Voice gateway is a device used to terminate and originate voice traffic using tdm interfaces and the ip network to route the voice traffic. It typically uses dsps to transcode the voice traffic and uses codec algorithms to compress the voice.
Voice Gatekeeper is a device that is used in keeping a centralized dialplan as well as providing call admission control for h323 endpoints. Gatekeepers keep registratiopn database of endpoints and entertain call and bandwidth requests from endpoints and provide a more manageable solution.
Hope this answers your questions.
