This will allow services that provide SRV records for CalDAV and CardDAV to be detected automatically by domain name.
For instance, if a user enters “icloud.com” as the host name, the corresponding services can be detected:
$ host -t SRV _caldavs._tcp.icloud.com
_caldavs._tcp.icloud.com has SRV record 0 0 443 caldav.icloud.com.
$ host -t SRV _carddavs._tcp.icloud.com
_carddavs._tcp.icloud.com has SRV record 0 0 443 contacts.icloud.com.
The advantage is that when CalDAV and CardDAV services are on different servers (like on iCloud), they can be used in one account when SRV services discovery is used.