I ² BGP: A Privacy-Preserving Intra-AS State-Assisted Inter-AS Routing Scheme

BGP is the most widely employed inter-AS routing protocol, connecting millions of ASes worldwide. While it is possible to select the egress for outgoing flows based on administrators’ configurations, such schemes are localized due to the privacy of the intra-AS network state. The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AS_Path</i> field of BGP records all crossed ASes, which can be used to prevent routing loops and select paths, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i.e.</i>, selecting the minimum AS-hop path among available paths. Although this scheme is simple, effective, and offers a certain degree of global perspective, selecting paths at AS granularity ignores the transmission performance within each intra-AS, which may result in selecting non-optimal routing paths. To enable the use of private intra-AS data for inter-AS routing, we proposed a privacy-preserving intra-AS state-assisted inter-AS routing scheme, which can select optimal inter-AS paths without disclosing specific intra-AS state data. Specifically, we added an additional BGP header field to carry path performance features and designed a three-step data masking mechanism to protect intra-AS state data, enabling the selection of inter-AS paths with intra-AS state awareness. I<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>BGP has been deployed in the Greater Bay Area Future Network and a large-scale network simulator based on real network topologies. The results show that I<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>BGP outperforms BGP in terms of specified forwarding hops, delay, and bandwidth metrics.