RFC 3258 (rfc3258) - Page 3 of 11
Distributing Authoritative Name Servers via Shared Unicast Addresses
Alternative Format: Original Text Document
RFC 3258 Distributing Authoritative Name Servers April 2002 e) coordination of the switchover times for the servers in the mesh f) institution of a failure process to ensure that servers that did not receive correct data or could not switchover to the new data ceased to respond to incoming queries until the problem could be resolved. Depending on the size of the mesh, the distribution host may also be a participant; for authoritative servers, it may also be the host on which zones are generated. This document presumes that the usual DNS failover methods are the only ones used to ensure reachability of the data for clients. It does not advise that the routes be withdrawn in the case of failure; it advises instead that the DNS process shutdown so that servers on other addresses are queried. This recommendation reflects a choice between performance and operational complexity. While it would be possible to have some process withdraw the route for a specific server instance when it is not available, there is considerable operational complexity involved in ensuring that this occurs reliably. Given the existing DNS failover methods, the marginal improvement in performance will not be sufficient to justify the additional complexity for most uses. 2.4 Server Placement Though the geographic diversity of server placement helps reduce the effects of service disruptions due to local problems, it is diversity of placement in the network topology which is the driving force behind these distribution practices. Server placement should emphasize that diversity. Ideally, servers should be placed topologically near the points at which the operator exchanges routes and traffic with other networks. 2.5 Routing The organization administering the mesh of servers sharing a unicast address must have an autonomous system number and speak BGP to its peers. To those peers, the organization announces a route to the network containing the shared-unicast address of the name server. The organization's border routers must then deliver the traffic destined for the name server to the nearest instantiation. Routing to the administrative interfaces for the servers can use the normal routing methods for the administering organization. One potential problem with using shared unicast addresses is that routers forwarding traffic to them may have more than one available route, and those routes may, in fact, reach different instances of Hardie Informational
