random idea: constraint communities

[Randy Bush]

>>> Well-known-community-PREFIX: 65535.  Suffix=ASN to which we DO NOT ANNOUNCE
>>>                              65534.         ASN to which we DO ANNOUNCE
>> don't you want those target asns to be a set with more than one element?
> yes

i fear that i was probably too terse again.

  o the set would be large

  o the fine-grained, per-as tuning, as opposed to the peer/transit
    dichotomy which i proposed, could make this terribly hard to debug in
    reality, and might lead to exciting routing anomalies

randy