> Of course there is. You cannot distinguish routing from host without looking > at external control channels, such as a routing or configuration protocol; > and you certainly cannot determine the subnet mask of a network without that > external information, since it's not in the ?> packet. And it's not even in > the control plane if the route has been aggregated. Does that make the > information "ambiguous"? The point is that the subnet mask of a network is > part of a context that you discussed, and you might not have it.
This analogy doesn't really work for me. In the case of an SRH - the router acts on the packet based on local configuration - how it gets that config doesn't really matter. The SID size in use by each router may or may not be exposed by an IGP for reading - and could differ at each node. In the case of standard forwarding you have a FIB entry - inserted from the RIB - that goes a certain place. In the case of this - a router could be using either 16bit SID or 32bit SID - entirely configured locally - and dependent on the configuration - will determine if the node in question shifts the information by 16 or 32 bits - before the FIB lookup. Therefore - in a standard scenario - you know that packet X is going to be forwarded using a FIB entry lookup of Y - in the case of this - you have no idea what the router is actually going to be looking up - because you don't know if its going to be doing a 16 or 32 bit sid without knowing the specific local configuration on the router. That’s a very different level of complexity in terms of operations and debugging on a large network Andrew _______________________________________________ spring mailing list [email protected] https://www.ietf.org/mailman/listinfo/spring
