Gatekeepers: The necessary functions that a gatekeeper implements are address translation, bandwidth control, zone management and admission control, call authorization, call control signalling, bandwidth management and call management.It is used to drive the characteristics of a LAN endpoint to a switched circuit network endpoint or contrariwise where the call setup, control and translation is carried out by gateways. It can be eliminated when there is no other network is connected. Gateways: A connection path is provisioned between the packet switched network and circuit switched network is known as Gateways.A terminal can provide signalling and control, two-way communication in real time and codecs.

Terminal: As the name suggests, it is used as the endpoints within an IP network.

H.323 protocol suite involves some fundamental components for its functioning : Typically, H.323 is comprised of a collection of a protocol designed for encoding, decoding, and packetization of video and audio signals in order to employ call signalling and control. H.323 is the most pervasively used multimedia communication system across packet-switched and IP network as it the oldest multimedia communication protocol standard defined by ITU. Reusable elements easily conduct the implementation. Need of special parser complicate the deployment and debugging. Well defined protocols and complete backward compatibility makes it interoperable. Redirect and location server provides routing information The gatekeeper provides the routing information. Utilizes alias (which is mapped by gatekeepers).

ITU (International Telecommunication Union) Previously, telephony services were provided over the circuit switched network known as PSTN (Public Switched Telephone Networks) or POTS (Plain Old Telephone Services), which is still used in some areas. Hence, establishing a data call is more cost-effective than establishing a voice call. This type of additional charge is not pertinent to the long distance data transferring. IP telephony (Voice over IP) was evolved to implement cost savings, which actually produces from regulative taxes levied on long distances voice calls.

Session initiation protocol