[BBC-Micro] econet bridge protocol

Rob robert at irrelevant.com
Sat Jul 4 21:42:13 BST 2009

There's some discussion on Bridges in here:

They definitely spread information about other reachable networks
based on this paragraph:
"There is a limit of eight on largest number of "hops" a frame could make on
a connected set of networks. If there are more than 8 nets in any possible
route, the protocol used by a bridge to ask all the other bridges where nets
are falls over, because it uses broadcast packets which have a limit of 8
bytes of data associated with them."

Unfortunately it's a bit thin on the detail...

I've not come across anything else, though I was only looking for AUN


2009/7/4 Phil Blundell <philb at gnu.org>:
> Does anybody have documentation on the port &9c protocol used by
> bridges?  Chapter 10 of the MDFS book gives some details but doesn't
> describe the messages with control bytes &80 and &81.
> Observing the single bridge that I have here, at power up it seems to
> send a broadcast with control byte &80, containing in its payload the
> number of its other local network; I guess this is the "reset packet"
> that the MDFS book talks about.
> If I send the bridge one of those packets (cb &80) then it responds with
> a series of packets with control byte &81 and, again, the network number
> of its far side in the payload.  I'm not entirely sure what the meaning
> of these packets is, or how (if at all) I am meant to respond to them.
> Can anybody shed any light on that?  Or, absent any documentation, is
> there anybody with two or more bridges who would be prepared to capture
> some packet dumps showing them talking to each other?
> thanks
> p.
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