Specifications

2-12
Reference Guide
Model No.
Running Head
Data Modules and Applications Applications
2.4.4 FRAD Card
The 8231 Frame Relay Assembler/Disassembler (FRAD) user card provides eight ports for
transport of low speed data across Frame Relay Networks. The FRAD can encapsulate HDLC
protocols (such as SDLC). Each port can be independently configured for asynchronous,
transparent synchronous data or HDLC.
When taking data from the on-board RS-232 port, the FRAD card supports speeds of 2.4, 4.8,
9.6, 14.4, 19.2, 28.8 and 38.4 Kbps, independently configured on a per port basis. The
aggregate Frame Relay encapsulated traffic coming out of the WAN card can be configured to
transmit at 56 or 64 Kbps.
When processing HDLC data, the flags and the CRC are removed before assembling the
frames. For asynchronous data, start and stop bits are removed before the frames are
assembled. Other data is treated as a transparent data stream and all bits will be encapsulated
into transmitted frames. The FRAD card supports proprietary sub-addressing over a PVC.
This sub-addressing is transparent to the Frame Relay Transport Network, but allows multiple
ports on a single FRAD to share the same PVC, resulting in lower costs.
The FRAD card also maintains performance statistics detailing the number of frames
transmitted, number of frames received, number of octets transmitted, number of octets
received, number of frames dropped before being received during a 15 minute interval and a
status field describing the conditional that caused the dropped packets (DTE port down, loop
back in progress or port in standby). All these performance statistics are gather for 24 hours,
in 1 hour intervals. The FRAD card also provides test frame generators for additional
diagnostics.
In the application represented by the Figure 2-6, the router on the left (at a remote office) is
connected to the system via the FRAD card at 9.6Kbps, along with other voice traffic from a
PBX. The router traffic is mapped onto a DS0 on the T1 link to the Central Office where it is
separated by a DACS and directed towards a Frame Relay network and switched/routed to the
destination router at the headquarters. See Figure 2-6 for an illustration of the FRAD Card’s
capabilities.