EXFO FTB-8510B Guia Del Usuario página 1301

Glossary
Next-Gen - Generic Framing Procedure (GFP)
Functionally, GFP consists of both common and client-specific aspects.
Common GFP aspects apply to all GFP-adapted traffic (i.e., both GFP-F and
GFP-T) and cover functions such as packet data unit (PDU) delineation,
data link synchronization and scrambling, client PDU multiplexing, and
client-independent performance monitoring. Client-specific aspects of GFP
cover issues such as mapping of the client PDU into the GFP payload,
client-specific performance monitoring, as well as operations,
administration, and maintenance (OA&M). This is illustrated in figure Client
Signal Mapping over GFP on page 647.
GFP Frame Structure
As illustrated in figure below, Two basic GFP frame types have been
defined: GFP client frames and GFP control frames. GFP client frames are
categorized into two types: client data frames (CDFs) and client
management frames (CMFs). CDFs are used to transport the client data,
while CMFs are used to transport information associated with the
management of the client signal or GFP connection.
As for GFP control frames, at this time, only one category has been defined
by the standard so far; i.e., GFP idle frames.
GFP Frames Types
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SONET/SDH Application