treerouting.notes

tinyos-2.0源代码！转载而已！要的尽管拿！

Miscelaneous notes on the TreeRoutingP module details.
Rodrigo Fonseca

The RoutingTable is a table with information about *routing* information of neighbors: their hopcount, quality, etc. It is used to periodically choose the best route, and to find backup routes.

It is strictly a subset of the LinkEstimator table, meaning that no node that is not in the link estimator table is in the routing table. However, not all neighbors will be here. The policy for managing this table is a generalization of the regular tree routing: we keep the K best paths to *a* root.


Timer has period P jittered with +- P/2

RouteInfo:
    metric is a 16 bit number that measures quality to the root. See below.
    hopcount
    parent: a link neighbor address (next hop)

Root:
    rootControl interface.
    if isRoot()
      parent = self
      hopcount = 0
      metric = 0
      has_route = true
      

Update task updates the parent before sending out beacon.
This is not done right when you receive a beacon, because the qualities may change right before you send. This is a policy question, anyway, and can be changed easily.

Quality is converted to a 'path metric' by evaluateMetric().
Path metric is ADDITIVE along a path, and smaller metric is always better.
Currently, it is 10*ETX along the path.