Physical environment for frame relay

 

The equipment that attaches to a frame-relay network, such as a System i™ model, is the terminal equipment (TE). A frame-relay network node is a frame handler (FH).

The connection from the TE to the FH normally exists through a data service unit (DSU) and channel service unit (CSU) pair. This DSU and CSU pair converts the TE physical interface to the FH interface that is used by the frame-relay network.

The System i platform supports these types of physical interfaces for attachment to the DSU and CSU pair:

• EIA RS-449, ITU-T V.36.

• ITU-T X.21.

• ITU-T V.35.

 

Create Network Interface (Frame Relay) command

Use the Create Network Interface (FR) (CRTNWIFR) command to specify both the physical interface (INTERFACE parameter) and data transmission rate (LINESPEED parameter). The type of physical interface that you specify depends on the cable that you use. The following table lists the supported physical interfaces, cable lengths, network interface (NWI) clock parameters, and the maximum data transmission speed available for each interface:

Table 1. Device types 2699, 2721, 2742, 2745, 2771, and 2793 high-speed communications IOAs

Physical interface	Cable length	NWI clock parameter	Maximum data transmission rate
*RS-449	6.1 m (20 ft)	*MODEM, *LOOP, *INVERT	2 048 000 bps
	15.2 m (50 ft) 24.4 m (80 ft) 45.7 m (150 ft)	*MODEM	64 000 bps
	15.2 m (50 ft) 24.4 m (80 ft) 45.7 m (150 ft)	*LOOP	2 048 000 bps
*V.35	20 ft (6.1 m) 50 ft (15.2 m)	*MODEM, *LOOP, *INVERT	2 048 000 bps
	24.4 m (80 ft)	*MODEM, *LOOP, *INVERT	64 000 bps
*X.21	6.1 m (20 ft)	*MODEM	2 048 000 bps
	15.2 m (50 ft)	*MODEM, *INVERT	64 000 bps

Notes:

1. *LOOP requires DCE support for looped clocking.

2. Data transmission rates greater than 512 000 bps might require *LOOP or *INVERT clocking.

On the frame-relay-supported hardware, the specified value for the INTERFACE parameter must match the physical interface and cable that you attached to the input-output adapter (IOA).

 

CLOCK parameter

The CLOCK parameter on the CRTNWIFR command specifies the method by which the clocking function is provided for the network interface. The parameter supports the following values:

*MODEM

The default value. The modem provides the clocking.

*LOOP

Loop indicates that the data circuit-terminating equipment (DCE) received clock is looped back to the DCE on the data terminal equipment (DTE) transmit clock. This value improves high-speed data transmission, but it is valid only if it is supported by the modem.

*INVERT

All three interfaces support *INVERT.

 

Parent topic:

Frame relay