draft-ietf-mpls-rsvp-unnum-07.txt states that: With this in mind, the ERO processing in the presence of the Unnumbered Interface ID subobject follows the rules specified in section 4.3.4.1 of [RSVP-TE]. If the Unnumbered Interface ID subobject is used, is the IPv4 Prefix subobject defined in 3209 still required? Thanks Michael Mandelberg FirstWave SION