Design Principles of Policy Languages for Path-Vector Protocols

摘要

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.