A method for 
Internet content delivery in a 
content delivery network established at network locations, the 
content delivery network comprising a plurality of content servers for serving content resources. The plurality of content servers includes a plurality of subsets of content servers, each subject being located at one of a plurality of Internet data centers. For each 
Internet Protocol (IP) address block from which requests for content resources are expected to be received, the method generates a candidate 
list of Internet data centers to be used to service the requests for content resources. For the 
IP address block, the method selects at least one of 
the Internet data centers from the candidate 
list to be used to service the requests for content resources. The selected 
Internet data center for the 
IP address block is written into a network map. The selecting step is carried out concurrently for each 
IP address block from which requests for content resources are expected to be received such that the network map comprises the selected 
Internet data center for each IP address block. The network map is then provided to 
a domain name service (DNS) associated with the 
content delivery network. In response to a DNS query received at the 
domain name service associated with the 
content delivery network, the network map is used to identify one of 
the Internet data centers from the candidate 
list to be used to service a request for a content resource.