some musings on PI v. PA

Thu Jul 12 23:52:55 UTC 2007

David Meyer wrote:
>       OTOH, if I announce PI space, "switching to the new path"
>       is controlled by the announcement/withdrawal of the PI
>       prefix, and can happen much closer to the source. So in
>       this sense aggregation breaks a certain kind of "path
>       selection". I think we all realize that there is no free
>       lunch, and that this is a property (such as it is) of the
>       fact that aggregation throws away information in the
>       interest of computability (a standard technique).
>
>       So folks are using PI for reasons other than the
>       well-known standard laundry list. In particular,
>       advertising PI space can cause the "switch" to an
>       alternate path during an outage to happen much closer to
>       the source and some providers find this to be a desirable
>       property.
>
>       I am interested in hearing about anyone who is relying on
>       this property of PI, or any other comments on what I've
>       said above.
>

I always thought that *was* one of the major reasons to use PI space -
no aggregation of your space into another announcement. Not having to
renumber is ancillary to me.

~Seth