Short Term Challenges
The short-term challenges for SIP implementations in the market are described
in our companion book, SIP Beyond VoIP [1]. We provide here only a short
summary.
■■ NAT traversal using ICE as described in Chapter 10, “NAT and Firewall
Traversal.” The importance of stabilizing the emerging standard for ICE
cannot be overemphasized, since without ICE, ubiquitous interdomain
SIP-based communications will not be trivial to set up. Part of the NAT
traversal challenge is finalizing the work on the Globally Routing User
Agent URI (GRUU) [2].
■■ Abandoning the fixation on telephony, “PSTN over IP” style islands
that cannot connect directly over the Internet.
■■ High-quality voice endpoints with Internet codecs, echo control, and
so on. See Chapter 18, “Quality of Service for Real-Time Internet
Communications.”
■■ SIMPLE standards based presence and IM.
■■ Emergency services using the Internet.
■■ Internet communications for the disabled.
■■ Identity and security for interdomain communications.Future Services: The Internet Is the Service
Paul McFedries says [3], “The combination of ubiquity and necessity makes
the Net analogous to an atmosphere.” In this light, all real-time communica-
tions mentioned in this book are just applications living in the “atmosphere”
that is the Internet. An example for such services is the interdomain presence
service [4] from Tello, which helps professionals to contact their business cor-
respondents in the most convenient and effective way.
It is not practical to enumerate (and even less possible to predict) all the var-
ious real communication services and applications on the Internet.
Still to Develop: Peer-to-Peer SIP Standards
The first edition of this book in 2001 did not predict the emergence of P2P and
its dominance on the Internet. As discussed in Chapters 6 and 20, P2P SIP has
the potential of completely disrupting the VoIP industry (just as Skype has
already done) and to make obsolete most business models in the “traditional”
Conclusions and Future Directions 355