Application Layer Flashcards
(37 cards)
What is a Process?
A program running on a computer
What is a socket?
The interface applications use to access the networking layer. Facilitates transmission between the application layer and the transport layer,
What are the two primary transport layer protocols?
TCP and UDP
What is TCP?
Transport layer protocol that provides congestion control, reliable end-to-end service, and establishes a connect between sockets.
What is SSL?
An enhancement to TCP that provides data encryption
The Web’s application-layer protocol?
HyperText Transfer Protocol (HTTP)
What is HTTP?
A protocol that defines the format of messages shared between a client and server and how the messages are shared.
What is HTTP’s underlying transport protocol?
TCP
What are the two types of connections in client-server communication?
Non-persistent connections and persistent connections
Non-persistent connections close after each request/response pair, while persistent connections keep the connection open for multiple requests/responses.
In the context of HTTP, what is the default mode regarding connections?
HTTP uses persistent connections in its default mode
HTTP clients and servers can be configured to use non-persistent connections if desired.
What is the first step in transferring a Web page using non-persistent connections?
The HTTP client initiates a TCP connection to the server on port number 80
Port 80 is the default port for HTTP.
How many TCP connections are generated when a user requests a Web page with 11 objects using non-persistent connections?
11 TCP connections
Each TCP connection transports exactly one request message and one response message.
What happens after the HTTP server sends the response message in non-persistent connections?
The HTTP server tells TCP to close the TCP connection
TCP does not terminate the connection until it confirms that the client received the response message intact.
How do modern browsers handle the retrieval of multiple JPEG objects?
Browsers can open 5 to 10 parallel TCP connections
This allows multiple request-response transactions to occur simultaneously.
What is RTT in the context of client-server communication?
Round-trip time, the time for a small packet to travel from client to server and back
RTT includes propagation delays, queuing delays, and processing delays.
What is the total response time for requesting and receiving an HTML file using non-persistent connections?
Two RTTs plus the transmission time at the server of the HTML file
One RTT is for establishing the TCP connection and one RTT for the request/response.
What are the shortcomings of non-persistent connections?
Connections must be established for each object and each object suffers a delivery delay of two RTTs
This can burden the Web server, especially with many simultaneous requests.
How does HTTP 1.1 handle persistent connections?
The server leaves the TCP connection open after sending a response
This allows multiple requests and responses to be sent over the same connection.
What is pipelining in the context of persistent connections?
Requests for objects can be made back-to-back without waiting for replies to pending requests
This improves efficiency in data transmission.
What is a key feature of HTTP/2 compared to HTTP 1.1?
Allows multiple requests and replies to be interleaved in the same connection
It also includes a mechanism for prioritizing HTTP message requests and replies.
What does DNS do?
Translates host names to IP addresses (e,g, google.com -> 8.8.8.8) and vice versa.
What layer does DNS operate on?
Application layer
How is DNS implemented?
As a distributed database implemented as a hierarchy of many name servers
True/False DNS occurs within routers and switches
False; DNS occurs at the network edge
