thinQmaster Virtual testing partner Adaptive practice exams that find your weak spots and drill them. Every answer explained. From $69
Enroll

thinQmaster

Find your exam

Five questions free, before you decide.

Step 1 · choose a vendor

In one of our camps? Your practice exams come with the tuition — they are on your study page already.

Collaboration, Voice & AV · Advanced

H.225

The H.323 protocol for call signaling (Q.931-based, TCP 1720) and Registration, Admission and Status (RAS, UDP 1719).

Definition

H.225.0 has two parts. Call signaling uses Q.931-style SETUP, ALERTING and CONNECT messages to establish the call. RAS handles gatekeeper discovery, registration (RRQ), admission requests (ARQ), bandwidth requests and disengage messages between endpoints and a gatekeeper.

Example

An H.323 gateway sends ARQ to its gatekeeper, receives ACF with the destination address, then sends H.225 SETUP.

Exam tip

RAS is UDP 1719 and only exists when a gatekeeper is used; call signaling is TCP 1720.

Related terms