HTTP has a mechanism that allows a cache to verify that its objects are up to date. The mechanism is( ).
A. persistent connections
B. cookies
C. Web Caching
D. conditional GET
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In the following descriptions about persistent connection, which one is not correct?( )
A. The server leaves the TCP connection open after sending a response.
B. Each TCP connection is closed after the server sending one object.
C. There are two versions of persistent connection: without pipelining and with pipelining.
D. The default mode of HTTP uses persistent connection with pipelining.
FTP uses two parallel TCP connections to transfer a file, there are( ).
A. control connection and data connection
B. receiving connection and sending connection
C. client connection and sever connection
D. program connection and process connection
If the status code in HTTP response message is 404, it means( ).
A. Request succeeded.
B. The requested document doesn’t exit on this server.
C. This is a generic error code indicating that the request could not be understood by the server.
D. Requested object has been permanently mover.
DNS means ( ).
A. Data Name System
B. Data National System
C. Domain Name System
Domain National System
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