This topic provides information about interface options for connecting equipment to a frame-relay network.
The equipment that attaches to a frame-relay network,
such as an IBM® 
iSeries™ system, 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 iSeries system supports three physical interface types 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) (CRTNWIFR) command
Use the 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. Table 1 lists the supported physical interfaces, cable lengths, network interface (NWI) clock parameters, and the maximum data transmission speed available for each interface:
| 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 |
- *LOOP requires DCE support for looped clocking.
- 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. Possible values are:
- *MODEM
- The default value. The modem provides the clocking.
- *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 supported by the modem.
- *INVERT
- All three interfaces support *INVERT.