Internet

Question 1

What are individual computer(“nodes”) on the internet called and what do they do?

Answer 1

Host: they collect into networks on different scales; household, corporate, regional, national.

Question 2

What is the internet?

Answer 2

A massive worldwide system of inter-networked hosts.

Question 3

What is inter-networking?

Answer 3

Networks that are joined with other networks.

Question 4

True or False, is your computer connect to a router and if so what is the rounder connect to?

Answer 4

True our computer is in fact connected to a router. The router is connected to a modem.

Question 5

What does your modem connect to? Add examples.

Answer 5

It connect to your internet service provide (ISP).
ex: Bell, Videotron (we pay to connect to their ISPs, hardware they maintain and operate.

Question 6

What does the internet service provider (ISP) connect to?

Answer 6

They connect to n even bigger network called Network Service Providers (NSPs)

Question 7

What does NSPs provide access to?

Answer 7

They provide access to the “internet backbone”, the high speed “highways” of the internet.

Question 8

How do we send messages to and from Europe? Asia, Africa, etc? How are these wires connected?

Answer 8

Network services provides have access to seafloor cables. (Re,beer that they are deep in the water, and that there are so many of them just in case a cable malfunctions and we need to keep the flow going)

Question 9

The World Wide Web ( internet) uses clients-server architecture. What happens when a web browser (client) sends a request to a web server?

Answer 9

When the client sends a request to a web server it’s to create or retrieve a resource ( like an HTML page, a single webpage)

Question 10

What are the two ways to access a webpage?

Answer 10

1. Know the exact Internet protocol (IP) address of the side.
2. Have a link or reference from another webpage ( which is why we call it web!)

Question 11

What does linkrot mean?

Answer 11

It means that we are slowly loosing references to these webpages, which means the web is always slowly dying.

Question 12

What happens when you access your IG, Tik Tok, etc?

Answer 12

You are sending a request to view that website from your client(phone or laptop). Part of this request, you provide your credentials(email, password ) to prove you are you, and have correct access to these documents.

Question 13

What do we call when data is broken down into fixed-sized bundles?

Answer 13

Packets equipped with meta data.

Question 14

What does metadata include?

Answer 14

It includes the source and destination address to identify where it came from and is going (think of a piece of mail).

Question 15

What did we used to do before packet switching?

Answer 15

Circuit switching ( we simply connected each device physically to one another!).

Question 16

How does the 4 layer structure work?

Answer 16

Link: Network hardware handles this layer.
Network: This is where packets come in. OS handles this layer.
Transport: Abstraction on top of packets. Applications are programming against this layer.
Application: What are we actually doing with this network, all previous examples are applications.

Question 17

What is each node ( a host or a router) in the internet assigned with?

Answer 17

It’s assigned an IP address, which looks like 142.251.41.46. This is a 4 byte integer, separated by decimal.

Question 18

What are Domain Name systems “DNS”?

Answer 18

Servers which map URLs(Uniform Resource Locators) to IP adresses.

Question 19

Routers are intermediary devices. What solves the routing problem?

Answer 19

The network layer solves the routing problem.

Question 20

Given a destination address where should a router forward a packet to next?

Answer 20

Routers use a data structure called a routine table that expresses for a given range of destination address, where the package should be sent next?

Question 21

Why is IP unreliable?

Answer 21

IP does not guarantee message deliver.
-Messages could be lost or corrupted in transit.
-Messages could arrive out of order at their destination
A transport-layer protocol accounts for this.

Question 22

There are several Transport Layer Protocols (ex: TCP and UDP)
What are the characteristics of TCP (transport control protocol)?

Answer 22

TCP is built on top of IP.
-Connection oriented. Enpoitns wanting to communicate first establish a connection by a special back-and-forth exchange of IP packets
-Stream abstraction. The connected endpoints communicate by sending streams of bytes, not breaking it up into packets
-Reliability. TCP includes acknowledge of receipt fo data. Data loss or corruption is detected and packets are re-esnt automatically as needed
The OS implements TCP for you.

Question 23

What does TCP establish and what is the “handshake” procedure?

Answer 23

TCP establishes a connection between two parties
One party is the server, the other is the client
“Handshake” procedure:
1.A server starts listening for incoming connections
2.A client requests to connect to the listening server
3.The server accepts or rejects the connection
4.The client acknowledges the connection was rejected or accepted

Question 24

What is HTTP?

Answer 24

HTTP is one protocol of application layer that structure requests and responses of server. Most commonly, HTTP is used to request HTML pages from web sites, but it also facilitates the exchange of all sorts of data.

Question 25

HTTP structure request

Answer 25

HTTP specifies very clearly what kinds of requests you can make and the kinds of réponses you can expect. This is the purpose of an application layer protocol: to structure communication to and from computers.

Question 26

What does the HTTP request have?

Answer 26

1.A request line specifying:
a)the HTTP method (GET, PUT, DELETE…), resource (name of the file we’re trying to access, like index.html), and HTTP version

2.Headers, providing metadata about the request, like:
a)the host (the url you’re trying to access), user-agent (your client), and accept (what kind of data it’s asking for (ex text))

3.A body (optional)
a)In the instance where we want to add data to server, it would go here.

Question 27

HTTP responses.

Answer 27

Just as requests are hugely structure, so are responses from servers.

HTTP responses have 3 main components:
1.Status line
a)The HTTP version, status code (100, 200, 300 etc.) indicating the kind of response and some human readable reason

2.Headers
a)Such as the content type of the response (text, json, etc), length of the response

3.Body (optional)
A)Contains the actual data requested. In the case of requesting HTML files, the body would be the actual code of the website in HTML!

Question 28

What are API calls?

Answer 28

APIs (Application Programming Interfaces) are rules that allow programs to communicate with each other. We use APIs to get data from servers, send data (like filling out forms), or even control computers remotely.

Question 29

Note; responses can include more request!

Answer 29

Websites often have extra files, like images, that also need to be loaded. Since browsers can only request one thing at a time, every time a page includes a <src>, <link></link>, or

 tag, another HTTP request is made to the server hosting that resource. This is why some images take time to lead your browser is still waiting for the HTTP response. You can see these requests in. Action by checking the “Network” tab in your browser’s developer tools.

</src>

Question 30

What is the curl command.

Answer 30

Short for Client URL is a command line library for transferring data to and from servers on the application layer. It supports many different protocols, and as we see it for HTTP!
We use -x GET, here we are literally programming our request will be a GET request.

Question 31

What are HTTP servers configured to accept?

Answer 31

They are configured to accept HTTP requests (usually on port 80) and serve the correct file depending on the request.
Python has a very convenient module that will turn my directory in an http server using python -m http.server.