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As of this writing, Instant Messaging (IM) services that also provide VoIP seem
to surpass by far the VoIP services offered by telephone companies, whatever
metric one may want to chose: Number of subscribers, revenue, or traffic sta-
tistics. Well-known IM services are available from large providers such as
Apple, AOL, Google, IBM, ICQ, Microsoft, Skype, Yahoo!, and also from an
increasing number of smaller providers.

NOTEAs mentioned in Chapter 4, “DNS and ENUM,” in the sidebar “Do you

really have VoIP?” we do not consider a service to be true VoIP unless the user

gets a URI and can initiate calls to other URIs, besides using phone numbers.

The dominance of IM services over VoIP services seems to be empirical
proof that voice may eventually be relegated to an application within an IM
service, together with video, white board, collaboration, application sharing,
file transfer, and so on. From this perspective, telephony seems to be a business
model that is being made obsolete by the Internet, for all users who have Inter-
net access, wired or wireless.
URIs enable presence and IM-based communications and applications,
while phone numbers and using the PSTN or PBX do not.

Presence and

Instant Messaging

CHAPTER

13