anchor.diff:  
           base_pkt  = Ether()/IP(dst="48.0.0.1")/TCP(dport=80,flags="S")
   
  -        vm = CTRexScRaw( [ STLVmFlowVar(name="ip_src",                              <1>
  +        vm = STLScVmRaw( [ STLVmFlowVar(name="ip_src",                              <1>
                                           min_value="16.0.0.0", 
                                           max_value="18.0.0.254", 
                                           size=4, op="inc"),
  
positive.code:                IP(src="16.0.0.1",dst="48.0.0.1")/
                 UDP(dport=12,sport=1025)/('x'*20)
  
          vm = CTRexScRaw( [ STLVmFlowVar(name="mlabel",                                 <1>
                                          min_value=1, 
                                          max_value=2000, 
                                          size=2, op="inc"), # 2 bytes var               <2>
  
negative.code: 
          base_pkt  = Ether()/IP(dst="48.0.0.1")/TCP(dport=80,flags="S")
  
          vm = STLScVmRaw( [ STLVmFlowVar(name="ip_src",                              
                                          min_value="16.0.0.0", 
                                          max_value="18.0.0.254", 
                                          size=4, op="inc"),
  