This VPN referred to https://www.digitalocean.com/community/tutorials/how-to-set-up-an-ikev2-vpn-server-with-strongswan-on-ubuntu-16-04#step-1-%E2%80%94-installing-strongswan
Download the StrongSwan app on your phone, and then import a certificate.
And add VPN profile.
Server: xxx.iptime.org
VPN Type: IKEv2 EAP(username/password)
Username: ???
password: ???
Then, check the box of 'Show advanced setting'
Go to at the end of page, and you can see some text boxes which are about ike and esp something.
Then put "aes256-sha1-modp1024" on ike
and put "aes256-sha1" on esp part