while thinking about your last addition,
consider this

open IN,'<1';
while (<IN>) {
        $a = 1 if /Endpoint/;
        $b = 1 if /-/ and $a;
        if($a and $b){
                if(/^\s+(.+)\s\(/){
                        $h{$1}{'x'} = ++$x if ! exists $h{$1};
                        $r .= $h{$1}{'x'}.".";
                }
        }
        $a = 0, $b = 0, ++$r{$r}, $r = '' if /data arrival time/ and $
+b;
}

close IN;

foreach (sort keys %r) {
        print "$_: $r{$_}\n";
}
[download]

algorithm:
find /Endpoint/
find /-/
assign every line pattern a unique code from 1 towards infinity
form the unique string number, count it as one occurence
find /data arrival time/
which will result in something like this:

1.2.2.3.3.4.4.5.6.7.8.9.10.10.11.11.12.12.: 8
[download]

which means I copied your example file eight times in my '1' file
update
regarding your patterns:
they are quite confusing
why did you pick up the middle line to form your pattern?
Please consider this snippet above, maybe it will suit your needs as well?
update 2
have you tried this soultion? has it worked? please tell.