wk 7 lecture.pdf

# Week 7 Notes ## Monday, October 07, 2024 ### Examples of Operating Systems - Desktop / Laptop - Windows - Mac OS - UNIX, Linux - TVs - Samsung Smart TV - Tizen - VIZIO - SmartCast OS - Roku and Roku TVs - Roku OS - Smartphones - Apple iOS...

# Week 7 Notes ## Monday, October 07, 2024 ### Examples of Operating Systems - Desktop / Laptop - Windows - Mac OS - UNIX, Linux - TVs - Samsung Smart TV - Tizen - VIZIO - SmartCast OS - Roku and Roku TVs - Roku OS - Smartphones - Apple iOS - BlackBerry OS - Android ### What Else? - IOT (Internet of Things) - Contiki - Amazon FreeRTOS - Embedded Linux - RIOT - TinyOS - Windows 10 IoT ### Functions of Operating Systems - Oversee operation of computer - Store and retrieve files - Provide the user interface to request execution of programs - Coordinate the execution of programs ### History of Operating Systems - Batch Processing (job queue) - Interactive processing (real time) - Time-sharing (one machine, many users) - Multitasking (one user, many tasks) - Multiprocessor machines (load balancing) - Embedded Systems (specific devices) ### Operating System Architecture - Application software - Performs specific tasks for users (productivity, games, software development) - System software - Provides infrastructure for application software - Consists of operating system and utility software ### Components of an Operating System - User Interface: Communicates with users - Text based (Shell) - Graphical user interface (GUI) - Kernel: Performs basic required functions - File manager - Device drivers - Memory manager - Scheduler and dispatcher ### Loading Software and Managing Memory 1. Machine starts by executing the boot loader program already in memory. Operating system is stored in mass storage. 2. Boot loader program directs the transfer of the operating system into main memory and then transfers control to it. ### Types of Networks - Personal Area Network (short-range) - Local Area Network (building/campus) - Metropolitan Area Network (community) - Wide Area Network (greater distances) ### Network Ownership - Closed - Proprietary Network - Open - Uses open standards - Provides services on an equal basis ### Network Topology 1. Bus - Ethernet 2. Star - Central Access Point ### Network Protocols - Protocol: Rule by which activities are conducted on a network - Products from different vendors all compatible - Data transmission control and coordination between nodes ### Transmission Protocols - CSMA/CD - Carrier Sense, Multiple Access / Collision Detection - Bus networks - CSMA/CA - Carrier Sense, Multiple Access / Collision avoidance - Star networks None of the end systems can hear each other although each can communicate with the access point. - Range of B - Building - Range of C - Access point - Range of A ### Combining Networks - Repeater: passes all messages across two busses - Bridge: passes only messages that are destined for computers on the other bus - Switch: acts like a bridge, but with connections to multiple busses - Router: connects two incompatible networks resulting in a network of networks called an internet ### An internet, not the Internet - WiFi network - Router - Router - Router - Ethernet network - Router - WiFi network #### Routers connecting two WiFi networks and an Ethernet network to form an internet ### Process Communication - Interprocess Communication: communication between network notes to coordinate actions and perform tasks - Client-server - Many clients, one server (executing continuously) - Clients make requests of other processes - Server satisfies requests made by clients - Peer-to-peer (P2P) - Two processes communicating as equals - Processes execute on a temporary basis ### Distributed Systems - Distributed Systems: Systems units that execute as processes on different computers - Cluster computing - Independent computers work closely together instead of a single, much larger machine - Grid computing - Millions of PCs (not connected to each other) work on a complex problem - Cloud computing - Provide services, hide the details ### The Internet - Internet: An internet that spans the world - Original Goal: DARPA Initiative - Link a variety of networks into a connected system - Connected system intended to not be disrupted by local disasters ### Internet Architecture - Tier 1 ISPs (Very few) - Internet Backbone - Tier 2 (Regional) - Tier 3 or Access - Provides connectivity to the Internet ### Addresses on the Internet - IP address: pattern of 32 or 128 bits often represented in dotted decimal notation - Coordinated by ICANN - Internet Corporation for Assigned Names and Numbers - Allocates blocks of IP addresses to ISPs - Block sizes vary by ISP size / need - Oversees the registration of domains and domain names ### Domains and Domain Names - Registrars: Company allowed to register a domain name on behalf of an organization - Mnemonic address - E.g.: monroecc.edu, youtube.com - Top-Level Domains (.com, .net, .org, .edu, .gov, .au, .uk, ...) - New TLDs (.biz, .museum, .tech, .info, .news, .mobi) - Subdomains (maps.google.com) - Domain name system (DNS) - Name servers Translate names to numbers - DNS lookup ### Early Internet Applications - Network News Transfer Protocol (NNTP) - File Transfer Protocol (FTP) - Telnet and Secure Shell (SSH) - Hypertext Transfer Protocol (HTTP) - Electronic Mail (email) - SMTP for sending - POP3 and IMAP for accessing ### More Recent Applications - Voice Over IP (VoIP) - Internet Multimedia Streaming - N-unicast - Multicast - On-demand streaming - Content delivery networks (CDNs) - Anycast - World-Wide Web - Hypertext combines internet technology with concept of linked-documents - Embeds hyperlinks to other documents - Browsers present materials to the user - Web servers provide access to documents - Documents are identified by URLs and transferred using HTTP (HTTPS) ### Anatomy of a URL - Mnemonic name of host holding the document - Protocol required to access the document. In this case itis hypertext transfer protocol (http). - Directory path indicating the location of the document within the host's file system - Document name ### Hypertext Markup Language (HTML) - Contains tags to communicate with browser - Appearance / Formatting - `<h1>` to start a level one heading `</h1> ` - `<p>` to start a new paragraph `</p>` - Links to other URL content - `<a href = "URL">` - Insert images - `<img src = "URL" >` ### Tag indicating beginning of document - Preliminaries - `<html>` - `<head>` - `<title>demonstration page</title>` - `</head>` - The part of the document that will be displayed by a browser - Tag indicating end of document - `</html>` ### Related Languages - Cascading Style Sheets (CSS) - A language used to describe styles and formatting of HTML and XML - Extensible Markup Language (XML) - A language for constructing markup languages similar to HTML - Semantic Web and search engines - XML Example: Music Encoding - `<staff clef = "treble">` - `<key>C minor</key>` - `<time> 2/4 </time>` - `<measure>` - `<rest> eighth </rest>` - `<notes> 1/8 G, 1/8 G, 1/8 G </notes>` - `</measure>` - `<measure>` - `<notes> half E </notes>` - `</measure>` - `</staff>` ### Client-Side vs. Server-Side - Client-side activities (browser) - Front End - Collects User Input - Visualization and user input - Languages: - JavaScript - CSS - jQuery - Server-side activities (webserver) - Back End - Processes User Input - Transactions and computations - Languages - PHP - Python / Django - ASP.NET ### Internet Protocols - Control how messages are transferred over the Internet - This software must reside on every computer in the Internet - Accomplished by a multi-level hierarchy - Origins: Prepares package for shipping - You: Places package in container for airline - Shipping company: Places container in airplane - Airline: Transfers container to another airplane - Airline: Sends container to shipping company - Airline: Sends container to shipping company - Final Destination: - Receives and opens package - Shipping company: Removes package from container - Friend: And delivers it to addressee ### Internet Software Layers - Application: Constructs message with address - Transport: Chops message into packets - Network: Handles routing through the Internet - Link: Handles actual transmission of packets - More Standards... - OSI Reference Model - TCP/IP Conceptual Layers - Application ### TCP/IP Protocol Suite - Application layer - Transport Layer - Transmission Control Protocol (TCP) - User Datagram Protocol (UDP) - Network Layer - Internet Protocol (IP) - IPv4 (32-bit) - 192.168.10.1 - IPv6 (128-bit) - 0:0:0:0:0:ffff:c0a8: 0a01 - 0000:0000:0000:0000:0000: ffff: c0a8: 0a01 ### Client-Server Programming... - Socket: an abstraction for processes at the application layer to connect to the network via the transport layer - Source address name (localhost) - Source Port Number (1023 ... 65535) - Destination address name (remotehost) - Destination Port Number ### Cybersecurity - Types of Attacks - Malware (viruses, worms, Trojan horses, spyware, phishing software) - Denial of service (DoS) - Spam (common medium for delivering malware) - Protection and Cures - Firewalls - Spam filters - Proxy Servers - Antivirus software ### Certificate - Cryptography - HTTPS for secure Internet access - Public key: Used to encrypt messages - Private key: Used to decrypt messages - Certificate Authorities - Trusted to maintain lists of public keys - Provide Certificates to clients containing a party's name and its public key ### Public / Private Key Encryption ### Legal Approaches to Network Security - Computer Fraud and Abuse Act - Electronic Communication Privacy Act - USA PATRIOT Act - Communications Assistance for Law Enforcement Act - Anticybersquatting Consumer Protection Act