Path Control bits handling

[nyrahul]

RPL provides a mechanism for installing multiple downwards routes to the nodes. These multiple routes could be used for reliability, latency control or mere load-balancing within a DODAG. The path control bits are usable in both storing/non-storing MOPs.

Having said this, there is no (open) implementation which supports this mechanism primarily due to;

1. higher memory and program space requirement
2. spec not clear about dealing with path control bits
3. spec does not give a high level overview with examples of the advantages of such mechanisms

Interestingly, Path control bits require mandatory handling as per Section 9.9 Point 9. An implementation needs to at-least set one active path control bit in the transit information option of the DAO message. No implementation follows this!