In some *music on hold* scenarios, the INVITE doesn't carry SDP, while 200 OK contains offer and ACK would contain answer.
For a detailed call flow you can look at http://tech-invite.com/Ti-sip-service-3.html In such cases, the ACK would require interaction from TU because it has to decide on codec negotiation etc. So, ACK will be sent to Transport Layer directly, I mean since ACK doesn't have any response, no transaction would be created but rather directly sent to Transport Layer. Somesh * Please do not take print out of this e-mail unless its absolutely necessary * -----Original Message----- From: priyank luthra [mailto:[email protected]] Sent: Mon 3/2/2009 2:03 PM To: Somesh S. Shanbhag Cc: [email protected] Subject: Re: [Sip-implementors] Why ACK is not part of the INVITE transactionfor 2xx reponse, but is part of transaction for non-2xx response? Hi Somesh, Could you shed more light on the last line? Whats meant by delayed media scenarios where ACK as a separate transaction is helpful? On Mon, Mar 2, 2009 at 12:55 PM, Somesh S. Shanbhag <[email protected] > wrote: > ACK is generated by the TU in case of 2xx is received and directly passed > onto > transport layer for sending. In the case of receiving non-2xx final > responses, the > ACK is generated by the transaction layer itself so, its part of the same > transaction. > > In case of 2xx final responses, ACK can be helpful in the delayed media > scenarios > where-in the TU can negotiate SDP's > > > Somesh > > * Please do not take print out of this e-mail unless its absolutely > necessary * > > > > > -----Original Message----- > From: [email protected] on behalf of priyank > luthra > Sent: Mon 3/2/2009 12:33 PM > To: [email protected] > Subject: [Sip-implementors] Why ACK is not part of the INVITE > transactionfor 2xx reponse, but is part of transaction for non-2xx > response? > > I would like to know that why is ACK not considered the part of INVITE > transaction when 2xx response is received. But when non-2xx response is > received, its considered to be part of same transaction. Why is that? > > > -- > Regards, > Priyank > _______________________________________________ > Sip-implementors mailing list > [email protected] > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors > > ------------------------------ > EMAIL DISCLAIMER : This email and any files transmitted with it are > confidential and intended solely for the use of the individual or entity to > whom they are addressed. Any unauthorised distribution or copying is > strictly prohibited. If you receive this transmission in error, please > notify the sender by reply email and then destroy the message. Opinions, > conclusions and other information in this message that do not relate to > official business of Mascon shall be understood to be neither given nor > endorsed by Mascon. Any information contained in this email, when addressed > to Mascon clients is subject to the terms and conditions in governing client > contract. > > Whilst Mascon takes steps to prevent the transmission of viruses via > e-mail, we can not guarantee that any email or attachment is free from > computer viruses and you are strongly advised to undertake your own > anti-virus precautions. Mascon grants no warranties regarding performance, > use or quality of any e-mail or attachment and undertakes no liability for > loss or damage, howsoever caused. > > -- Regards, Priyank EMAIL DISCLAIMER : This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. Any unauthorised distribution or copying is strictly prohibited. If you receive this transmission in error, please notify the sender by reply email and then destroy the message. Opinions, conclusions and other information in this message that do not relate to official business of Mascon shall be understood to be neither given nor endorsed by Mascon. Any information contained in this email, when addressed to Mascon clients is subject to the terms and conditions in governing client contract. Whilst Mascon takes steps to prevent the transmission of viruses via e-mail, we can not guarantee that any email or attachment is free from computer viruses and you are strongly advised to undertake your own anti-virus precautions. Mascon grants no warranties regarding performance, use or quality of any e-mail or attachment and undertakes no liability for loss or damage, howsoever caused. _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
