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<title>Forward protocol (Appendix 9)</title>
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<h1 align="Center"> FBB forward protocol<small>.</small> </h1>
<p align="Center"> (Appendix 9) </p>
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<pre> FBB software includes two forward protocols. The first one is standard with<br>MBL/RLI protocol. The second one was developed to allow <br>efficiency, particularly on long links where propagation time of data are<br>long. The exchange of commands is reduced to a minimum, and not acknowledged<br>to get time. The data transfer direction is changed every block of data, a<br>block of data holding up to five messages. This uses the "pipeline" effect of<br>long links (Nodes and digipeaters), and gain some time over short links<br>(HF...).<br><br> FBB protocol is very simple in its principle. It is based on MID/BID usage.<br>The identification is made by the F letter in the SID (system type identifier<br>contained in square brackets). All command lines must start in first column<br>with the 'F' character. All command lines are ended by a return (CR)<br>character.<br><br> Suppose I call another BBS to forward some mail. When I connect another BBS<br>using FBB protocol, I will receive the SID followed by a text and the prompt<br>(">"). If the SID contains the F flag, I will send immediately my SID and the<br>first proposal.<br><br> Proposals looks like :<br><br> FB P F6FBB FC1GHV FC1MVP 24657_F6FBB 1345<br> F> HH<br><br> FB : Identifies the type of the command (proposal)<br> P : Type of message (P = Private, B = Bulletin).<br> F6FBB : Sender (from field).<br> FC1GHV : BBS of recipient (@field).<br> FC1MVP : Recipient (to field).<br> 24657_F6FBB : BID ou MID.<br> 1345 : Size of message in bytes.<br> F> : End of proposal.<br> HH is optional. It is the checksum of the whole proposal in hexadecimal.<br><br> ALL the fields are necessary. This kind of command must hold seven fields.<br>If a field is missing upon receiving, an error message will be send<br>immediately followed by a disconnection.<br><br> A proposal can handle up to five FB command lines. If the total size of<br>messages seems to be too important, the proposal can handle less lines. In<br>FBB software, a parameter is defined in INIT.SRV file to tell the maximum<br>size of the message block. It is set by default to 10KB.<br><br> Example of proposal :<br><br> FB P F6FBB FC1GHV.FFPC.FRA.EU FC1MVP 24657_F6FBB 1345<br> FB P FC1CDC F6ABJ F6AXV 24643_F6FBB 5346<br> FB B F6FBB FRA FBB 22_456_F6FBB 8548<br> F> HH<br><br> This proposal is limited to three FB lines, as the amount of messages<br>overran the 10KB limit.<br><br> When receiving the proposal, the other BBS will reject, accept or defer the<br>message. This command is made by a FS line :<br><br> FS -+=<br><br> This means :<br><br> - I don't want the first message (-).<br> - I need the second message (+).<br> - I defer the third message, as I'm still receiving it.<br><br> In the new version 1 of FBB protocol there are 3 more responses:<br> R, E or H:<br><br> "FS +R++" means that the second message is rejected. Only works with new <br> version of the protocol.<br> The information is also written in the LOG like :<br> MJ B:Message_Bid V:Callsign_Rejecting<br> A warning message may be sent to the sending sysop when his message is <br> rejected (see <a href="fmtinit.htm#Warning">INIT.SRV</a> for more info on warning messages).<br> The message is not marked as 'F', and still can be forwarded to another BBS<br><br> "FS +H++" means that the second message is held. Only works with new <br> version of the protocol.<br> The information is also written in the LOG like :<br> MH B:Message_Bid V:Callsign_Rejecting<br> A warning message may be sent to the sending sysop when his message is <br> held (see <a href="fmtinit.htm#Warning">INIT.SRV</a> for more info on warning messages).<br><br> "FS +E++" means that the second message has a format error. Only works <br> with new version of the protocol. <br> A warning message may be sent to the sending sysop when his message <br> proposal is wrong (see <a href="fmtinit.htm#Warning">INIT.SRV</a> for more info on warning messages).<br><br> It should interesting to defer a message if you are still receiving it on a<br>other channel, or if you think that the size is to big, or for another<br>reason. The message should be proposed again at the next connection.<br><br> FS line MUST have as many +,-,=, R, E, H signs as lines in the proposal.<br><br> When receiving the FS lines, I can send the block of messages. Each message<br>is made with the title on the first line, the text, and a Ctrl Z in the last<br>line. The is no blank line between the messages.<br><br> Title of 2nd message<br> Text of 2nd message<br> .....<br> ^Z<br><br> When the other BBS has received all the asked messages, it acknowledges by<br>sending its proposal, and the system is reversed.<br><br> If it has no message to send, it only sends a line :<br><br> FF<br><br> This line must not to be followed by a F>.<br><br> If the other hand has no message, it sends a line :<br><br> FQ<br><br> and asks for the disconnection.<br><br><br> Example :<br> ---------<br><br> F6FBB FC1GHV<br> ----------------------------------------------------------------<br><br> Connects FC1GHV<br><br> Connected<br><br> [FBB-5.11-FHM$]<br> Bienvenue a Poitiers, Jean-Paul.<br> ><br><br> [FBB-5.11-FHM$] (F6FBB has the F flag in the SID)<br> FB P F6FBB FC1GHV.FFPC.FRA.EU FC1MVP 24657_F6FBB 1345<br> FB P FC1CDC F6ABJ F6AXV 24643_F6FBB 5346<br> FB B F6FBB FRA FBB 22_456_F6FBB 8548<br> F> HH<br><br> FS +-+ (accepts the 1st and the 3rd).<br><br> Title 1st message<br> Text 1st message<br> ......<br> ^Z<br> Title 3rd message<br> Text 3rd message<br> ......<br> ^Z<br><br> FB P FC1GHV F6FBB F6FBB 2734_FC1GHV 234<br> FB B FC1GHV F6FBB FC1CDC 2745_FC1GHV 3524<br> F> HH<br><br> FS -- (Don't need them, and send immediately the proposal).<br> FB P FC1CDC F6ABJ F6AXV 24754_F6FBB 345<br> F> HH<br><br> FS + (Accepts the message)<br><br> Title message<br> Text message<br> ......<br> ^Z<br><br> FF (no more message)<br><br> FB B F6FBB TEST FRA 24654_F6FBB 145<br> F> HH<br><br> FS + (Accepts the message)<br><br> Title message<br> Text message<br> ......<br> ^Z<br><br> FF (still no message)<br><br> FQ (No more message)<br><br> Disconnection of the link.<br><br><br> In this example, FBB protocol is used as the two BBS were identified by the<br>F flag in the SID. If F6FBB had sent the SID [FBB-5.11-MH$] when answering<br>FC1GHV, the protocol should be the standard MBL/RLI.<br><br> All callsigns are only examples !<br><br><br><br>
<font color="#800000">This page was last updated 17-Apr-99</font>
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