[Bier] comments on draft-zwzw-bier-prefix-redistribute

[Tony Przygienda <[e-mail]>]

Read with interest draft-zwzw-bier-prefix-redistribute. Comments

1. Figure 2 is mildly confusing. Where is area 0? Once we have area 0 the
current OSPF RFC (upcoming) is already dealing with redistribution within
OSPF. So I think a realistic problem is redistributing from OSPF into ISIS
or vice versa (or multiple instances of OSPF/ISIS edge/core facing) ...
2. The really hard problem of how to prevent redistribution loops is not
tackled. As long we assume a star topology the tie-breaking is trivial but
when e.g. two ASBRs from two different OSPF areas attach to ISIS we already
have a problem and even worse if spokes have e.g. ASBR shortcuts to prevent
going through the backbone. And what happens if two different protocols
pick up same BFR-id or advertise conflicting information. Basically we need
a DV/PV protocol to make that work in generic sense.
3. Alternately we could introduce the concept of a proxy-BFR that
advertises a BFR-id into two subdomains and forwards between them but I
think when this is thought through it will looks like PMSI stitching and
with that implode into MVPN overlay solution doing inter-domain multicast.

Let's see the discussion on the floor

--- tony