Digital Literacy - Basic Technical Concepts (Session 1)


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Basic Digital Literacy, including Internet connectivity, DNS, Email, HTTP Process, and Troubleshooting.

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Digital Literacy - Basic Technical Concepts (Session 1)

  1. 1. Digital Literacy Series Digital Literacy Session 1 - Basic Technical Concepts Prepared by Bill Condo
  2. 2. Digital Literacy Series What We’re Covering • How the Internet is connected and by who • How the Domain Name System (DNS) works • How email is transmitted and stored • How web servers and browsers work • How to troubleshoot internet issues Technical FoundationalTopics This is the first session of a multipart series that will help fill in any deficiencies around the Internet and digital technologies. ! In this first session, we’ll start with the foundational elements that enable the Internet to work, and tips and tools to troubleshoot when things aren’t working as expected. ! ! ! Series Introduction
  3. 3. Digital Literacy Series The Internet • The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite (TCP/IP) to link several billion devices worldwide. It is a network of networks that consists of millions of private, public, academic, business, and government networks, of local to global scope, that are linked by a broad array of electronic, wireless, and optical networking technologies. 1 • The Internet (internetworking) dates back in part to ARPANET and other networks, and is commonly attributed in part to Vint Cerf. 1)
  4. 4. Digital Literacy Series The Internet • The total count of Internet users continues to grow exponentially. • The number of devices are growing even faster, as many people have multiple devices connected. 1) 0 750 1500 2250 3000 1990 1995 2000 2005 2010 2013 Internet Users in Millions 1 2.7 b 44 m
  5. 5. Digital Literacy Series The Internet Tier 1 ISP Tier 1 ISP Tier 2 ISP Tier 2 ISP Tier 2 ISP Tier 3 ISP Tier 3 ISP Tier 3 ISP Tier 3 ISP Customers (Business and Consumers) P P • 3 Tiers of ISPs connect the Internet, with Tier 1 being the largest, core companies. P Peering points connect major ISPs to one another and are what enable the Internet to work. P
  6. 6. Digital Literacy Series The InternetTIER1TIER2TIER3 Local and Regional ISPs
  7. 7. Digital Literacy Series The Internet • The Internet is not the same as the World Wide Web, but instead enables it. The HTTP and HTTPS protocols (“Web Browsing”) run on 
 top of the Internet, just as SMTP and IMAP (“Email”), and FTP (File Transfer Protocol). WWW Email FTP
  8. 8. Digital Literacy Series Domain Name System • DNS usage is typically transparent to the end-user, tied internally to web browsing, email, and other Internet services. • DNS operates on what are called “zones”, which consists of a top level domain name, such as The zone file usually contains multiple records, some of which are address resolution (‘a’, ’cname’ records), mail pointers (‘mx’), and text records (‘txt’). • DNS records are normally cached after a request by a user’s computer, and by third-party DNS servers.
  9. 9. Digital Literacy Series Domain Name System 1 2 3The local computer references a domain name and a DNS lookup request is created. Your request is sent to the server as configured from your computer, and then may be sent upstream to other servers until the server responsible for the domain provides the authoritative answer. Your ISP’s Local DNS Server Another ISP DNS Server Domain’s DNS Server Response 1 4 5 6 2 3 The result is then sent back through the original path and provided to the computer. 4 The resulting IP address is then used to make the final request (website, email, etc.) [5,6].
  10. 10. Digital Literacy Series Email • Behind web browsing, email is second most common use of the web. Desktop email clients remain behind the standards of web browsers, and a large number of people use web mail (ie Gmail). • Email works a lot like the post office, working in a hub and spoke manner. Email messages themselves are most like postcards, in that anyone along the route can read the full message.
  11. 11. Digital Literacy Series Email 1 3The sender drafts the email and authenticates with their outgoing (SMTP) mail server. The message passes through one or more third-party mail servers until a connection can be made to the final server. Sender’s Mail Server Mail Server Mail Server Recipient’s Mail Server Recipient’s AccountSender’s Account 1 2 3 4 5 2 The sender’s server accepts the message for delivery and passes it to another mail server, closer to the the recipients server. 4 The final mail server checks for the addressed account and stores it locally if the user exists, otherwise sending an error message back. 5 The recipient will be notified/ receive the message on their next connection to their mail server.
  12. 12. Digital Literacy Series Web Servers • Web server software is built to process a web request, compile the data, and deliver a response. • Web servers can process simple requests, such as those for an image or style sheet, or more complex ones, such as pages with back-end programming and resource intensive database connections. • Web servers typically handle multiple requests from a single user concurrently, letting a browser load multiple assets at the same time.
  13. 13. Digital Literacy Series Web Servers • The most popular web server is from the Apache Foundation. Apache HTTP Server and Nginx (“Engine X”), both open source projects, account for over 66% of all active web servers. 0 15 30 45 60 4/10 4/11 4/12 4/13 4/14 Microsoft IIS Other Nginx Apache 52% 1) Active Web Servers % 1 14%
  14. 14. Digital Literacy Series Web Process 1 3Browser Requests URL Web ServerClient Computer 1 2 Request is routed to the correct web server 5 6 Request is received and any 
 back-end logic is processed Response is routed back to the client’s browser Response is loaded into the browser and any external items (i.e. images) are requested 6 3 4 2 5 4 Response is formatted and sent
  15. 15. Digital Literacy Series Web Browsers • Web Browsers render websites, locally run javascript, interpret style sheets, and store session and local data. • Browsers build on top of this core functionality with bookmarks, history, extension support, and UI components. • Each browser has it’s own rendering engine, script interpreter, and API layer. It’s up to each browser to implement their components against the latest HTML, Javascript, and CSS standards, which some have historically done better than others.
  16. 16. Digital Literacy Series Web Browsers 17.5% 35% 52.5% 70% 2009 2011 2013 2014 Internet Explorer Default browser for Windows that’s continuing to lose marketshare each year Safari Default browser for OSX that’s 
 benefited from the increased 
 popularity of Macs Chrome Introduced in 2008, it has become the most popular browser, it renders quickly, and has a vibrant third-party extension ecosystem Firefox From the roots of early browsers Mosaic and Netscape, Firefox was previously the most popular browser and continues to be a common choice 1) Browser Market Share % 1 Other Notable Browsers Opera / Opera Mini Opera has a small following on the desktop and is 
 installed on some phones Android Browser Shares some features of Chrome
  17. 17. Digital Literacy Series Troubleshooting ! • When troubleshooting an issue, it’s important to be able to isolate the cause to one of three areas: user, network, or server. • Using a series of questions, we can determine what path we should explore with additional effort. User/Computer Level Network/Internet Level Datacenter/Server Level If the problem(s) are within a local computer or local network. If the problem(s) are within a local ISP, or backbone provider. If the problem(s) are within the final datacenter or within the web server.
  18. 18. Digital Literacy Series Troubleshooting • Do you have trouble access all websites (or other services)? • Do you have trouble sending all email? • Do you get an authentication error message? User/Computer Level
  19. 19. Digital Literacy Series Troubleshooting • Do only a certain group of websites (or services) not function, while others work successfully? • Has your ISP communicated an outage? • Is only one type of service (web, email, ftp, chat) unavailable, while others are functional? Network/Internet Level
  20. 20. Digital Literacy Series Troubleshooting • Has a service published a report of an outage (i.e. Gmail)? • Have you isolated the trouble to only one single website (or service)? • Do you get a specific service error message indicating a connectivity, functional, or over capacity message for this resource? Datacenter/Server Level
  21. 21. Digital Literacy Series Troubleshooting • Mac OSX has a group of network tools available inside of the Network Utility app. This provides an easier interface compared to using some of the items on the command line. • Windows also has some of the tools via the command line. Built-inTools for OSX
  22. 22. Digital Literacy Series Troubleshooting • A number of tools exist which test the availability of websites from third party locations. This will help you understand where a problem might be located. Down For Everyone?
  23. 23. Digital Literacy Series Troubleshooting • Ping is a tool that tests connectivity to a host by passing a small data packet to the machine and verifying that the response is received. • Note: ping is not 100% accurate because some hosts block this communication. Ping
  24. 24. Digital Literacy Series Troubleshooting • Trace route is a tool that will display each step (host) that was used along the way in order to access a specified host. • This data can be combined with address IP info to track the geographic path taken. Trace Route
  25. 25. Digital Literacy Series Troubleshooting • Whois is the look up tool for domain registration, which gives you the registration dates, company, and DNS server settings. • Some whois data may be set as private, hiding the company that registered a domain. Domain Whois
  26. 26. Digital Literacy Series Troubleshooting • Whois data may only be available directly from the domain service that the TLD (Top Level Domain) is registered through. • In this example, we need to visit to get a full whois record. Domain Whois
  27. 27. Digital Literacy Series Troubleshooting • DNS records may be looked easily up with number of web- based tools. Verify a new IP address setting or debug existing settings. • Website records typically use what’s called “A” records, but may also use “CNAME” records as well. DNS Record Lookup
  28. 28. Digital Literacy Series Troubleshooting • With this result, we can see the domain is pointed to the IP Address of The TTL, or time-to-live is set for one hour. This in an instruction to cache (or remember) the result for that long. DNS Record Lookup
  29. 29. Digital Literacy Series Troubleshooting • If you’re not sure where a site is hosted (Squarespace, Godaddy, etc), or want to see what type of web server a site is running, you can look it up with this tool from Netcraft. • Because most servers return this info with a request, it can be captured and documented. Web Server Information
  30. 30. Digital Literacy Series Troubleshooting • In this example we can see the web host is Godaddy, the server is running the Linux operating system, and using the Apache web server. In some cases you’ll see a longer, historical list. Web Server Information
  31. 31. Digital Literacy Series Additional Resources • Internet • • • DNS • • • Email • •
  32. 32. Digital Literacy Series Additional Resources • Web Servers • • • Web Browsers • • • Troubleshooting • •
  33. 33. Digital Literacy Series What did you do to get better today?