= Сообщение: 35703 из 46150 =============================== RU.FIDONET.TODAY = От : Michael Dukelsky 2:5020/1042 14 Jul 23 22:29:40 Кому : Nil A 14 Jul 23 22:29:40 Тема : Не надо делать петель в ru.fidonet.today FGHI : area://RU.FIDONET.TODAY?msgid=2:5020/1042+64b1a3d2 На : area://RU.FIDONET.TODAY?msgid=2:5015/46+64b19f18 = Кодировка сообщения определена как: CP866 ================================== ==============================================================================
* Originally in nino.046.local * Crossposted in ru.fidonet.today
Привет, Nil!
14 July 2023 21:46, Nil A послал(а) письмо к Michael Dukelsky:
MD>> Дупы могут привести к потере писем.
NA> Я пока теоритического и практического обоснования этому не знаю.
Забыл уже? Тогда запощу ещё раз. Прошу прощения, что на английском.
================================================================== * Area : WWB_Z2 (WWB_Z2) * From : Michael Dukelsky, 2:5020/1042 (16 January 2014 11:50) * To : Tommi Koivula * Subj : Producing a diode in a loop ================================================================== Hello Tommi,
15 Jan 14, Tommi Koivula wrote to Markus Reschke:
TK> Dupes are a good thing.
I cannot agree with that. A dupe is a sign of a loop existing in an echo distribution. And a loop can produce a diode (when mail between two links goes in only one direction) and other fails in the echo distribution. Here is an explanation by Pavel Gulchouck 2:463/68 which he wrote in February 2007.
Let us consider such a loop in an echo distribution:
B-C / |\ P-A | F-Q \ |/ D-E
Here a simple loop A-B-C-F-E-D is additionally closed by a triangle C-E-F.
Suppose the link between the nodes C and F breaks but the nodes retain the subscription and thus continue adding SEEN-BYs of each other. A message from the node Q to the node P will not be lost except at the node C and its downlinks: the node E will not pack the mail to C (neither B will do it) because the node C is in SEEN-Bys produced by the node F. If there is no link between C and E and it is a simple loop, then nothing changes for the node C when Q sends a message, the node C will not see it.
Now P sends a message. Whether Q will receive it depends on the balance of the transfer times in the branches A-B-C-E and A-D-E. If a message from P comes to E first via the path P-A-B-C-E and after that via the path P-A-D-E, then the nodes F and Q will not see it, since C puts F in SEEN-BYs and the second copy of the message is discarded as a dupe. Here we have a diode, where messages go from Q to P, but not from P to Q.
Nothing changes if there is no B and there is a chain D-X-Y-Z instead of D. Then it becomes more obvious that the transfer time via A-C-E is less than via A-D-X-Y-Z.
So loops are in no way a means of increasing echo distribution reliability and dupes signal us that a loop has appeared.
