Dell 3-DNS Administrator's Manual page 111

Figure 7.2 DNS query resolution to content delivery network provider
®
3-DNS Administrator Guide
CDN provider (2C). The CDN provider's DNS server responds with the IP
address of the best virtual server for resolution among those in the CDN
(2D). The CDN provider's cache servers resolve to the origin site virtual
servers for cache refreshes using a different domain name
(origin.download.siterequest.com).
Configuring a Content Delivery Network
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