Confronted with a whole new bunch of terms and acronyms, it can be confusing for someone new trying to make sense of the alphabet soup in the field of Unified Communications and Collaboration. Let us kick off this little tutorial series to introduce the basics when looking at Voice over IP (VoIP) and related technologies.
In VoIP, common standards-based signaling protocols include the well known Session Initiated Protocol (SIP), the H.323 family of protocols, Media Gateway Control Protocol (MGCP), H.248 and Cisco’s proprietary Skinny Client Control Protocol (SCCP). The first two are peer-to-peer protocols whereas the latter three are client server based. Both SIP and MGCP are ASCII plain text protocols.
Signaling covers the important tasks of end-to-end call initiation and termination, event notifications and the handling of call control messages such as connect and disconnect messages.
End points (devices or gateways) that support SIP and H.323 have on-board call control intelligence. Settings for route patterns and dial plans must be performed directly on the devices which can make configuration complex. On the other hand, MGCP, H.248 and SCCP rely on external call control devices (”call agent”) where the configuration information reside for centralized administration. Cisco Unified Communications Manager (UCM, CCM Server or “Call Manager”) is an example of a call agent.
It is worthwhile to note that H.323 is the de-facto standard for voice and video-conferencing in today’s packet-switched network. Designed to enhance IP networks with traditional telephony functionality, H.323 compliant end points, gateways and gatekeepers work seamlessly with SCCP in a Cisco environment.
H.323 = ITU-T H.32x standard protocol suite
SIP = IETF Multi-party Multimedia Session Control (MMUSIC Working Group) RFC 2543, 3261, 3665
MGCP = RFC 2705, 3660, 3435, 3661