Why can't the ROS master automatically determine the caller ID when a publisher registers.
As part of this API: http://wiki.ros.org/ROS/Master_API
When a ROS node registers as a publisher of a topic it has to pass in the URI where it can be reached, which is then used to hook the subscribers up to the publisher.
Why can't the master automatically determine the IP of the publisher? In systems with multiple network connections the routing is determined by the network driver, and someone implementing the ROS node may not know what interface/IP will be used to contact the master. It seems like the Master should be able to determine this on it's own (at least by default).
Shouldn't it be "why does the ROS master not .."? It probably can, but someone consciously decided not to (at least, that's what I assume).
And I can think of one reason (which you already mentioned): IP routing may interfere, so it would seem more robust to include the IP in the request.