Video Content Lesson 7 Flashcards
OSI Reference Model
Protocols Standards Organizations OSI Overview Logical Data Flow Physical Data Flow
Protocols
Computers need formal rules to communicate
Protocol - Formal set of rules that govern communication
Proprietary protocols only allow communication with similar machines (originally)
Standards Organizations
ISO - International Organization for Standardization (basic communication protocols)
IEEE - Institute of Electrical and Electronics Engineers (low level physical standards)
NSA - National Security Agency (Different levels for security being maintained)
NIST - National Institute for Standards and Technology
ANSI - American National Standards Institute (character sets)
CCITT - International Telegram and Telephone Consultative Committee
OSI Overview
OSI Open Systems Interconnection reference model Developed by ISO (also known as ISO/OSI) Open network architectural guide Specifies how dissimilar systems can communicate 7 distinct protocol layers Application Presentation Session Transport Network Data-link Physical This standard allows developers to write software that works on many dissimilar machines
Logical Data Flow
Flows from one layer on source machine to same layer on target machine (don’t have to worry about what happens in stack below us)
Physical Data Flow
Physically have to go down through every layer below, across medium, and back up each layer to the original layer)
Each Layer adds header and trailer to message (chunked into packets)
OSI Layers
Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data-link Layer Physical Layer TCP-IP Model
Application Layer
Provides services for high-level program (it is NOT the application)
HTTP, FTP, SMTP, EDI, POP3, IMAP, SNMP
Presentation Layer
Provides data representation between systems
GIF, JPEG, MPEG
Responsible for encryption and compression (decryption and decompression)
Session Layer
Manages sessions and synchronizes data flow
NFS, SSL, RPC, Xwindows, AppleTalk
Transport Layer
Responsible for end-to-end transmission integrity
Provides a logical connection between machines
Ensures message delivery
TCP, UDP, SPX
Network Layer
Determines the best way to get data to the destination
Providing Routing Capabilitites
IP, ICMP, IPX, RIP
Data-link Layer
Handles data packet transfer
Handles physical addressing, error handling, and flow control
SLIP, PPP, ARP, RARP, FDDI, ISDN
Physical Layer
Transmits the bit stream onto the physical media
Can use transmission mechanism that is wireless
TCP-IP Model
Developed by the DOD Simplified medel containing 4 layers Application Layer Transport Layer Network Layer Link Layer
Application Layer
All issues specific to a session or application
OSI layers 5, 6, and 7
Transport Layer
Supports moving data between applications
OSI layer 4
Corresponds (supported by) to TCP and UDP protocols
Network Layer
Supports moving data between netowrks
OSI layer 3
Corresponds to IP protocol
Link Layer
Provides physical communication and routing
Encapsulates 2 layers (physical layer 1 and data-link layer 2)
Media-LAN Topologies
Twisted Pair Coaxial Fiber Optics Wireless Technologies Star Topology Bus Topology Ring Topology Tree Topology Mesh Topology
Twisted Pair
Regular copper wire with each pair twisted around each other
UTP -Unshielded Twisted Pair
STP - Shielded Twisted Pair
Least expensive media
Coaxial
Same media used for cable TV (copper cable core, insulator, wire mesh transmits data)
more expensive and harder to install
Fiber Optics
Any transmission of light waves along glass or plastic wires
More expensive and costly to terminate
Not effected by EMI Electromagnetic interference
Wireless Technologies
DSSS Direct-Sequence Spread Spectrum (transmission spread over large frequency band, reduces interference percentage)
FHSS Frequency-Hopping Spread Spectrum (Uses rapidly changing frequencies, reduces overall interferences)
OFDM Orthogonal Frequency Division Multiplexing (signal is subdivided into sub-bands, sub-bands can be transmitted together)
FDMA Frequency Division Multiple Access (analog-only sub-bands)
TDMA Time Division Multiple Access (can carry multiple conversations on each sub-band, each conversation gets a time slice)
CDMA Code Division Multiple Access (Spread spectrum like DSS, CDMA 2000 (tranmission rates up to 153.6 Mbps), Wideband CDMA (wider band that increases carrier input)
GSM Global Service for Mobile Communication (Most popular cellular technology, uses time-division multiplexing (can support up to 8 callers per simplex channel)
Various Topologies
Star (multiple machines connected through one)
Bus (multiple machines connected through bus)
Ring (multiple machines connected to its neighbor)
Tree (variation of Bus Topology)
Mesh (most complex of topologies)
Star Topology
All nodes are connected to a central device
All Messages must travel through the center
advantage simple, disadvantage single point of failure
Bus Topology
All nodes are connected to a shared media, often called the backbone or bus
the messages travel the length of the bus
end of bus must be terminated
Ring Topology
each computer is connected to its neighbor on each side
messages travel from node to node until they reach their destination
advantage no sigle point of failure because NIC passes message automatically if disconnected
Tree Topology
Variation of Bus Topology (nodes may be connected to more than one bus)
multiple bus connections create the branches of the tree
single point of failure only exists on the node that crosses multiple branches
Mesh Topology
every node is connected to every other node
very complex, but highly fault tolerant
partial mesh (not connected to all machines but to many so there are multiple paths)
LAN-WAN-Remote Access
Ethernet Other Access Methods Signaling Types Network Types Dial-up ISDN DSL Wireless-Cable
Ethernet
Most common LAN access method
IEEE 802.3 standard
uses CSMA/CD (Carrier Sense Media Access with Collision Detection)
Listen first and then talk (Carrier signal is sampled off physical media, hardware listens for carrier signal (if carrier signal is heard this tells it that noone else is talking, headware sends message off wire) (listens to what is being echoed back to him, if same message then it was correctly sent otherwise retransmits)
Cable standards (ThinNet-10Base2, coaxial up to 185 meters; ThickNet-10Base5, coaxial up to 500 meters; most common used is UTP-10BaseT, 100BaseT, 1000BaseT used with central hub (Star Typology))
Other Access Methods
ARCnet (one of earliest LAN technologies, token passed methods, have to hold token to talk, uses bus or ring typology
Ring typology uses MAU Multistation Access Unit which has all end nodes connected to it
FDDI Fiber Distributed Data Interface (token passing method, 100 Mbps using dual fiber-optic rings, rings operate in opposite directions, if one ring breaks, other ring is used to maintain a complete network)
Signaling Types
Baseband transmission (digital signal, entire media filled with one signal) Broadband (analog signal, Cable TV, multiple communication channels used simultaneously, tranmitted in channels on a carrier, digital data must be modulated first)
Network Types
LAN Local Area Network (Group of networked computers and devices in relatively close proximity to one another)
WAN Wide area network (Network of computers and devices that spans a large geographic area)
Remote access/telecommuting (method of connecting to a WAN or LAN through dial-up or high-speed access lines
Dial-up
POTS Plain Old Telephone Service (uses MODEM 56 Kbps, speed based on proximity to central office, condition of line, noise on the line, multiplexing, bandwidth artificially limited)
ISDN
Integrated Services Digital Network (ISDN)
Basic Rate Interface (BRI) (Two 64-KB channels (digital, audio, video, communication) and one 16-KB channel (digital transfer)
Primary Rate Interface (PRI) (23 64-KB channels and one 16-KB channel)
Expensive
DSL
Digital Subscriber Line (higher speed connection than dial-up using existing twisted pair)
inexpensive option
ADSL (Asynchronous digital subscriber line) used at home because higher speed for downloads and slower speeds for uploads
SDSL (Synchronous digital subscriber Line) same upload and download capability
VDSL (Very-high-speed digital subscriber line)
DSL Lite (doesn’t require splitter used by ADSL, SDSL, and VDSL)
Wireless-Cable
Wireless (networking without wires)
Several emerging standards (802.11a, 802.11b, 802.11g)
Cable Modems (great alternative to DSL) (can be substantially faster than DSL if number of concurrent users is not excessive)
Remote Access Security
VPN PPTP IPSec Connection Security User Authentication Node Authentication
VPN
Virtual Private Network
Tunnel (like envelope–encapsulation technique)
often associated with secure transmissions
can connect two systems or two networks
offers an inexpensive secure communication using public networks
PPTP
Point-to-Point Tunneling Protocol
Built to provide encrypted PPP tunnel
After negotiation all PPP traffic is encrypted
L2F Layer 2 Forwarding (developed by Cisco to provide mutual authentication tunneling)
L2TP Layer 2 Tunneling Protocol (extended PPTP and L2F, supports TACACS+ and RADIUS)
IPSec
Operates as a standalone VPN protocol OR along with L2TP can provide encryption for L2TP Transport mode (payload is encrypted but header is NOT) for connecting two systems Tunnel mode (both payload and header are encrypted) for connecting two networks
Connection Security
Remote access without VPN
SSH - Secure Shell (more secure than Telnet) provides a sure method to access a remote machine
SSL/TLS - Secure Sockets Layer (secures communication between client and web server) (ONLY encrypts communication between client and web server not behind them)
User Authentication
Centralized remore user authentication
1-RADIUS Remote Authentication Dial-in User Service
2-TACACS - Terminal Access Controller Access Control System
TACACS+ (adds two-factor authentication)
Node Authentication
Password Authentication Protocol (PAP) (this is standard authentication protocol for PPP; no encryption; user IDs and passwords passed in the clear)
Challenge Handshake Authentication Protocol (CHAP) (similar to PAP; encrypts user IDs and password; operates over PPP)
