[SR-Users] Parallel forking call drop scenario

[Koray Vatansever]

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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