ths. For one thing, it is an ITU standard. In addi- tion, it is a mature protocol with many large-scale deployments. It has widespread vendor support and market acceptance, and it facilitates interoperability between vendors. Finally, it has defined standards for supplementary services, the network retains the call state for the duration of the call (providing greater call control for the user), and application services are available through the gatekeeper and best- of-breed application platforms. H.323 suffers from some limitations as well: As mentioned earlier, it is com- plex, it is tuned for PC conferencing rather than telephony, it has very bad scaling properties, and getting it to work reliably over firewalls is quite a challenge, espe- cially if both parties in a call are behind firewalls (e.g., only four TCP connections per call are allowed). Maintaining call state in the network actually increases the cost to scale. Many soft phones are proprietary, SO they are not widely deployed. Megaco and MGCP Both Megaco (Media Gateway Controller) and MGCP (Media Gateway Control Protocol) are protocols for control of elements in a physically decomposed multi- media gateway, which enables separation of call control from media conversion. This means that the system is composed of a call agent, at least one media gateway whose function is to perform the conversion of media signals between circuits and packets, and at least one signaling gateway when connected to the PSTN. Both Megaco and MGCP are media/device control protocols. They both embrace a phi- losophy in which the network is smart and the endpoint is dumb. Services are pro- vided by intelligent network elements. So why are there two standards, Megaco and MGCP? As usually is the case, it is the result of different parties with different interests and agendas. Megaco was created by joint efforts of the IETF and the ITU. Megaco is the IETF name and is defined in IETF RFC 3525. Within the ITU it is known as ITU Recommendation H.248. MGCP originated with Cisco and 