Skinny is a lightweight protocol for relaying stimulas between end devices and CM or a router setup/teardown cisco proprietary.
Have a look at some of the documentation on the web in regards to SIP.
And if your keen you can download SER from iptel.org
SIP Express Router (ser) connect some phone and messanger clients and have fiddle around.
Features: iptel.org's flagship: A high-performance, configurable SIP server. It can act as registrar, proxy or redirect server. It features an application-server interface, presence support, SMS gateway, SIMPLE2Jabber gateway, RADIUS/syslog accounting and authorization, server status monitoring, FCP security, etc.
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Taking advantage of its foundation in Internet protocols, SIP enhances the ability to create services that integrate telephony with Web-based services such as instant messaging and presence. Though SIP has its roots in Internet technology, it facilitates seamless interoperability with traditional telephony networks and helps packet-based networks achieve the scaling, reliability, and voice quality of the global switched telephone network.
The telecommunications industry has matured since SIP was introduced three years ago, and now the promise of SIP—a lightweight, Internet-friendly protocol that provides the ability to create converged services that integrate traditional voice-based services with Internet-based services—has become a reality. Major carriers in every geographical market have deployed SIP technology, proving that SIP is mature and world ready.
As part of Cisco's multiprotocol voice strategy, Cisco has developed a broad offering of SIP-enabled products and solutions. With the broadest portfolio of packet telephony products and solutions in the market today, Cisco enables service providers to cost-effectively take advantage of the strength of standards-based protocols to reliably scale networks and manage them effectively. The protocol flexibility inherent in Cisco solutions gives service providers the ability to offer a broader service portfolio, including traditional voice services and new services such as IP Centrex, unified messaging, hosted call center, and second-line residential services.
References
http://www.iptel.org/products/
http://www.cisco.com/en/US/tech/tk652/tk701/technologies_white_paper09186a0080092947.shtml
