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BGP is unique among IP-routing protocols in that routing is determined using semantically rich routing policies. However, this expressiveness has come with hidden risks. The interaction of locally defined routing policies can lead to unexpected global routing anomalies, which can be very difficult to identify and correct in the decentralized and competitive Internet environment. These risks increase as the complexity of local policies increase, which is precisely the current trend. BGP policy languages have evolved in a rather organic fashion with little effort to avoid policy-interaction problems. We believe that researchers should start to consider how to design policy languages for path-vector protocols in order to avoid routing anomalies while obtaining desirable protocol properties. We take a few steps in this direction by identifying the important dimensions of this design space and characterizing some of the inherent design trade-offs. We do this in a general way that is not constrained by the details of BGP.

We propose a focus on accountability as a mechanism for ensuring security in information systems. To that end, we present a formal definition of accountability in information systems. Our definition is more general and potentially more widely applicable than the accountability notions that have previously appeared in the security literature. In particular, we treat in a unified manner scenarios in which accountability is enforced automatically and those in which enforcement must be mediated by an authority; similarly, our formalism includes scenarios in which the parties who are held accountable can remain anonymous and those in which they must be identified by the authorities to whom they are accountable. Essential elements of our formalism include event traces and utility functions and the use of these to define punishment and related notions.

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