Generic framing procedure
Generic Framing Procedure ( GFP ) is a multiplexing technique that is defined in ITU-T G.7041. It enables data streams from applications from a higher network layer to be routed via a transport network such as SDH / SONET , whereby the packet sizes can be variable.
Variations
The packets can be Protocol Data Unit (PDU) -oriented, such as IP / PPP or Ethernet Media Access Control , or they can be block-oriented, such as Fiber Channel . GFP has two modes: Generic Framing Procedure - Framed (GFP-F) and Generic Framing Procedure - Transparent (GFP-T):
- GFP-F maps each application package into a single GFP package. GFP-F is used when packaging from the application protocol.
- GFP-T, on the other hand, allows multiple 8B / 10B block-coded application data streams to be efficiently packed into a common 64B / 65B block code that is transported with GFP.
GFP uses a length / HEC-based mechanism that is more robust than that of High-Level Data Link Control (HDLC), which is based on single octet flags.
Nortel implements two types of GFP packages: a GFP client frame and a GFP control frame. The former can in turn be a data or a management frame for the application and always transports application data. The control frame, on the other hand, transports point-to-point management information such as signal loss, etc. It can also only contain header information without user data in order to fill gaps in the data stream of the application if it sends more slowly than the medium can transport. One also speaks of idle frames .
Packet format
A GFP package consists of:
- Core header
- Data header
- GFP payload
- Optional Frame Check Sequence (FCS)
- Optional extension header.
Modes
- Framed GFP (GFP-F) makes optimal use of bandwidth, at the expense of latency. It encapsulates complete application packages (e.g. Ethernet) and provides them with a GFP header.
- Transparent GFP (GFP-T) is used to transport block-coded data such as Gigabit Ethernet , Fiber Channel , ESCON , FICON and Digital Video Broadcasting (DVB) with low latency. Smaller groups of 8B / 10B symbols may also be transported here instead of waiting for a full packet size to be reached.
Web links
Individual evidence
- ↑ Archive link ( Memento of the original from May 1, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
