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Chapter 6

Chapter 6: Networks & Collaboration

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Department
Computer Science
Course
Computer Science 1032A/B
Professor
Shauna Burke
Semester
Spring

Description
Chapter 6: Networks & Collaboration 1 Networks & Collaboration: • collaboration: when 2 or more people work together to achieve a common goal, result, or product 1. communication skills & culture: critical feedback to improve performance 2. communication systems: email, virtual private networks, instant messaging, etc. 3. content management: databases make sure conflicts are handled correctly; different rights & privileges (i.e. permission to create, edit & delete content, read-only status, etc.) 4. workflow: process/procedure by which content is created, edited, used & disposed of; deliver good/service internally to other employees; particular ordering of tasks Network Externalities: • network externality: larger the number of people using a network, the more valuable the network becomes • critical mass: point at which value of being part of network is larger than cost of being on it • natural monopoly: support all users; switching is hard • limits: network growth - > congestion- rate of growth diminishes, flattens or becomes negative Computer Network: • network: collection of computers that transmit and/or receive electronic signals through transmission media - > physical (copper cable, optic fibre cable) & wireless (cellular, satellite systems) • local area network (LAN): connects computers within small, single geographical location; 2- several hundred; single location • wide area network (WAN): connects computers at different geographical locations; contract w/ communications vendor, licensed by government & already has lines/authority to run lines • internet: network of networks; connect LANs, WANs & internets - the Internet: (capital ‘I’) email, access website - internets: private network of networks • protocol: set of rules 2 communicating devices follow Components of LAN: Chapter 6: Networks & Collaboration 2 • kilometer or so of each other & located on property owned/controlled by company • switch: special-purpose computer that receives & transmits messages • network interface card (NIC): connects circuitry to network cable • onboard NIC: newer machines; NIC built into computer • MAC (media access control) address: unique identifier • unshielded twisted pair (UTP) cable: contains 4 parts of twisted wire - RJ-45 connector: connect UTP cable into NIC devices • twisting wires: reduces cross-wire signal interference - > when wires run parallel over long distances • switches on each floor: connected by central switch in communications room • optical fibre cable: replace UTP- if carry a lot of traffic/far apart - light rays - core surrounded by cladding (contain light signals); cladding- wrapped w/ outer layer=protect IEEE 802.3, or Ethernet, Protocol: • Institute for Electrical & Electronic Engineers: sponsors committees that create/publish protocols & other standards- LAN - > IEEE 802 Committee • IEEE 802.3 protocol (Ethernet): hardware (i.e. which wires carry which signals, how messages are to be packaged, processed & transmission) • 10/100/1000 Ethernet: onboard NIC - transmission at rate of 10, 100, 1000 Mbps (megabits per second) - 100 Mbps=100 000 000 bits/second - speeds=bits; memory=bytes Wireless LANs: laptop, tablet, smartphone- equipped w/ wireless NIC (WNIC) • • move around w/o needing to plug into cable • 802.11 or Wi-Fi • access points (APs): connect users to wired network; 40-100 m Chapter 6: Networks & Collaboration 3 - factors: location (indoors, outdoors-wider range), weather, obstructions (steel-reinforced concrete pillars), power output of devices - repeaters & reflectors: amplify & reflect signals to extend range - i.e.AP- process messages on 802.3 & 802.11 standards b/c wireless protocol uses 802.11 protocol & switch using 802.3 protocol Mobile Computing: • computer- more likely to be portable laptop than desktop & smartphone- ‘on the go’ • access email, instant message, voice or text messages, browse internet • m-commerce (mobile commerce): conduct online transactions • WANs & storing personal information smartphone: ‘speed’& ‘bandwidth’- 3G network • - standards defined by International Telecommunication Union - i.e. iPhone OS (Apple), Blackberry OS (RIM) • e-readers: readings books/magazines; use electronic ink- good in sunlight - > less strain to eyes • tablets: general use; use LCDs (liquid crystal displays) Bring Your Own Device (BYOD): use own devices for work • Connecting to Internet: • router: special purpose computers that implement protocol for WANs - connects computer to computers owned/operated by International service provider (ISP) - functions: 1. Internet address, 2. gateway to internet, 3. ISPs help pay for internet (collect money from customers & pay access fees on their behalf) • Web: subset of internet- sites & users that process hypertext transfer protocol (HTTP) • browser: program that implements HTTP protocol • SMTP: simple mail transfer- email; HTTP: webpages; FTP: file transfer protocol Names &Addresses: • top-level domain (TLD): i.e. Canada= .ca Chapter 6: Networks & Collaboration 4 • visit website for Internet Corporation forAssigned Names & Numbers (ICANN); determine which agencies ICANN has licensed to register domains for that TLD; follow registration process required by those agencies • if domain is already in use=disallowed • uniform resource locator (URL): address on Internet • IP address: 4 numbers separated by period; logical address (assigned through software), not physical (MAC, NIC) Obtaining IPAddress: • public: assigned to ISPs & major institutions in blocks by ICANN; each=unique • private: private networks & internets; controlled only by specific organization • connect computer to LAN - > program will search for DHCP server (dynamic host configuration protocol) - > finds & requests temporary IP address from DHCP server - > loaned while connected to LAN - > disconnect: available again for reuse Finding Domain Names: • domain name system (DNS): convert human friendly URLs - > IP addresses (computer) • domain name resolution: conversion • domain name resolvers: done by computers; keep track of domain name requests & store locations for future use - reside at ISPs, academic institutions, large companies, government organizations • home & small business: DSL line & cable TV line (few used in Canada) • analog: wavy, signal before being sent • modulator/demodulator (modem): performs conversions - same protocols & different speeds=slower speed is one at which they operate • digital subscriber line (DS
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