[rbridge] Parent node ID selection for multi destination trees

[varshah <[e-mail]>]

Hi,

Reading section 4.5 of RFC 6325
(http://tools.ietf.org/html/rfc6325#section-4.5) it seems that the selection
of a parent node  (7 byte- node ID) for a node N on a multi destination tree
j; should be based on j % p, where p is the number of equal cost parent
nodes to reach node N from root node R.

The intent seems to use lowest parent node ID for tree 1, next for tree 2
and so on.... And circle through if we have more possible trees than parent
nodes.

However, the trees are numbered starting 1, and the parent node IDs are
indexed starting 0 to (p ­ 1).  So, for a node N, when the network supports
2 trees and with two possible parent nodes,  we would use

parent node indexed at 1 for tree 1, j % p --> 1 % 2 = 1 and
Parent node indexed at 0 for tree 2, j % p --> 2 % 2 = 0.

To stay with the real intention, it would help if we had (j - 1) %p.

In that case,
parent node indexed at 0 for tree 1, (j  - 1)% p --> 0 % 2 = 0 and
Parent node indexed at 1 for tree 2,( j ­ 1) % p --> 1 % 2 = 1.

Thanks,
-Varun

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