[SR-Users] Parallel forking call drop scenario

[James Browne]

The scenario, as I see it, is that
- the call is parallel-forked from kamailio to B1 and B2
- B1 answers the call and this works fine
- Kamailio sends a CANCEL to B2, but this CANCEL gets lost
- B2 answers the call
- B2 sends a BYE and kills the call

The user A should be responsible for handling this situation (it
should BYE the call to B2 when it gets the 200-OK).

Miconda answered this a few years ago here.
https://github.com/kamailio/kamailio/issues/570

James

On Wed, 30 Mar 2022 at 05:36, Koray Vatansever
<koray.vatansever at gmail.com> wrote:
>
> Hi,
>
> I would appreciate if anyone has any suggestions regarding the following?
>
>
> On Thu, Mar 24, 2022 at 3:38 PM Koray Vatansever <koray.vatansever at gmail.com> wrote:
>>
>> Hi everyone,
>>
>> I'm facing the following situation.
>>
>> Clients are connected over TLS. Therefore there is no retransmission in Kamailio.
>>
>> How can I prevent this call drop?
>>
>>
>>
>> +---+                             +-----------+              +-----+                      +-----+
>> | A |                             | Kamailio  |              | B1  |                      | B2  |
>> +---+                             +-----------+              +-----+                      +-----+
>>   |                                     |                       |                            |
>>   | INVITE                              |                       |                            |
>>   |------------------------------------>|                       |                            |
>>   |                                     | -------------------\  |                            |
>>   |                                     |-| Parallel forking |  |                            |
>>   |                                     | |------------------|  |                            |
>>   |                                     |                       |                            |
>>   |                                     | INVITE                |                            |
>>   |                                     |---------------------->|                            |
>>   |                                     |                       |                            |
>>   |                                     | INVITE                |                            |
>>   |                                     |--------------------------------------------------->|
>>   |                                     |                       |                            |
>>   |                                     |           180 Ringing |                            |
>>   |                                     |<----------------------|                            |
>>   |                                     |                       |                            |
>>   |                                     |                       |                180 Ringing |
>>   |                                     |<---------------------------------------------------|
>>   |                                     |                       | ------------------------\  |
>>   |                                     |                       |-| User answers the call |  |
>>   |                                     |                       | |-----------------------|  |
>>   |                                     |                       |                            |
>>   |                                     |                200 OK |                            |
>>   |                                     |<----------------------|                            |
>>   |                                     |                       |                            |
>>   |                              200 OK |                       |                            |
>>   |<------------------------------------|                       |                            |
>>   |                                     |                       |                            |
>>   | ACK                                 |                       |                            |
>>   |------------------------------------>|                       |                            |
>>   |                                     |                       |                            |
>>   |                                     | ACK                   |                            |
>>   |                                     |---------------------->|                            |
>>   | ------------------------------\     |                       |                            |
>>   |-| Session established with B1 |     |                       |                            |
>>   | |-----------------------------|     |                       |                            |
>>   |                                     |                       |                            | ----------------------------\
>>   |                                     |                       |                            |-| Client changes network    |
>>   |                                     |                       |                            | | LTE to Wifi or vice versa |
>>   |                                     |                       |                            | | Temporary connection lost |
>>   |                                     | CANCEL                |                            | |---------------------------|
>>   |                                     |----------------------------------------------X     |
>>   |                                     |                       |                            | -------------------------------------------------\
>>   |                                     |                       |                            |-| Reconnected with different IP                  |
>>   |                                     |                       |                            | | CANCEL is missed and client continues ringing. |
>>   |                                     |                       |                            | | User answers the call.                         |
>>   |                                     |                       |                     200 OK | |------------------------------------------------|
>>   |                                     |<---------------------------------------------------|
>>   |                                     |                       |                            |
>>   |                              200 OK |                       |                            |
>>   |<------------------------------------|                       |                            |
>>   |                                     |                       |                            |
>>   |                                     |                       |                        BYE |
>>   |                                     |<---------------------------------------------------|
>>   |                                     |                       |                            |
>>   |                                 BYE |                       |                            |
>>   |<------------------------------------|                       |                            |
>>   | ---------------------------\        |                       |                            |
>>   |-| Session terminated by B2 |        |                       |                            |
>>   | | Call Drop                |        |                       |                            |
>>   | |--------------------------|        |                       |                            |
>
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