According to official Microsoft documentation the domain hwcdn.net is used by the Highwinds Content Delivery Network to perform Windows updates.
Highwinds Network Group, Inc. (Highwinds) is a company that was founded in 2002 and offers IP services including CDN (content delivery), cloud storage, IP transit, transport and colocation.
Microsoft has always used a combination of third-party content delivery networks including Akamai, Limelight, Level 3, EdgeCast, ChinaCache and Highwinds.
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