This document describes SPP4 v.1.0, a signalling protocol implemented on Programmable Protocol Processing Pipeline (P4) platform. Protocol has been implemented on P4 v.1. It is expected that P4 v.2 will use a modified version of this protocol to support new features. Current version of the signaling protocol allows P4 boards to synchronize their activities. Protocol Boosters model is supported and it is assumed that the mechanism modules are already available at each of the P4 enhanced nodes. Providing the mechanism modules from by the end user is not supported yet. The signaling protocol is specified to support non-transparent boosters (i.e. boosters that require deboosters). If only transparent boosters are used (i.e. those that can operate without debooster), some of the features may be unnecessary. The existing implementation can work with transparent boosters but it will have more overhead than necessary. This document covers protocol specification, interaction between signaling protocol and policy modules and software architectures of current implementation. The purpose of this document is to explain, not to formally specify the SPP4.