Hi Pekka Pessi;
a) Does the Sofia-SIP soa module support “Delayed Offer” ?
b) How can this call scenario be implemented with the soa module?
SOFIA-SIP (soa)
A (UAC) B (UAS)
| |
|<---------- INVITE ----------|
| |
|------- 100 Trying --------->|
|------- 180 Ringing -------->|
| |
|------- 200 (offer) -------->|
|<------ ACK (answer) --------|
| |
c) How can this call scenario be implemented with the soa module?
SOFIA-SIP (soa)
A (UAC) B (UAS)
| |
|---------- INVITE ---------->|
| |
|<------- 100 Trying ---------|
|<------- 180 Ringing --------|
| |
|<------- 200 (offer) --------|
|------ ACK (answer) -------->|
| |
Note: RFC 3261 defines two ways that SDP messages can be sent in the Offer and
Answer. These methods are commonly known as Delayed Offer and Early Offer, and
support for both methods by User Agent Client/Servers is a mandatory
requirement of the specification. In the simplest terms, an initial SIP Invite
sent with SDP in the message body defines an Early Offer, whereas an initial
SIP Invite without SDP in the message body defines a Delayed Offer.
In an Early Offer, the session initiator (calling device) sends its
capabilities (for example, codecs supported) in the SDP contained in the
initial Invite (thus allowing the called device to choose its preferred codec
for the session). In a Delayed Offer, the session initiator does not send its
capabilities in the initial Invite but waits for the called device to send its
capabilities first (for example, the list of codecs supported by the called
device, thus allowing the calling device to choose the codec to be used for the
session).
Best regards
Edson G. Leme
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