Network Fundamentals PDF

1. An advantage of networks is networks enable multiple users to share resources. 2. Peer-to-peer model ensures that no computer on the network has more authority than another. Traditional peer-to-peer networks are usually simple and inexpensive to set up. 3. Client/server networks are the most popu...

1. An advantage of networks is networks enable multiple users to share resources. 2. Peer-to-peer model ensures that no computer on the network has more authority than another. Traditional peer-to-peer networks are usually simple and inexpensive to set up. 3. Client/server networks are the most popular type of network for medium- and large-scale organizations. The client-server model for access control relies on a centrally administered server using a NOS that manages shared resources for multiple clients. 4. A LAN network is confined to a relatively small space. A LAN is a network of computers and other devices that can directly address all other nodes. 5. Separate LANs are interconnected and rely on several servers running many different applications and managing resources other than data. LANS can be interconnected to form WANS, which traverse longer distances in two or more geographical areas. 6. A MAN network connects clients and servers from multiple buildings. A MAN covers a small geographical area, and a WAN covers a large geographical area. 7. In a star topology, all computers and network devices connect to one central device. 8. A backbone is a central conduit that connects parts of a network and might use the bus topology. 9. A router manages traffic between two or more LANS. 10. The seven layers of the OSI model are layer 7 - Application, layer 6 - Presentation, layer 5 - Session, layer 4 - Transport, layer 3 - Network, layer 2 - Data Link, and layer 1- Physical. 11. Application layer initiates the flow of information. 12. The Presentation layer manages data encryption. 13. TCP operates at the Transport layer. 14. An IP transmission is called a packet. A message at the Data Link layer is called a frame. 15. HVAC systems are responsible for controlling humidity and temperature in a data center. 16. A connectivity device is a specialized device that allows multiple networks or multiple parts of one network to connect and exchange data. 17. Star network topology is the most common network. In a star topology, all computers and network devices connect to one central device. 2 18. In the client-server model, HTTP is the primary protocol used for communication between a browser and Web server. 19. SSL and TLS are two encryption protocols might be used to provide secure transmissions for browser and Web server communications. 20. POP3 allows an email client to download email messages to the local computer. IMAP4 allows an email client to read mail stored on the mail server. 21. Telnet allows an administrator to control a remote computer, but does not encrypt or secure the communication between client and server. Remote Desktop embedded in Windows operating systems allows remote control of a computer and uses the RDP secure protocol for transmissions. 22. A user complains that Skype drops her videoconference calls and she must reconnect. You should begin troubleshooting in Application layer. Session layer is responsible for not dropping the Skype connection. 23. A computer is unable to access the network. When you check the LED lights near the computer’s network port, you discover the lights are not lit. You should use Physical layer to troubleshoot this problem. The network adapter works in Data Link layer Physical layer. Chapter 2: How Computers Find Each Other on Networks 1. A computer turns to Default gateway first when attempting to make contact with a host on another network. 2. If you are connected to a network that uses DHCP, and you need to terminate your Windows workstation’s DHCP lease using “ipconfig /release”. 3. Root servers are the highest authorities in the Domain Name System hierarchy. 4. FTP sometimes uses a random port for data transfer, but an FTP server always, unless programmed otherwise, listens to port 21 for session requests from clients. 5. The goal of ISO is to establish international technological standards to facilitate the global exchange of information and barrier free trade. 6. Last part of an FQDN is called the top-level domain (TLD). For example, in the domain name www.abc.net,.net is the top-level domain (TLD). 7. IPv4 addresses have 32 bits and are written as four decimal numbers called octets. IPv6 addresses have 128 bits and are written as eight blocks of hexadecimal numbers. 8. “ipconfig” is useful for viewing and adjusting a Windows computer’s TCP/IP settings. 3 9. On a Windows computer, “ipconfig /all” is for showing IP address, subnet mask, default gateway, DNS servers. 10. A FQDN includes both a host name portion and a domain name portion. Name resolution is the process of matching an FQDN to its IP address. DNS is an automated name resolution service that operates at the Application layer. 11. NAT is used to allow devices that have private IP addresses access to the Internet. NAT is a technique designed to conserve public IP addresses needed by a network. 12. Port Address Translation (PAT) - process of assigning a TCP port number to each ongoing session between a local host and Internet host. 13. There are four addressing methods: a. Application layer FQDNs, computer names, and host names. b. Transport layer port numbers. c. Network layer IP address. d. Data Link layer MAC address (physical address). 14. Traditional MAC addresses contain two parts: a. First 24 bits are known as the OUI (Organizationally Unique Identifier) or block ID or company-ID. Assigned by the IEEE. b. Last 24 bits make up the extension identifier or device ID. Manufacturer’s assign each NIC a unique device ID. 15. In IPv4 addressing, each IP address is a unique 32-bit number. 16. In IPv6 addressing, each IP address is a unique 128-bit number. 17. There are 5 IP address classes in total. 18. Class A supports most hosts per network; Class C supports fewest hosts per network. 19. IPv4 addresses are divided into five classes: Class A, Class B, Class C, Class D, and Class E. Class D and Class E addresses were not available for general use. Class D begin with 224-239 and are used for multicasting and Class E begin with octets 240-254 and are used for research. 20. Class A, B, and C licensed IP addresses are available for use on the Internet, this is called public IP addresses. A company can use private IP addresses on its private networks. 21. NICs operate at Physical and Data Link. 22. IEEE recommends the following IP addresses be used for private networks: 10.0.0.0 through 10.255.255.255 172.16.0.0 through 172.31.255.255 192.168.0.0 through 192.168.255.255 23. Static IP addresses are assigned manually by the network administrator. Dynamic IP addresses are automatically assigned by a DHCP server. 24. Connectionless protocols are useful when data must be transferred quickly. 25. DNS is an application layer client-server system of computers and databases made up of these elements: namespace, name servers, resolvers. 26. “nslookup” is being used for finding the host name of a device whose IP address you know. 27. nslookup - allows you to query the DNS database from any computer on a network: a. To find the host name of a device by specifying its IP address, or vice versa. b. Useful for verifying a host is configured correctly or for troubleshooting DNS resolution problems. Chapter 3: How Data Is Transported Over Networks 1. Network layer is responsible for directing data from one LAN to another. 2. Static route is created when a network administrator configures a router to use a specific path between nodes. 3. Hop/router limitation of RIP routing protocol is 15. 4. A routing protocol’s reliability and priority are rated by Administrative Distance (AD). AD is the feature that routers use in order to select the best path when there are two or more different routes to the same destination from two different routing protocols. The smaller the administrative distance value, the more reliable the protocol. 5. Routing protocols are used by routers to communicate with each other to determine the best path. 6. Three characteristics distinguish TCP from UDP: TCP is connection-oriented, uses sequencing and checksums, and provides flow control. 7. TCP Three-way handshake is used to establish a TCP connection. 5 8. IGMP operates at the Network layer of OSI model to manage multicasting. 9. All routers perform four functions: a. Connect dissimilar networks. b. Interpret Layers 3 and 4 addressing and other information. c. Determine the best path for data to follow. d. Reroute traffic if a primary path is down but another path is available. 10. Routing metrics used by routers to determine the best of various available routing paths: Hop count, theoretical bandwidth, actual throughput, path latency (or delay), path load, MTU, cost, reliability. 11. TCP is a connection-oriented protocol - TCP ensures that a connection or session is established by using a three-step process called a three-way handshake. 12. TCP three-way handshake: Step 1 - request for a connection (SYN) Step 2 - response to the request (SYN/ACK) Step 3 - connection established (ACK) 13. UDP provides no error checking or sequencing. makes UDP more efficient than TCP. UDP is useful for live audio or video transmissions over the Internet. 14. IP operates at the Network layer of the OSI model. IP enables TCP/IP to internetwork. IP is an unreliable, connectionless protocol. Means that IP does not guarantee delivery of data and no connection is established before data is transmitted. IP depends on TCP to ensure data packets are delivered to the right address. 15. Router categories include Interior routers, Border routers, Exterior routers. a. Interior routers - direct data between networks within the same autonomous system. b. Border routers - connect an autonomous system with an outside network. c. Exterior routers - direct data between autonomous systems. 16. Routing table is a database that maintains information about where hosts are located and the most efficient way to reach them. Routers rely on them to identify which router is the next hop to reach a particular destination host. Routing tables contain IP addresses and network masks that identify a network that a host or another router belongs to. 17. Static routing: Network administrators configures a routing table to direct messages along specific paths. 18. Dynamic routing: Automatically calculates the best path between two networks and maintains this information in a routing table. 19. Routing protocols are used by routers to communicate with each other to determine the best path Routers rate the reliability and priority of a routing protocol’s data based on these criteria: a. Administrative distance (AD) - a number indicating the protocol’s reliability. 6 b. Convergence time - time it takes to recognize a best path in the event of a change or network outage. c. Overhead - the burden placed on the underlying network to support the protocol. 20. IGP (interior gateway protocols) - used by interior routers and border routers within autonomous systems and are often grouped according to the algorithms they use to calculate best paths: (a) Distance-vector routing protocols. (b) Link-state routing protocols. 21. EGP (exterior gateway protocols) - used by border routers and exterior routers to distribute data outside of autonomous systems. The only EGP currently in use is BGP. 22. TCP is an OSI Transport layer, connection-oriented protocol that provides reliability through checksum, flow control, and sequencing information. 23. UDP is a Transport layer and connectionless protocol that provides no delivery guarantees. 24. ARP operates at the Data Link layer and obtains the MAC address of a host. 25. ICMP is a Network layer core protocol that reports on the success or failure of data delivery using the Ping utility. 26. A router is a multiport device that can connect dissimilar LANs and WANs running at different transmission speeds, using a variety of protocols. 27. Static routing is when a network administrator programs a router to use specific paths between nodes. 28. To determine best path, routers communicate with each other through routing protocols. 29. Routing metrics may factor in the number of hops between nodes, throughput, delay, MTU, cost, load, and reliability. 30. RIP is a distance-vector routing protocol, is the slowest and least secure routing protocol. 31. OSPF is a link-state routing protocol used on interior or border routers. 7 32. BGP uses the most complex best-path calculation of all commonly used routing protocols. 33. The traceroute utility, known as tracert on Windows-based system, uses ICMP to trace the path from one networked node to another. 34. The route command allows you to view a host’s routing table and add, delete, or modify preferred routes. Chapter 4: Structured Cabling and Networking Elements 1. Commercial Buildings Components：Entrance facilities, MDF (main distribution frame) IDF (intermediate distribution frame), Horizontal wiring, Backbone wiring, Work area. 2. In a typical rack system, airflow through the chassis is typically designed to move from front to back 3. A SAN is a network of storage devices that communicate directly with each other and with other networks. 4. SANS use one of two types of Transport layer protocols: Fibre Channel (FC), iSCSI. 5. Power flaws that can damage your equipment: Surge - momentary increase in voltage due to lightning strikes, solar flares, or electrical problems Noise - fluctuation in voltage levels caused by other devices on the network or EMI Brownout - momentary decrease in voltage; also known as a sag Blackout - complete power loss 6. UPS - a battery-operated power source directly attached to devices and to a power supply; Prevents undesired fluctuations of power from harming the device or interrupting its services. 7. Two UPS categories: Standby UPS - provides continuous voltage to a device by switching to the battery when it detects a loss of power from the wall outlet. Online UPS - uses the AC power from the wall outlet to continuously charge its battery, while providing power to the device through its battery. 8. Generator - backup power source, providing power redundancy in the event of a total blackout. 9. TIA/EIA created a joint cabling standard known as structured cabling 10. Coaxial is not recognized by the TIA/EIA for horizontal wiring. 11. Patch panel does nothing to the data transmitted on a line other than pass it along through the connection. 12. NICs operate at Layers 1 and 2. 13. 19 inches and 23 inches are the two primary standard widths for rack systems. 8 14. KVM switch provides a central control portal for all devices on a rack. 15. Surge protector protects computer equipment from a momentary increase in voltage due to lightning strikes, solar flares, or electrical problems. 16. Providing a backup power source is called power redundancy. 17. The standard suggests how networking media can best be installed to maximize performance and minimize upkeep. 18. The MDF, which may contain the demarc and other connectivity devices, such as switches and routers, and media, such as fiber-optic cable. 19. A plenum-rated cable is coated with a flame-resistant jacket that produces less smoke than regular cable coated with polyvinyl chloride (PVC). In the event of a fire, smoke produced by plenum cabling is less toxic than that produced by PVC cabling. 20. A loopback plug is a connector that plugs into a port and crosses over the transmit line to the receive line so that outgoing signals can be redirected into the computer for testing. 21. The industry standard height of Rack unit is 42U (about 6 feet) 22. The two general categories of UPSs are standby and online. 23. Some elements that are typically included in network diagrams may include physical layout, logical topology, perimeter, access method, protocols, and network devices and connections. 24. A wiring schematic is a graphical representation of a network’s wired infrastructure 25. The TIA/EIA standard for wall jacks in a work area require that at least one outlet be provided for data and one for voice. 26. Each type of cable has a prescribed bend radius , which is the radius of the maximum arc into which you can loop a cable without impairing data transmission. 27. A NIC card cannot determine whether the frames it transmits and receives are using IP packets or a different layer 3 protocol, because the NIC does not operate higher than Layer 2 of the OSI model. 28. Full-duplex allows signals to travel in both directions over a medium simultaneously. 29. Vertical cross connect runs between a building's floors and can be used to connect an MDF and IDF or multiple IDFs. 30. Fiber optic comes in two different modes, single mode and multimode. 31. Half duplex allows signals to travel in both directions over a medium but in only one direction at a time. 32. Entrance facility serves as the location where an incoming network interface enters a building and connects with the building's backbone cabling. 9 33. Transformer changes the voltage of an AC current, such as when power over the main line from an electric company is changed before being delivered to a home. 34. During termination of twisted pair cabling, “No more than 1 inch of the cable should be exposed” should be done to ensure minimal cross talk is introduced. 35. Cable should be installed at least 3 feet away from fluorescent lights or other sources of EMI. 36. A demarc located in the Main Distribution Frame (MDF) to the structured cabling of an enterprise environment. 37. In order to simplify console access to computers in a rack, KVM switch is typically used to provide a central portal for all devices on the rack?. 38. Ethernet exists at Layer 2 of the OSI model. 39. The maximum allowable distance for horizontal wiring is 100 m. 40. One watt is equal to 1.4 volt-amps. 41. Noise involves a fluctuation in voltage levels caused by other devices on the network or by EMI. 42. TIA/EIA recognizes three possible cabling types for horizontal wiring: UTP, STP, or fiber optic cable. UTP (unshielded twisted pair) cable is a type of copper-based cable that consists of one or more insulated twisted-wire pairs encased in a plastic sheath. STP (shielded twisted pair) cable is a type of copper-based cable containing twisted-wire pairs that are not only individually insulated, but also surrounded by a shielding made of a metallic substance such as foil. Fiber-optic cable is a form of cable that contains one or several glass or plastic fibers in its core and comes in two types: single-mode fiber (SMF) or multimode fiber (MMF). Copper-based cable transmits data via electric signals, and fiber-optic cable transmits data via pulsing light sent from a laser or light-emitting diode (LED). 43. A brownout is a momentary decrease in voltage; also known as a sag. An overtaxed electrical system can cause brownouts, which you might recognize in your home as a dimming of the lights. Such voltage decreases can cause computers or applications to fail and potentially corrupt data. A blackout is a complete power loss. A blackout could cause significant damage to your network. For example, if a server loses power while files are open and processes are running, its NOS might be damaged so extensively that the server cannot restart and the NOS must be reinstalled from scratch. A backup power source, however, can provide power long enough for the server to shut down properly and avoid harm. Chapter 5: Network Cabling 1. Analog transmission is measured by baud rate. 2. Coaxial cable uses BNC connectors and F-connectors. F-connector is likely to be used by cable TV. 3. Cat 5e and higher twisted-pair cable can support Gigabit Ethernet. 10 4. Cat 6 is the earliest twisted-pair cabling standard that meets the minimum requirements for 10GBase-T transmissions. 5. Amplifier can boost an analog signal. Repeater can boost a digital signal. 6. The four fundamental properties of an analog signal: Amplitude, frequency, wavelength, and phase. 7. A modem modulates digital signals into analog signals at the transmitting end, then demodulates analog signals into digital signals at the receiving end. 8. The core of SMF is much narrower than that of MMF, and reflects very little. The light does not disperse as much along the fiber. That is the reason why SMF is more efficient over long distances than MMF. 9. Analog signals are characterized by four properties: Amplitude: Measure of strength at given point in time. Frequency: Number of times amplitude cycles over fixed time. Wavelength: Distance between one peak and the next. Phase: Progress of wave over time compared to a fixed point. 10. Baseband transmission: (a) Digital signals that are carried on a single channel. (b) Requires exclusive use of wire’s capacity. Example: Ethernet. 11. Broadband transmission: (a) Multiple transmissions share a single media. (b) Transmission sharing the same media rely on multiplexing to manage multiple signals. Example: Cable TV and cable Internet. 12. Multiplexing: A form of transmission that allows multiple signals to travel simultaneously over one medium. 13. TDM (Time division multiplexing): Divides channel into multiple time intervals. 14. WDM (Wavelength Division Multiplexing): (a) One fiber-optic connection. (b) Carries multiple light signals simultaneously. 15. DWDM (Dense Wavelength Division Multiplexing): (a) Used on most modern fiber-optic networks. (b) Extraordinary capacity. (c) Typically used on high-bandwidth or long-distance WAN links. 16. CWDM (Coarse Wavelength Division Multiplexing): (a) Developed after DWDM in an effort to lower the cost of the transceiver equipment needed. (b) Channels are spaced more widely apart across entire frequency band. 17. Straight-through cable: Terminate RJ-45 plugs at both ends identically Crossover cable: Transmit and receive wires on one end reversed Rollover cable: All wires are reversed; Terminations are a mirror image of each other; Also called Yost cables or Cisco console cables; Used to connect a computer to the console port of a router. 18. Throughput: Amount of data transmitted during given time period. Also called payload rate or effective data rate. Expressed as bits transmitted per second. 11 19. Bandwidth: Difference between highest and lowest frequencies medium can transmit. Range of frequencies. Expressed as bits transmitted per second, called bit rate. 20. Twisted-Pair cable: Color-coded insulated copper wire pairs. 0.4 to 0.8 mm diameter. Encased in a plastic sheath. Every two wires are twisted together. 21. Twisted-pair cable consists of color-coded pairs of insulated copper wires that are twisted in pairs. 22. STP cable consists of twisted-pair wires that are not only individually insulated, but also surrounded by a shielding made of a metallic substance. 23. UTP does not contain additional shielding. 24. TIA/EIA has specified two different methods of inserting wires into RJ-45 plugs: 568A and 568B. 25. A rollover cable uses a reverse image of the pinout of the other end of a cable. 26. Fiber-optic cable contains one or more several glass or plastic fibers at its core. 27. SMF accommodates the highest bandwidths and longest distances of all network transmission media. 28. MMF contains a core with a larger diameter. 29. Fiber-optic cabling is the best medium for delivering high throughput. 30. A common source of noise is EMI. 31. Cross-talk occurs when a signal traveling on one wire or cable infringes on the signal traveling on an adjacent wire or cable. 32. Attenuation is the loss of a signal’s strength. 33. Latency is the delay between the instant data leaves the source and when it arrives at its destination. 34. Tools used to test cables: cable checkers, continuity testers, cable testers, and light meters (for fiber). 35. STP (Shielded Twisted Pair): (a) Individually insulated. (b) Surrounded by metallic substance shielding (foil) - Barrier to external electromagnetic forces; Contains electrical energy of signals inside; May be grounded. 36. UTP (Unshielded Twisted Pair): One or more insulated wire pairs - Encased in plastic sheath; No additional shielding; Less expensive, less noise resistance. 37. SMF (Single Mode Fiber): Consists of narrow core (8-10 microns in diameter); Can carry signals many miles; Can carry signals many miles. 38. MMF (Multimode Fiber): Contains a core with a larger diameter than single mode fiber; Common sizes: 50 or 62.5 microns; Laser or LED generated light pulses travel at different angles; Greater 12 attenuation than single-mode fiber; Common uses- Cables connecting router to a switch, cables connecting server on network backbone. 39. Noise: Any undesirable influence degrading or distorting signal. 40. Types of noise: EMI (electromagnetic interference), example: radio frequency interference; 41. Cross-talk; Signal on one wire infringes on adjacent wire signal; Alien cross-talk occurs between two cables; Near end cross-talk (NEXT) occurs near source; Far end cross-talk (FEXT) occurs at the far end. 42. Attenuation: Loss of signal’s strength as it travels away from source. 43. Throughput is the measure of how much data is transmitted during a given time period. 44. Cross-talk occurs when a signal traveling on one wire or cable infringes on the signal traveling on an adjacent wire or cable. 45. STP cable consists of twisted-pair wires that are not only individually insulated, but also surrounded by a shielding made of a metallic substance. UTP cable does not contain additional shielding. 46. When an Ethernet NIC has been configured by the OS to use half-duplex, the transmit pair of the twisted-pair cable uses Simplex transmissions, the receive pair in the cable uses simplex transmissions, and the twisted-pair cable uses half-duplex transmissions. 47. Ethernet is not an example of a broadband transmission. 48. Analog transmission is measured by baud rate. 49. Coaxial cable uses BNC connectors; coaxial cable uses F-connectors; F-connector is likely to be used by cable TV. 50. Cat 5e and higher of twisted-pair cable can support Gigabit Ethernet. 51. Cat 6 is the earliest twisted-pair cabling standard that meets the minimum requirements for 10GBase-T transmissions. 52. Amplifier can boost an analog signal; Repeater can boost a digital signal. 53. Four fundamental properties of an analog signal: Amplitude, frequency, wavelength, and phase. 54. A modem modulates digital signals into analog signals at the transmitting end, then demodulates analog signals into digital signals at the receiving end. 55. Twist ratio is the number of twists per meter or foot. The more twists per foot in a pair of wires, the more resistant the pair will be to cross-talk or noise. 56. The core of SMF is much narrower than that of MMF, and reflects very little. The light does not disperse as much along the fiber. 57. A fiber cleaver scores the fiber strand for breaking, but does not cut it. 13 58. A short circuit is one where connections exist in places they shouldn’t, whereas an open circuit is one where needed connections are missing. 59. A continuity tester should not be used on a live network segment. 60. Multimode fiber contains a core that is larger than a single mode fiber core. 61. Digital signals are composed of pulses of precise, positive voltages and zero voltages. 62. It needs four cable pairs for 1000Base-T transmission over CAT5e cable. 63. 10Base2 is also referred to as "thinnet". 64. Standard PoE devices must be provided with 15.4 watts power in order to function. 65. Using a form of transmission that allows multiple signals to travel simultaneously over one medium is known as multiplexing. 66. A device that is responsible for modulating digital signals into analog signals, and demodulating analog signals into digital signals at the receiving end, is known as a modem. 67. Sheath is used to describe the outer-most layer of protective covering of a coaxial cable. 68. 10 Gbps is the maximum supported throughput of a CAT6 cable. 69. MT-RJ connectors is the most common for multimode fiber. 70. Near end cross talk occurs between wire pairs near the source of a signal. 71. A measure of a signal's strength at any given time is known as amplitude 72. The number of times that a wave's amplitude cycles from its starting point, through its highest amplitude and its lowest amplitude, and back to its starting point over a fixed period of time, is known as frequency. 73. Ethernet is an example of baseband. 74. Since cable TV and cable Internet can share the same coaxial cable, they are considered to be broadband technology. 75. The most common multiplexing technology used in conjunction with fiber optics is DWDM.