ETag or entity tag is part of HTTP. It is one of mechanisms that HTTP provides for web cache validation and which allows a client to make conditional requests. This allows caches to be more efficient and saves bandwidth because a web server does not need to send a full response if the content has not changed.
SkyparkCDN nodes support the ETag header. SkyparkCDN nodes adopt and use the header as long as the header is used at the origin source. This option is enabled on all servers by default. You do not need to apply additional settngs to CDN Resource.