The objective function in RPL is the main source of parent selection. Usually only one objective function is used. My question is not to have many, but dynamically change the usage of objective function, as per the resources available and the constraints. Is it possible?
You can do this if you use a simulator. Just write an IF function to determine which Obj function is to be used when
Dear A. S. Joseph Charles,
yes, it is theoretically possible to use more than one Objective Function (OF) in the RPL. But only one OF can be use to build one DODAG in a LLN.
The RPL is a universal, widely applicable routing protocol and (theoretically!) it makes possible to use simultaneously different OFs. The routes at RPL can be optimized according to different criteria defined by different OFs. These OFs – exactly the OF Types – can be registered at IANA. In this way OF receives the unique identification (unique Type Number) on the world.
The type of OF (OF Type, OF identification) is indicated as OCP (Objective Code Point) in the option "DODAG Configuration". See figure 24 in RFC 6550 and the OCP values under:
https://www.iana.org/assignments/rpl/rpl.xhtml
The option "DODAG Configuration" is included in the messages DIO.
In a LLN, several DODAGs (as virtual topologies) can be establish simultaneously. These DODAGs represent a RPL Instance. Since an Identification (DODAGID) is assigned to each DODAG in each RPL instance, several virtual topologies (even with different OFs) can be establish in each LLN. In this way is the multi-topology routing in LLNs with RPL possible.
See Figure 14 in RRC 6550. Everyone DODAG has a unique DODAGID and a unique Version Number (DODAGVersionnumber). A new DODAG version can even be built according to another ("new") OF.
Good luck and best regards
Anatol Badach
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