From 5333cada0dfc4dfc3be728e6c78d8d42dc2ace52 Mon Sep 17 00:00:00 2001 From: Guus Sliepen Date: Sun, 22 Jul 2001 17:41:52 +0000 Subject: [PATCH] Written down a possible solution. --- doc/CONNECTIVITY | 54 ++++++++++++++++++++++++++++++++---------------- 1 file changed, 36 insertions(+), 18 deletions(-) diff --git a/doc/CONNECTIVITY b/doc/CONNECTIVITY index 96636ae7..8ccc0de6 100644 --- a/doc/CONNECTIVITY +++ b/doc/CONNECTIVITY @@ -12,7 +12,7 @@ maintain a stable network. provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. - $Id: CONNECTIVITY,v 1.1.2.4 2001/07/22 15:25:13 guus Exp $ + $Id: CONNECTIVITY,v 1.1.2.5 2001/07/22 17:41:52 guus Exp $ 1. Problem ========== @@ -182,34 +182,52 @@ Then C---F authentication finishes, the following actions are taken: 1.2.1 Augmenting ADD_HOST ------------------------- -A solution would be to augment ADD_HOST with an extra parameter, for example -the host which told us about the new host. From A's point of view, D told it -about itself, E and F. So, A would send out ADD_HOST(D, D) to B, and -ADD_HOST(E,D) and ADD_HOST(F,D). Lets review what happens at point 3 in the -preceding example: +A solution would be to augment ADD_HOST with an extra parameter, the nexthop of +the added host: - 3 B receives ADD_HOST(D,D) from A, - B sends ADD_HOST(D,D) to C + 3 B receives ADD_HOST(D,A) from A, + B sends ADD_HOST(D,A) to C B receives ADD_HOST(E,D) from A: B sends ADD_HOST(E,D) to C - B receives ADD_HOST(F,D) from A: - B sends ADD_HOST(F,D) to C - E receives ADD_HOST(A,A) from D: - E sends ADD_HOST(A,A) to F + B receives ADD_HOST(F,E) from A: + B sends ADD_HOST(F,E) to C + E receives ADD_HOST(A,D) from D: + E sends ADD_HOST(A,D) to F E receives ADD_HOST(B,A) from D: E sends ADD_HOST(B,A) to F - E receives ADD_HOST(C,A) from D: - E sends ADD_HOST(C,A) to F + E receives ADD_HOST(C,B) from D: + E sends ADD_HOST(C,B) to F - B receives ADD_HOST(F,F) from C, and notes that F is already known: + B receives ADD_HOST(F,C) from C, and notes that F is already known: - B receives ADD_HOST(D,F) from C, and notes that D is already known: + B receives ADD_HOST(D,E) from C, and notes that D is already known: B receives ADD_HOST(E,F) from C, and notes that E is already known: - E receives ADD_HOST(C,C) from F, and notes that C is already known: + E receives ADD_HOST(C,F) from F, and notes that C is already known: - E receives ADD_HOST(A,C) from F, and notes that A is already known: + E receives ADD_HOST(A,B) from F, and notes that A is already known: E receives ADD_HOST(B,C) from F, and notes that B is already known: + +So, B and E have to make a choice. Which ADD_HOST is going to win? Fortunately, +since the ADD_HOST messages are augmented, they have an extra piece of +information they can use to decide in a deterministic way which one is going to +win. For example, B got ADD_HOST(F,E) and ADD_HOST(F,C). Since "E" > "C", it +could let ADD_HOST(F,E) win. + + B receives ADD_HOST(F,C) from C, and notes that F is already known: + since "C" < "E", B ignores ADD_HOST(F,E) + B sends ADD_HOST(F,C) to A + ... + E receives ADD_HOST(C,F) from F, and notes that C is already known: + since "F" > "B", E removes the ADD_HOST(C,B) in favour of the new one + E sends ADD_HOST(C,F) to D + + 4 A receives ADD_HOST(F,E) from B, and notes that F is already known: + since "E" < "D", A ignores ADD_HOST(F,D). + ... + D receives ADD_HOST(C,F) from E, and notes that C is already known: + since "F" > "B", D removes the ADD_HOST(C,B), + closes the connection with C, in favour of the new one. -- 2.39.5