Terminology » GFP-T vs. GFP-F: Understanding the Differences

GFP-T vs. GFP-F: Understanding the Differences

gfp gfp-t gfp-f fiber optic networking

This article compares GFP-T and GFP-F modes, explaining the key differences between them. GFP stands for Generic Framing Procedure, and these modes are used to carry client data within GFP frames.

GFP-F is generally used for most packet data types, while GFP-T is typically used for 8B/10B coded signals.

GFP-F Mode

  • GFP-F maps each client frame into a single GFP frame.
  • GFP-F (Frame-Mapped GFP) is used when the client signal is already framed or packetized by the client protocol.
  • It’s well-suited for PDU-based protocols like Ethernet, IP, MPLS, or HDLC-based protocols such as PPP.
  • The client PDU is placed directly into the GFP payload field.

GFP-T Mode

  • GFP-T allows mapping multiple 8B/10B block-coded client data streams into an efficient 64B/65B block code for transport within a GFP frame.
  • GFP-T stands for Transparent GFP.
  • It’s suitable for protocols that directly leverage physical layer capabilities.
  • GFP-T is transparent to codes like 8B/10B, GbE, FICON, ESCON, DVB, etc.
  • GFP-T doesn’t necessarily require the entire PDU to be received.

GFP-F versus GFP-T

Figure 1 depicts GFP-F and GFP-T frame structures.

GFP-T vs. GFP-F: A Detailed Comparison

The following table highlights the key differences between GFP-T and GFP-F modes:

SpecificationsGFP-TGFP-F
Full formTransparent GFPFrame-mapped GFP
FunctionMaps bytes to SONET framesMaps frames (e.g., Ethernet) to SONET frames
Protocol transparencyHighLow
EfficiencyLowHigh
Encapsulation protocol levelLayer-1 (PHY)Layer-2 (PDU)
Isocronic or delay sensitiveYESNO
Optimized forSAN, DVBEthernet
Statistical multiplexing of several client signalsNOYES
SAN transportYESNO
Ethernet transportPOSSIBLEOPTIMUM