GNU Gatekeeper is an open-source project that implements an H.323 gatekeeper. A gatekeeper provides call control services to the H.323 endpoints. It is an integral part of most useful internet telephony installations that are based on the H.323 standard.

According to Recommendation H.323, a gatekeeper shall provide the following services:

Address Translation
Admissions Control
Bandwidth Control
Zone Management
Call Control Signaling
Call Authorization
Bandwidth Management
Call Management
The GNU Gatekeeper implements most of these functions based on the OpenH323 protocol stack.