HTTP Protocol Basics

Question 1

HTTP (Hypertext Transfer Protocol)

Answer 1

• clear-text
• most used app protocol
• client-server
• transfers web pages and web app data
• can be intercepted
• does not provide strong authentication between parties

Question 2

HTTP first step

Answer 2

client (usually web browser) connects to web server (MS IIS r Apache HTTP Server)

Question 3

HTTP second step

Answer 3

client and server exchange messages (request & response)

Question 4

How is HTTP related to TCP protocol?

Answer 4

It works on top of TCP.

1. TCP connection is made
2. client sends request
3. server processes request
4. server send back answer w/ status code and data

Question 5

What is the format of an HTTP message?

Answer 5

1. Headers\r\n
2. \r\n
3. Message Body\r\n

Question 6

How do you end lines in HTTP?

Answer 6

\r : carriage return

\n: newline

Question 7

What is the format of an HTTP header field?

Answer 7

Header-name: header value

Question 8

HTTP verb

Answer 8

• aka: request method

- state the type of request

Question 9

GET request

Answer 9

used when opening web resources

Question 10

After the HTTP verb, there is a path. What does the path do?

Answer 10

tells server which resources the browser is asking for

Question 11

After the HTTP verb and path, there is the protocol version. What is the protocol version?

Answer 11

tells server how to communicate with the browser

Question 12

What is the structure of the first line of an HTTP request?

Answer 12

HTTP VERB, path, protocol version

Question 13

What does the HTTP Request Host header field specify?

Answer 13

• it specifies the internet hostname and port number of the resource being requested
• tells server which site client is asking for

Question 14

URI

Answer 14

identifies a specific resuorce: page, book, document

Question 15

URL

Answer 15

• type of URI

- tells you how to access the resource: HTTPS, FTP

Question 16

User-Agent

Answer 16

tell server what client software & version is issuing the request: Firefox, Safari, Chrome, etc

Question 17

Accept header field

Answer 17

specifies which document type it is expecting in response

Question 18

Accept-Encoding

Answer 18

restricts content encoding, not the content itself.

• for example, the browser will accept two types of compression if read “: gzip, deflate”

Question 19

Connection header

Answer 19

allows sender to specify options that are desired for that particular connection

• for example, future comms w/ server will reuse current connection if “keep-alive”

Question 20

HTTP Response: Status-Line

Answer 20

• protocol version (HTTP 1.1)
• status code (200)
• relative textual meaning (OK)

Question 21

Status Code: 200

Answer 21

• OK

- resource found

Question 22

Status Code: 301

Answer 22

• Moved Permanently

- resource has been assigned a new permanent URI

Question 23

Status Code: 302

Answer 23

• Found

- temporarily under another URI

Question 24

Status Code: 403

Answer 24

• Forbidden

- client doesn’t have enough privileges, server refuses to fulfill request

Question 25

Status Code: 404

Answer 25

• Not Found

- server cannot find a resource matching the request

Question 26

Status Code: 500

Answer 26

• Internal Service Error

- server does not support the functionality required to fulfill request

Question 27

Cache-Control header

Answer 27

• server informs client about cached content

Question 28

Content-Type header

Answer 28

lets client know how to interpret body of message

Question 29

Content-Encoding header (for HTTP response)

Answer 29

extends content type - for example, “gzip” would mean message body is compressed with gzip

Question 30

Server header

Answer 30

contains the header of the server that generated the content

ex: “Apache/2.2.15 (CentOS)

Question 31

Content-Length header

Answer 31

indicates length of bytes of the message body