Following up on my message about the link estimator, I was also wondering about CTP's parent switching threshold. As is, CTP will switch parents if the new parent offers a path ETX that is 1.5 hops better than its current parent, if I am not mistaken. Now, this is set fairly conservatively, because a node would not replace a two-hop, 2.4 ETX parent with a direct, perfect link to the sink. However, "in the back" of the tree, where lots of link ETXs are added up, you don't want a low threshold or nodes would switch parents all the time.
Now, would it be an idea to base this threshold on a percentage of the path ETX? For example, at 20%, a node with a path ETX of 2 would replace its parent by one that offers a path ETX of 1.6, whereas a node that has a path ETX of 10 would only switch if the new path has an ETX of 8 or lower. That way, it would favour optimal routes near the sink, where traffic is highest, and favour stable routes further down the tree. A cap would probably be needed on top of the percentage, so that it doesn't become impossible to switch in very large networks. Kind regards, Michiel Michiel Konstapel Software Engineer T: +31 (0)15 26 00 44 6 F: +31 (0)15 26 00 40 5 W: www.sownet.nl
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