digital literacy - basic technical concepts (session 1)

Digital Literacy Series

Digital LiteracySession 1 - Basic Technical Concepts

Prepared by Bill Condo


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 Foundational Topics

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. !

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Series Introduction


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


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


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.

PPeering points connect major ISPs to one another and are what enable the Internet to work.

P


The InternetTI

ER 1

TIER

2TI

ER 3

Local and Regional ISPs


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


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.


Domain Name System1 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


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.


Email1 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.


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.


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%


Web Process1 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


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.


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


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.


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


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


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


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-in Tools for OSX


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?


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


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


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


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


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


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


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/


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


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

http://en.wikipedia.org/wiki/Internet_service_provider

http://computer.howstuffworks.com/internet/basics/internet-versus-world-wide-web.htm

http://computer.howstuffworks.com/dns.htm

http://www.dnsfaqs.com

http://en.wikipedia.org/wiki/Email

http://computer.howstuffworks.com/e-mail-messaging/email.htm


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

http://computer.howstuffworks.com/web-server.htm

http://en.wikipedia.org/wiki/Comparison_of_web_server_software

http://en.wikipedia.org/wiki/History_of_the_web_browser

http://internet-browser-review.toptenreviews.com

http://network-tools.com

http://who.is


What did you do to get better today?

digital literacy - basic technical concepts (session 1)

Internet

internet tier

isp tier

digital literacy series

internet services

internet internetworking

digital technologies

multipart series

series introduction