Source Packet Routing in Networking (SPRING) architecture for unicast traffic has been proposed to cope with the use cases in traffic engineering, fast re-reroute, service chain, etc. It can leverage existing MPLS dataplane without any modification. In fact, the label stack capability in MPLS would have been utilized well to implement flexible path programming to satisfy all kinds of requirements of service bearing. But in the distributed environment, the flexible programming capability is difficult to implement and always confined to reachability. As the introducing of central control in the network, the flexible MPLS programming capability becomes possible owing to two factors: 1. It becomes easier to allocate label for more purposes than reachability; 2. It is easy to calculate the MPLS path in a global network view. Moreover, the MPLS path programming capability can be utilized to satify more requirements of service bearing in the service layer which is defined as service-oriented MPLS path programming. This document defines the concept of MPLS path programming, then proposes use cases, architecture and protocol extension requirements in the service layer for the Source Packet Routing in Networking (SPRING) architecture.