BA 479 Midterm Review1. Intro: LAN5 Layer Network Model1. Physical Layera. Air, cables, actual transmission2. Data Link Layera. Ethernetb. Traffic cop (MAC)c. Error detection/correctiond. Message delineation3. Network Layera. Internet protocol (IP)4. Transport Layera. Transmission control protocol (TCP)5. Application Layera. Web address/email address (http)Database Server: Computer assigned to be a network server, which can perform specific functionsFile Server: Stores data and software that can be used by computers on the networkDatabase Server: More powerful than a file server. Provides access to files and database processing on those filesClient: This type of computer requests services from another computer- Obtaining software applications, files, data, ect…Web Server: Stores documents/graphics that can be accessed by any web browserPrint Server: Manages all printing requests from the clients on the networkRemote Access Server (RAS): Allows users to dial into and out of a LANNetwork Architectures4 Basic Functions Among Different Sets of Computers1. Data storage logic a. Data must be stored/retrieved 2. Data access logica. The processing required to access datab. Database queries3. Application (or Business) Logica. Rules of the system (or business)4. Presentation logica. The presentation of the information to the user and the acceptance of the users commandsHost Based Architecture- The server (usually a large mainframe computer) performs all 4 functions- Clients (usually terminals) enables users to send/receive messages to/from host computer- Some presentation logic executed by “dumb terminal” Client Based Architecture- File server executes data storage logic and most of the 4 functions are executed by clients (except data storage logic)n-tier Architectures2-tier Architecture-Client executes Application Logic and Presentation Logic -DB Server executes Data Storage/Data Access Logic3-tier Architecture- Client executes presentation logic- Web server executes application logic-DB server executes Data Storage/Data Access Logic4-tier Architecture- Car dealership has application logic distributed between web server and another server (application server) that houses Java appletso Java applet is a monthly payment calculator- Client executes presentation logic- Web server and application server execute Data storage logic and Dataaccess logicn-tier Architecture- Business logic is distributed among 2 or more serversThin Client: Little or no application logic executed by client- Easier to manage- If application changes, only the server with the application logic needs to updatedFat Client: Most or all application logic executed by clientAttenuation: Weakening of signal over distance Turnaround Time (Retain time or Re-clocking time): The amount of time half-duplex communication takes to switch between sending and receiving BA 479 Midterm Review2. Virtualization and Cloud Computing- Some organizations implement 5x more computing capacity than their average need… just to be ready for peak hours- Most servers run at 20-30% of their capacity o A.K.A. servers are idle 70-80% of the time- IBM typical data center size of 3 football stadiumsn-Tier Client/Server- Each server focuses on what it does besto Windows server, web server, application server, DB server- Many “dedicated” servers per organizationStorage Area Network: A dedicated (and very fast) network connects serversto secondary storage- This storage can be shared, backed up and managed independent of individual serversRack mount computers: Each computer has their own power supply, networkcards, fan…Data Centers- Typical size is 3 football stadiums packed with servers and data storage units- Temp controlled at 68F- If air-conditioning fails for two minutes temp rises to 120F and half of the equipment will be destroyed- Carbon footprint is heavyo Use 3% of all power generated in USo Exceeds automobile manufacturing industry- Individual IT related carbon footprinto Our mobile devices… when we send a text, we use these servers- Cost $1.6 million a year to power a 8,000 sqft data centero 10% increase a yearVirtualization: “Technology that allows encapsulation of resources on a singlemachine such that it supports the functionality of multiple machines by sharing its resources across multiple environmentsHypervisor: Virtualization layer/software that allows a physical server to run one or more logical partitions- These logical partitions are referred to as virtual machines (VM’s) or virtual servers2 Types of Hypervisors1. Type 1: Bare Metal Hypervisora. Doesn’t require an OS to beinstalled first… thehypervisor is the layerabove the hardwarei. VMWare’s ESXi2. Type 2: Hosted Hypervisora. Hypervisors resides as an application or service on another OS such as Microsoft Windows Server OS or Linux OSi. VMWare Workstation2 Popular Types of Virtualization1. Server Virtualizationa. Server consolidationb. Better utilization of server/energy resources2. Desktop Virtualizationa. One server can run multiple desktopsb. Move desktop workloads from the endpoint to the data centerAdvantages of Virtualization- Reduces number of servers- Better utilization of resources- Lower energy consumption- Lower TCODisadvantages of Virtualization- Need powerful host (physical) machines- Single point of failure- Network load- New performance issues (hard to predict)- Complex root cause analysisCloud Computing- Infrastructure as a Service (IaaS): Rent server resources instead of buying and maintaining your own- Hardware as a Service (HaaS): Pay as you go for using the CPU, data storage, backup storage, and network bandwidth related serviceso Ex: Amazon’s web services- Software as a Service (SaaS): Instead of installing the application yourself, let vendors install it and run it for you on their serverso Ex: Salesforce CRM, Facebook, G-mail, Linked-in, ect.- Platform as a Service (PaaS): Vendors provide IT platform to develop software for your businesso Vendors configure and manage web hosting facilities for you3 Deployment Models- Private cloud: one enterprise as the user- Public cloud: many clients share the cloud- Community cloud: A private/public cloud with users having a common connection or affiliationo Nike’s customer communities- Hybrid cloud: Any combo of 2 or more of the above 3 BA 479 Midterm Review3. Topology, MAC, Ethernet, FDDI, Hubs/SwitchesTopology: Geometric layout of network- Physical vs Logical