H.323: H.323 version 5, H.245 fast connect
Enblock dialing, Overlapped sending
RAS Gatekeeper routed signaling (support for external Gatekeeper)
Security (encrypted password authentication H.235)
Supplementary Services: H.450.1
H.450.2 Call transfer
H.450.3 Call diversion
H.450.4 Call hold
H.450.5 Call Pick-up
H.450.6 Call waiting
H.450.7 Message Waiting Indication
H.450.8 Name identification
H.450.9 Call Completion busy (CCBS) and Call Completion no Reply (CCNR)
DTMF: H.245 Alphanumeric oder Signal Type
SIP: SIP version 2 (including HTTP digest authentication) conform RFC 3261
SIP over UDP, TCP, TLS (SIPS, V 7.0 or higher)
SIP services: MWI (rfc3842/rfc3265 "Subscription für message-summary")
DTMF (rfc2833 "RTP payload for DTMF")
Name Identification (Display String, rfc3325 "Asserted Identity")
Hold/Retrieve (rfc3264 "Offer/Answer Model for SDP")
Transfer (rfc3515 "REFER Method", rfc3891 "Replaces Header)
Coder Change, T.38 (rfc3264 "Re-Negotiation")
Call Forwarding (PBX internal, "183 Call Is Being Forwarded", "Diversion Header")
Overlap Dialing (rfc3578)
Dialoge State monitoring, partner Key (rfc 4235)
Instant Messaging (rfc 3428)

etc...