Notes
1. SDP - Offer /Answer
2. Tags are not part of the To or From URI, but are part of the header and always placed outside any "<>"
3. PRACK - Provisional acknowledgement for 180 Ringing
a) In 180 Ringing response, UAS will send the "RSEQ 314".
b) To response that PRACK will send as acknowldgement to the 180 Ringing response with "RACK 314" and CSEQ as "2" (Seperate transaction from the Invite)
c) And a 200OK will send from the UAS for PRACK with CSEQ as 2
4. To update the session parameters for the established session. ReINVITE is used. Where as for the pending sessions (i.e INVITE send, but no final response recieved), UPDATE method is used
Uses of UPDATE method are: Muting, placing on hold pending media streams, performing QOS or other prior to the session establishment.
5. Methods - INVITE, REGISTER, ACK, BYE, CANCEL, OPTIONS, PRACK, SUBSCRIBE, NOTIFY, PUBLISH, UPDATE, INFO, REFER, MESSAGE.
6. When a user agent recieves a method, which is not supported, Then it replies with 501 - Not implemented response
7. User Agents indicates the supported methods in the Allow header
8. Expires header - used when requests are not responsed by the other end point before session
Session -Expires - Used when requests are not responsed by the other end point after session establishment.
9. SBC - Used to connect IP-PBX to the Voip Service providers. Its installed in the end network to connect to the voip service provider. Acts as as Media conversion (i.e G729 to G711, SIP to SIP-I to SIP-TLS) Firewall, NAT Traversal and provides network security to the internal networks, Call admission control etc
Whereas VOIP Gateway is used to connect IP-PBX to PSTN & ISDN service providers.
1. SDP - Offer /Answer
2. Tags are not part of the To or From URI, but are part of the header and always placed outside any "<>"
3. PRACK - Provisional acknowledgement for 180 Ringing
a) In 180 Ringing response, UAS will send the "RSEQ 314".
b) To response that PRACK will send as acknowldgement to the 180 Ringing response with "RACK 314" and CSEQ as "2" (Seperate transaction from the Invite)
c) And a 200OK will send from the UAS for PRACK with CSEQ as 2
4. To update the session parameters for the established session. ReINVITE is used. Where as for the pending sessions (i.e INVITE send, but no final response recieved), UPDATE method is used
Uses of UPDATE method are: Muting, placing on hold pending media streams, performing QOS or other prior to the session establishment.
5. Methods - INVITE, REGISTER, ACK, BYE, CANCEL, OPTIONS, PRACK, SUBSCRIBE, NOTIFY, PUBLISH, UPDATE, INFO, REFER, MESSAGE.
6. When a user agent recieves a method, which is not supported, Then it replies with 501 - Not implemented response
7. User Agents indicates the supported methods in the Allow header
8. Expires header - used when requests are not responsed by the other end point before session
Session -Expires - Used when requests are not responsed by the other end point after session establishment.
9. SBC - Used to connect IP-PBX to the Voip Service providers. Its installed in the end network to connect to the voip service provider. Acts as as Media conversion (i.e G729 to G711, SIP to SIP-I to SIP-TLS) Firewall, NAT Traversal and provides network security to the internal networks, Call admission control etc
Whereas VOIP Gateway is used to connect IP-PBX to PSTN & ISDN service providers.
