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115 Cards in this Set
- Front
- Back
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YR-Phone Invented
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1876
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YR-First trans-continental and transatlantic phone connections
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1915
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YR-Rotary Phones
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1919
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YR-Microwave trunk lines
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1948
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YR-Telstar (telecommunications via satellite), Fax services, Digital transmission
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1962
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YR-Picurefone
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1969
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YR-Packet-switched data communications
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1976
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YR-Cellular Phone
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1984
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YR-Batch Processing
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1950s
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YR-Data communication over phone lines becomes common
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1960s
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YR-Online realtime transaction oriented systems (replace batch processing, DBMSs become common
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1970s
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YR-PC revolution
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1980s
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YR-PC Lans become common
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1990s
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YR-Networks everywhere
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2000s
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YR-ARPANET began
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1969
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YR-ARPANET splits into Milnet and internet
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1983
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YR-NSFNet created as US Internet backbone
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1986
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YR-Commercial access to the Internet begins
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1990
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YR-Gove funding of the backbone ends
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1994
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Over 240 million servers and 400 million users
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2001
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LAN
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Local Area Network, for room, building - to link a group of PCs that share a circuit
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BN
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Backbone Network, less than a few km, links LANs at various locations
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MAN
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Metropolitan Area Network - < few 10 kms; connects LANs and BNs
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WAN
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Wide Area Network - >few 10 kms; same as MAN but on a wider scale
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Network Models
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Open Systems Interconnections (OSI)Model & Internet Model
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OSI Model
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Created by ISO (1984) - 7 layers
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OSI Model - 7 layers
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1. Physical Layer
2. Data Link Layer 3. Network Layer 4. Transport Layer 5. Session Layer 6. Presentation Layer 7. Application Layer |
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Internet Model
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Created by Darpa (1970s) - based on TCP/IP - 5 layers
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Internet Model - 5 layers
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1. Physical Layer
2. Data Link Layer 3. Network Layer 4. Transport Layer 5. Application Layer |
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Function-Application Layer
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Set of utilities used by application programs
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Function-Presentation Layer
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Formats data for presentation to the user; provides data interfaces, data compression and translation between different data formats
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Function-Session Layer
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Initiates, maintains and terminates each logical session between sender and receiver
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Function-Transport Layer
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Deals with end-to-end issues such as segmenting the message for network transport and maintaining the logical connections between sender and receiver
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Function-Network Layer
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Responsible for making rouing decisions
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Function-Data Link Layer
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Deals with message delineation, error control and network medium access control
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Function-Physical Layer
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Defines how individual bits are formatted to be transmitted through the network
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ISO
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International Organization for Standardization
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ITU
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International Telecommunications Union
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ANSI
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Americal National Standards Institute
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IEEE
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Institute for Electrical and Electronic Engineers
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IETF
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International Engineering Task Force
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Application Architectures
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Host-based (server performs almost all functionqs); Client-based (Client performs most functions); Client-Server (Functions shared between client and server
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Problems with Host-based
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Processing bottleneck; Upgrades Expensive and Jumpy
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Problems with Client-based
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Data must travel back and forth between server and client, makes for poor performance
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Advantages/Disadvantages of Client-Server
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(ADV)More efficient because of distributed processing, different hardware vendors can be used together; (DIS) Difficulty getting software to work together, may require middleware
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Multi-tier Architectures
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2-tier; 3-tier; N-tier
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Multi-tier advantages/dis-advantages
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(ADV) Better load balancing, more scalable; (DIS) More processing/exchanges, difficult to program and test due to complexity.
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Criteria for choosing Architecture
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Infrastructure cost; Development Cost; Scalability
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HTTP
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Hyper-Text Transfer Protocol
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SMTP
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Simple Mail Transfer Protocol
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POP
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Post Office Protocol
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IMAP
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Internet Mail Access Protocol
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MIME
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Multipurpose Internet Mail Extension (for multimedia files)
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FTP
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File Transfer Protocol
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Telnet
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Allows one computer to log into other computers
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IM
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Instant Messaging
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Videoconferencing
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Real time trasmission of video and audio signals
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HTML
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Hyper-Text Markup Language (used to format webpages)
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Types of Data Transmitted
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Analog or Digital Data
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Analog Transmissions
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Produced by tleephones, sound waves that vary continuously over time
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Digital Transmissions
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Can only take on 0s or 1s; Made of square waves with a clear beginning and ending
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Communication Media
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Guided (UTP, coaxial, fiber optic) OR Wireless (flows thru air - radio, infrared)
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MAC
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Media Access Control - the need to control when computers transmit
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Controlled Acess
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X-ON/X-OFF; Polling
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Contention
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Check then sends whenever they have data to send
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Examples of Contention
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CDMA/CD - Carrier Sense Multiple Access with Collision Detection; CDMA/CA - Carrier Sense Multiple Access with Collision Avoidance
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Sources of Errors
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Line outages, white noise, impulse noise, corss-talk, echo, attenuation, intermodulation noise, jitter, harmonic distortion
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Types of error detection
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Parity Checking; Longtitudinal Redundancy Checking; Polynomial Checking
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Transmission Modes
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Parallel(used for shorter distances) and Serial (used over longer distances, bits stay in the order they were sent)
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Different sound modulations
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Frequency(#), Amplitude(height), and Phase (distance from crest to trough) modulation.
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Bit
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a unit of information
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Baud
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A unit of signaling speed
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Baud rate
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# of symbols tranmitted per second
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Modem
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Translates from Digital to Analog
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Codec
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Translates from Analog to Digital
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PAM
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Pulse Amplitude Modulation (Measures signal; Encodes signal as a binary data sample; takes samples of the data)
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PCM
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Pulse Code Modulation (Converts analog signals to digital data using PCM, similar to PAM)
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DSL
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Digital Line Subscriber
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Parity Checking
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A single bit added to each character (even parity vs odd parity)
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LRC
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Logitudinal Redundancy Checking - Adds an additional character (instead of a bit)-98% error detection
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Polynomial Checking
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Adds 1 or more characters to the end of message (based on a mathematical algorithm); Checksum & CRC (Cyclical Redundancy Check)l detects 100% of errors
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Error Correction Techniques
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ARQ (Automatic Repeat Request); Stop and Wait ARQ (waits for acknowledgements); Continuous ARQ (sliding window)
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Datalink Protocols
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Asynchronous vs Synchronous
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Asynchronous Transmission
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Start-Stop Transmission, uses idles to separate characters; uses stop-wait ARQ
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Synchronous Transmission
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Data sent in large blocks, including addressing information
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SDLC
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Synchronous Data Link Control
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HDLC
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High-Level Data Link Control
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TCP/IP
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Tranmission Control Protocol / Internet Protocol
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IPv4 vs IPv6
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IPv4 = 32 bit addresses; IPv6 = 128 but addressing (because we were running out of addresses)
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X.25
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Protocol to send packets; Widely used in Europe
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Connection Oriented Messaging
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Sets up a TCP connection (cirtual circuit) between the sender and receiver.
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Connectionless Messaging
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Each packet is treated separately and makes its own way through the network.
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QoS
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Quality of Service Routing; Different connections are assigned different priorities (#1=Videoconferencing; #10=emails)
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IPX/SPX
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Internet Packet Exchange/Sequenced Packet Exchange; routing protocol developed by Xerox, used to be used by Novell, now not so much
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Internet Addresses
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Managed by ICANN (Internet Corporation for Assigned Names and Numbers)
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Subnet
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Group of computers on the same LAN with IP numbers with the same prefix; additional bits added to length.
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DHCP
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Dynamic Host Control Protocol; develop in 1993
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Address Resolution
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Server Name Resolution (DSN-Domain Name Service); Data Link Layer Resolution
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Routing
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Determining the route or path through the netowrk
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Types of Routing
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Centralized routing; Static routing; Dynamic Routing
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Centralized Routing
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All routing decisions are made by one central computer or router
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Static Routing
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Routing table developed by network manager determines routing from one centralized computer
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Dynamic Routing
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Routing decisions are made in a decentralized mananer by individual computers
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Routing Protcols (Def)
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A protocol that is used to exhcnage information among computers to enable them to build and maintain their routing tables.
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Types of Routing Protocols
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RIP (Routing Information Protocol); OSPF (Open Shortest Path First); BGP (Border Gateway Protocol)
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Why use a LAN ?
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Information and Resource sharing
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Types of Dedicated Servers
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Web servers, e-mail servers, database servers, file servers, print servers, remote access servers
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Peer-to-Peer Network
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Requires no dedicated server; for small networks, lower cast, slower than dedicated server networks, difficulat to manage
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NIC
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Network Interface Cards (has datalink layer address-MAC Address)
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Hubs
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Acts as junction boxes, linking cables from several computers on a network
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Network Profiles
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Kept by servers; Specify resources available for use by other computers (includes data files, printers, etc.)
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User Profiles
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One profile for each user, used for security reasons; describes what each user on a LAN has access to; Includes access codes assigned to devices and users
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Ethernet (IEEE 802.3)
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Used by almost all LANs today, standardized
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Types of Ethernets
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Shared Thernet (uses Hubs) & Switched Ehternet (Uses switches)
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Topology
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Basic geometric layout of the network
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