Route Filtering by Network Size

["Marsh, Jerry" <MarshJ () wsdot wa gov>]

I've changed jobs and been off the NANOG list for some time, so please
excuse the question.

I know some providers (such as SPRINT) filter BGP routing announcements
based on minimum announcement size.  The questions are:

1)      Who all has such policies?

2)      What are the specific sizes and address blocks being filtered?

3)      Do they affect "portable" (provider independent) and "non-portable
(provider supplied) addressing in the same way.

Thanks.