Encouraging Interoperability
SIP uses a text-based language. That doesn’t mean that SIP
supports only text; it means that SIP’s messages are easy to
program and interpret, making it easier to achieve interoper-
ability between different vendor implementations. SIP is also
very modular and extensible, allowing for the integration of
existing legacy protocols. These properties make SIP an ideal
protocol for implementing a standards-based converged com-
munications network.
The SIP standard is defined in RFC 3261 by the Internet
Engineering Task Force (IETF). The IETF is a large open
international community of network designers, operators,
vendors, and researchers concerned with the evolution of
the Internet architecture and its operation. Several neutral
consortiums, including SIPit, SIP Foundry, and SIP Forum,
arrange meetings and events where companies with SIP-based
hardware and software products can test interoperability with
other SIP-based products. This testing helps to promote
smoother integration of SIP-based products in carrier and
enterprise networks. We tackle this subject in depth in Part 5.
Some vendors have gone beyond these efforts with active
SIP interoperability and ecosystem programs. In a well-run SIP
ecosystem, devices and services obviously need to work
together seamlessly, and the only way to ensure that they do
is for many kinds of vendors to test their SIP-based products
together. For example, Avaya has made a commitment to
establishing openness and interoperability for SIP through its
Developer Connection program, which support software
developers, systems integrators, and service providers in
testing interoperability and developing SIP-based solutions
with Avaya products and services. You can find more infor-
mation about interoperability efforts in Part 5.
The impact of SIP goes beyond internal communications
within an enterprise. SIP has become a signaling standard for
carrier networks. Service providers have started to provide
SIP-based trunk services that can reduce costs and extend
an enterprise’s SIP environment into the public network.
The adoption of SIP for external connectivity will lead to a
Part 1: The Case for SIP
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