In prior work we analysed the global Internet interdomain routing system based on BGP policy atoms: equivalence classes of prefixes based on common AS path as observed from a number of topological locations. In this paper we define a variant of policy atoms, called declared atoms, and outline a new routing architecture, called atomised routing, based on declared atoms. Atomised routing aims for a reduction in the number of routed objects in the default-free zone of the Internet (around 21K atoms covering around 115K prefixes), and an improved convergence behaviour of the interdomain routing system. We also demonstrate the viability of incremental deployment of atomised routing.

We present an analysis of origin link sets, which serve as an approximation of declared atoms. An origin link of an AS path is the origin AS together with the AS it peers with. Our analysis is based on BGP updates collected by the RouteViews updates collector, and shows that over an 8 hour period more than 80% of update packets contain only prefixes belonging to one declared atom. Of BGP update packets that contain more than one prefix, 60% contain only prefixes belonging to one atom. This suggests that atoms are mostly preserved in the flow of BGP updates and indicates that atoms reflect properties of the routing system. Very few atoms (2%) change their prefix count over the same period. [ will be replaced by percentage of change to actual prefixes ] This suggests that the membership of atoms is very stable.