A gateway in this context is a network device capable of converting between interface types. One type of gateway is a SIP to PSTN gateway. A gateway does not handle registration and authentication of devices. The Cisco 2600 can be configured as a SIP to PSTN gateway.
Gatekeeper is a term used in H.323 networks. A Gatekeeper handles the registration and authentication of devices. The Cisco SIP Proxy would perform this function in a SIP network. The SIP Proxy directs calls between endpoints and gateways.
This was first published in February 2004