The Internet has shifted to the current 128-bit IP protocol but some networksare still lagging behind. This talk is about issues with the dual stackscenario, changes to protocols needed and real world experiences ofimplementations. The Internet has shifted to the current 128-bit IP protocol but some networksare still lagging behind. This talk is about issues with the dual stackscenario, changes to protocols needed and real world experiences ofimplementations. SIP was written for both IPv4 and IPv6, but not for both at the same time. Thetalk is about experiences from SIPit tests, code and real worldimplementations on mobile networks - what happens with your software whenbeing faced with both protocols? Can this affect your old IPv4-onlyimplementation as well? What is the best option when my software crashes andgenerates core dumps?