Re: [sipcore] 4028bis: memory refresh - proxy assumptions

[Roman Shpount <[e-mail]>]

On Thu, May 14, 2020 at 10:08 AM Christer Holmberg <
[e-mail]> wrote:

> >1. Defining proxy behavior based on having a transaction in progress:
> This is hard to implement in practice since initial INVITE and UPDATE
>
> >might not even go over the same path and the same proxies.
>
>
>
> Section 8 of RFC 4028 says:
>
>
>
>    “Proxies that ask for session timers SHOULD record-route, as they
>
>    won't receive refreshes if they don't.”
>
>
>
> In my opinion it should be possible to mandate that a proxy that asks for
> session timers, or modifies a session timer value (S-E or Min-SE), also
> record-route.
>
>
>
I have mentioned before that even requiring record-route would be
insufficient. First of all, having a transaction in progress for a proxy is
something that can be ambiguous due to network delays or message
re-ordering even if it is always on the dialog path. Second, the amount of
state maintained by proxy, if it needs to track transactions vs dialogs
increases significantly. Third, even if the proxy can be the same "logical
proxy", it can actually be multiple physical servers sharing an address
behind a load balancer, so UPDATE and INVITE transactions can end up on the
different servers.

Best Regards,
_____________
Roman Shpount