[SIPForum-discussion] SIP to PSTN

[Dave McBride]

RFC 3960 may be worth a read.

Cheers
David
On 22 Jan 2013 21:05, "Stephen James" <sjames_1958 at yahoo.com> wrote:

> Remember, that ISUP is a protocol where the far end is supposed to provide
> ringback. A SIP -> PSTN gateway should open a backwards path when sending
> the IAM and send SDP backwards when sending the 18x. We have seen problems
> where a ACM (with subscriber status of free - indicating terminating party
> is ringing) results in a 180 with SDP and the receiver of that 180 not
> cutting through the far end ringback. The ACM with subscriber free may have
> to be sent as a 183 w/SDP to ensure correct interworking.
>
> Stephen James
> sjames_1958 at yahoo.com
>
> We are not princes of the earth, we are the descendants of worms, and any
> nobility must be earned.
>
>
> ------------------------------
> *From:* Abhisek Acharya <abhisek.acharya at gmail.com>
> *To:* Suryakanta Behera <skbehera321 at gmail.com>
> *Cc:* discussion at sipforum.org
> *Sent:* Sun, January 20, 2013 11:23:34 PM
> *Subject:* Re: [SIPForum-discussion] SIP to PSTN
>
>
> Question--:In SIP to PSTN Call Flow In-between GW are there, Someone tell
> me after sending ACM message "from SSP to GW" then GW what  it will send
> 180/183, if it is sending 183-Res to SIP then Two-way RTP will flowing in
> between SIP to GW  and one-way media will flowing SSP to GW"
>
> ANSWER--
>
> 1.The above one is a very very tricky situation.When ACM message comes
> from ISUP side ideally it means the phone is ringing on the ISUP side and
> the calling party should hear the ring-back tone.
>
> 2.Again the ring back can be  local ring back or remote back.if 18x
> response contains sdp body then this should be remote ring back and if it
> does not contain sdp body then this will be local ring back.
>
> 3.Also at times ACM message comes bit early than expected just to satisfy
> T9 timer which is otherwise called as early ACM.In this case the called
> party phone may not be ringing.It may be in roaming (in case of called
> subscriber is out of its HLR/MSC).In that case 183 response goes to SIP
> side and a subsequesnt CPG from ISUP side will comes from ISUP side to
> denote ringing.
>
>
> Ideally in case of 183 response two way RTP should not flow from the SIP
> end and GW is this is only for ringback.One way audio should flow.Are you
> sure two way audio is flowing from SIP entity to GW?I believe while
> ringback is there calling party is only hearing the ringback so  RTP should
> flow only one way.
>
> First Question:-
>
> "In between two user agent a C5 switch is present and one is sip user
> another is isup user , So who is responsible to convert SIP message to ISUP
> message in C5 switch. Actually what C5 are doing there & What are the
> functionality/Element contain C5 switch in particular situation".
>
> ANSWER
>
> C stands for CLASS which means Custom Local Area Signaling System and
> this is an ancient term since the old days of telecom when Graham bell
> started the legacy and Catagorisation started by AT&T folks where C5 stands
> for end switches and C4 switches are interconnecting switches where they
> connect multiple C5 switches.
>
> But in modern day telephony where various protocols are involved and
> interworking is a MUST then there is entity which is called as TANDEM
> switch/NGN switch which takes care of the SIGNALING conversion from one
> protocol to other protocol.Like ISUP to SIP.SIGNALING conversion is doen by
> the NGN switch and the media is also converted from CIRCUIT SWITCHED MEDIA
> to PACKETISED MEDIA and this is done by with the help of  MEDIAGATEWAYS.
>
> Ideally C5 elements maintain the end point phone informations like its
> number,its balance,etc.Ideally modern day MSCs are clasic examples of
> CLASS5 switches and old day telephone exchanges are also the
> exmaples.Please let me know if something is not clear here.
>
> SSP---------NGN---------SIP
>
>
> Abhisek Acharya
> GS-LAB,PUNE
>
>
> On Tue, Jan 15, 2013 at 5:07 PM, Suryakanta Behera <skbehera321 at gmail.com>wrote:
>
>> Hi,
>>
>> I have a question. Can Anyone help
>>
>> "In between two user agent a C5 switch is present and one is sip user
>> another is isup user , So who is responsible to convert SIP message to ISUP
>> message in C5 switch. Actually what C5 are doing there & What are the
>> functionality/Element contain C5 switch in particular situation".
>>
>> Another Question
>> "In SIP to PSTN Call Flow In-between GW are there, Someone tell me after
>> sending ACM message "from SSP to GW" then GW what  it will send 180/183, if
>> it is sending 183-Res to SIP then Two-way RTP will flowing in between SIP
>> to GW  and one-way media will flowing SSP to GW"
>>
>> Is it Correct ! If Correct, how two-way RTP will flowing in between SIP
>> to GW  and one-way media will flowing SSP to GW.
>>
>>
>>
>> Please, describe briefly about this....
>>
>> Thanks & Regards
>> Surya
>>
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>
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