Linking the Internet and conventional telephony, SIP will be the
key to 3G services, writes Nick Langley.
What is SIP?
Session Initiation Protocol (SIP) is used
for setting up communications sessions - such as conferencing,
telephony, whiteboarding and instant messaging - on the Internet.
It bridges the gap between the Internet and conventional telephony.
Commercial SIP-based products and services already include IP
(Internet Protocol) phones, PC clients, SIP servers and IP
telephony gateways. It has huge potential for use in
third-generation (3G) wireless networks, in mobile applications,
and in providing the essential infrastructure for Internet
telephony, including quality of service and security. Multimedia
applications for SIP include spontaneous video calling and picture
caller ID. SIP is gradually replacing an earlier protocol, H.323.
Where did it originate?
SIP was developed by the
Internet Engineering Task Force (IETF), which also created the Web
protocol HTTP.
What's it for?
At a recent comms show in the US, SIP
was demonstrated at work in softswitches and softswitch-compliant
media servers, "presence" products (which detect whether people you
know are online at the same time as you) for mobile and fixed
networks, IP gateways, desktop phones and application
servers.
What makes it special?
SIP is a standard protocol which
addresses the needs of IP telephony from a wholly Internet-based
perspective, rather than evolving from the hierarchical and
deterministic world of legacy telephony systems. It has the
potential to break up the traditional private branch exchange-style
phone system into a number of commoditised, easily obtainable
components that can be mixed and matched.
This means customers will no longer be locked into the very
expensive value chains of conventional telephony. This could be
further bad news for already beleaguered telecoms equipment
suppliers - although some of the leading suppliers are in the
vanguard of SIP development.
How difficult is it?
SIP itself is an extremely simply
protocol, but its applications can be complex. See, for example,
the IETF paper An Application Server Component Architecture for SIP
at
www.sipforum.org.
Where is it used?
Initially SIP is being used to
provide IP telephony services which parallel those available in
conventional telephony. Network providers Level 3 and WorldCom both
offer SIP-based voice over IP services. But more revolutionary SIP
infrastructures and applications are being developed.
Not to be confused with
The Society of Internet
Professionals; the Stop Internet Plagiarism campaign.
What does it run on?
The leading SIP suppliers include
Convedia, Hotsip, Lucent, Mitel, Nortel, Pingtel and Radvision. BT
is using it for instant messaging. Others that have signed up
include Nokia and Deutsche Telecom.
AOL Time Warner has adopted SIP for the Instant Messaging and
Presence Leverage (Simple) messaging protocol.
Perhaps the most significant boost for SIP comes from Microsoft,
which has included a SIP stack in Windows XP and plans to make SIP
a main plank of its .net technology.
What's coming up?
SIP will be embedded in 3G phone
handsets and personal digital assistants.
In time, a SIP-based infrastructure may be used for both wireless
and wireline phones on public networks.
Training
SIP training is available from conventional
and Internet telephony equipment suppliers and independent training
organisations such as Learning Tree (
www.learningtree.co.uk/).
The jobs market
"With this sort of momentum behind it,
demand for SIP knowledge will increase as the telecommunications
industry emerges from recession, and related skills will inevitably
be in short supply," says E-Skills UK. Few jobs request SIP as yet,
and with the continued layoffs and recruitment freezes in the comms
sector, investing in this skill may require faith.