How does SIP relate to MGCP/Megaco?
MGCP/Megaco and SIP are not peers; they can and will co-exist in converged networks. Though MGCP/Megaco can control end-points, the services thus enabled are very limited. SIP, therefore, is required to control end-points and also to communicate between softswitches. MGCP/Megaco is used to internally control the media gateway. This topic is dealt with in the relevant About SIP section. What is a Softswitch? A softswitch sits at the interconnect point between an IP network and other networks and controls the media gateways using a master/slave protocol such as MGCP. It also translates signalling protocols from one environment to another (e.g SIP to SS7). Softswitches are also known as Media Gateway Controllers (MGCs) and Call Agents.
