Registration, admission, and status (RAS) is a component of a network protocol that involves the addition of (or refusal to add) new authorized users, the admission of (or refusal to admit) authorized users based on available bandwidth, and the tracking of the status of all users. Formally, RAS is part of the H.225 protocol for H.323 communications networks, designed to support multimedia bandwidths. RAS is an important signaling component in networks using voice over IP (VoIP).
RAS messages are exchanged on a specific frequency called the RAS channel. The RAS channel is the first to be opened, and precedes any communications between endpoints and gatekeepers in the network. Signals in RAS can be categorized as (1) gatekeeper discovery requests and responses; (2) admission, registration, and unregistration messages and responses; (3) location requests and responses; (4) status requests and responses; and (5) bandwidth-control requests and responses.
The abbreviation RAS also stands for "reliability, availability, and serviceability" and for row address strobe.