Internet Fundamentals
Last updated
Was this helpful?
Last updated
Was this helpful?
Define what a server is
Diagram the request response cycle
Describe the different parts of a URL
Explain what Node.js is and why it's useful
Diagram how the internet works
Explain what DNS is
Describe what packets are and how they travel to servers
A server is just a computer that is always turned on and connected to the internet
There are four different types of requests we can make which correspond to four basic ways we can manipulate data
POST (Create data)
GET (Read data)
PUT/PATCH (Update data)
DELETE (Destroy data)
URL stands for Uniform Resource Locator, and it's just a string of text characters used by Web browsers, email clients and other software to format the contents of an internet request message.
Let's breakdown the contents of a URL:
Element
About
protocol
the most popular application protocol used on the world wide web is HTTP. Other familiar types of application protocols include FTP, SSH, GIT, FILE, HTTPS
host/domain name
the host or domain name is looked up in DNS to find the IP address of the host - the server that's providing the resource
port
a server can have multiple applications listening on multiple ports. This allows users to access a different application on the same host
path
web servers can organize resources into what is effectively files in directories; the path indicates to the server which file from which directory the client wants
query-string
the client can pass parameters to the server through the query-string (in a GET request method); the server can then use these to customize the response - such as values to filter a search result
hash/fragment
this URL fragment is generally used by the client to identify some portion of the content in the response; interestingly, a broken hash will not break the whole link - it isn't the case for the previous elements
Node is just a command line application that reads a JavaScript file and executes it within the context of the terminal
until recently, JavaScript could only be executed within a browsers
Node allows JavaScript to become the first programming language that can be executed in both the browser and in a terminal application
Makes it easier to find a developer who can build all aspects of a web application
Asynchronous
Uses event handlers (just like click, hover, etc) so you can tell an application to run code while waiting for other commands to finish executing
previously, long running commands like updating a database would have to finish before the application could continue running
Request starts at local computer
Goes to Router (can have multiple computers hooked up to it, forming a Local Area Network)
Goes to Modem
Goes ISP (internet service provider)
ISP is connected to other ISPs and similar institutions
we're in the actual net at this point
If the ISP isn't connected to the Network containing the final destination
it will ask the networks it is connected to if they are connected to the final destination's network
this process continues, building up a path to the final destination
each path to the final destination contains how many nodes it must visit to get to destination
can determine shortest path to final destination
Once connection to final destination is made, it goes to final destination's network (ISP)
From ISP it goes to the modem
From the modem, it goes to the router
From the router, it goes to the host computer
When requests and responsese are made 2 things are sent
headers
body
Request/Response Headers Always sent, which give details about the request/response. Things like:
Accept: types of media allowed (ie text/plain)
Date: the date
Host: domain name of host
The other portion is the body of the request. The body may be empty, but generally includes the actual content being sent.
Express and our browser will be handling most of the details of our request/response headers.
However, we often will want to send HTTP Status Codes. The most common ones we encounter is propbably 404 Not Found.
We can get a sampling of codes, with memorable visuals here or here Or, here is a link to the offical documents
Domain Name Servers help convert a domain (example.com) to an IP address. Similar to how people and places have phone numbers and you can use a phone book to look up the phone numbers. So rather than having to remember an arbitrary set of numbers, you can have a name for it that is easier to remember/ type.
If RNS doesn't have info in memory, it will ask the Root Name Servers
Root Name Server know where TLD (Top Level Domain) servers are (.com, .edu, .gov, etc)
TLDs know where Authoritative Name Servers are (example.com)
Authoritative Name Servers knows the IP address of final destination
Resolving Name Server gives IP to the operating system
When a domain is purchased
the registrar (company that registers the domain name, e.g. godaddy) is told which Authoritative Name Severs to use
The Authoritative Name Server is also told which IP address to use
The registrar then notifies the organization responsible for TLD name servers (the registry)
The registry tells the TLD name servers (.com, .net, etc) which Authoritative Name Servers to use for that new domain
How Packet Travels in Network Watch on your oqn
Everything you do on the Internet involves packets. For example, every Web page that you receive comes as a series of packets, and every e-mail you send leaves as a series of packets. Networks that ship data around in small packets are called packet switched networks. Source
Problem
If a problem occurs, data in transit is lost forever
Sender would have to send entire data all over again
think about resending an entire movie just because something dropped for a moment at the last second
Solution
Break each transmission up into tiny chunks
Receiver reassembles the chunks as they are received
If one piece is missing, sender just resends that tiny chunk
This lesson was adapted from SEIR-MAE