Calculate the md5 hash of a string. The hash is a 32-character hexadecimal number. I use it to generate keys which I use to identify users etc. If I add random no techniques to it the md5 generated now will be totally different for the same string I am using.

$result = mysql_query($sql, $db_link);
$num_rows = mysql_num_rows($result);
echo "$num_rows rows found";

we can always fetch from one database and rewrite to another. Here is a nice solution of it.$db1 = mysql_connect("host","user","pwd")
mysql_select_db("db1", $db1);
$res1 = mysql_query("query",$db1);$db2 = mysql_connect("host","user","pwd")
mysql_select_db("db2", $db2);
$res2 = mysql_query("query",$db2);At this point you can only fetch records from you previous ResultSet, i.e $res1 – But you cannot execute new query in $db1, even if you supply the link as because the link was overwritten by the new db.so at this point the following script will fail
$res3 = mysql_query("query",$db1); //this will failSo how to solve that?

take a look below.
$db1 = mysql_connect("host","user","pwd")
mysql_select_db("db1", $db1);
$res1 = mysql_query("query",$db1);

$db2 = mysql_connect("host","user","pwd", true)
mysql_select_db("db2", $db2);
$res2 = mysql_query("query",$db2);

So mysql_connect has another optional boolean parameter which indicates whether a link will be created or not, as we connect to the
$db2 with this optional parameter set to 'true', so both link will remain live.

Now the following query will execute successfully.
$res3 = mysql_query("query",$db1);

By default the maximum size is 2MB. and we can change the following
setup at php.iniupload_max_filesize = 2M

By using
$_SERVER['HTTP_USER_AGENT']
variable.

Answer : C

Explanation:

Virtual circuits (VC)s are identified by DLCIs. DLCI values typically are assigned by the Frame Relay service provider. Frame Relay DLCIs have local significance.  A DLCI identifies a VC to the equipment at an endpoint. A DLCI has no significance beyond the single link. Two devices connected by a VC may use a different DLCI value to refer to the same connection.

Answer : A , D

Explanation:

An IPv6 Unicast address identifies a single network interface. The Internet Protocol delivers packets sent to a unicast address to that specific interface.

Answer : A

Explanation:

Remember,  most network is still build on IPv4 structure and IPv4 is not going away in a hurry… one of the many techniques used to migrate to IPv6 is Tunneling.

Tunneling is a method that a network built on IPv4 structure can be configured to traffic IPv6 packet simultaneously.