Download - Networking fundamental
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Networking Fundamentals Review
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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
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Networking Categories
Two basic categories: Server-based
Peer-to-peer
Enterprise networks Combine peer-to-peer and server-based
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Network Topologies
Bus Star Ring Hybrid networks Mesh
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Layers of the OSI/RM
Application All
Presentation People
Session Seem
Transport To
Network Need
Data link Data
Physical Processing
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Application Layer
User interface Supports file transfer Network management Accepts requests and passes them down to the
presentation layer
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Presentation Layer
Converts text from what is viewable to the user to what is understandable to the computer
Passes data to session layer
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Session Layer
Establishes, manages, and terminates connections between cooperating applications
Adds traffic flow information
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Transport Layer
Reliable, transparent transport between end points Supports end to end error recovery and flow
control Connection-oriented protocols reside at this layer
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Network Layer
Responsible for forwarding and routing datagrams Connectionless protocols reside at this layer
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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
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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
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Application-Layer Protocols
SMTP BOOTP FTP HTTP AFP
SNMP SMB X.500 NCP NFS
Network Management, File Transfers, User Interface
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Transport-Layer Protocols
TCP SPX NWLink ATP NetBEUI
Reliable, Connection-Oriented, Error Recovery, and Flow Control
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Network-Layer Protocols
IP IPX NWLink NetBEUI X.25 Ethernet
Connectionless (best effort delivery), Forwards and Routes Datagrams
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Major Networking Protocols
Connection-oriented (stateful)
Connectionless (stateless)
Routable – Most protocols are routable
Nonroutable
NetBios
NetBeui
LAT
DLC
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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
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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
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NetBEUI
Non-routable Fast Easiest to configure and maintain Low overhead
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AppleTalk
Used only on Apple Macintosh networks Divides groups of computers into zones
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Common Network Components
NICs Repeaters Hubs Bridges Routers Brouters
Switches Gateways CSU/DSU Modems Patch panels Internet-in-a-box
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NIC card
Network
Node
Network InterfaceCards (NICs)
NIC is the interface between the computer and the network
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MAC Address Components
00 – 80 – 5F – EA – C6 – 10
Vendor Code Interface Serial Number
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Node Node
Repeater
Repeaters
•Amplifies electronic signal
•Strengthens signal by re-transmitting it when segment approaches its maximum length
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Node Node Node
Hub
Hubs
•Concentration point of network
•Used with a star configuration
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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
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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
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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
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Gateways
Network runningTCP/IP
Gateway(Protocol Converter)
Network runningIPX/SPX
•Can operate at any level of the OSI model
•Protocol converter – Appletalk to TCP/IP
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CSU/DSU
CS U/ DS URouter
TelecomNetwork
Network
Channel Service Unit/Data Service Unit
•Operates at the physical layer
•Terminates physical connections
•Used for bringing T1 lines into a building
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Modems
TelecomNetwork
Network
Modem Modem
Network
•Uses POTS phone line to connect to internet
•Can dial RAS connection directly to another
computer
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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
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Transmission Media
Twisted pair cable Coaxial cable Fiber optic cable Wireless media
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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)
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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
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Transmission Media (cont.)
Fiber optic cable Two strands of optical fiber, one sends, one receives, with pulses of light FDDI and ATM technologies622 mbps (100-1,000mbps), 2,000 meters Expensive and difficult to install Very secure No EMI 100BASE-FX
Wireless media
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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
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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)
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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
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Internet Address Classes
Class A – 1-126 0
Class B – 128-191 10
Class C – 192-223 110
Class D – 224-239 1110
Class E – 240-247 11110
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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
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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
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Subnetworks
Subnet masks – used to distinguish network and host portions of addresses efault subnet masks
Class A 255.0.0.0
Class B 255.255.0.0
Class C 255.255.255.0
IPv6 – 128 bit address instead of 32 bit
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Diagnostic Tools forInternet Troubleshooting
ping tracert netstat ipconfig winipcfg arp network analyzers
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Internetworking Servers
File and print HTTP Proxy Caching Mail Mailing list Media
DNS FTP News Certificate Directory Catalog Transaction
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Fault Tolerance
Two primary types of drive fault tolerance:RAID
Mirroring
Duplexing
Striping with Parity
Clustering
Backups
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Other Types ofData Protection
Uninterruptible Power Supply Folder replication Removable media
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Classifying Hackers
Casual attacker - 99.5% Determined attacker - usually on ideological
grounds, or a disgruntled employee
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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
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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
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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
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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
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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
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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
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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)
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Encryption
Encryption always uses algorithms, text strings that scramble and de-scramble information
Symmetric-key encryption Asymmetric-key encryption One-way encryption (hash encryption)