12 Jul
2017
12 Jul
'17
12:05 p.m.
Hi,
I have a question regarding calls and Kamailio restarts.
Suppose Kamailio crashes (and started again), is restarted or failed over to a different
server (same IP). What then happens with calls?
Let's suppose the following scenario:
- 1000 calls active on the machine
- Some are in call setup, some are in call, some are in teardown phases
- The proxy is stateful
- The proxy forwards calls from B2BUA machines to an ITSP (outbound only)
- Uses record-routing
- Uses loose routing
What will be the likely outcome of the restart with regards to the calls in the different
phases and accounting for said calls?
All the best,
Samuel
12 Jul
12 Jul
12:53 p.m.
On Wed, Jul 12, 2017 at 09:05:27AM +0000, Samuel F. wrote:
Suppose Kamailio crashes (and started again), is
restarted or failed
over to a different server (same IP). What then happens with calls?
Speaking generically, not a lot.
All SIP messages passing through the proxy can be forwarded statelessly
and based on properties of the SIP message alone. This may break route
advance or failover scenarios reliant on state, but it will not break
the fundamental end-to-end SIP message reachability. In other words, a
proxy restart does not fundamentally prevent subsequent signalling for
the same call, or even subsequent messages within an open transaction,
from reaching their intended destination.
"Loose routing" and "record routing" are not opposed; loose routing is
a
concept that incorporates Route header processing.
The impact on accounting will depend on whether the accounting is done
with recourse to TM or dialog state, which exists in runtime, or in a
stateless manner based on received SIP messages.
-- Alex
--
Alex Balashov | Principal | Evariste Systems LLC
Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free)
Web: http://www.evaristesys.com/, http://www.csrpswitch.com/
13 Jul
13 Jul
5:39 p.m.
Hi,
On Wed, Jul 12, 2017 at 11:53 AM, Alex Balashov
<abalashov(a)evaristesys.com> wrote:
All SIP messages passing through the proxy can be
forwarded statelessly
and based on properties of the SIP message alone.
There's one thing that could happen: Calls that get cancelled after a
restart, could possibly keep on ringing on the far end. At least if
you check for an active transaction in your kamailio config.
if (!t_check_trans()) {
sl_send_reply("481", "Call/Transaction does not exist");
xlog("L_ERR", "CANCEL: found no matching transaction F=$fu T=$tu
R=$ru\n");
return;
}
And if you do some sort of random dispatching, CANCELs could end up on
a different gateway.
But other than that, a restart shouldn't cause much trouble.
Especially in-call requests get routed by Route headers only.
Regards,
Sebastian
9:22 p.m.
Thank you for the responses! As a follow up question, how do companies with large loads on
their Kamailios handle restarts especially considering the CANCELs?
What is a good (business) process to restart a Kamailio without incurring any
interruptions at all? What other components in the infrastructure would be in place and
which ones are in use in the wild?
// Samuel
________________________________
From: sr-users <sr-users-bounces(a)lists.kamailio.org> on behalf of Sebastian Damm
<damm(a)sipgate.de>
Sent: Thursday, July 13, 2017 2:39:39 PM
To: Kamailio (SER) - Users Mailing List
Subject: Re: [SR-Users] What happens to calls when Kamailio restarts?
Hi,
On Wed, Jul 12, 2017 at 11:53 AM, Alex Balashov
<abalashov(a)evaristesys.com> wrote:
All SIP messages passing through the proxy can be
forwarded statelessly
and based on properties of the SIP message alone.
There's one thing that could happen: Calls that get cancelled after a
restart, could possibly keep on ringing on the far end. At least if
you check for an active transaction in your kamailio config.
if (!t_check_trans()) {
sl_send_reply("481", "Call/Transaction does not exist");
xlog("L_ERR", "CANCEL: found no matching transaction F=$fu T=$tu
R=$ru\n");
return;
}
And if you do some sort of random dispatching, CANCELs could end up on
a different gateway.
But other than that, a restart shouldn't cause much trouble.
Especially in-call requests get routed by Route headers only.
Regards,
Sebastian
_______________________________________________
Kamailio (SER) - Users Mailing List
sr-users(a)lists.kamailio.org
https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
9:29 p.m.
Yeah, Sebastian is quite right. CANCELs do make for an especially
challenging case, since they are hop-by-hop. Kamailio has to have some
transaction state in order to have an idea of where to relay them.
A good business process is to have two Kamailio instances, tried by all
gateways on all sides if the primary is unavailable (whether by means of
SRV or just statically configured secondary gateway entries) and some
option, set externally at runtime (for example, using $shv() shared
variables), which causes Kamailio to refuse further calls. Existing
calls would drain off the system, new calls would fail over to the other
Kamailio, and then you can restart it.
On Thu, Jul 13, 2017 at 06:22:55PM +0000, Samuel F. wrote:
Thank you for the responses! As a follow up question,
how do companies with large loads on their Kamailios handle restarts especially
considering the CANCELs?
What is a good (business) process to restart a Kamailio without incurring any
interruptions at all? What other components in the infrastructure would be in place and
which ones are in use in the wild?
// Samuel
________________________________
From: sr-users <sr-users-bounces(a)lists.kamailio.org> on behalf of Sebastian Damm
<damm(a)sipgate.de>
Sent: Thursday, July 13, 2017 2:39:39 PM
To: Kamailio (SER) - Users Mailing List
Subject: Re: [SR-Users] What happens to calls when Kamailio restarts?
Hi,
On Wed, Jul 12, 2017 at 11:53 AM, Alex Balashov
<abalashov(a)evaristesys.com> wrote:
All SIP messages passing through the proxy can be
forwarded statelessly
and based on properties of the SIP message alone.
There's one thing that could happen: Calls that get cancelled after a
restart, could possibly keep on ringing on the far end. At least if
you check for an active transaction in your kamailio config.
if (!t_check_trans()) {
sl_send_reply("481", "Call/Transaction does not exist");
xlog("L_ERR", "CANCEL: found no matching transaction F=$fu T=$tu
R=$ru\n");
return;
}
And if you do some sort of random dispatching, CANCELs could end up on
a different gateway.
But other than that, a restart shouldn't cause much trouble.
Especially in-call requests get routed by Route headers only.
Regards,
Sebastian
_______________________________________________
Kamailio (SER) - Users Mailing List
sr-users(a)lists.kamailio.org
https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users _______________________________________________
Kamailio (SER) - Users Mailing List
sr-users(a)lists.kamailio.org
https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
--
Alex Balashov | Principal | Evariste Systems LLC
Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free)
Web: http://www.evaristesys.com/, http://www.csrpswitch.com/
9:34 p.m.
That said, while there are doubtless some environments so large that
this becomes a significant business question, I would think carefully
about whether this problem is truly worth solving before designing any
overly Rube-Goldbergian coping mechanism.
So, CANCELs for a small amount of calls in flight don't make it out the
door. Big deal? The two endpoints will sooner rather than later, by
various kinds of dead peer detection, discover that the other end is
dead. If you restart during a quiet / low-volume time, you can probably
keep this sort of thing to a minimum.
If it truly counts, by all means do it, but in my experience there are a
lot of folks with "high volume" ideas that are more fantasy than reality
who spend a lot of capital designing and optimising for availability
scenarios that never turn out to be a problem. I don't know how many
times I have heard in Kamailio consulting work that this registrar needs
to support five million endpoints and never be down and ... well, that
bridge is just never remotely crossed. Off by a few orders of
magnitude. :-)
-- Alex
On Thu, Jul 13, 2017 at 06:22:55PM +0000, Samuel F. wrote:
Thank you for the responses! As a follow up question,
how do companies with large loads on their Kamailios handle restarts especially
considering the CANCELs?
What is a good (business) process to restart a Kamailio without incurring any
interruptions at all? What other components in the infrastructure would be in place and
which ones are in use in the wild?
// Samuel
________________________________
From: sr-users <sr-users-bounces(a)lists.kamailio.org> on behalf of Sebastian Damm
<damm(a)sipgate.de>
Sent: Thursday, July 13, 2017 2:39:39 PM
To: Kamailio (SER) - Users Mailing List
Subject: Re: [SR-Users] What happens to calls when Kamailio restarts?
Hi,
On Wed, Jul 12, 2017 at 11:53 AM, Alex Balashov
<abalashov(a)evaristesys.com> wrote:
All SIP messages passing through the proxy can be
forwarded statelessly
and based on properties of the SIP message alone.
There's one thing that could happen: Calls that get cancelled after a
restart, could possibly keep on ringing on the far end. At least if
you check for an active transaction in your kamailio config.
if (!t_check_trans()) {
sl_send_reply("481", "Call/Transaction does not exist");
xlog("L_ERR", "CANCEL: found no matching transaction F=$fu T=$tu
R=$ru\n");
return;
}
And if you do some sort of random dispatching, CANCELs could end up on
a different gateway.
But other than that, a restart shouldn't cause much trouble.
Especially in-call requests get routed by Route headers only.
Regards,
Sebastian
_______________________________________________
Kamailio (SER) - Users Mailing List
sr-users(a)lists.kamailio.org
https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users _______________________________________________
Kamailio (SER) - Users Mailing List
sr-users(a)lists.kamailio.org
https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
--
Alex Balashov | Principal | Evariste Systems LLC
Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free)
Web: http://www.evaristesys.com/, http://www.csrpswitch.com/
9:27 p.m.
The instance which is closed supports the onhoing sessions,means calls
arent dropped
On 12-Jul-2017 3:02 PM, "Samuel F." <samuel_is_kewl(a)hotmail.com> wrote:
Hi,
I have a question regarding calls and Kamailio restarts.
Suppose Kamailio crashes (and started again), is restarted or failed over
to a different server (same IP). What then happens with calls?
Let's suppose the following scenario:
- 1000 calls active on the machine
- Some are in call setup, some are in call, some are in teardown phases
- The proxy is stateful
- The proxy forwards calls from B2BUA machines to an ITSP (outbound only)
- Uses record-routing
- Uses loose routing
What will be the likely outcome of the restart with regards to the calls
in the different phases and accounting for said calls?
All the best,
Samuel
_______________________________________________
Kamailio (SER) - Users Mailing List
sr-users(a)lists.kamailio.org
https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
2689
days inactive
2690
days old
6 comments
4 participants
participants (4)
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Alex Balashov -
Samuel F. -
Sebastian Damm -
shubh diwase