HTTP Of Application Layer

Question 1

What connection type does HTTP use?

Answer 1

TCP

Don’t want to lose data

Question 2

What is the life cycle of HTTP?

Answer 2

1. TCP connection established
2. Server accepts connection
3. HTTP messages exchanged
4. Connection closed

Question 3

What is RTT?

Answer 3

Round trip time

Time between initiating request and receiving response

Question 4

What is the RTT for HTTP?

Answer 4

1 RTT for initiating TCP connection
1 RTT for HTTP request and 1st few bytes

Total time = 2RTT + object transmission time

Question 5

What is persistent HTTP and it’s RTT?

Answer 5

One object fetched per socket

22RTT + object transmission time

Question 6

What is non-persistent HTTP and it’s RTT?

Answer 6

Multiple objects sent over single persistent HTTP connection

12RTT + object transmission time

Question 7

What are the 2 HTTP message structures?

Answer 7

Request and response

Question 8

What are the 5 types of HTTP request messages and their functions?

Answer 8

GET: retrieve info
POST: submit data to server
PUT: save object at location 
DELETE: delete object at location
HEAD: retrieve resource info

Question 9

What are the 2 ways of optimising HTTP?

Answer 9

1. Pipelining persistent HTTP: allows multiple requests at once with parallel sockets for each member of queue
2. Multiplexing: sending different requests/responses on same TCP connection

Question 10

What are cookies?

Answer 10

Stored on client side
Have ID
Stored on server side in backend database
Helps track state of exchange

Question 11

What is a web cache?

Answer 11

Used if web server at a big distance from client

Browser points to cache, if object in cache return request, if not go to main web server

Question 12

What is a conditional GET?

Answer 12

Only fetches object is modified past a certain date

Avoids sending original object if updates version exists in cache

If not updated, updated version sent to cache then cache updates and sends on