consistent policy != consistent announcements

Alan Barrett apb at
Fri Mar 14 16:57:51 UTC 1997

> >                     M
> >                   /   \
> >                  A     B      * Peer link
> >                  |     *      | Customer link
> >                  RRRRRRR
> >           Point1 *     * Point2
> >                  VVVVVVV

> How is R supposed to recognize some likely disjoint set of of what A
> announces to R as coming from M through B so as to recognize it as a
> customer prefix?  Note that the paths from M to R through A and B can
> be longer than depicted and that M's address space may not be taken
> from R's, A's, or B's.

R could request A to provide it with a list of ASes for indirect
customers behind A.  (R probably already does that.)  That would be
sufficient information for R's router at the R/B interconnection to tag
M's routes as customer routes.  Essentially, when R's router at the R/B
interconnection receives a route with path "B M", it could use the fact
"M is an indirect customer" rather than "B is a non-customer" to tag the
route appropriately.

Alternatively, R could make the decision using prefixes rather than AS
numbers, and could make it at the R/V[Point2] outbound announcement
point rather than at the B/R inbound announcement point.

--apb (Alan Barrett)

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