10.4 ISDN and Switched 56K Framing

Initially, ISDN B channels (not D channels) should be used. Multiple B channel support is done through multilink support provided for by the WAN Wrapper. Initially, bit-synchronous HDLC framing with NRZ encoding should be used. Transparency should be provided for by the driver or ISDN hardware. It also the responsibility of the ISDN driver or hardware to provide for NRZ encoding, to calculate the Frame Check Sequence (FCS), to add the PPP end flag (0x7E) and to insert any inter-frame time fill. Switched 56K drivers should frame in the same manner as ISDN.