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

1. Digital Literacy Series
Digital Literacy
Session 1 - Basic Technical Concepts
Prepared by Bill Condo

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. 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) http://en.wikipedia.org/wiki/Internet

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) http://www.internetlivestats.com/internet-users/
0
750
1500
2250
3000
1990 1995 2000 2005 2010 2013
Internet Users in Millions 1
2.7 b
44 m

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. Digital Literacy Series
The InternetTIER1TIER2TIER3
Local and Regional ISPs

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. 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 lmgresults.com. 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. 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
lmgresults.com
184.168.206.1 Another ISP
DNS Server
Domain’s
DNS Server
184.168.206.1
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].
lmgresults.com

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. 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. 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. 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) http://news.netcraft.com/archives/category/web-server-survey/
Active Web Servers % 1
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. 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. 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) http://en.wikipedia.org/wiki/Usage_share_of_web_browsers
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. 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. 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. 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. 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. 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. Digital Literacy Series
Troubleshooting
http://www.downforeveryoneorjustme.com
• 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. 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. 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. 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
http://who.is

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 whois.godaddy.com to
get a full whois record.
Domain Whois

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
http://mxtoolbox.com/DNSLookup.aspx

28. Digital Literacy Series
Troubleshooting
• With this result, we can see the domain is pointed to the IP Address
of 184.168.206.1. 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. 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
http://www.netcraft.com/whats/

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. Digital Literacy Series
Additional Resources
• Internet
• http://en.wikipedia.org/wiki/Internet_service_provider
• http://computer.howstuffworks.com/internet/basics/internet-versus-world-wide-web.htm
• DNS
• http://computer.howstuffworks.com/dns.htm
• http://www.dnsfaqs.com
• Email
• http://en.wikipedia.org/wiki/Email
• http://computer.howstuffworks.com/e-mail-messaging/email.htm

32. Digital Literacy Series
Additional Resources
• Web Servers
• http://computer.howstuffworks.com/web-server.htm
• http://en.wikipedia.org/wiki/Comparison_of_web_server_software
• Web Browsers
• http://en.wikipedia.org/wiki/History_of_the_web_browser
• http://internet-browser-review.toptenreviews.com
• Troubleshooting
• http://network-tools.com
• http://who.is

33. Digital Literacy Series
What did you do to
get better today?