Scalable Support for Multi-homed Multi-provider Connectivity

Status of this Memo This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited. 2. Abstract This document describes addressing and routing strategies for multi-homed enterprises attached to multiple Internet Service Providers (ISPs) that are intended to reduce the routing overhead due to these enterprises in the global Internet routing system. 3. Motivations An enterprise may acquire its Internet connectivity from more than one Internet Service Provider (ISP) for some of the following reasons. Maintaining connectivity via more than one ISP could be viewed as a way to make connectivity to the Internet more reliable. This way when connectivity through one of the ISPs fails, connectivity via the other ISP(s) would enable the enterprise to preserve its connectivity to the Internet. In addition to providing more reliable connectivity, maintaining connectivity via more than one ISP could also allow the enterprise to distribute load among multiple connections. For enterprises that span wide geographical area this could also enable better (more optimal) routing. The above considerations, combined with the decreasing prices for the Internet connectivity, motivate more and more enterprises to become multi-homed to multiple ISPs. At the same time, the routing overhead that such enterprises impose on the Internet routing system becomes more and more significant. Scaling the Internet, and being able to support a growing number of such enterprises demands mechanism(s) to contain this overhead. This document assumes that an approach where routers in the "default-free" zone of the Internet would be required Bates & Rekhter Informational [Page 1]