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Chapter 1 Introduction Installation and Operation Manual

1-22 Functional Description Egate-100 Ver. 4.0

The Payload Area contains between 4 and 64 bytes, according to the following:

Figure

1-15. GFP Encapsulation – Payload Area

• PTI – Payload Type Identifier – indicates the content of the GFP frame: user

frame or management frame (Egate-100 does not generate management

frames in the Tx direction)

• PFI – indicates whether the packet includes PFCS

• EXI – indicates the type of extension header encapsulated in the frame.

Egate-100 supports transmission of a Null extension header (i.e., no

extension header is added)

• UPI - indicates the type of user data encapsulated in the GFP format.

Egate-100 transmits an Ethernet-over-GFP payload identifier when the GFP

frames are user frames. When there is no user packet to be transmitted over

GFP, Egate-100 generates idle packets.

Idle packets - The GFP Idle frame is a special four-octet GFP control frame

consisting of only a GFP Core Header with the PLI and cHEC fields set to 0. These

frames are generated by the transmitter in order to keep the frame-delineation

mechanism in the far-end receiver in a sync state.

The GFP signal is mapped into TDM according to the following. The procedure of

mapping the GFP packets over the PDH signals is described in the G.8040

standard.

• The PDH signal works in multiframe mode: CRC-4 multiframe mode for E1 (31

timeslots) and ESF framing mode for T1 (24 timeslots) are supported

• The first timeslot in each multiframe is used for transferring the VCAT header

information

• In all other timeslots there is user data after the encapsulation of GFP

according to G.7041 (as described above).

The VCAT header information is the LCAS CONTROL packet, as described in the

G.7043 standard. One control packet is transmitted in a period of

16 multiframes.

Egate-100 can work as a non-LCAS transmitter if all the fields such as MST,

RSACK, SQ, GID, CONTROL & CRC & MFI2 MSB are set to zero. The MFI 1

parameter is incremented in a round-robin manner.

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RAD Data comm 100 Spezifikationen Seite 54