INTERNET telephony or Internet TELEPHONY?

Internet telephony (or VoIP) has been viewed in two different ways. First, some hold that it is largely similar to earlier architectural changes in the PSTN, continuing the transition from analog to circuit-switched digital and now to packet-switched transmission. Others believe that Internet telephony is primarily another Internet application that happens to interconnect with a “legacy” network. In this note, we argue that the latter is closer to technical reality, as Internet telephony is largely indistinguishable from other Internet applications at all layers of the protocol stack and that the integration of Internet telephony and other applications is likely to increase rather than decrease, while similarities to the existing voice network are likely to be transition phenomena. • Voice traffic is essentially indistinguishable from other data traffic, particularly if the senders of such traffic have incentives to mask the true nature of the traffic. • Signaling and media flows can traverse completely disjoint network paths, with signaling servers located essentially anywhere in the world relative to the caller or callee. The functionality of common channel signaling has been split into two completely independent functions, with the media path setup usually unnecessary due to the connectionless nature of IP networks. • With the advent of presence and instant messaging, the limitations of ring-andanswer telephony will become apparent, leading to a transition to rich presence and negotiated communications. • Calls are likely to contain a mixture of voice, video and data streams, added and removed dynamically within a session. • The notion of a call as a symmetric, duplex voice session of relatively short duration may vanish as modes closer to push-to-talk, intercom or continuous voice monitoring take over. • Calls are likely to be embedded into other applications, including interactive computer games, rather than being placed by manual dialing. • The centrality of telephone numbers will diminish, replaced by email-like identifiers that avoid the problems of scarcity. Telephone numbers will no longer necessarily identify a PSTN-connected device.