We can choose which sort of IK would be appropriate for our model by referring to the following page: http://openrave.org/docs/latest_stable/openravepy/ikfast/#ik-types. However, the most common IK type is transform6d.
We have to provide link index numbers for the base_link and end_link between which the IK will be calculated. We can count the number of links by checking them in the .dae file. Alternatively, if we have OpenRAVE installed, we can view a list of links in our model:
$ openrave-robot.py my_robot.dae --info links
As usual, the 6-DOF manipulator should have six arm links and a dummy base_link, as required by ROS specifications. If there are no extra links present in the model, this gives baselink=0 and eelink=6