In HTTP response message, if the status code is 404, it means ( ).
A. request succeeded and the information is returned in the response
B. requested object has been permanently moved
C. the requested HTTP protocol version is not supported by the server
D. the requested document does not exist on this server
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( )is a network entity that satisfies HTTP requests on the behalf of an origin Web server.
A. proxy server
B. local server
C. DNS server
D. Web server
In the following four options about web cache, which one is not correct?( )
A web cache is both a server and a client at the same time.
B. A web cache is purchased and installed by an ISP.
C. A web cache can raise the response time for a client request.
D. A web cache can reduce traffic on an institution’s access link to the Internet.
FTP uses two parallel connections to transfer a file, they are ( ).
A. TCP and UDP connection
B. connection with pipelining and without pipelining
C. control an data connection
D. client-server and browser-server connection
In the following four services, which one can not provide by DNS?( )
A. Host aliasing
B. Mail server aliasing
C. translate hostname to IP addresses
D. translate MAC addresses to IP addresses
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