[Tinyos-help] CTP parent switching

[Michiel Konstapel]

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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