anchor.diff:  
   ==== Tutorial: advanced simulator 
   
  -TBD need to update information here 
  -
   *Goal*:: Use the TRex ASTF advanced simulator.
   
   It is like the simple simulator but simulate multiple templates and flows exacly like TRex server would do with one DP core 
  
positive.code: 
  We are using for the first version the same STF python API framework, we are working to move to interactive mode like the STL mode
  
  image::images/trex_control_plane_modules.png[title="RPC Server Components",align="left",width={p_width}, link="images/trex_architecture_01.png"]
  
  *File*:: link:{github_stf_examples_path}/stf_tcp.py[stl_tcp.py]
  
  
negative.code: 
  ==== Tx Scale to millions of flows
  
  image::images/t_c5.png[title="TCP Tx side",align="center",width={p_width}, link="images/t_c5.png"]
  
  Most TCP stacks have an API that allow the user to provide his buffer for write (push) and the TCP module will save them until the packets are acknowledged by the remote side. Figure 4 shows how one TX queue of one TCP flow looks like on the Tx side. This could create a scale issue in worst case. Let's assume we need 1M active flows with 64K TX buffer (with reasonable buffer, let's say RTT is small). The worst case buffer in this case could be
  1M x 64K * mbuf-factor (let's assume 2) = 128GB. The mbuf resource is expensive and needs to be allocated ahead of time.
  