Rayanchu and Barua provide another spin on this approach (called DERM). Their approach is similar in that they wish to use and encoded IP address of the input interface in the fragment id field of the packet. Where they differ from Belenky and Ansari is that they wish to encode the IP address as a 16-bit hash of that IP address. Initially they choose a known hashing function. They state that there would be some collisions if there were greater than 2^16 edge routers doing the marking.