Distributed systems K07

LH 2  23-24.1.2007
Tanenbaum Ch 1 tai CoDoKi Ch 1,2 ... viitteet kuntoon

1. The peformance and scalability of a global directory service (such as
   DNS) can be improved by using partitioning, replication and caches.
   a) How can these techniques be used for a tree structured directory?
   b) How does each of these techniques
      - improve performance
      - decrease performance
      - improve scalability?

2. Design and evaluation (length 1-2 pages)

   The goal is to design a messaging system that works on the middleware
   level of an ad hoc network. The messaging system should provide what
   the client describes loosely as "dependable multicast that everyone
   receives". The network consist of portable computers, connected by
   short range radio links. The radio links are typically reached only
   by a few neighbours. The limited resources in the network are battery
   lifetime and the throughput capasity of the radio link. 

   Make a schetch of the software architecture including the user
   interface and the messaging system. The computers are assumed to
   provide an operating system layer with actual communication protocosl
   (you can choose yourself which ones you assume). Describe the actors,
   their responsibilities and their locations.

   Evaluate the usability of different messaging styles (see Tanenbaum,
   kuva 2-22) for communication between different layers and differet
   actors (cllient components, middleware components, operating system
   components).

   Assume that you are explaining the design for another
   student at the course -- with some but not deep knowledge about
   the concepts used.

3. Maintaining consistency in a distributed system is of some
   importance. Give examples of embarassing occurrencies of lacking
   consistency, which are related with data updates, replicates,
   caching, server failures, clocks, and user interfafes (consistency of
   keyboard and screen). Give examples related with www use, updating
   name-service database, or something else.


   
Assignment HT 2

Write a learning diary about basic ideas on performance analysis

Performance analysis provides an important tool for evaluating
architectures and choosing between them. At the department,
these things are occasionally taught, see:
http://www.cs.helsinki.fi/kurssit/syventavat/581372-6/ .

A textbook is availabe in the web:
http://www.cs.washington.edu/homes/lazowska/qsp/ .

From this book, read the chapter 1. An Overview of Queueing Network Modelling
(and chapter 3. Fundamental Laws, if interested to learn more) 
and write 2-4 pages for your learning diary. What are the tools 
suggested and when are they useful? In what kind of situations should
you come back to the book and learn more?

Oppimispäiväkirjan laatimisen yleiset ohjeet ovat tiedostossa
http://www.cs.helsinki.fi/u/alanko/hj/K06/laskuharj/oppimispaivakirja.

The essay should be returned by e-mail as an attached file (preferably
in pdf format, with the name [last name].[format type]) at the latest on
the 1st of February at 8 o'clock to Lea.Kutvonen@cs.helsinki.fi,
mika.karlstedt@cs.helsinki.fi . Liitetiedoston nimi voisi olla muotoa
[sukunimi].[tiedostotyyppitunnus]. Use "distributed systems coursework"
as subject line.