Mobile Internet telephony: mobile extensions to H.323

Internet telephony realizes the transmission of two-way and real-time traffic over IP-based networks. The dominant standard for Internet telephony is ITU-T Rec. H.323. With the current version of H.323, Internet telephony allows interoperability with circuit-switched telephone, but IP host mobility is not supported. In this paper, mobile extensions to H.323 that enable mobile Internet telephony service are proposed. The proposed approach combines the characteristics of both cellular phone system and mobile IP mechanism with Internet telephony, and therefore realizes the transmission of real-time voice traffic for both stationary and mobile hosts over IP-based networks. The most striking feature of the proposed approach is that the complicated mobility management functions are handled by the procedures for dynamically joining and departing from a conference, functions already defined in H.323. Therefore, our approach allows mobility support without the need for additional new entities, and with minimal modifications to existing H.323 standard. Such mobility extensions can serve as an add-on feature for the existing Internet telephony systems compliant to the H.323 standard