provided that the entire resulting derived work is distributed
under the terms of a permission notice identical to this one.
- $Id: CONNECTIVITY,v 1.1.2.6 2001/07/23 22:06:22 guus Exp $
+ $Id: CONNECTIVITY,v 1.1.2.7 2001/07/24 08:51:36 guus Exp $
1. Problem
==========
hand, we mustn't keep to many inactive edges, because we want to keep the
number of known edges linear to the number of hosts (otherwise the size of the
problem will grow quadratically).
+
+So, since B didn't deactivate one of it's own edges, it forwards the
+ADD_EDGE(C,F) to A, which also does a BFS, and so on, until it reaches F. F of
+course also does a BFS, notes that is is one of it's own edges. It deactivates
+the edge (C,F), and consequently will not forward the ADD_EDGE(C,F) to C
+anymore. In the mean time, C got messages from B which will make C do the same.
+
+Ok, suppose a DEL_EDGE was sent, and it means an inactive edge has to be
+reactivated. The vertices connected by that edge must exchange their entire
+knowledge of edges again, because in the mean time other messages could have
+been sent, which were not properly forwarded. Take this example:
+
+ X C-----D
+ | | |
+ | | |
+ v | |
+ A-----B- - -E
+
+The edge (B,E) is inactive. X is trying to make a new connection with A. A
+sends an ADD_EDGE(A,X) to B, which forwards it to C. At that time, the
+connection between C and D goes down, so C sends a DEL_EDGE(C,D) to B, and D
+sends a DEL_EDGE(C,D) to E. If we just allow (B,E) to be reactivated again
+without anything else, then E and D will never have received the ADD_EDGE(A,X).
+So, B and E have to exchange edges again, and propagate them to the hosts they
+already know.
projects / meshlink / commitdiff