head -25000000 /var/sipenv-91.121.75.124/log/sip.log.0 | perl -e '
  $answ1="SIP/2.0 100 Your Re-INVITE is received";
  $answ2="SIP/2.0 488 Your Re-INVITE is ignored";
  $n=1;
  while(<>)
  {
    #03 Feb 16:37:39.932/GLOBAL/ser[76763]: SENDING message to 83.77.6.211:5060:
    #03 Feb 16:37:40.035/GLOBAL/ser[76765]: RECEIVED message from 84.73.184.232:64309:
    if(/^\d\d ... ..:..:..\.\d\d\d.*: (SENDING message to|RECEIVED message from) .*:[\r\n]*$/)
    {
      $h1=$_;
      $nh1=$n;
    }
    #See http://www.ietf.org/rfc/rfc3261.txt [Page 253]
    if(/^(SIP\/2.0|INVITE|ACK|BYE|CANCEL|REGISTER|OPTIONS|INFO|NOTIFY|SUBSCRIBE) /)
    {
      $h2=$_;
      $nh2=$n;
    }
    if(/^Call-ID: /)
    {
      $id=$_;
      $nid=$n;

      if($h2=~/^(BYE|SIP\/2.0 \d\d\d Your Re-INVITE is) /)
      {
        if($nid-$nh1<=25 && $nid-$nh2<=25 && $nh2==$nh1+1)
        {
          $h2=~s/[\r\n]//g;
          $id=~s/[\r\n]//g;
          $id=~s/^Call-ID: //;
          #
          $h1=~/^(\d\d) (...) (..):(..):(..)\.(\d\d\d).*: (SENDING|RECEIVED) message (to|from) (.*):[\r\n]*$/;
          $dd=$1;
          $mmm=$2;
          $hh=$3;
          $mm=$4;
          $ss=$5;
          $ms=$6;
          $dir=($8 eq "from")?"R":"T";
          $comm=$9;
          $time=$hh*3600+$mm*60+$ss+$ms/1000;
          #
          if($h2 eq $answ1)
          {
            $call{$id}=$time;
            $nansw1++;
          }
          else
          {
            if(defined $call{$id})
            {
              if($h2 ne $answ2)
              {
                printf "%s %s %s:%s:%s %9.4f %s\n",$mmm,$dd,$hh,$mm,$ss,$time-$call{$id},$h2;
              }
              delete $call{$id};
            }
          }
          #printf "%s %02d %02d:%02d:%02d.%03d,%s,%s,%s,%s\n",
          #  $mmm,$dd,$hh,$mm,$ss,$ms,$id,$dir,$comm,$h2;
        }
        else
        {
          #printf "\nERROR: headers of Call-ID are not found\n";
          #exit;
        }
      }
    }
    $n++;
  }
  #foreach $id (keys %call)
  #{
  #  print $call{$id}." ".$id."\n";
  #}
'