04 - HTTP Overview and Message Formats

Question 1

rules that define how entities in a network communicate with each other

Answer 1

network protocols

Question 2

network protocols cover how to: (3)

Answer 2

• identify and establish communication
• transmit and receive data
• message formats

Question 3

network protocol that runs on top of TCP and IP

governs communication over the Web

Answer 3

HTTP

Question 4

HTTP was designed by ____ & ___ in ___

Answer 4

Tim Berners-Lee
Robert Cailliau
1990

Question 5

latest version of HTTP

Answer 5

HTTP/2.0 finalized in 2015

Question 6

most used version of HTTP

Answer 6

HTTP/1.1 finalized in 1997

Question 7

characteristics of http (3)

Answer 7

client-server
request-response
stateless

Question 8

requests are sent to a server either by another server or client programs called user-agents

Answer 8

client-server

Question 9

programs that make http requests for human users

Answer 9

user-agents

Question 10

most common user agent

Answer 10

browsers

Question 11

http communication is done through exchanges of request and response messages

Answer 11

request-response

Question 12

request messages are sent to a ___ which handles it then sends back a response

Answer 12

web server

Question 13

client and server are only aware of each other during the current request-response exchange

Answer 13

stateless

Question 14

1:1 exchange of request and response

Answer 14

HTTP transaction

Question 15

how does a http transaction work (7)

Answer 15

browser:
- extracts server’s hostname from the url
- resolves the ip address via dnr
- extracts the port from the url
- establishes a tcp connection with the web server
- sends an http request to the server
- receives a response from the server
- tcp connection may/may not be closed

Question 16

what does the browser do with the response from the server (4)

Answer 16

• browser parses the returned HTML doc
• fetches additional resources as needed (images, yt vids)
• server may have to send requests to other servers
• additional requests are transparent

Question 17

web servers that act as intermediaries between client and server

Answer 17

proxies

Question 18

used to pass messages from one part of the internet to another

Answer 18

forward proxy

Question 19

used as an entrance to private networks

usually used for regulation of access

Answer 19

reverse proxy

Question 20

proxies can be described as: (2)

Answer 20

transparent: doesn’t modify passing reqs
non-transparent: modifies passing reqs

Question 21

proxy functions (5)

Answer 21

caching
filtering
load balancing
authentication
logging

Question 22

cache data that may be commonly requested by clients

Answer 22

caching

Question 23

requests can be filtered to block or prioritize certain requests

Answer 23

filtering

Question 24

distributes requests to different servers based on server load, proximity to client, etc

Answer 24

load balancing

Question 25

only pass request msgs if they contain appropriate authentication details

Answer 25

authentication

Question 26

maintain a log of the messages it passes along

Answer 26

logging

Question 27

proxies usually have to act as ____

Answer 27

both server and client

Question 28

types of http messages (2)

Answer 28

request response

Question 29

parts of a request message (3)

Answer 29

request line - method - path - protocol version headers body (optional)

Question 30

defines the operation that the client wants to perform

Answer 30

method

Question 31

used to fetch a resource

Answer 31

GET

Question 32

used to send data

Answer 32

POST

Question 33

path from the URL

Answer 33

path

Question 34

indicates the version of http to be used

Answer 34

protocol version

Question 35

convey additional information about the sender/msg

Answer 35

headers

Question 36

actual payload of the message (optional)

Answer 36

body

Question 37

parts of a response message (3)

Answer 37

status line - protocol version - status code - reason phrase/status message headers body

Question 38

number that indicates if the request was successful or not

Answer 38

status code

Question 39

short english description of the status code

Answer 39

reason phrase

Question 40

reason phrase is also called ___

Answer 40

status message

Question 41

found in some response messages, depending on the method used

Answer 41

body