ologies ▁for ▁travers ing ▁fire w alls ▁and ▁NAT . ▁ ▁R TP ▁and ▁SR TP ▁– ▁I ET F ▁standards ▁for ▁deliver ing ▁real - time ▁and ▁encrypted ▁media ▁streams ▁for ▁Vo IP . ▁ ▁Upon ▁the ▁launch ▁of ▁the ▁iPhone ▁ 4 , ▁Job s ▁stated ▁that ▁Apple ▁would ▁immediately ▁start ▁working ▁with ▁standards ▁bodies ▁to ▁make ▁the ▁Face Time ▁protocol ▁an ▁" open ▁industry ▁standard ". ▁While ▁the ▁protocol s ▁are ▁open ▁standards , ▁Apple ' s ▁Face Time ▁service ▁requires ▁a ▁client - side ▁certificate . ▁ ▁Face Time ▁calls ▁are ▁protected ▁by ▁end - to - end ▁encryption ▁so ▁that ▁only ▁the ▁sender ▁and ▁receiver ▁can ▁access ▁them . ▁Apple ▁cannot ▁dec rypt ▁this ▁data . ▁ ▁Comp ared ▁to ▁most ▁S IP ▁implementations , ▁Fac etime ▁adds ▁techniques ▁that ▁enh ance ▁performance ▁at ▁the ▁cost ▁of ▁breaking ▁inter oper ability : ▁port ▁multiple x ing , ▁SD P ▁minim ization ▁and ▁SD P ▁compression . ▁ ▁Face Time ▁Audio ▁A ▁new ▁audio - only ▁version ▁of ▁Face Time , ▁named ▁Face Time ▁Audio , ▁was ▁announced ▁during ▁the ▁annual ▁Apple ▁World wide ▁Develop ers ▁Conference ▁( W W DC ) ▁ke yn ote ▁speech ▁on ▁June ▁ 1 0 , ▁ 2 0 1 3 , ▁and ▁released ▁with ▁iOS ▁ 7 ▁on ▁September ▁ 1 8 , ▁ 2 0 1 3 . ▁As ▁an ▁audio - only ▁version ▁of ▁Face Time , ▁it ▁effectively ▁makes ▁the ▁protocol ▁into ▁a ▁voice ▁over ▁Internet ▁Pro tocol ▁(