HTTP (overview and message formats)

Question 1

Network protocols are _______ that define how entities in a network communicate with each other.

Answer 1

Rules

Question 2

Network protocols cover how to? (3 items)

Answer 2

1. Identify and establish communication with the other party.
2. Transmit and receive data.
3. Message formats

Question 3

HTTP is a _______ _________ that runs on top of TCP and IP. It governs communication over the Web.

Answer 3

network protocol.

Question 4

HTTP is used to request and send resources such as: (5)

Answer 4

1. HTML Pages
2. Style sheets
3. Scripts
4. Images
5. Fonts

Question 5

Who designed HTTP?

Answer 5

Tim Berners-Lee and Robert Cailliau

Question 6

Latest Version of HTTP?

Answer 6

HTTP/2.0 (finalized in 2015)

Question 6

Most used version of HTTP

Answer 6

HTTP/1.1 (finalized in 1997)

Question 6

Characteristics of HTTP

Answer 6

1. Client Server
2. Request Response
3. Stateless

Question 6

Requests are either sent to a server either by:

Answer 6

1. another server
2. or client programs called user-agents

Question 6

Programs that make HHTP requests for human users.

Answer 6

User-Agents

Question 7

Beside web browsers, user agents can also be:

Answer 7

1. Mobile apps
2. Desktop apps
3. Machine-automated user-agents (robots/crawlers)

Question 7

The most common user-agent

Answer 7

Web-browser

Question 7

Request messages are sent to a ___________ which handles it, then sends back a response.

Answer 7

Web server.

Question 8

HTTP communication is done through exchanges of ___________ and ________________.

Answer 8

request and response messages.

Question 9

It’s usually not a direct connection between user-agent and web server. Sometimes, there are ___________ acting between the client and the server.

Answer 9

Proxy

Question 10

Characteristic of HTTP that makes the client and server are only aware of each other during the current request-response exchange.

Answer 10

Stateless

Question 11

An HTTP transaction is the ____________ of request and response.

Answer 11

1:1 exchange

Question 12

1. Browser extracts server’s ___________ from the url.

Answer 12

hostname

Question 13

2. Browser resolves the ___________ via Domain Name Resolution.

Answer 13

IP address.

Question 14

3. Browser extracts the __________ from the URL.

Answer 14

port

Question 15

4. Browser establishes a _______________ with the server.

Answer 15

TCP connection

Question 16

4. Browser sends an ___________________ to the server.

Answer 16

HTTP Request

Question 17

5. Browser receives a _________ from the server.

Answer 17

response

Question 18

6. TCP connection may or may not be ________ (depends on HTTP version).

Answer 18

closed

Question 19

What does the browser do with the response from the server?

Answer 19

The browser parses the returned HTML doc, fetching additional resources as needed.

Question 20

A server may have to send requests to ______________ in order to fulfill a request sent to it.

Answer 20

Other servers

Question 21

Web servers that act as intermediaries between client and server.

Answer 21

Proxies

Question 22

Two main types of Proxy

Answer 22

Forward Proxy and Reverse Proxy

Question 23

Proxies used to pass messages from one part of the Internet to another.

Answer 23

Forward Proxies

Question 24

Proxies used as an entrance to private networks.

Answer 24

Reverse Proxy

Question 25

Proxies usually placed at the 'edge' of a local network to direct internal traffic to the public internet.

Answer 25

Forward Proxies

Question 26

Normally used for regulation of access from the public internet to a private network.

Answer 26

Reverse Proxy

Question 27

Proxy can also be described as: (2)

Answer 27

Transparent and Non Transparent.

Question 28

Proxies that does not modify passing requests.

Answer 28

Transparent

Question 29

Proxies that modifies passing requests.

Answer 29

Non-transparent

Question 30

Proxies perform functions such as: (5)

Answer 30

Caching, filtering, load balancing, authentication, logging.

Question 31

Reduces load on the actual server

Answer 31

Caching

Question 32

__________ cache data that maybe commonly requested by clients.

Answer 32

Caching servers.

Question 33

Request can be filtered to block or prioritize certain requests.

Answer 33

Filtering

Question 34

A single font-facing server accepts all requests and distributes them across different servers based on factors such as server load, proximity to client, etc.

Answer 34

Load Balancing

Question 35

Proxies that only pass messages if they contain appropriate authentication details.

Answer 35

Authentication Proxies.

Question 36

These proxies maintain a log of the messages that it passes along.

Answer 36

Logging

Question 37

Proxies usually have to act as both _________ and _________.

Answer 37

server and client

Question 38

A proxy is also a ______ when it makes a request on behalf of a browser/user-agent.

Answer 38

Client

Question 39

A web server is also a ______ when it requests data from another web server.

Answer 39

Client

Question 40

2 types of HTTP Messages.

Answer 40

Request or Response.

Question 41

Parts of a request message: (3)

Answer 41

1. Request line (method, path, protocol version) 2. Headers 3. Body (optional)

Question 42

Defines the operation that the client wants to perform

Answer 42

Method

Question 43

HTTP method that is used if a client wants to fetch a resource.

Answer 43

GET

Question 44

HTTP method is used if a client wants to send data.

Answer 44

POST

Question 45

Indicates the version of the HTTP to be used for the transaction.

Answer 45

Protocol Version

Question 46

Part of HTTP message that convey additional information about the sender or the message payload.

Answer 46

Headers

Question 47

Part of HTTP message that is the actual payload of the message.

Answer 47

Body

Question 48

Messages may or may not be required to have a body based on the _________ used.

Answer 48

method

Question 49

Parts of a response message: (3)

Answer 49

1. Status Line (protocol version, status code, Reason Phrase) 2. Headers 3. Body

Question 50

A number that indicates if the request was successful or not, and why.

Answer 50

Status code

Question 51

There is a list of valid status codes defined by the W3C.

Answer 51

Status code

Question 52

A short English description of the status code. Also called status message.

Answer 52

Reason Phrase