The concept of Software-Defined Networking (SDN) has been successfully applied to data centers and campus networks but it has had little impact in the fixed wireline and mobile telecom domain. Although telecom networks demand fine-granular flow definition, which is one of SDN's principal strengths, the scale of these networks and their legacy infrastructure constraints considerably limit the applicability of SDN principles. Instead, telecom networks resort to tunneling solutions using a plethora of specialized gateway nodes, which create high operation cost and single points of failure. We propose extending the concept of SDN so that it can tackle the challenges of the telecom domain. We see vertical forwarding, i.e. programmable en- and decapsulation operations on top of IP, as one of the fundamental features to be integrated into SDN. We discuss how vertical forwarding enables flow-based policy enforcement, mobility and security by replacing specialized gateways with virtualized controllers and commoditized forwarding elements, which reduces cost while adding robustness and flexibility.