Product specifications

Dialogic® BorderNet™ 4000 SBC Product Description Document
36
Call Flow/Type Description
slow-start)
H.323 fast-start upstream, SIP
downstream
If the H.323 fast-start offer includes alternative
codec options, the SDP offer sends the list of
alternative codecs to the downstream SIP device in
the same order of preference provided by H.323. The
most preferred codec is listed first.
The SIP endpoint can accept more than one codec;
the H.323 fast-start response cannot. In this case,
the BorderNet 4000 SBC prunes the codec list to a
single codec option and responds with a single codec
answer.
H.323 slow-start upstream, SIP
downstream
A default SDP offer is made to the SIP downstream;
this offer contains a single media channel with the
following codecs in order of preference: G.729,
G.711 U-law, G.71 1 A-law, and G.723.
Capabilities are then negotiated with the H.323
endpoint and a channel is opened with the selected
codec. A re-INVITE on the SIP side re-negotiates the
codec.
DTMF interworking
DTMF interworking between SIP and H.323 is
supported in the signaling plane using the
alphanumeric method of UserInputIndication.
Fax handling (T.38) T.38 fax calls are supported for interworking calls.
Interworking for basic call hold
features
Basic call hold features (codec change, hold and
resume signaling) are supported in H.323 and SIP
calls.
Early Media in SIP-to-H.323 Fast-Start Calls
Early media is supported for SIP endpoints calling H.323 fast-start endpoints. In this case,
the caller (SIP endpoint) makes a media proposal on the initial call setup request. The callee
(H.323 endpoint) responds to the offer before the call is connected.
H.323 may send a “progress indicator” on any H.225 message that is sent to the BorderNet
4000 SBC. A progress indicator with a value of 1 or 8 indicates that the H.323 endpoint will
send early media. The BorderNet 4000 SBC processes early media calls as follows:
• In an interworking call, only the first progress indicator received from the H.323
endpoint is used.
• In an interworking call with a SIP upstream call, if sufficient media parameters were
negotiated with the H.323 endpoint, the BorderNet 4000 SBC returns a 183
provisional response to the SIP caller with the SDP indicating early media.
• In an interworking call with a SIP upstream call, if insufficient media parameters
were negotiated with the H.323 endpoint, the BorderNet 4000 SBC waits for media