ɪnðə lˈæɾɚ kˈeɪs, ðə pɹˈɑːksi kəntɹˈoʊlz ðə tɹænsmˈɪʃənz ʌvðə tˌiːsˌiːpˈiː sˈɛɡmənts ɪn bˈoʊθ dᵻɹˈɛkʃənz, baɪ ˈæk fˈɪltɚɹɪŋ ænd ɹˌiːkənstɹˈʌkʃən ɪnðɪ ɛɡzˈɪstɪŋ kənˈɛkʃən sˈiː pɹˈoʊɾəkˌɑːl spˈuːfɪŋ.
In the latter case, the proxy controls the transmissions of the TCP segments in both directions, by ack filtering and reconstruction in the existing connection (see protocol spoofing).