Altigen MAXCS ACC 6.5 Administration Manual page 347

Parameter
G.729 RTP Packet
Length (ms)
DTMF Delivery
(Applies to SIP protocol
only)
SIP Early Media
(Applies to SIP protocol
and SIP trunk only)
Chapter 25: Enterprise VoIP Network Management
Description
Lets you configure the length of the RTP packets for
G.729 in milliseconds. The RTP packet length can be
set to 10, 20 or 30 milliseconds.
Default—If SIP INFO is used to deliver DTMF.
RFC 2833—The DTMF pay load is embedded with
RTP. Most 3rd-party SIP gateways support this
standard.
In band—If DTMF tone is delivered over the voice
band. It's not reliable over G.711 codec and will not
work over G.729/G.723 codec
SIP Early Media allows two SIP devices to
communicate before a SIP call is actually
established. It is important for interoperability with
the SIP trunk carrier's PSTN gateway. If SIP Early
Media is not checked, the caller may not hear the
exact ringback tone provided by the CO (the caller
may not hear any ringback tone at all).
MAXCS ACC 6.5 Administration Manual 333