Why do Office365 Network Connectivity Principles include IPs & URLs?

[virtanet]

I'm trying to understand why Office365 Network Connectivity Principles include IPs & URLs? 

Typically when the branch edge network device / dns resolver make a query for the office URL the aDNS server will respond with the "front door" / public IP nearest to that DNS resolver based on the global IANA database or a ping to measure latency.  What should the branch edge network device / dns resolver do with the list of public IP addresses?  .. should it do it's own set of pings to measure latency, then cache/map that Public IP to the target URL? 

[#2]

@virtanet no, please don't cache these outside of a DNS server. The IP Addresses are published for large enterprise customers who require these for perimeter network firewalls. This could be in order to bypass proxy server processing for Office 365 network connectivity and to send traffic directly to an egress firewall therefor improving performance.

Regards,

Paul

[#3]

Makes sense, thanks for the reply Paul