App layer Flashcards
application layer
what does a socket do?
sends/receives messages to/from the process
what does an App-Layer protocol define? (4)
- types of messages
- message syntax
- message semantic
-rules for when/how messages are sent/received
what is HTTP
Hypertext transfer protocol
What is the HTTP model?
Client/Server :
client: browser that requests/receives/displays web objects
server: sends objects in response to requests
Is HTTP stateless ? What does that mean?
Is stateless, meaning it doesn´t store any past information about previous requests
What transport protocol does HTTP use?
TCP :
the client is the web browser
the server is the web server
what types of HTTP connections can we have?
Non-presistent or presistent
How much time does it take to get 1 object ? (Non-persistent)
2 RTT + time to transmit file
How much time does it take to get 1 object? (persistent)
as little as 1 RTT
what are the two methods for input ?
POST and URL
post : input form in body of post message
URL : uses GET , input in URL , after ‘
?’
How are Status codes displayed in HTTP responses ?
Protocol -> status code -> status phrase
what does cookies do ?
transfor HTTP into a state oriented protocol , storing protocol endpoints ( maintain state at sender/receiver over multiples transactions)
what does DNS mean?
Domain Name Service
what does DNS do?
Resolve names into ips
what are some DNS services ?
- hostname to ip translation
-host aliasing (resolve complicated names) - mail server aliasing
- load distribuition
is DNS secure?
No, your IP is public, so every server knows who made the query
