Re: [sipcore] RFC4028 : Very basic question in 8.1

[Roman Shpount <[e-mail]>]

On Thu, Jul 9, 2020 at 10:42 AM OKUMURA Shinji <[e-mail]>
wrote:

> > SE is the maximum allowed value.
>
> UAC can send again with a greater Session-Expires and Min-SE. The proxy
> CAN NOT reject the INVITE just because "Session Interval Too Large".
> Therefore SE isn't the maximum allowed value


Why do you think it cannot? Proxy can reject a new INVITE for any reason it
sees fit.


> .> If Proxy needs a higher SE interval, it needs to renegotiate maximum
> allowed session timer value with all the parties upstream.
>
> If Proxy needs a higher SE interval, the proxy need only increase
> SE-value. This procedure definitely works. Because this is the very
> procedure for when the UAC does not support timer.
> Again, proxies can't reject the INVITE just because the timer is too large.
>

The higher SE interval value might be too high for proxies upstream. Your
procedure breaks it. Again, proxies can reject INVITE for any reason.

> Once again, may I ask, what is your motivation for proposing this change?
>
> My motivation is that bis become to be more clear and error-free.
>

I have zero interest in this. Session Timer (and most of SIP related
specifications) are effectively legacy specifications in maintenance mode.
You need to show serious reasons to introduce major changes at this point.

> Are you seeing an issue with a deployment somewhere?
>
> No, You seem to attach great importance to that point, but I don't
> understand the importance of that.
> Do you argue that it is enough for each developer to address any issues on
> their own?
>

I am arguing that this is an old and widely deployed specification.  It
might not be clearly written but it is widely implemented which resulted in
some general consensus on how it is supposed to work. Making changes to it
is dangerous unless they are targeting specific issues.

There is something to be said about redoing the entire SIP specification to
be clearer and more logical, but this would be a different and much bigger
effort. Also, I do not see that enough people have interest in doing and,
what is much more important, implementing this new SIP specification. I
understand your desire in cleaning up the Session Timer specification, but
it would effectively render the resulting document irrelevant due to most
people refusing to implement changes which are too great.

Best Regards,
_____________
Roman Shpount