[mat-wg] some thoughts on add-path and bmp at ripe/ris

i have some small thoughts on add-path and BMP in RIPE/RIS.  this may
hinder more than help, unfortunately.

as a researcher, of course i would love a wider view into the AS graph
and the views of as many ASs as possible.  nom nom.  but ...

add-path, if not done very carefully, and documented in detail for each
peer, will produce views i will not understand.  it is analogous to not
knowing what view a BGP peer gives RIS today.  did it give me a full Nth
view into peer X?  is the path that of a peer, a customer, a provider?
and add-path is worse because it prunes in configuration and vendor-
dependent and otherwise unpredictable ways.

and, as an operator

if P is a RIS peer, and they give RIS BMP showing their input from their
peers, upstreams, and customers, those peers, upstreams, and customers
have not given thir consent to have their internals published!  if they
want to have RIS publish their internals, they would peer with RIS and
choose what view they present.

and, of course, the researcher does not know what view, peer, upstream,
or customer P's BMP peer is giving them.  same problem as above under
add-path.

randy