Chapter 4. Applications
Transparent Application
In cases when the user protocol is not supported by the FSU, the transparent mode may be used. Transparent bit-oriented protocol (BOP) or transparent asynchronous protocol may be selected. This can be used for point-to-point connections only because the FSU is transparent to the protocol address formats.
In the transparent BOP protocol, the FSU accepts an HDLC-like protocol and encapsulates the information field of the HDLC frames, transporting them across the frame relay network to the specified virtual circuit and remote FSU port number. The incoming frames must be spaced with at least one flag byte (0x7E) and contain two bytes of CRC16 at the end of each frame.
Asynchronous protocols are supported by using the transparent async mode. The FSU buffers async characters and encapsulates the data portion of each character for transport across frame relay using a programmable DLCI and remote FSU port number.
See Figure 4-5 and Table 4-D for an example of a transparent BOP configuration. See Figure 4-6 and Table 4-E for an example of a transparent asynchronous application.
DTE1
HDLC
Router
FSU
Figure 4-5
Transparent BOP Application
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