RFC 2260 (rfc2260) - Page 2 of 12
Scalable Support for Multi-homed Multi-provider Connectivity
Alternative Format: Original Text Document
RFC 2260 Multihoming January 1998 to maintain a route for every multi-homed enterprise that is connected to multiple ISPs does not provide an adequate scaling. Moreover, given the nature of the Internet, this document assumes that any approach to handle routing for such enterprises should minimize the amount of coordination among ISPs, and especially the ISPs that are not directly connected to these enterprises. There is a difference of opinions on whether the driving factors behind multi-homing to multiple ISPs could be adequately addressed by multi-homing just to a single ISP, which would in turn eliminate the negative impact of multi-homing on the Internet routing system. Discussion of this topic is beyond the scope of this document. The focus of this document is on the routing and addressing strategies that could reduce the routing overhead due to multi-homed enterprises connected to multiple ISPs in the Internet routing system. The strategies described in this document are equally applicable to both IPv4 and IPv6. 4. Address allocation and assignment A multi-homed enterprise connected to a set of ISPs would be allocated a block of addresses (address prefix) by each of these ISPs (an enterprise connected to N ISPs would get N different blocks). The address allocation from the ISPs to the enterprise would be based on the "address-lending" policy [RFC 2008]. The allocated addresses then would be used for address assignment within the enterprise. One possible address assignment plan that the enterprise could employ is to use the topological proximity of a node (host) to a particular ISP (to the interconnect between the enterprise and the ISP) as a criteria for selecting which of the address prefixes to use for address assignment to the node. A particular node (host) may be assigned address(es) out of a single prefix, or may have addresses from different prefixes. 5. Routing information exchange The issue of routing information exchange between an enterprise and its ISPs is decomposed into the following components: a) reachability information that an enterprise border router advertises to a border router within an ISP b) reachability information that a border router within an ISP advertises to an enterprise border router Bates & Rekhter Informational
