title: PCIe peer to peer communication
body: <p>Can two independent devices(endpoints) communicate with each other without Root Complex being involved in PCIe (according to PCIe specification yes but how)?</p>
  
  <p>How can one endpoint know address of other endpoint in case of memory and IO transactions?</p>
  
  <p>How are the packets routed by switch between two downstream ports?</p>
  
  <p>Thanks and regards</p>