstract, that's true. But for your project, for example, just do the simplest thing possible (iterative, non-concurrent clients and servers) and if that doesn't work, then get more complicated.

6. Topic: Concurrent and iterative servers. Well, I guess we wasted time today digressing; our doubt was only state (well couldn't help it I understand).

   Unclear: I understood everything this week.

7. Topic: We talked about state vs. stateless; concurrency vs. iterative servers; performance characteristics; characteristics of server loads.

   Unclear:

8. Topic: Iterative server, concurrency server, characteristic and architecture of server reliability.

   Unclear:

9. Topic: State and statefull; I guess I got a good idea. Single-process concurrency [?] were good.

   Unclear: Can you explain if you have time what is multiplexing?

   Explanation: I have one minute. Roads are multiplexed; many cars, each for a different reasons, can be on the road at the same time. If roads weren't multiplexed, only one car at a time can use them. Multiplexing increases efficiency by increasing utilization (more cars) and decreasing latency (less waiting at the on-ramp), at the cost of greater management complexity (cops) and more delay (traffic jams).

10. Topic: Concurrent and iterative servers.

    Unclear: The difference between low latency and delay. Not too much was clear.

    Explanation: Suppose you sit in the waiting room for 45 minutes before you see a doctor; that's high latency. Suppose you see the doctor as soon as you walk in; that's low latency. Suppose you spend one hour with doctor and end up with a recommendation to take two aspirins; that's high delay. Suppose the doctor looks at you and immediately recommends two aspirin; that's low delay.

11. Topic: Iterative servers, concurrent servers, characteristics, issues involved, performance, scalability, reliability.

    Unclear: Everything is ok.

12. Topic:

    Unclear: You said in the class that once a server is down, the client has to search for another available server. I could not understand that, echo server's are not available in the college.

    Explanation: Unless the system administrator has done something funny, the echo server should be at TCP/UDP port 7 on any system.

13. Topic: Got more understanding of statefull/stateless server.

    Unclear: Still confused about how to chose between iterative servers and concurrent servers. Latency and delay (still confused).

    Explanation: The choice between state and statelessness depends on lots of different factors, including client-server protocol complexity and the amount of design and implementation.

14. Topic: Iterative servers; state-stateless servers; characteristics of clients/servers.

    Unclear:

15. Topic: We talked about client, server architectures, issues, concurrency, iterative servers.

    Unclear: I could not understand the full distinction between stateless and statefull servers.

    Explanation: Stateless servers have nothing to forget.

16. Topic: Where to use concurrent and where to use iterative servers in practical cases.

    Unclear:

This page last modified on 25 February 2003.