Aside from what Daniel says about Sprint and MCI's routing policy mismatch, this statement is interesting on another level. For Dan says: MCI aggregates all its customer's routes into /19's. This is new is it not? Also it says *MCI* does the aggregating and not the customer. Would someone please explain how this differs from what I understand to be Sprints policy which says (i believe) that it is the CUSTOMER's responsibility to aggregate the routes they present to sprint???

The difference is that MCI refers to addresses assigned out of their CIDR block. They are saying that they are aggregating nets on a /19 basis- one might assume on a per pop basis, or something similar.

Why would MCI do the aggregating? Is such mci policy good for mci or good for the customer or equally good for both?

They are not referring to proxy aggregation of PI address space. That is another religious war altogether. This is good policy, in that they are aggregating. They are most likely prevented from aggregating their announcements further to their peers in the interests of maintaining better routing policy to the individual nets- for example, say part of the space was in new york, and another was in dallas. If they only announced the aggregated /16 to their peers, their peers would pass off traffic to the closest announcement of the aggregate, as opposed to passing the net off to the closest place to the destination. 'Course, I remember that some poeple are shortest exit to MCI anyway- but that may have changed. _k