Packet Radio - Hitchhikers Guide to becoming a BPQ SysOp

This Hitchhikers Guide to becoming a BPQ SysOp (aka. HG2BPQ) is a compilation of the notes I collected during my journey to set up a BPQ node.
Even though I'm a amateur radio operator since 1976, I was on hiatus for some years and missed the Packet Radio boom of the 80's.
With the encouragement of another OM, I went on this journey to learn what I had missed and I found that there is a lot of information out there, but hardly organized, mostly outdated and not updated. The best one I found so far is from Charles R. Verdon, W5KAV Digital Traffic Network (DTN) but there where still some roadblockers that took me some time to resolve and some are still mysteries which we could chase together
I will not give you here the full recipes, specially regards some of the Raspberry Pi and Linux skills, which you will have to find somewhere else.
The following SysOps (in order of appearance) contributed significantly to my learning:

Eduardo Castillo, LU9DCE
Jean Pierre Roussarie, F1OYP
Red R.R. Tuby, PE1RRR
Brian Rogers, N1URO
Mark Taylor, N5MDT
Aly Badawy, AL0Y
I would also suggest very strongly to subscribe to the BPQ support group https://groups.io/g/bpq32 with a very active community and the extraordinary support from John Wiseman himself and don't forget to check out the links I have put in the reference section at the bottom of this page.
73 and have fun, because that is what Amateur Radio is all about.
May the Layers of the Ionosphere be with You


Configuring message forwarding
(by Aly Badawy, AL0Y)
BPQ differentiates between three types of messages
Flood bulls
Directed Bulls
Personal messages
There is a very small difference between "Personal Messages" and "Directed bulls" that I will be mentioning later, but to keep it simple and to not confuse, let's talk about bulls first.
When you first setup your BBS using BPQ, one of the fields you enter is the BBS HA (Hierarchical Address) route. I will use mine as an example: AL0Y.#NNJ.NJ.USA.NOAM
This field is very important, as this is how the BBS later differentiates between directed bulls and flood bulls. So, let's assume I receive a message on my BBS (locally or forwarded to my BBS), the BBS will then examine the destination flood area. If the message is addressed to @NJ.USA.NOAM, this message will be considered to have reached its flood area (because my BBS is in NJ.USA.NOAM). If the message is addressed to @USA.NOAM, it's also considered to have reached its flood area, because my BBS is in USA.NOAM. Same applied if I received a message for @NOAM.. You get the idea.
So, the 3 previous examples are considered by the BBS to be "FLOOD Bulls"
Now, let's assume I receive a message for KY.USA.NOAM.
Even though I am located in USA.NOAM, this message is directed to only KY state, and not NJ. The BBS considers this a "DIRECTED BULL". Same applies if I receive a message for @CAN.NOAM or even if I receive a message addressed to @EURO, @AUNZ, @SOAM, etc. They are all considered as "Directed BULL". We now know how the BPQ system differentiates between DIRECTED and FLOOD bulls.
But what difference does it make? The difference is how and where the messages are routed.
When the BBS wants to forward a "Flood bulls", it will send it to *ALL* BBSs that have the route in their forward configuration, where "Directed Bulls" are forwarded to *ONLY* one BBS which has the best match for a HR. The best match, is based on WHICH LEVEL of the HR is matched.
So, I usually send all EURO messages to PE1RRR but I have a GB7YEW configured to receive @GBR.EURO. If I have a message for FRA.EURO (and I have no configured BBS to receive FRA), my message will go to PE1RRR for relay, but a message for GBR, will go to GB7YEW since GB7YEW matches 2 levels of the route, but PE1RRR matches only one level.
If I am configuring forwarding with N5MDT, who is in #STX.TX.USA.NOAM. N5MDT and I'm in a different state, but both are in USA.NOAM. So, in my BPQ forwarding configuration for N5MDT, I put "USA.NOAM" in the "FLOOD BULLS". I can also add "WW" in "Flood bulls" since any WW message is a flood bulls by definition. See, we both are in USA.NOAM.WW (if you will).
However, I also want to send him "Directed Bulls" addressed to @TX.USA.NOAM. So, I add "TX.USA.NOAM" in the field of "DIRECTED BULLS and PERSONAL MESSAGES" I also know (by having a conversation with N5MDT) that he has an out let to AR.USA.NOAM and GA.USA.NOAM. Since I don't have any forwarding partner to those states, I can add those HRs for AR, and GA in N5MDT's "directed bulls" field.
Now, let's say I receive a bull directed to "IN.USA.NOAM", and I don't have IN.USA.NOAM in any of my forwarding partners configurations. This message will die on my BBS. the same happens for messages directed to un-recognized areas like "LATNET" for example, but we will get to that in a moment.
I hope the previous explained the difference between Flood and Directed Bulls. Flood are directed to your same area, and are sent to ALL who match. Directed bulls are for areas outside your HR, and are sent ONLY to best match.
So, where do personal messages fit? Personal messages are routed EXACTLY as directed bulls (and hence share same configuration field). But there are two difference still:
if you receive a Personal message on your BPQ BBS, and you don't have a route to forward, your BBS will generate a Service message to the "FROM" callsign informing them that the BBS is unable to forward that message and it may not reach its destination. For directed bulls, a similar message is generated but to the SYSOP of that BBS instead of the bull's originator.
the second difference, is in BPQ, you can choose to "SEND P messages to more than one BBS" This is a checkbox that you can choose in BPQ. Enabling this options sends the P message to ALL matching routes and not only the best match. It adds confidence that the message will be received by allowing multiple paths (in case one route is incorrected, forwarding station across the route is no longer functional, or lost forwarding with another station) Remember that BBSs will not receive a message twice though (they still have same BID)but it allows multiple paths (I recommend having this option enabled)
I mentioned earlier that there are non-recognized (HR-wise) area like LATNET, VKNET, etc. To forward those to a specific station, you will need to add those in the "ATSIGN" field of that station. In BPQ you can also add "ALIASES", so for me, I added the following aliases to my BBS:
AMSAT:WW
ARRL: USA
LATNET:SOAM
VKNET:AUNZ
But note that aliases in BPQ are not a re-write of the HR. It only tells your own BBS to treat LATNET as if it was addressed to SOAM. but it doesn't change that to the receiving station (not as rewrite.sys in FBB where it actually changed the destination)
So, unless your forwarding partner (assuming running BPQ) has configured LATNET as an alias, or added it to some other station's ATSIGN field... messages to @LATNET will die there.
The official document referencing this topic could be found here