Legacy Data System Reference - Comtech EF Data

1.2 NetPerformer Support of HDLC
HDLC Protocol
The NetPerformer’s HDLC driver is a transparent driver developed to support all HDLClike
protocols. It does not interpret or alter any bits in the ADDR, CTRL and DATA fields.
This driver has the following characteristics:
• The maximum frame size is 8200 bytes.
• Frame length should be a multiple of 8 bits, with a minimum length of 16 bits.
• Flags are stripped before transmission and regenerated at the remote end.
• Two coding modes: normal (NRZ) or NRZI.
• Two idle modes: FLAG or MARK.
The HDLC driver is used when a WAN/user port is configured with the HDLC or X.25
protocol. In the case of X.25, the HDLC driver:
• Performs flag and CRC stripping
• Integrally copies the X.25 into a Frame Relay frame (LAPB header and data),
• In the case of FRF.3 Annex F encapsulation, adds a Frame Relay header (2 bytes
of DLCI) and a 6-byte frame identifier to the frame,
• In the case of FRF.3 Annex G encapsulation, encapsulated all frame types that
are received on the HDLC port (INFO, UI, SUPERVISOR).
NOTE: A PVC must be configured to transport the encapsulated X.25 data to the
remote side. For details, refer to the WAN/Frame Relay module of this document
series. Configuration of an X.25 data port is dealt with in the chapter
“X.25 Protocol” on page 9-1.
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