1. Networking Fundamentals Review

2. Networking Evolution Network: – Two or more connected computers that share data Paradigms: Client/server model Mainframe model Peer to peer Web-based networking Sneakernet: The transfer of files from one computer to another using a floppy disk or other removable medium

3. Networking Categories Two basic categories: Server-based Peer-to-peer Enterprise networks Combine peer-to-peer and server-based

4. Network Topologies Bus Star Ring Hybrid networks Mesh

5. Layers of the OSI/RM ApplicationA ll PresentationP eople SessionS eem Transport T o NetworkN eed Data linkD ata PhysicalP rocessing

6. Application Layer User interface Supports file transfer Network management Accepts requests and passes them down to the presentation layer

7. Presentation Layer Converts text from what is viewable to the user to what is understandable to the computer Passes data to session layer

8. Session Layer Establishes, manages, and terminates connections between cooperating applications Adds traffic flow information

9. Transport Layer Reliable, transparent transport between end points Supports end to end error recovery and flow control Connection-oriented protocols reside at this layer

10. Network Layer Responsible for forwarding and routing datagrams Connectionless protocols reside at this layer

11. Data Link Layer Provides reliable data transfer across the physical link Frames are transmitted with the necessary synchronization error control and flow control Prepares information so it can be sent to the physical wire

12. Physical Layer Concerned with the transmission of unstructured bit stream over a physical link Responsible for the mechanical, electrical, and procedural characteristics to establish, maintain, and deactivate the flow of bits

13. Application-Layer Protocols SMTP BOOTP FTP HTTP AFP SNMP SMB X.500 NCP NFS Network Management, File Transfers, User Interface

14. Transport-Layer Protocols TCP SPX NWLink ATP NetBEUI Reliable, Connection-Oriented, Error Recovery, and Flow Control

15. Network-Layer Protocols IP IPX NWLink NetBEUI X.25 Ethernet Connectionless (best effort delivery), Forwards and Routes Datagrams

16. Major Networking Protocols Connection-oriented (stateful) Connectionless (stateless) Routable – Most protocols are routable Nonroutable NetBios NetBeui LAT DLC

17. TCP/IP Default protocol for the following network operating systems: Windows 2000 Windows NT 4.0 UNIX NetWare 5 … plus the Internet! Computers are each identified with an IP address and subnet mask

18. IPX/SPX IPX is responsible for forwarding packets to sockets SPX ensures reliable data delivery and manages sessions Must identify a frame type during setup

19. NetBEUI Non-routable Fast Easiest to configure and maintain Low overhead

20. AppleTalk Used only on Apple Macintosh networks Divides groups of computers into zones

21. Common Network Components NICs Repeaters Hubs Bridges Routers Brouters Switches Gateways CSU/DSU Modems Patch panels Internet-in-a-box

22. Network Interface Cards (NICs) NIC is the interface between the computer and the network

23. MAC Address Components

24. Repeaters Amplifies electronic signal Strengthens signal by re-transmitting it when segment approaches its maximum length

25. Hubs Concentration point of network Used with a star configuration

26. Bridges Operates on the data link layer Reduce network traffic by dividing the network into two segments Recognize mac addresses rather than IP addresses Can connect two different topologies

27. Routers Operates on the network layer Forwards or route data according to routing tables Determine IP address needed and then most efficient route Conserves network bandwidth by reducing broadcasting

28. Switches Can operate at the data link and network layers Directs the flow of information from one node to another. Faster because it give each sender/receiver the entire bandwidth of a line instead of sharing

29. Gateways Can operate at any level of the OSI model Protocol converter – Appletalk to TCP/IP

30. CSU/DSU Channel Service Unit/Data Service Unit Operates at the physical layer Terminates physical connections Used for bringing T1 lines into a building

31. Modems Uses POTS phone line to connect to internet Can dial RAS connection directly to another computer

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. Transmission Media Twisted pair cable Coaxial cable Fiber optic cable Wireless media

34. Transmission Media Twisted pair cable UTP and STP 100 meter length maximum Twisted pair or 8 wires in 4 pairs, RJ-45 connectors Category 3 – Ethernet 10BASE-T, 10mbps nics and hubs (16mbps maximum) Category 4 – Used for token ring, generally at 16mbps (20mbps maximum) Category 5 – Ethernet 100BASE-T, 100mbps nics and hubs (155mbps maximum)

35. Transmission Media (cont.) Coaxial cable No concentrator is needed Requires a terminator at each end Thicknet - 500 meters,.5” (10BASE5) Thinnet - 185 meters,.25” (10BASE2) RG-58 cable, BNC connectors Up to 255 devices can be attached to a single segment

36. Transmission Media (cont.) Fiber optic cable Two strands of optical fiber, one sends, one receives, with pulses of light FDDI and ATM technologies 622 mbps (100-1,000mbps), 2,000 meters Expensive and difficult to install Very secure No EMI 100BASE-FX Wireless media

37. Port Numbers Well-known port numbers 25 – SMTP 20, 21 – FTP 110 – POP 53 – DNS 80 – HTTP Numbers can also be assigned for security purposes

38. Internet Addressing Internet addresses are divided into the following parts: Network Host Four fields separated by periods are a common notation for specifying addresses: – field1.field2.field3.field4 (222.41.1.25)

39. 1 1 1 1 1 1 1 1 = 8 128 64 32 16 8 4 2 1 = 255 1 = On 0 = Off IP Address Fields Contain eight bits per field Range from 0 to 255 decimal field1.field2.field3.field4

40. Internet Address Classes Class A – 1-1260 Class B – 128-19110 Class C – 192-223110 Class D – 224-2391110 Class E – 240-24711110

41. IP Addressing Rules Loopback addresses - 127.0.0.1 Broadcast addresses - 255.255.255.255 Network addresses - netid.255.255.255 Special-case source addresses - 0.0.0.0

42. Reserved (LAN) IP Addressing 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

43. Subnetworks Subnet masks – used to distinguish network and host portions of addresses efault subnet masks Class A255.0.0.0 Class B255.255.0.0 Class C255.255.255.0 IPv6 – 128 bit address instead of 32 bit

44. Diagnostic Tools for Internet Troubleshooting ping tracert netstat ipconfig winipcfg arp network analyzers

45. Internetworking Servers File and print HTTP Proxy Caching Mail Mailing list Media DNS FTP News Certificate Directory Catalog Transaction

46. Fault Tolerance Two primary types of drive fault tolerance: RAID Mirroring Duplexing Striping with Parity Clustering Backups

47. Other Types of Data Protection Uninterruptible Power Supply Folder replication Removable media

48. Classifying Hackers Casual attacker - 99.5% Determined attacker - usually on ideological grounds, or a disgruntled employee

49. Types of Attacks Spoofing (masquerade) attacks - alters ip so it looks like it came from a trusted network Man-in-the-middle (hijacking) attacks - capture packets sent between two hosts Denial-of-service attacks - uses up all the system resources and crashes the system, usually with ping requests Insider attacks – eavesdropping and snooping for information Brute-force attacks - repeated logon attempts with a dictionary

50. Types of Attacks Trapdoor attacks - diagnostics programs can view and possibly execute system applications Replay attacks - altered header info on packets to gain entrance to system Trojan horse attacks – files placed on system by user that believes the program is a valid program, user executes Social-engineering attacks – users tricked into giving out their personal information (this info is then used to crack passwords) Front Door - stolen user name and password

51. Viruses Virus types: Macros - Word and Excel contain macro script writing programs that used to execute commands Executables - execute batch file Boot sector – very hard to remove, virus attaches to the boot sector program so it runs every time the computer is started Bios - attacks flash bios programs by overwriting the system bios and makes the system unbootable Polymorphic (stealth) virus - changes form each time it invades a system

52. The Hacker Process Stage 1—Discovery - gather info on services, ports, physical topology, and placement of services Stage 2—Penetration - go for the weakest link Stage 3—Control - destroy evidence of activity, obtaining root and admin access, creating new accounts, moving to other systems/servers

53. Defeating Attacks Authentication - user login and password Access control - file or directory permissions granted to users Data confidentiality - encryption Data integrity - provides protection against altered files Nonrepudiation - can’t deny transaction occurred

54. Security Standards NCSC security levels: D – minimal (MsDos) C1 – rudimentary access control C2 – differentiate users B1 – varied security levels B2 – hardware protection B3 – security domains A1 – verified design, rigorous mathematical proof

55. Key Security Organizations Computer Emergency Response Team (CERT) Computer Security Resource and Response Center (CSRC) at the National Institute of Standards and Technology (NIST) Computer Incident Advisory Capability (CIAC) at the Department of Energy (DOE)

56. Encryption Encryption always uses algorithms, text strings that scramble and de-scramble information Symmetric-key encryption Asymmetric-key encryption One-way encryption (hash encryption)