Theory Assessment

• Theory Assessment
  Plan and Build Computer Network (1A)
  
  ICAITS029B Install network hardware to a network
  ICAITS021C Connect internal hardware components
  ICAITS030B Install software to networked computers
  ICAITS116B Undertake capacity planning
  
  
  Time Allowed: 3 hours
  Pass Mark: 15
  (Assessor’s Copy)
  NOTE: the theory focus on capacity planning
  
  
  Table of Contents
  
  
  Question 1: What is meant by capacity planning in information technology?. 2
  Question 2: What are some of the factors that capacity planning needs to consider?. 2
  Question 3: Briefly describe the following terms. 3
  Question 4: What are the stages in capacity planning?. 4
  Question 5: Describe some of the commerce site metrics in capacity planning for a business that is moving into e-commerce. 4
  Question 6: Describe some of the differences in a corporate site as against a high-end e-commerce site that directs the activities for capacity planning. 6
  Question 7: Describe the steps in capacity planning for your organization that has moved onto e-commerce utilization of computer systems. 7
  Question 8: Describe the difference between Tier 1, 2 and 3 system configurations for capacity planning for an organization that has moved onto e-commerce utilization of its computer systems. 7
  Question 9: Discuss the term “persistence: in capacity planning. 9
  
  
  
  
  
  
  
  
  
  
  
  Question
  Marks
  1
  2
  2
  1
  3
  4
  4
  1
  5
  5
  6
  4
  7
  4
  8
  5
  9
  4
  Total Marks
  30
  
  Table 1 Assessment Grid
  UNIT
  Theory/Project
  Practical/Project
  ICAITS029B (All elements)
  
  X
  ICAITS021C (All elements)
  
  X
  ICAITS030B (All elements)
  
  X
  ICAITS116B (All elements)
  X
  
  Marks
  30
  70
  Grade : < 50 Not Yet Competent, 50 - 72 competent, 73 – 82 competent with credit, 83+ competent with distinction
  
  
  
  Question 1: What is meant by capacity planning in information technology?
  
  Answer Suggestion:
  
  
  Capacity Planning is the activity relating to the management of the information communication infrastructure to ensure that the output of the facility is maximized and the input is minimized.
  
  The activity involves the use of tools to measure inputs and outputs that may be competing. Constraints come in the form of labour, material availability, equipment utilization and limited space. Planning, the use of mathematical models and flexibility in resource utilization is needed
  Capacity planning in information communication technology systems is needed when:
  Starting a new system, or a service organization
  Extending the operations of an existing business system.
  Considering additions/modifications to the system
  Introducing new techniques, equipment and materials
  
  
  
  Question 2: What are some of the factors that capacity planning needs to consider?
  
  
  Answer Suggestion:
  Bottlenecks that will determine the capacity for any particular stage of the process.
  Peak demand rate
  Communication Bandwidth
  Load balance within the system
  Existing Hardware and scalability
  Cost
  Technology changes in hardware and software
  
  
  Question 3: Briefly describe the following terms
  
  a. Design Capacity
  
  Answer Suggestion:
  
  Target output level
  Note: It could be reached or exceeded in practice.
  It is the agreed % between vendor contractor and customer of the system
  
  b. Effective Capacity
  
  Answer Suggestion:
  
  It is the actual capacity to reflect current conditions.
  Note: could be less than or more than design capacity.
  Required because of; limited resources, increased equipment breakdowns when run at higher capacity for long periods and the impact of the environment.
  
  
  c. Utilization
  
  Answer Suggestion:
  Measures use of resources i.e actual running time.
  Measure as % of effective capacity.
  Note: measurement is often different between organizations and systems.
  
  d. Yield
  
  Answer Suggestion:
  Measures output of product in % against equivalent, potential or maximum products or systems’ input.
  Yield is concerned with avoidable and unavoidable losses due to downtime as a result of system or equipment problems.
  
  
  Question 4: What are the stages in capacity planning?
  
  Answer Suggestion
  1. Analyse existing system capacity
  2. Determine future capacity requirements
  3. Plan for capacity enhancement
  4. Install capacity enhancements
  
  
  
  
  Question 5: Describe some of the commerce site metrics in capacity planning for a business that is moving into e-commerce.
  
  Answer Suggestion
  
  
  a. Hits: Results of multiple hits from the browser to the Web server
  
  A hit is any request from the browser to the Web server this includes requests for dynamic content, images, or streamed video
  
  b. Average hits per page: The average number of Web server hits per page.
  
  The suggested configurations used stores with 1 hit per page. The test tool did not load any images, nor did it use frames. The test tool only made one HTTP request per page.
  
  c. Commerce/non-commerce page ratio
  
  Most pages are generated by issuing a database query and rendering the results by using JSP (Java Server Page) templates.
  
  Typical stores also contain some static content, such as HTML page requests. The suggested configurations did not contain any requests for purely static pages. Static pages are served at roughly the same rate as static images.
  
  Requests for static pages can be ignored in capacity planning, if the ratio of dynamic requests to static requests is fairly high. A site which serves two dynamic pages for every static page can be sized without regard for the static pages.
  
  This is because dynamic pages require substantially more resources to serve.
  
  
  d. Database size
  
  The database size affects performance of the system. Sites that include many shoppers, merchants, or catalogue items usually cannot serve requests as quickly as those that do not.
  
  Various factors will affect the throughput of the system, including database tuning, hardware capacity, and physical topology.
  
  
  e. Megabytes of data that are served per unit of time
  
  It is important to plan your site to have sufficient resources for serving expected network throughput. This includes sizing all firewall, routing, and other network components to be able to handle the peak workload expected of your site. The suggested configurations can be measured using a full duplex 100 Mbps Ethernet between the load generator and Web server.
  
  A 100 Mbps switch can be used between the Web server and database server.
  
  It must be noted that added equipment results in the Internet communication being significantly slower.
  
  If the site is running web casts or real time audio, this will demand bandwidth. This has to be taken into account in the overall capacity planning solution.
  
  
  f. Performance Test Scripts
  
  The commands executed affect system workload.
  
  
  Te set up and the commands run as part of performance tests can be like the following.
  
  Components:
  
  A basic store that contains a set of use cases commonly used in shopping model:
  
  – New shopper registration
  – Registered shopper logon
  – Browse categories, products, and items
  – Add item to shopping cart
  – View shopping cart with tax and shipping details
  – Modify quantity of items in the shopping cart
  – Delete items from the shopping cart
  – Checkout by entering billing and shipping information
  
  
  A script to generate the following:
  
  – Up to 5 000 categories
  – Up to 50 000 items
  – Up to 50 000 registered customers
  – Up to 50 000 orders
  
  A script to simulate various shopper scenarios
  – Browse
  – Add
  – Prepare
  – Buy
  
  A script to define the regular shopping mix
  
  The regular shopping mix depends on two variables:
  1. Customer type
  New registered customer
  Existing registered customer
  Guest shopper
  
  2. Shopping flow
  
  Browse
  
  Visit the home page
  
  Logon using registered customer id (existing registered customer only) or register as a new customer (new registered customer only
  
  Select “Multiple Category Display” then “Multiple Product Display”
  
  Browse and Add
  
  Browse, and then randomly add one, two, or three items to the shopping cart.
  
  Browse and Prepare
  
  Browse and add, then enter address book information (guest shopper only) or specify which address to use (new registered customer or existing registered customer).
  
  Browse and Buy
  
  Browse and prepare, then display order information. Enter a credit card number with expiry date, finally submit the order.
  
  Question 6: Describe some of the differences in a corporate site as against a high-end e-commerce site that directs the activities for capacity planning
  
  
  Answer Suggestion
  
  Typical corporate site
  High-end commerce site
  Page Views
  Approximately 15,000
  More than 50,000
  Connection (Note 1)
  Single DSI
  Multiple DS3s
  Back-end integration
  Optional
  Mandatory: inventory, logistics, and sales demand integration
  Availability
  OK – Networks rarely fully redundant
  24x7x365 – Network has no single point of failure
  Scalability
  Poor – little content monitoring
  Good – Local and geographic mirrors
  Impact of downtime
  Embarrassment, inconvenience
  Financial loss, customer loss
  Source: Forrester Research, Inc.
  Note 1: IEEE 802.6, Metropolitan Area Network, DQDB Media Access Control (PHYSICAL LAYER: Interfaces between network medium and network devices; Defines electrical and mechanical characteristics)
  
  Question 7: Describe the steps in capacity planning for your organization that has moved onto e-commerce utilization of computer systems
  
  Answer Suggestion
  
  Steps
  
  1: Complete a worksheet with calculated system capacity metrics.
  2: Select the number of server tiers
  3: Determine requirements for availability
  4: Select hardware
  5: Configure the appropriate number of disk drives
  6: Configure memory for each system
  7: Configure the network requirements
  8: Is a separate Payment Manager server required?
  9: Is a separate server required for search?
  10: Will a Staging server be used?
  
  Reference: IBM® WebSphere® Commerce Suite, Capacity Planning Guide, Version 5.1
  Question 8: Describe the difference between Tier 1, 2 and 3 system configurations for capacity planning for an organization that has moved onto e-commerce utilization of its computer systems.
  
  Answer Suggestion
  
  
  1–Tier
  In this configuration the Commerce Server, the database server, and the Web server are all on the same machine.
  
  
  
  2-Tier
  In this configuration the Web server and Commerce Suite is on one machine, the database server is a separate machine
  
  
  3-Tier
  In this configuration the Web server, Commerce Suite and the database are on separate machines
  
  
  
  
  
  
  Question 9: Discuss the term “persistence: in capacity planning
  
  Answer Suggestion
  Persistence is a term that comes into play when using a Controller to load balance multiple servers at a site which is designed to have customers return to the same server during a session. Persistence is required to seamlessly process customer requests while keeping the link between your site and your customer unbroken. However, E-commerce poses its own special challenges for persistence, specifically in regard to scalability and performance of the load balancing device.
  
  
  No Persistence No SSL Persistence
  No Persistence: Left example shows the effects of a customer source IP address changing over the course of a session. Customer accesses server (A), and fills a shopping cart full of goods. Customer decides to visit other areas of the site before purchasing. Customer returns to shopping cart and finds it apparently empty because customer was accidentally rerouted to the wrong server (B).
  No SSL Persistence: Example on right shows the results of IP users being funneled into very few IP addresses. Four customers log on to AOL (An ISP) and are directed to a Web site. All end up concentrated in a single server (A), giving customers sluggish site performance while other available resources (servers B, C and D) sit idle.
  
  For example, a customer uses regular HTTP to select items from a catalog, and places them into a shopping cart. When the customer wishes to purchase the items, however, most sites use SSL – a secure, encrypted protocol required for transmitting sensitive information like credit card numbers. In some cases, site design dictates that customer traffic for both HTTP and SSL be sent to the same server in order to keep the buying process seamless. This can be handled by persistence settings available on Controllers
  
  Example:
  BIG-IP Controller has SSL (Secure Socket Layer) Persistence. It tracks persistence using SSL Session ID, and allows BIG-IP Controller to properly load balance SSL traffic when it is originating from a site using proxy servers or multiple firewalls. These types of traffic sources concentrate a large number of users into a small number of IP addresses, or cause the end users’ IP address to change over the course of the session. Both of these scenarios cause standard persistence based on source IP to "break". In the case of IP address concentration, source IP persistence will concentrate the load on a single server, giving end users poor performance while other available resources sit idle. When a user’s IP address changes over the course of a session, source IP persistence will no longer be able to associate the user with the server that she was sent to, thereby causing things like shopping carts to appear empty. SSL Session ID Persistence solves these problems.
  BIG-IP Controller With Persistence BIG-IP Controller With SSL Persistence