[Ekiga-list] ekiga call flow

[Ramachandran M <ram tataelxsi co in>]

hi all

 

i have some doubt in the SIP call flow.Please help me....

 

STEPS:

1.sender receives the 180 ringing, so onrecivedRinging() is to be called.

 

void SIPConnection::OnReceivedRinging(SIP_PDU & /*response*/)
{
  PTRACE(2, "SIP\tReceived Ringing response");

 

  if (phase < AlertingPhase)
  {
    phase = AlertingPhase;
    OnAlerting();
  }

 

2.In OnReceivedRinging() function,OnAlerting is also called.

BOOL OpalCall::OnAlerting(OpalConnection & connection)
{
  PTRACE(3, "Call\tOnAlerting " << connection);

 

  BOOL ok = FALSE;

 

  if (!LockReadWrite())
    return FALSE;

 

  partyB = connection.GetRemotePartyName();

 

  UnlockReadWrite();

 

  BOOL hasMedia = connection.GetMediaStream(OpalMediaFormat::DefaultAudioSessionID, TRUE) != NULL;

 

  for (PSafePtr<OpalConnection> conn(connectionsActive, PSafeReadOnly); conn != NULL; ++conn) {
    if (conn != &connection) {
      if (conn->SetAlerting(connection.GetRemotePartyName(), hasMedia))
        ok = TRUE;
    }
  }

 

  return ok;
}

3. See this line in OnAlerting() function:  conn->SetAlerting(connection.GetRemotePartyName(), hasMedia))

 

 

here we are calling setAlerting()

 

 

 

4.the setalerting() definition is given below:

 

BOOL SIPConnection::SetAlerting(const PString & /*calleeName*/, BOOL /*withMedia*/)
{
  if (IsOriginating()) {
    PTRACE(2, "SIP\tSetAlerting ignored on call we originated.");
    return TRUE;
  }

 

  PTRACE(2, "SIP\tSetAlerting");

 

  if (phase != SetUpPhase)
    return FALSE;

 

  SIP_PDU response(*originalInvite, SIP_PDU::Information_Ringing);
  SendPDU(response, originalInvite->GetViaAddress(endpoint));
  phase = AlertingPhase;

 

  return TRUE;
}

 

 

Here we are sending SIP_PDU::Information_Ringing to the "PartyB",why it is so?

 

But actual flow i studied in SIP TUTORIAL is

partyA has to send the invite,

the partyB has to send the 180::Ringing,200::OK

then PartyA has to send the ACK

 

 

Can you clarify me?

 

 

thanks