CS3260 Tutorial 9    -    (week Oct 27 – Oct 31)

9A.  Great Asia Industries Ltd is an electronic component manufacturer headquartered in Singapore.  Its factories are located at Kaohsiung (Taiwan) and Surabaya (Indonesia), and distribution warehouses at Kaohsiung (Taiwan), Chennai (India), Bangkok, Surabaya (Indonesia), Shenzhen (China), and Singapore.

Presently, Great Asia uses Singtel's ConnectPlus Frame Relay to connect headquarters with the factories and regional warehouses.  Data traffic includes real-time updating of manufacturing orders, purchase orders, shipments, inventory, as well as administrative and financial information.

Great Asia is considering switching to an alternative vendor.  Compare Singtel Frame Relay with (i) Frame Relay, and (ii) IP-based virtual private networks provided by MCI-Worldcom, Cable and Wireless, and Sprint in terms of points of presence and service level guarantees. (Notes: Not all carriers provide both services in the region. Some of this information may not be publicly available.)

9B. SoCProperty.com is a local real estate agent that provides property listings for both rental and sales.  The company is currently providing an online price quotation system, called PQS, whereby customers can enquire property prices through the company’s website.  The PQS is served by one integrated web-database server, which typically takes about 0.4 second to retrieve and format the data that a customer needs.  It takes, on average, 1.5 seconds for a customer request to reach the server and 1.75 seconds for the server to return the results back to the customer.

a) The integrated server has a buffer that allows unlimited users to queue up when the system is busy handling a particular customer.  On average, there is one customer request in every five seconds.  What is the average number of customers inside the system?  Inside the PQS, on average, how long does a customer need to wait for his/her turn to query the database?  After sending the request, what is the average total waiting time for a customer to see an answer on his/her PC screen?

b) The peak demand for the system lies in 6 – 8 pm everyday.  In that two hours, on average, there are two customer requests in each second.  Again, within that period, after sending the request, what is the average total waiting time for a customer to see an answer on his/her PC screen?   

c) The company wants to provide better service in the peak period.  Suppose there are two options: (1) buy a better server that can fulfill a request in 0.3 second; (2) host the server in the ISP’s premise so that the access time to and from the server is reduced to 1 and 1.25 seconds respectively.  Consider only the peak demand, which option is better and why?