Host-Centric Site-Exit Router Selection in IPv6 Site Multihoming Environment

Site-multihoming is an architecture which brings the benefit of reliability and load-sharing in a small scale network like a home network by connecting multiple ISPs (Internet Service Providers). In the discussion of IETF Multi6 Working Group, multihoming by multi-PA (Provider Aggregatable) addressing became rough consensus as the architecture for IPv6 site-multihoming. However, issues on multi-PA addressing, like how a host selects the source IP address for each packet or how to cope with ingress filtering by ISP, remain not discussed. In this paper, we propose a new routing architecture for site-multihoming, based on the idea of host-centric multihoming by Huitema et al. Host-centric multihoming has a difficulty in deployment as it essentially needs source address dependent routing. In our architecture, 1) Site-internal routes and site-external routes are distinguished. A packet that goes out of the site is routed to the site-exit router associated with the source IP address, while a packet that goes to a host in the site is routed based on the destination address. 2) Site-external routes are limited to the default routes (::/0) associated with the PA addresses only. This architecture simplifies the intra-site routing but still fully has the advantage of host-centric multihoming that a host in a site can select an ISP through which a packet from the host goes, namely, source address selection by a sender host decides the path of the packet. We have also implemented a dynamic source address dependent routing protocol for our architecture and have confirmed the effectiveness of it.