Networking fundamental

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Networking fundamental

  1. 1. Networking Fundamentals Review
  2. 2. Networking Evolution <ul><li>Network: </li></ul><ul><ul><li>Two or more connected computers that share data </li></ul></ul><ul><li>Paradigms: </li></ul><ul><ul><li>Client/server model </li></ul></ul><ul><ul><li>Mainframe model </li></ul></ul><ul><ul><li>Peer to peer </li></ul></ul><ul><ul><li>Web-based networking </li></ul></ul><ul><ul><li>Sneakernet: The transfer of files from one computer to another using a floppy disk or other removable medium </li></ul></ul>
  3. 3. Networking Categories <ul><li>Two basic categories: </li></ul><ul><ul><li>Server-based </li></ul></ul><ul><ul><li>Peer-to-peer </li></ul></ul><ul><li>Enterprise networks </li></ul><ul><ul><li>Combine peer-to-peer and server-based </li></ul></ul>
  4. 4. Network Topologies <ul><li>Bus </li></ul><ul><li>Star </li></ul><ul><li>Ring </li></ul><ul><li>Hybrid networks </li></ul><ul><li>Mesh </li></ul>
  5. 5. Layers of the OSI/RM <ul><li>Application A ll </li></ul><ul><li>Presentation P eople </li></ul><ul><li>Session S eem </li></ul><ul><li>Transport T o </li></ul><ul><li>Network N eed </li></ul><ul><li>Data link D ata </li></ul><ul><li>Physical P rocessing </li></ul>
  6. 6. Application Layer <ul><li>User interface </li></ul><ul><li>Supports file transfer </li></ul><ul><li>Network management </li></ul><ul><li>Accepts requests and passes them down to the presentation layer </li></ul>
  7. 7. Presentation Layer <ul><li>Converts text from what is viewable to the user to what is understandable to the computer </li></ul><ul><li>Passes data to session layer </li></ul>
  8. 8. Session Layer <ul><li>Establishes, manages, and terminates connections between cooperating applications </li></ul><ul><li>Adds traffic flow information </li></ul>
  9. 9. Transport Layer <ul><li>Reliable, transparent transport between end points </li></ul><ul><li>Supports end to end error recovery and flow control </li></ul><ul><li>Connection-oriented protocols reside at this layer </li></ul>
  10. 10. Network Layer <ul><li>Responsible for forwarding and routing datagrams </li></ul><ul><li>Connectionless protocols reside at this layer </li></ul>
  11. 11. Data Link Layer <ul><li>Provides reliable data transfer across the physical link </li></ul><ul><li>Frames are transmitted with the necessary synchronization error control and flow control </li></ul><ul><li>Prepares information so it can be sent to the physical wire </li></ul>
  12. 12. Physical Layer <ul><li>Concerned with the transmission of unstructured bit stream over a physical link </li></ul><ul><li>Responsible for the mechanical, electrical, and procedural characteristics to establish, maintain, and deactivate the flow of bits </li></ul>
  13. 13. Application-Layer Protocols <ul><li>SMTP </li></ul><ul><li>BOOTP </li></ul><ul><li>FTP </li></ul><ul><li>HTTP </li></ul><ul><li>AFP </li></ul><ul><li>SNMP </li></ul><ul><li>SMB </li></ul><ul><li>X.500 </li></ul><ul><li>NCP </li></ul><ul><li>NFS </li></ul>Network Management, File Transfers, User Interface
  14. 14. Transport-Layer Protocols <ul><li>TCP </li></ul><ul><li>SPX </li></ul><ul><li>NWLink </li></ul><ul><li>ATP </li></ul><ul><li>NetBEUI </li></ul>Reliable, Connection-Oriented, Error Recovery, and Flow Control
  15. 15. Network-Layer Protocols <ul><li>IP </li></ul><ul><li>IPX </li></ul><ul><li>NWLink </li></ul><ul><li>NetBEUI </li></ul><ul><li>X.25 </li></ul><ul><li>Ethernet </li></ul>Connectionless (best effort delivery), Forwards and Routes Datagrams
  16. 16. Major Networking Protocols <ul><li>Connection-oriented (stateful) </li></ul><ul><li>Connectionless (stateless) </li></ul><ul><li>Routable – Most protocols are routable </li></ul><ul><li>Nonroutable </li></ul><ul><ul><li>NetBios </li></ul></ul><ul><ul><li>NetBeui </li></ul></ul><ul><ul><li>LAT </li></ul></ul><ul><ul><li>DLC </li></ul></ul>
  17. 17. TCP/IP <ul><li>Default protocol for the following network operating systems: </li></ul><ul><ul><li>Windows 2000 </li></ul></ul><ul><ul><li>Windows NT 4.0 </li></ul></ul><ul><ul><li>UNIX </li></ul></ul><ul><ul><li>NetWare 5 </li></ul></ul><ul><ul><li>… plus the Internet! </li></ul></ul><ul><li>Computers are each identified with an IP address and subnet mask </li></ul>
  18. 18. IPX/SPX <ul><li>IPX is responsible for forwarding packets to sockets </li></ul><ul><li>SPX ensures reliable data delivery and manages sessions </li></ul><ul><li>Must identify a frame type during setup </li></ul>
  19. 19. NetBEUI <ul><li>Non-routable </li></ul><ul><li>Fast </li></ul><ul><li>Easiest to configure and maintain </li></ul><ul><li>Low overhead </li></ul>
  20. 20. AppleTalk <ul><li>Used only on Apple Macintosh networks </li></ul><ul><li>Divides groups of computers into zones </li></ul>
  21. 21. Common Network Components <ul><li>NICs </li></ul><ul><li>Repeaters </li></ul><ul><li>Hubs </li></ul><ul><li>Bridges </li></ul><ul><li>Routers </li></ul><ul><li>Brouters </li></ul><ul><li>Switches </li></ul><ul><li>Gateways </li></ul><ul><li>CSU/DSU </li></ul><ul><li>Modems </li></ul><ul><li>Patch panels </li></ul><ul><li>Internet-in-a-box </li></ul>
  22. 22. Network Interface Cards (NICs) NIC is the interface between the computer and the network
  23. 23. MAC Address Components
  24. 24. Repeaters <ul><li>Amplifies electronic signal </li></ul><ul><li>Strengthens signal by re-transmitting it when segment approaches its maximum length </li></ul>
  25. 25. Hubs <ul><li>Concentration point of network </li></ul><ul><li>Used with a star configuration </li></ul>
  26. 26. Bridges <ul><li>Operates on the data link layer </li></ul><ul><li>Reduce network traffic by dividing the network into two segments </li></ul><ul><li>Recognize mac addresses rather than IP addresses </li></ul><ul><li>Can connect two different topologies </li></ul>
  27. 27. Routers <ul><li>Operates on the network layer </li></ul><ul><li>Forwards or route data according to routing tables </li></ul><ul><li>Determine IP address needed and then most efficient route </li></ul><ul><li>Conserves network bandwidth by reducing broadcasting </li></ul>
  28. 28. Switches <ul><li>Can operate at the data link and network layers </li></ul><ul><li>Directs the flow of information from one node to another. </li></ul><ul><li>Faster because it give each sender/receiver the entire bandwidth of a line instead of sharing </li></ul>
  29. 29. Gateways <ul><li>Can operate at any level of the OSI model </li></ul><ul><li>Protocol converter – Appletalk to TCP/IP </li></ul>
  30. 30. CSU/DSU <ul><li>Channel Service Unit/Data Service Unit </li></ul><ul><ul><li>Operates at the physical layer </li></ul></ul><ul><ul><li>Terminates physical connections </li></ul></ul><ul><ul><li>Used for bringing T1 lines into a building </li></ul></ul>
  31. 31. Modems <ul><li>Uses POTS phone line to connect to internet </li></ul><ul><li>Can dial RAS connection directly to another computer </li></ul>
  32. 32. Modem Initialization Commands AT – Precedes most commands ATDT – Dials the number ATA – Answers an incoming call manually ATH0 – Tells modem to hang up AT&F – Resets the modem to factory defaults ATZ – Resets modem to power up defaults , - Pause *70 or 1170 – Turns off call waiting
  33. 33. Transmission Media <ul><li>Twisted pair cable </li></ul><ul><li>Coaxial cable </li></ul><ul><li>Fiber optic cable </li></ul><ul><li>Wireless media </li></ul>
  34. 34. Transmission Media <ul><li>Twisted pair cable </li></ul><ul><ul><li>UTP and STP </li></ul></ul><ul><ul><li>100 meter length maximum </li></ul></ul><ul><ul><li>Twisted pair or 8 wires in 4 pairs, RJ-45 connectors </li></ul></ul><ul><ul><li>Category 3 – Ethernet 10BASE-T, 10mbps nics and hubs (16mbps maximum) </li></ul></ul><ul><ul><li>Category 4 – Used for token ring, generally at 16mbps (20mbps maximum) </li></ul></ul><ul><ul><li>Category 5 – Ethernet 100BASE-T, 100mbps nics and hubs (155mbps maximum) </li></ul></ul>
  35. 35. Transmission Media (cont.) <ul><li>Coaxial cable </li></ul><ul><ul><li>No concentrator is needed </li></ul></ul><ul><ul><li>Requires a terminator at each end </li></ul></ul><ul><ul><li>Thicknet - 500 meters, .5” (10BASE5) </li></ul></ul><ul><ul><li>Thinnet - 185 meters, .25” (10BASE2) </li></ul></ul><ul><ul><li>RG-58 cable, BNC connectors </li></ul></ul><ul><ul><li>Up to 255 devices can be attached to a single segment </li></ul></ul>
  36. 36. Transmission Media (cont.) <ul><li>Fiber optic cable </li></ul><ul><ul><li>Two strands of optical fiber, one sends, one receives, with pulses of light </li></ul></ul><ul><ul><li>FDDI and ATM technologies </li></ul></ul><ul><ul><li>622 mbps (100-1,000mbps), 2,000 meters </li></ul></ul><ul><ul><li>Expensive and difficult to install </li></ul></ul><ul><ul><li>Very secure </li></ul></ul><ul><ul><li>No EMI </li></ul></ul><ul><ul><li>100BASE-FX </li></ul></ul><ul><li>Wireless media </li></ul>
  37. 37. Port Numbers <ul><li>Well-known port numbers </li></ul><ul><ul><li>25 – SMTP </li></ul></ul><ul><ul><li>20, 21 – FTP </li></ul></ul><ul><ul><li>110 – POP </li></ul></ul><ul><ul><li>53 – DNS </li></ul></ul><ul><ul><li>80 – HTTP </li></ul></ul><ul><li>Numbers can also be assigned for security purposes </li></ul>
  38. 38. Internet Addressing <ul><li>Internet addresses are divided into the following parts: </li></ul><ul><ul><li>Network </li></ul></ul><ul><ul><li>Host </li></ul></ul><ul><li>Four fields separated by periods are a common notation for specifying addresses: </li></ul><ul><ul><li>field1.field2.field3.field4 (222.41.1.25) </li></ul></ul>
  39. 39. 1 1 1 1 1 1 1 1 = 8 128 64 32 16 8 4 2 1 = 255 IP Address Fields <ul><li>Contain eight bits per field </li></ul><ul><li>Range from 0 to 255 decimal </li></ul><ul><li>field1.field2.field3.field4 </li></ul>1 = On 0 = Off
  40. 40. Internet Address Classes <ul><li>Class A – 1-126 0 </li></ul><ul><li>Class B – 128-191 10 </li></ul><ul><li>Class C – 192-223 110 </li></ul><ul><li>Class D – 224-239 1110 </li></ul><ul><li>Class E – 240-247 11110 </li></ul>
  41. 41. IP Addressing Rules <ul><li>Loopback addresses - 127.0.0.1 </li></ul><ul><li>Broadcast addresses - 255.255.255.255 </li></ul><ul><li>Network addresses - netid.255.255.255 </li></ul><ul><li>Special-case source addresses - 0.0.0.0 </li></ul>
  42. 42. Reserved (LAN) IP Addressing <ul><li>10.0.0.0 through 10.255.255.255 </li></ul><ul><li>172.16.0.0 through 172.31.255.255 </li></ul><ul><li>192.168.0.0 through 192.168.255.255 </li></ul>
  43. 43. Subnetworks <ul><li>Subnet masks – used to distinguish network and host portions of addresses </li></ul><ul><ul><li>efault subnet masks </li></ul></ul><ul><ul><ul><li>Class A 255.0.0.0 </li></ul></ul></ul><ul><ul><ul><li>Class B 255.255.0.0 </li></ul></ul></ul><ul><ul><ul><li>Class C 255.255.255.0 </li></ul></ul></ul><ul><li>IPv6 – 128 bit address instead of 32 bit </li></ul>
  44. 44. Diagnostic Tools for Internet Troubleshooting <ul><li>ping </li></ul><ul><li>tracert </li></ul><ul><li>netstat </li></ul><ul><li>ipconfig </li></ul><ul><li>winipcfg </li></ul><ul><li>arp </li></ul><ul><li>network analyzers </li></ul>
  45. 45. Internetworking Servers <ul><li>File and print </li></ul><ul><li>HTTP </li></ul><ul><li>Proxy </li></ul><ul><li>Caching </li></ul><ul><li>Mail </li></ul><ul><li>Mailing list </li></ul><ul><li>Media </li></ul><ul><li>DNS </li></ul><ul><li>FTP </li></ul><ul><li>News </li></ul><ul><li>Certificate </li></ul><ul><li>Directory </li></ul><ul><li>Catalog </li></ul><ul><li>Transaction </li></ul>
  46. 46. Fault Tolerance <ul><li>Two primary types of drive fault tolerance: </li></ul><ul><ul><li>RAID </li></ul></ul><ul><ul><ul><li>Mirroring </li></ul></ul></ul><ul><ul><ul><li>Duplexing </li></ul></ul></ul><ul><ul><ul><li>Striping with Parity </li></ul></ul></ul><ul><ul><ul><li>Clustering </li></ul></ul></ul><ul><ul><li>Backups </li></ul></ul>
  47. 47. Other Types of Data Protection <ul><li>Uninterruptible Power Supply </li></ul><ul><li>Folder replication </li></ul><ul><li>Removable media </li></ul>
  48. 48. Classifying Hackers <ul><li>Casual attacker - 99.5% </li></ul><ul><li>Determined attacker - usually on ideological grounds, or a disgruntled employee </li></ul>
  49. 49. Types of Attacks <ul><li>Spoofing (masquerade) attacks - alters ip so it looks like it came from a trusted network </li></ul><ul><li>Man-in-the-middle (hijacking) attacks - capture packets sent between two hosts </li></ul><ul><li>Denial-of-service attacks - uses up all the system resources and crashes the system, usually with ping requests </li></ul><ul><li>Insider attacks – eavesdropping and snooping for information </li></ul><ul><li>Brute-force attacks - repeated logon attempts with a dictionary </li></ul>
  50. 50. Types of Attacks <ul><li>Trapdoor attacks - diagnostics programs can view and possibly execute system applications </li></ul><ul><li>Replay attacks - altered header info on packets to gain entrance to system </li></ul><ul><li>Trojan horse attacks – files placed on system by user that believes the program is a valid program, user executes </li></ul><ul><li>Social-engineering attacks – users tricked into giving out their personal information (this info is then used to crack passwords) </li></ul><ul><li>Front Door - stolen user name and password </li></ul>
  51. 51. Viruses <ul><li>Virus types: </li></ul><ul><ul><li>Macros - Word and Excel contain macro script writing programs that used to execute commands </li></ul></ul><ul><ul><li>Executables - execute batch file </li></ul></ul><ul><ul><li>Boot sector – very hard to remove, virus attaches to the boot sector program so it runs every time the computer is started </li></ul></ul><ul><ul><li>Bios - attacks flash bios programs by overwriting the system bios and makes the system unbootable </li></ul></ul><ul><ul><li>Polymorphic (stealth) virus - changes form each time it invades a system </li></ul></ul>
  52. 52. The Hacker Process <ul><li>Stage 1—Discovery - gather info on services, ports, physical topology, and placement of services </li></ul><ul><li>Stage 2—Penetration - go for the weakest link </li></ul><ul><li>Stage 3—Control - destroy evidence of activity, obtaining root and admin access, creating new accounts, moving to other systems/servers </li></ul>
  53. 53. Defeating Attacks <ul><li>Authentication - user login and password </li></ul><ul><li>Access control - file or directory permissions granted to users </li></ul><ul><li>Data confidentiality - encryption </li></ul><ul><li>Data integrity - provides protection against altered files </li></ul><ul><li>Nonrepudiation - can’t deny transaction occurred </li></ul>
  54. 54. Security Standards <ul><li>NCSC security levels: </li></ul><ul><ul><li>D – minimal (MsDos) </li></ul></ul><ul><ul><li>C1 – rudimentary access control </li></ul></ul><ul><ul><li>C2 – differentiate users </li></ul></ul><ul><ul><li>B1 – varied security levels </li></ul></ul><ul><ul><li>B2 – hardware protection </li></ul></ul><ul><ul><li>B3 – security domains </li></ul></ul><ul><ul><li>A1 – verified design, rigorous mathematical proof </li></ul></ul>
  55. 55. Key Security Organizations <ul><li>Computer Emergency Response Team (CERT) </li></ul><ul><li>Computer Security Resource and Response Center (CSRC) at the National Institute of Standards and Technology (NIST) </li></ul><ul><li>Computer Incident Advisory Capability (CIAC) at the Department of Energy (DOE) </li></ul>
  56. 56. Encryption <ul><li>Encryption always uses algorithms, text strings that scramble and de-scramble information </li></ul><ul><li>Symmetric-key encryption </li></ul><ul><li>Asymmetric-key encryption </li></ul><ul><li>One-way encryption (hash encryption) </li></ul>

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