ETRI ETRI The I2RS (the Interface to the Routing System) is a programmatic asynchronous interface for transferring state into and out of the routing system. The I2RS can provide programmable control planes for network service providers (NSPs). In this sense, the I2RS could be also considered as one of candidates to facilitate CDNI Request Routing. This document discusses how I2RS can be used for downstream CDN selection within CDNI request routing.