Is zebra's route flap damping implementation standard?

[Z. Morley Mao]

Hi,

        Zebra's route flap damping implementation only increments the
penalty when an explicit withdrawal is received (in bgp_damp_withdraw()).
It doesn't penalize routes when they are re-announced or when implicit
withdrawal occurs (in bgp_damp_update()).

        I am wondering whether this is done intentional.  What is this
implementation modeled after?  Does anyone know the commerical router
(Cisco and Juniper)'s practice?

Thanks very much for your help!

--Morley