Web Architecture

Question 1

Which layers do these fall into?

FTP, UDP, IP, Ethernet, TCP, SMTP

Answer 1

FTP - Application
UDP - Transport
IP - Network
TCP - Transport
Ethernet - Network Interface
SMTP - Application

Question 2

What must HTTP provide?

Answer 2

• A subset of the file transfer functionality
• The ability to request an index search
• Automatic format negotiation
• The ability to refer the client to another server

Question 3

4 properties of HTTP:

Answer 3

• HTTP is an application-level protocol
• HTTP is a request-response protocol
• HTTP is a synchronous protocol
• HTTP is a stateless protocol

Question 4

URL and URI

Answer 4

URL - Used to uniquely identify a resource over the web
URI - String of characters that unambiguously identifies a particular resource
URL is a subset of URI

Question 5

What is in a HTTP request

Answer 5

• Request Line
• Header
• Empty line
• Message Body

Question 6

Main http methods?

Answer 6

GET Get resource from the server
POST Used to post the data up to the Web server
HEAD Get the header that a GET request would have obtained
PUT Ask the server to store the data
DELETE Ask the server to delete the data

Question 7

3 properties of a http request line?

Answer 7

• Request Method
• Resource
• Protocol Version

Question 8

What did the HTTP updates add?

Answer 8

HTTP 0.9
• Only GET method
HTTP 1.0
• Adds HEAD and POST
• Separate connection to the same server is made for every resource request
HTTP 1.1
• Adds OPTIONS, PUT, DELETE, TRACE, and CONNECT
• Can reuse a connection multiple times!
HTTP 2.0
• Allows the server to "push" content.
• respond with data for more queries than the client requested
HTTP 3.0
• Faster Connection time
• Runs over UDP

Question 9

What is a HTTP header?

Answer 9

Colon-separated key-value pairs

Terminated by a carriage return (CR) and line feed (LF) character sequence

Question 10

What are the HTTP request headers?

Answer 10

Host
Accept
Content-Type
Cookie
User-Agent

Question 11

What does a HTTP header empty line mean?

Answer 11

Must consist of only

Must not contain other whitespace

Question 12

What does a HTTP request message body contain?

Answer 12

• Optional

* Useful for post and put

Question 13

What are the HTTP response parts?

Answer 13

• Status Line
• Header
• Empty line
• Message Body

Question 14

What is a response status line?

Answer 14

Contains:
• Version
• Status Code

Question 15

What are the categories of HTTP status codes

Answer 15

1xx informational response
2xx successful
3xx redirection
4xx client error
5xx server error

Question 16

Examples of HTTP response headers?

Answer 16

Age
Date
Server
Last-Modified
Content-Length
Content-Type

Question 17

What is the HTTP response message body?

Answer 17

• Contains the actual data

* May be HTML but also other data

Question 18

Summarise HTTP

Answer 18

1) User issues URL from a browser
2) Browser sends a request message
3) Server maps URL to a file or program under the document directory
4) Server returns a response message
5) Browser formats the response and displays