App layer

Question 1

what does a socket do?

Answer 1

sends/receives messages to/from the process

Question 2

what does an App-Layer protocol define? (4)

Answer 2

• types of messages
• message syntax
• message semantic
  -rules for when/how messages are sent/received

Question 3

what is HTTP

Answer 3

Hypertext transfer protocol

Question 4

What is the HTTP model?

Answer 4

Client/Server :
client: browser that requests/receives/displays web objects
server: sends objects in response to requests

Question 5

Is HTTP stateless ? What does that mean?

Answer 5

Is stateless, meaning it doesn´t store any past information about previous requests

Question 6

What transport protocol does HTTP use?

Answer 6

TCP :
the client is the web browser
the server is the web server

Question 7

what types of HTTP connections can we have?

Answer 7

Non-presistent or presistent

Question 8

How much time does it take to get 1 object ? (Non-persistent)

Answer 8

2 RTT + time to transmit file

Question 9

How much time does it take to get 1 object? (persistent)

Answer 9

as little as 1 RTT

Question 10

what are the two methods for input ?

Answer 10

POST and URL
post : input form in body of post message
URL : uses GET , input in URL , after ‘
?’

Question 11

How are Status codes displayed in HTTP responses ?

Answer 11

Protocol -> status code -> status phrase

Question 12

what does cookies do ?

Answer 12

transfor HTTP into a state oriented protocol , storing protocol endpoints ( maintain state at sender/receiver over multiples transactions)

Question 13

what does DNS mean?

Answer 13

Domain Name Service

Question 14

what does DNS do?

Answer 14

Resolve names into ips

Question 15

what are some DNS services ?

Answer 15

• hostname to ip translation
  -host aliasing (resolve complicated names)
• mail server aliasing
• load distribuition

Question 16

is DNS secure?

Answer 16

No, your IP is public, so every server knows who made the query