UI Broadcasting

Name

BCAST -- UI Broadcasting.

Description

XRPi has the ability to "re-broadcast" a received UI frame on several ports at once. This can be thought of as a "one-to-many" PIPE, but there are subtle differences:

Whereas pipes conduct all frames of the selected type(s), virtually regardless of source and destination addresses (unless they are selective pipes), the broadcast function acts only upon UI frames, and only if the source and destination addresses match those specified by the sysop.

Another difference is that frames may be broadcast to different groups of ports depending on the destination address. For example, FBB unproto headers from a BBS may be rebroadcast on certain user-access ports only, while mail beacons may be distributed to a different, possibly overlapping, set of ports.

You may alternatively use this feature as a "filtered pipe" between two ports, allowing only UI frames with acceptable source and destination callsigns to pass through.

Note that this feature does not require a "connection" to XRPi, it is purely an unconnected mode. It was developed to allow BBS's to distribute mail beacons and "unproto" mail headers. You may use it (or not) how you wish.

You should be aware that broadcast traffic takes precedence over all other frames, so an excessively high level of broadcast activity may cause other outbound traffic on the destination port to be delayed. However, it is unlikely that anyone will notice this effect unless the channel is seriously overloading.

Broadcasting is controlled by two keywords in each PORT section of the XROUTER.CFG file. The first keyword is BCAST, which is used to specify the destination addresses to be broadcasted.

For example, BCAST=MAIL,FBB will re-broadcast received non-digipeater UI frames addressed either to FBB or MAIL. The frames addressed to FBB will be broadcast on all ports which have FBB in their BCAST list, and those addressed to MAIL will be broadcast on all ports which have MAIL in the BCAST list. If no matching ports are found, the frame is broadcast only on the port upon which it is received. If you don't need the broadcast function, simply omit (or comment out) the BCAST directive.

The second keyword is BCFROM, which is used to specify a list of callsigns from whom frames will be accepted for broadcast. You may use this to restrict the broadcast facility to certain senders only.

BCFROM applies only to frames *directly* received on the port for which it is specified. e.g. BCFROM=GB7PZT,GB7MAX stipulates that only frames from GB7MAX and GB7PZT will be accepted for broadcast. If the keyword is omitted, the broadcast facility is unrestricted. For both keywords, the list of callsigns must be separated by commas, and must include no spaces.

Caveats

Be careful not to configure BCAST and PIPE together in a way which causes infinite loops. This is a common cause of crashes.

See also

PIPES(9) -- Frame Pipes.
XROUTER.CFG(8) -- Main Configuration File.