Table 2.2 (continued)PSTN Class services
Mobile cellular roaming
Desktop call manager
Replacement for Computer Telephony Integration (CTI)
Group calling
Click-to-connect
Internet call waiting
“Dialing” an e-mail address or URLThe signaling protocol for Internet multimedia real-time communications is
the Session Initiation Protocol (SIP).Protocols for Media Description, Media Transport,
and other Multimedia Delivery
The Internet has established itself as the most adequate platform for multime-
dia communications and for the delivery of streaming multimedia content.
Though signaling (the topic of this book) is most critical, it is not the only pro-
tocol required for multimedia communications. Internet standards feature a
pretty clean breakdown of functionality, and each function is performed by
one single protocol. Duplication of functions on two or more protocols is care-
fully avoided so that different implementations can have only one single way
of being standard-compliant. Table 2.1 shows the key standard Internet multi-
media protocols. The complete list is, however, bigger that what is shown in
the table.
The wise design decision of the Internet architects to make it equally suit-
able for any application has, however, led to the surprise of multimedia file
sharing and real-time communications that are not based on standards, mostly
using peer-to-peer protocols (P2P), some of which are described in Chapter 20.
A useful observation is that P2P traffic is dominant on the Internet, according
to several sources. An interesting source on Internet usage statistics that
include P2P traffic are given in [3] and [4]. P2P applications (such as replace-
ments of centralized IP PBXs) are also being deployed in the enterprise.14 Chapter 2