Re: [asterisk-dev] Subscription behavior when an incoming registration goes away?

[Olle E. Johansson]

> On 22 Dec 2016, at 18:13, George Joseph  wrote:
> 
> 
> 
> On Thu, Dec 22, 2016 at 9:22 AM, Olle E. Johansson  > wrote:
> 
>> On 22 Dec 2016, at 17:14, Matthew Jordan > > wrote:
>> 
>> 
>> 
>> On Thu, Dec 22, 2016 at 9:32 AM, George Joseph > > wrote:
>> When an incoming registration goes away, either because it expires or it was 
>> explicitly expired, what should we do with subscriptions the contact may 
>> have?  Right now we do nothing which means that activity for those 
>> subscriptions will trigger NOTIFYs which will time out and retry until 
>> timer_b expires.  Only then will they be deleted.
>> 
>> Should we:
>> Leave the behavior as is?
>> Automatically remove the subscriptions for a contact that has been deleted?
>> Create a global option to control auto deletion?
>> Create an aor option to control auto deletion?
>> Opinions?
>> 
>> 
>> If an AoR only has dynamic contacts, and those dynamic contacts are no 
>> longer valid (or the AoR no longer has any contacts), then at the very least 
>> I would think we wouldn't want to send the NOTIFY requests until the AoR has 
>> valid contacts. There's certainly no reason to use memory/CPU cycles on 
>> something that will never succeed.
>> 
>> You may or may not want to actually remove the underlying subscription. I 
>> could see a scenario in which a phone's REGISTER request goes "missing", and 
>> so the registration drops - maybe for just a short period of time. When the 
>> new REGISTER request does succeed, the phone may or may not send a new 
>> SUBSCRIBE request (which may have a very different timer). If we 
>> auto-deleted the underlying subscription, we could have a situation where 
>> the phone is re-registered but no longer receives state updates.
>> 
>> I'll grant the above scenario is pretty unlikely, but it is plausible.
> 
> Without knowing the details of the PJSIP channel this conversation seems all 
> upside down to me.
> Subscriptions provide their own contact for the NOTIFY and have no 
> relationship to the REGISTER message.
> 
> There's no protocol level relationship but there is a functional 
> relationship.  If a phone with 15 BLF subscriptions goes missing and we can 
> correlate the expired registration contact with the subscription contact, 
> should we bother sending NOTIFYs that we know will timeout and need to be 
> retried?
>  
It all depends on how you determine that a device “goes missing” but the cool 
thing with subscriptions is that a server can
terminate the subscription early by sending a notify. If the phone considers 
itself alive and kicking, it will send a re-subscribe
to fight your decision. I would say that the correlation should be 
“sip-instance”, the UUID of the device, to be good enough
to do this.

I think this happens in chan_sip if an extension disappears at dialplan reload 
and we have active subscriptions for it
- we terminate the subscription from the server side. Kevin and I worked on 
that part a long time ago.

/O-- 
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Re: [asterisk-dev] Subscription behavior when an incoming registration goes away?

[George Joseph]

On Thu, Dec 22, 2016 at 9:22 AM, Olle E. Johansson  wrote:

>
> On 22 Dec 2016, at 17:14, Matthew Jordan  wrote:
>
>
>
> On Thu, Dec 22, 2016 at 9:32 AM, George Joseph  wrote:
>
>> When an incoming registration goes away, either because it expires or it
>> was explicitly expired, what should we do with subscriptions the contact
>> may have?  Right now we do nothing which means that activity for those
>> subscriptions will trigger NOTIFYs which will time out and retry until
>> timer_b expires.  Only then will they be deleted.
>>
>> Should we:
>>
>>- Leave the behavior as is?
>>- Automatically remove the subscriptions for a contact that has been
>>deleted?
>>- Create a global option to control auto deletion?
>>- Create an aor option to control auto deletion?
>>
>> Opinions?
>>
>>
> If an AoR only has dynamic contacts, and those dynamic contacts are no
> longer valid (or the AoR no longer has any contacts), then at the very
> least I would think we wouldn't want to send the NOTIFY requests until the
> AoR has valid contacts. There's certainly no reason to use memory/CPU
> cycles on something that will never succeed.
>
> You may or may not want to actually remove the underlying subscription. I
> could see a scenario in which a phone's REGISTER request goes "missing",
> and so the registration drops - maybe for just a short period of time. When
> the new REGISTER request does succeed, the phone may or may not send a new
> SUBSCRIBE request (which may have a very different timer). If we
> auto-deleted the underlying subscription, we could have a situation where
> the phone is re-registered but no longer receives state updates.
>
> I'll grant the above scenario is pretty unlikely, but it is plausible.
>
>
> Without knowing the details of the PJSIP channel this conversation seems
> all upside down to me.
> Subscriptions provide their own contact for the NOTIFY and have no
> relationship to the REGISTER message.
>

There's no protocol level relationship but there is a functional
relationship.  If a phone with 15 BLF subscriptions goes missing and we can
correlate the expired registration contact with the subscription contact,
should we bother sending NOTIFYs that we know will timeout and need to be
retried?


>
>
> Unless you are discussing a Subscription for registration status - but
> even so your discussion is not parseable in my eyes ;-)
>
> Sorry for the intrusion
>
> /O
>
>
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-- 
George Joseph
Digium, Inc. | Software Developer
445 Jan Davis Drive NW - Huntsville, AL 35806 - US
Check us out at: www.digium.com & www.asterisk.org
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Re: [asterisk-dev] Subscription behavior when an incoming registration goes away?

[Joshua Colp]

On Thu, Dec 22, 2016, at 12:14 PM, Matthew Jordan wrote:



> If an AoR only has dynamic contacts, and those dynamic contacts are no
> longer valid (or the AoR no longer has any contacts), then at the very
> least I would think we wouldn't want to send the NOTIFY requests until
> the
> AoR has valid contacts. There's certainly no reason to use memory/CPU
> cycles on something that will never succeed.

An AoR is only consulted for unsolicited NOTIFY messages, right now
those wouldn't happen without any contacts. Subscriptions themselves
don't consult the AOR as they already have a target in them.

> 
> You may or may not want to actually remove the underlying subscription. I
> could see a scenario in which a phone's REGISTER request goes "missing",
> and so the registration drops - maybe for just a short period of time.
> When
> the new REGISTER request does succeed, the phone may or may not send a
> new
> SUBSCRIBE request (which may have a very different timer). If we
> auto-deleted the underlying subscription, we could have a situation where
> the phone is re-registered but no longer receives state updates.
> 
> I'll grant the above scenario is pretty unlikely, but it is plausible.

Agreed. On the client side each are usually considered separate and only
upon initial startup does everything occur (registration/subscriptions).
The fact that a re-registration has occurred doesn't itself trigger new
subscriptions or refreshes. It may "work" if we still send a NOTIFY
saying the subscription is terminated (which you're trying to avoid I
believe), the device might then start a new subscription... but we're
into client side behavior here.

-- 
Joshua Colp
Digium, Inc. | Senior Software Developer
445 Jan Davis Drive NW - Huntsville, AL 35806 - US
Check us out at: www.digium.com & www.asterisk.org

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Re: [asterisk-dev] Subscription behavior when an incoming registration goes away?

[Olle E. Johansson]

> On 22 Dec 2016, at 17:14, Matthew Jordan  wrote:
> 
> 
> 
> On Thu, Dec 22, 2016 at 9:32 AM, George Joseph  > wrote:
> When an incoming registration goes away, either because it expires or it was 
> explicitly expired, what should we do with subscriptions the contact may 
> have?  Right now we do nothing which means that activity for those 
> subscriptions will trigger NOTIFYs which will time out and retry until 
> timer_b expires.  Only then will they be deleted.
> 
> Should we:
> Leave the behavior as is?
> Automatically remove the subscriptions for a contact that has been deleted?
> Create a global option to control auto deletion?
> Create an aor option to control auto deletion?
> Opinions?
> 
> 
> If an AoR only has dynamic contacts, and those dynamic contacts are no longer 
> valid (or the AoR no longer has any contacts), then at the very least I would 
> think we wouldn't want to send the NOTIFY requests until the AoR has valid 
> contacts. There's certainly no reason to use memory/CPU cycles on something 
> that will never succeed.
> 
> You may or may not want to actually remove the underlying subscription. I 
> could see a scenario in which a phone's REGISTER request goes "missing", and 
> so the registration drops - maybe for just a short period of time. When the 
> new REGISTER request does succeed, the phone may or may not send a new 
> SUBSCRIBE request (which may have a very different timer). If we auto-deleted 
> the underlying subscription, we could have a situation where the phone is 
> re-registered but no longer receives state updates.
> 
> I'll grant the above scenario is pretty unlikely, but it is plausible.

Without knowing the details of the PJSIP channel this conversation seems all 
upside down to me.
Subscriptions provide their own contact for the NOTIFY and have no relationship 
to the REGISTER message.


Unless you are discussing a Subscription for registration status - but even so 
your discussion is not parseable in my eyes ;-)

Sorry for the intrusion

/O

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Re: [asterisk-dev] Subscription behavior when an incoming registration goes away?

[Richard Mudgett]

On Thu, Dec 22, 2016 at 10:14 AM, Matthew Jordan  wrote:

>
>
> On Thu, Dec 22, 2016 at 9:32 AM, George Joseph  wrote:
>
>> When an incoming registration goes away, either because it expires or it
>> was explicitly expired, what should we do with subscriptions the contact
>> may have?  Right now we do nothing which means that activity for those
>> subscriptions will trigger NOTIFYs which will time out and retry until
>> timer_b expires.  Only then will they be deleted.
>>
>> Should we:
>>
>>- Leave the behavior as is?
>>- Automatically remove the subscriptions for a contact that has been
>>deleted?
>>- Create a global option to control auto deletion?
>>- Create an aor option to control auto deletion?
>>
>> Opinions?
>>
>>
> If an AoR only has dynamic contacts, and those dynamic contacts are no
> longer valid (or the AoR no longer has any contacts), then at the very
> least I would think we wouldn't want to send the NOTIFY requests until the
> AoR has valid contacts. There's certainly no reason to use memory/CPU
> cycles on something that will never succeed.
>
> You may or may not want to actually remove the underlying subscription. I
> could see a scenario in which a phone's REGISTER request goes "missing",
> and so the registration drops - maybe for just a short period of time. When
> the new REGISTER request does succeed, the phone may or may not send a new
> SUBSCRIBE request (which may have a very different timer). If we
> auto-deleted the underlying subscription, we could have a situation where
> the phone is re-registered but no longer receives state updates.
>
> I'll grant the above scenario is pretty unlikely, but it is plausible.
>

I was originally thinking to dump the subscriptions.  But Matt's reasoning
makes plain that we
should only just skip sending the NOTIFY's when we have no AOR available.

Richard
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Re: [asterisk-dev] Subscription behavior when an incoming registration goes away?

[Matthew Jordan]

On Thu, Dec 22, 2016 at 9:32 AM, George Joseph  wrote:

> When an incoming registration goes away, either because it expires or it
> was explicitly expired, what should we do with subscriptions the contact
> may have?  Right now we do nothing which means that activity for those
> subscriptions will trigger NOTIFYs which will time out and retry until
> timer_b expires.  Only then will they be deleted.
>
> Should we:
>
>- Leave the behavior as is?
>- Automatically remove the subscriptions for a contact that has been
>deleted?
>- Create a global option to control auto deletion?
>- Create an aor option to control auto deletion?
>
> Opinions?
>
>
If an AoR only has dynamic contacts, and those dynamic contacts are no
longer valid (or the AoR no longer has any contacts), then at the very
least I would think we wouldn't want to send the NOTIFY requests until the
AoR has valid contacts. There's certainly no reason to use memory/CPU
cycles on something that will never succeed.

You may or may not want to actually remove the underlying subscription. I
could see a scenario in which a phone's REGISTER request goes "missing",
and so the registration drops - maybe for just a short period of time. When
the new REGISTER request does succeed, the phone may or may not send a new
SUBSCRIBE request (which may have a very different timer). If we
auto-deleted the underlying subscription, we could have a situation where
the phone is re-registered but no longer receives state updates.

I'll grant the above scenario is pretty unlikely, but it is plausible.

Matt

-- 
Matthew Jordan
Digium, Inc. | CTO
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
Check us out at: http://digium.com & http://asterisk.org
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[asterisk-dev] Subscription behavior when an incoming registration goes away?

[George Joseph]

When an incoming registration goes away, either because it expires or it
was explicitly expired, what should we do with subscriptions the contact
may have?  Right now we do nothing which means that activity for those
subscriptions will trigger NOTIFYs which will time out and retry until
timer_b expires.  Only then will they be deleted.

Should we:

   - Leave the behavior as is?
   - Automatically remove the subscriptions for a contact that has been
   deleted?
   - Create a global option to control auto deletion?
   - Create an aor option to control auto deletion?

Opinions?


-- 
George Joseph
Digium, Inc. | Software Developer
445 Jan Davis Drive NW - Huntsville, AL 35806 - US
Check us out at: www.digium.com & www.asterisk.org
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