BIOS (Basic Input Output Service)

1. BIOS(Basic Input Output Service) • Contains system data used by the ROM BIOS service routines. • Serves as a standardized communication interface between the computer’s hardware and the operating system.

2. BIOS • Is a small ROM chip on the PC’s motherboard. • A basic software program containing all BIOS functions is permanently stored in the ROM. • This software functions as a basic operating system. • Is responsible for starting the PC. • This hardware integrated with software is also referred to as firmware.

3. Flow Chart of BIOS Functions Turn on Computer Pass through POST Error Free NO Output to Monitor YES Plug’n’Play Pass through POST Error Free Test Boot Drive NO Pass through POST Error Free Bootable media found NO YES Pass through POST Error Free Load boot program Start operating system

4. POST(Power On Self Test) • Takes place right after you power on. • Contains diagnostic routines for • initializing the hardware and peripherals • the video card, the main memory, the processor, the keyboard, etc. • Checking their functions • Error message on screen if an error is detected. If monitor cannot be detected, the beep codes are output by the system loud speaker.

5. Plug and Play • Bios next looks for additional BIOS memory chips – might be on a Plug and Play card such as video card or a SCSI controller. • If present, they run their routines and supplement or replace some functions of the system BIOS. • If components no longer match the data stored in the CMOS (i.e. hardware change), message appreas on screen to update.

6. Plug and Play • After all hardware components have been found and checked, Plug and Play goes to work. • Interrupts and DMA channels of the plug-in cards in the ISA and PCI buses are queried and distributed. • Onboard hardware, located on motherboard and in its ISA/PCI slots, are configured for operation.

7. Bootstrap Loader • BIOS next accesses the first sector of the hard drive, alos termed the boot sector, and starts the “bootstrap loader” • A small program that knows the file structure of the storage medium and can call the operating system’s start routine.

8. Operating System Kernel • Next, the operating system kernel is read into main memory and control of the hardware passes onto the operating system.

9. An Interpreter • In old operating systems (DOS 6.2), the BIOS acts as a mediator (or interface) between the hardware and the software. • New operating systems, circumvent the BIOS and communicate directly with the hardware through the appropriate drivers.

10. BIOS Updating • The BIOS is manufactured on FLASH technology. It is easily updated. • Previous versions of BIOS were developed on ROM, EPROM,and EEPROM chips.

11. DOS(Disk Operating System) Fundamentals • Consisted of two parts • The BIOS itself is one part of the operating system. • The other part consists of the operating system program files. • Program files consist of • Utilities • A kernel that is loaded into the main memory when the computer boots.

12. Microsoft Kernels • Kernel of a Microsoft operating system consists of • Msdos.sys • Io.sys • MSDOS.sys controls the keyboard input and the screen output. • IO.sys communicates with the BIOS and contains the actual program code of the operating system and a process control for the hardware.

13. BIOS Data Area, at Segment 0040h

14. Characteristics of an Operating System • Multi-user – Two or more users have individual accounts that allow them to work with programs and peripheral devices at the same time. • Multitasking – The computer is capable of operating multiple applications at the same time. • Multiprocessing– The operating system can support two or more CPUs. • Multithreading – A program can be broken into smaller parts that are loaded as needed by the operating system. Multithreading allows individual programs to be multitasked.

15. Basic Function of an Operating System • All computers rely on an operating system (OS) to provide the interface for interaction between users, applications, and hardware. • The operating system boots the computer and manages the file system. • The operating system has four main roles: • Control hardware access • Manage files and folders • Provide user interface • Manage applications

16. Processor Architecture • 32-bit Windows Operating System and x86 Processor Architecture • Capable of addressing 4 GB of RAM • x86 uses a Complex Instruction Set Computer (CISC) • x86 processors use fewer registers than x64 processors • 64-bit Windows Operating System and x64 Processor Architecture • Capable of addressing 128+ GB of RAM • Enhanced performance for memory management • Additional security features • x64 architecture is backward compatible with x86 • Process much more complex instructions at a much higher rate

17. Startup Modes Pressing the F8 key during the boot process opens the Windows Advanced Startup Options menu, which allows you to select how to boot Windows. • Safe Mode – Starts Windows but only loads drivers for basic components, such as the keyboard and display. • Safe Mode with Networking Support – Starts Windows identically to Safe Mode and also loads the drivers for network components. • Safe Mode with Command Prompt – Starts Windows and loads the command prompt instead of the GUI interface. • Last Known Good Configuration – Enables a user to load the configurations settings of Windows that was used the last time that Windows successfully started. It does this by accessing a copy of the registry that is created for this purpose.

18. The Windows Registry Files

19. Virtualization • Host machine uses its system resources to host a virtual machine. • Hosting a virtual machine allows users to access the functionality and resources provided by an OS that is not on the local PC. • Provides access to applications, file-sharing services, and other productivity tools. • Users can further increases the functionality of their system by running multiple virtual machines.

20. Virtualization • The software that creates and manages a virtual machine on a host machine is called the hypervisor, or Virtual Machine Manager (VMM). • Allocates the physical system resources, such as CPU, RAM, and hard drive, to each virtual machine as needed. • Windows Virtual PC is the virtualization platform for Windows 7 • Allows you to partition system resources for a Window OS among virtual machines .

21. Types of Backups

22. What is RAID? • Stands for Redundant Array of Independent Disks. • It’s a technology that enables greater levels of performance, reliability and/or large volumes when dealing with data. • How?? By concurrent use of two or more ‘hard disk drives’. • How Exactly?? Mirroring, Stripping (of data) and Error correction techniques combined with multiple disk arrays give you the reliability and performance.

23. RAID flavors • Commonly used ones: • RAID 0 • RAID 1 • RAID 5 • RAID 10 • Other types used…but rarely: RAID 2,3,4,6,50……

24. RAID 0 It splits data among two or more disks. Provides good performance. Lack of data redundancy means there is no fail over support with this configuration. In the diagram to the right, the odd blocks are written to disk 0 and the even blocks to disk 1 such that A1, A2, A3, A4, … would be the order of blocks read if read sequentially from the beginning. Used in read only NFS systems and gaming systems.

25. RAID 1 RAID1 is ‘data mirroring’. Two copies of the data are held on two physical disks, and the data is always identical. Twice as many disks are required to store the same data when compared to RAID 0. Array continues to operate so long as at least one drive is functioning.

26. RAID 5 RAID 5 is an ideal combination of good performance, good fault tolerance and high capacity and storage efficiency. An arrangement of parity and CRC to help rebuilding drive data in case of disk failures. “Distributed Parity” is the key word here.

27. RAID 10 Combines RAID 1 and RAID 0. Which means having the pleasure of both - good performance and good failover handling. Also called ‘Nested RAID’.

28. What’s happening present day? RAID 6: It is seen as the best way to guarantee data integrity as it uses double parity. Lesser MTBF compared to RAID5. It has a drawback though of longer write time.

29. Types of Networks • LAN (Local Area Network): A group of interconnected computers under one administrative control group that governs the security and access control policies that are in force on the network. • WLAN (Wireless Local Area Network): A group of wireless devices that connect to access points within a specified area. Access points are typically connected to the network using copper cabling. • PAN (Personal Area Network): Network that connects devices, such as mice, keyboards, printers, smartphones, and tablets within the range of an individual person. PANs are most often connected with Bluetooth technology.

30. Types of Networks • MAN (Metropolitan Area Network): Network that spans across a large campus or a city. Consisting of various buildings interconnected through wireless or fiber optic backbones. • WAN (Wide Area Network): Connections of multiple smaller networks such as LANs that are in geographically separated locations. The most common example of a WAN is the Internet.

31. Types of Networks (Continued) • Peer-to-peer networks: Devices which are connected directly to each other without any additional networking devices between them. Each device has equivalent capabilities and responsibilities. • Client/server networks: In a client/server model, the client requests information or services from the server. The server provides the requested information or service to the client.

32. Bandwidth and Latency • Bandwidth is the amount of data that can be transmitted within a fixed time period. • Bandwidth is measured in bits per second and is usually denoted by the following: • bps - bits per second • Kbps - kilobits per second • Mbps - megabits per second • Gbps - gigabits per second • Latency is the amount of time it takes data to travel from source to destination. • Data is transmitted in one of three modes: • Simplex (Unidirectional transmission) is a single, one-way transmission. • Half-duplex allows data to flow in one direction at a time. • Full-duplex allows data to flow in both directions at the same time.

33. IP Addressing - IPV4 • An IP address is a unique number that is used to identify a network device and is represented as a 32-bit binary number, divided into four octets (groups of eight bits): • Example: 10111110.01100100.00000101.00110110 • An IP address is also represented in a dotteddecimal format. • Example: 190.100.5.54 • When a host is configured with an IP address, it is entered as a dotted decimal number, such as 192.168.1.5. This IP address must be unique on a network to ensure data can be sent/received. • IP Classes • Class A: Large networks, implemented by large companies and some countries • Class B: Medium-sized networks, implemented by universities • Class C: Small networks, implemented by ISP for customer subscriptions • Class D: Special use for multicasting • Class E: Used for experimental testing

34. IP Addressing – IPV4 • Private Addresses - IETF reserved some Internet address space for private networks. • Private networks have no connection to public networks. • Private network addresses are not routed across the Internet. • Class A - 10.0.0.0 to 10.255.255.255 • Class B - 172.16.0.0 to 172.31.255.255 • Class C - 192.168.0.0 to 192.168.255.255

35. Subnet Masks • The subnet mask is used to indicate the network and the host portion of an IP address. • The default subnet masks for three classes of IP addresses. • 255.0.0.0 - Class A, which indicates that the first octet of the IPv4 address is the network portion. • 255.255.0.0 - Class B, which indicates that the first two octets of the IPv4 address is the network portion. • 255.255.255.0 - Class C, which indicates that the first three octets of the IPv4 address is the network portion.

36. IP Addressing – IPV6 • IPv6 address - 128 bits or 32 hexadecimal values. • 32 hexadecimal values are further subdivided into eight fields of four hexadecimal values separated by colons. • IPv6 address has a three-part hierarchy • Global prefix, also called a site prefix, is the first three blocks of the address. • Subnet ID includes the fourth block of the address. • Interface ID includes the last four blocks of the address.

37. Dynamic Host Configuration Protocol (DHCP) • DHCP automatically provides computers with an IP address. • The DHCP server can assign these to hosts: • IP address • Subnet mask • Default gateway • Domain Name System (DNS) server address

38. Internet Control Message Protocol (ICMP) • Internet Control Message Protocol (ICMP) is used by devices on a network to send control and error messages to computers and servers. • PING (Packet Internet Groper) is a simple command line utility used to test connections between computers. • Used to determine whether a specific IP address is accessible. • Used with either the hostname or the IP address. • Works by sending an ICMP echo request to a destination computer. • Receiving device sends back an ICMP echo reply message. • Four ICMP echo requests (pings) are sent to the destination computer to determine the reliability and reachability of the destination computer.

39. Internet Protocols • A protocol is a set of rules. Internet protocols govern communication within and between computers on a network. • Many protocols consist of a suite (or group) of protocols stacked in layers. • Devices and computers connected to the Internet use a protocol suite called TCP/IP to communicate with each other. • The main functions of protocols: • Identifying errors • Compressing data • Deciding how data is to be sent • Addressing data • Deciding how to announce sent and received data • The information is transmitted most often via two protocols, TCP and UDP.

40. TCP and UDP Protocols and Ports • A port is a numeric identifier used to keep track of specific conversations. Every message that a host sends contains both a source and destination port.

41. Physical Network Components A Modem is an electronic device that connects to the Internet via an ISP. • A modem converts digital data to analog signals for transmission over a phone line. • Internal modems plug into an expansion slot on the motherboard. • External modems connect to a computer through the serial and USB ports.

42. Network Devices • Hub • Extend the range of a signal by receiving then regenerating it and sending it out all other ports. • Allow for collisions on the network segment and are often not a good solution. • Also called concentrators because they serve as a central connection point for a LAN. • Bridges and Switches • A bridge has the intelligence to determine if an incoming frame is to be sent to a different segment, or dropped. A bridge has two ports. • A switch (multiport bridge) has several ports and refers to a table of MAC addresses to determine which port to use to forward the frame. • Power over Ethernet (PoE) • PoE switch transfers small amounts of DC current over Ethernet cable, along with data, to power PoE devices such as Wi-Fi access points.

43. Network Devices (Continued) • Routers • Devices that connect entire networks to each other. They use IP addresses to forward packets to other networks. • A router can be a computer with special network software installed or can be a device built by network equipment manufacturers. • Routers contain tables of IP addresses along with optimal routes to other networks. • Wireless Access Points (WAP) • Provide network access to wireless devices such as laptops and PDAs. • Use radio waves to communicate with radios in computers, PDAs, and other wireless access points. • Have limited range of coverage.

44. Network Devices • VoIP phones -  carry telephone calls over the data networks and Internet. • Hardware firewalls - use various techniques for determining what is permitted or denied access to a network segment. • Internet appliance – web TV, game consoles, Blu-ray players etc. • Purchasing Authentic Networking Devices - Computer and network problems can be related to counterfeit components.

45. LAN Physical Topologies • A physical topology defines the way in which computers, printers, and other devices are connected to a network. • Bus • Each computer connects to a common cable The ends of the cable have a terminator installed to prevent signal reflections and network errors. • Only one computer can transmit data at a time or frames will collide and be destroyed. • Ring • Hosts are connected in a physical ring or circle. • A special frame, a token, travels around the ring, stopping at each host to allow data transmission. • There are two types of ring topologies: • Single-ring and Dual-ring

46. The TCP/IP Reference Model • Frame of reference used to develop the Internet's protocols. • Consists of layers that perform functions necessary to prepare data for transmission over a network.

47. The OSI Model • The OSI model is an industry standard framework that is used to divide network communications into seven layers. • Although other models exist, most network vendors today build their products using this framework. • A protocol stack is a system that implements protocol behavior using a series of layers. • Protocol stacks can be implemented either in hardware or software, or in a combination of both. • Typically, only the lower layers are implemented in hardware, and the higher layers are implemented in software.

48. The OSI Model Remember the OSI layers with this mnemonic: • "Please Do Not Throw Sausage Pizza Away"

49. Compare OSI and TCP/IP Models

50. Virtual Private Network (VPN) • A Virtual Private Network (VPN) is a private network that uses a public network, like the Internet, to connect remote sites or users together