The Generic Framing Procedure(GFP) is used in Next-Generation SDH ( NG-SDH) and Optical Transport Network( OTN) to adapt discontinuous data streams, such as those encountered in frame-based services, to the continuous data stream from Synchronous Digital Hierarchy (SDH).
The adaptation problem occurs for service providers that want to transmit Ethernet over existing SDH networks or optical networks( ON), as in metro Ethernet networks. The GFP procedure, specified by the International Telecommunication Union( ITU-T) in Recommendation G.7041, describes numerous standardized and transparent mapping techniques. A distinction is made between GFP-F for frame-mapped and GFP-T for transparent-mapped.
GFP-F was developed for frame-structured services such as Ethernet frames, which can be transferred into suitable formats for Virtual Concatenation Groups( VCG). The frame mode operates with adaptive data rate, which adjusts to the data transfer rate. This allows network operators to modulate the data streams and adapt them to the customer's agreed service level agreements( SLA). In transparent mode, on the other hand, the incoming data stream is integrated directly into the SDH data stream with minimum latency.