[SR-Users] Kamailio propagates 180 and 200 OK OUT OF ORDER

Wed Apr 8 17:54:48 CEST 2020

I have a question on this, since 180 arrived before the 200, shouldn’t it
go out before? I.e.: FIFO? Or is this not happening because there are
multiple processes and one may take the 180 and the other the 200 and they
are processes independently?

I guess setting the childs to only 1 should prove this theory.

David

On Wed, 8 Apr 2020 at 16:51, Luis Rojas G. <luis.rojas at sixbell.com> wrote:

> Hi, Henning,
>
> No need to be ironic. As I mentioned on my first post, I tried stateful
> proxy and I observed the same behavior.
>
> *"I tried using stateful proxy and I obtained the same result."*
>
> The asynchronous sleep seems promising. I will look into it.
>
> Thanks,
>
> Luis
>
>
>
> On 4/8/20 9:30 AM, Henning Westerholt wrote:
>
> Hi Luis,
>
>
>
> I see. Well, you want to use Kamailio as a stateless proxy, on the other
> hand it should do things that are inherently stateful. 😉
>
>
>
> As mentioned, have a look to the dialog module to track the state of
> dialogs that you process. This will not work in a stateless mode, though.
>
>
>
> You can also use the htable module to just store some data about the
> processed messages in a shared memory table and use this to enforce your
> ordering. There is also the option to do an asynchronous sleep (with the
> async) module on the message that you want to delay but still processing
> other messages during it.
>
>
>
> Cheers,
>
>
>
> Henning
>
>
>
> --
>
> Henning Westerholt – https://skalatan.de/blog/
> <https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fskalatan.de%2Fblog%2F&data=02%7C01%7C%7C365ec3c445394a3b0dfa08d7dbc0fe3a%7Cab4a33c2b5614f798601bc921698ad08%7C0%7C0%7C637219494311846648&sdata=Rlxmq4vieb20HKUi4se4MfGJSuETpO%2Bd8uK0KzBTWO0%3D&reserved=0>
>
> Kamailio services – https://gilawa.com
> <https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgilawa.com%2F&data=02%7C01%7C%7C365ec3c445394a3b0dfa08d7dbc0fe3a%7Cab4a33c2b5614f798601bc921698ad08%7C0%7C0%7C637219494311846648&sdata=nAvHd08RTXoEAFfpOuoGQJnoRmOtzQ0RSfS2RYwIyQs%3D&reserved=0>
>
>
>
> *From:* Luis Rojas G. <luis.rojas at sixbell.com> <luis.rojas at sixbell.com>
> *Sent:* Wednesday, April 8, 2020 3:00 PM
> *To:* Henning Westerholt <hw at skalatan.de> <hw at skalatan.de>; Kamailio
> (SER) - Users Mailing List <sr-users at lists.kamailio.org>
> <sr-users at lists.kamailio.org>
> *Subject:* Re: [SR-Users] Kamailio propagates 180 and 200 OK OUT OF ORDER
>
>
>
> Hello, Henning,
>
>
>
> I am worried about this scenario, because it's a symptom of what may
> happen in other cases. For instance, I've seen that this operator usually
> sends re-invites immediate after sending ACK.   This may create race
> conditions like 3.1.5 of RFC5407
>
> https://tools.ietf.org/html/rfc5407#page-22
> <https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Ftools.ietf.org%2Fhtml%2Frfc5407%23page-22&data=02%7C01%7C%7C365ec3c445394a3b0dfa08d7dbc0fe3a%7Cab4a33c2b5614f798601bc921698ad08%7C0%7C0%7C637219494311856645&sdata=fwVfaNyZ7hCyBvYz%2BdlWBMf52MuFdhBxHpnYysjA0FA%3D&reserved=0>
>
> I'd understand that one happens because of packet loss, as it's in UDP's
> nature, but in this case it would be artificially created by Kamailio. if
> there was no problem at network level (packet loss, packets following
> different path on the network and arriving out of order), why Kamailio
> creates it?
>
> I'd expect that the shared memory is used precisely for this. If an
> instance of kamailio receives a 200 OK, it could check on the shm and say
> "hey, another instance is processing a 180 for this call. Let's wait for it
> to finish" (*). I know there could still be a problem, the instance
> processing the 180 undergoes a context switch just after it receives the
> message, but before writing to shm, but it would greatly reduce the chance.
>
>
>
> In our applications we use a SIP stack that always sends messages to the
> application in the same order it receives them, even though is
> multi-threaded and messages from the network are received by different
> threads. So, they really syncronize between them. Why Kamailio instances
> don't?
>
> I am evaluating kamailio to use it as a dispatcher to balance load against
> our several Application Servers, to present to the operator just a couple
> of entrance points to our platform (they don't want to establish
> connections to each one of our servers). This operator is very difficult to
> deal with. I am sure they will complain something like "why are you sending
> messages out of order? Fix that". The operator will be able to see traces
> and check that messages entered the Kamailio nodes in order and left out of
> order. They will not accept it.
>
> (*) Not really "wait", as it would introduce a delay in processing all
> messages. it should be like putting it on a queue, continue processing
> other messages, and go back to the queue later.
>
> Well, thanks for your answer.
>
> Luis
>
>
>
>
>
> On 4/8/20 3:01 AM, Henning Westerholt wrote:
>
> Hello Luis,
>
>
>
> as the 1xx responses are usually send unreliable (unless you use PRACK),
> you should not make any assumption on the order or even the arrival of this
> messages. It can also happens on a network level, if send by UDP.
>
>
>
> Can you elaborate why you think this re-ordering is a problem for you?
>
>
>
> One idea to enforce some ordering would be to use the dialog module in
> combination with reply routes and the textops(x)  module.
>
>
>
> About the shared memory question – Kamailio implement its own memory
> manager (private memory and shared memory pool).
>
>
>
> Cheers,
>
>
>
> Henning
>
>
>
>
>
> --
>
> Henning Westerholt – https://skalatan.de/blog/
> <https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fskalatan.de%2Fblog%2F&data=02%7C01%7C%7C365ec3c445394a3b0dfa08d7dbc0fe3a%7Cab4a33c2b5614f798601bc921698ad08%7C0%7C0%7C637219494311866648&sdata=HCaqkR5PR6BmByZVV5%2F59XWfNywkkedMaujpDOOG4dk%3D&reserved=0>
>
> Kamailio services – https://gilawa.com
> <https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgilawa.com%2F&data=02%7C01%7C%7C365ec3c445394a3b0dfa08d7dbc0fe3a%7Cab4a33c2b5614f798601bc921698ad08%7C0%7C0%7C637219494311866648&sdata=O1BqU4CI4M6M8OUaE10JvFbJIeH32uZRuQg3ihEkxN0%3D&reserved=0>
>
>
>
> *From:* sr-users <sr-users-bounces at lists.kamailio.org>
> <sr-users-bounces at lists.kamailio.org> *On Behalf Of *Luis Rojas G.
> *Sent:* Tuesday, April 7, 2020 10:43 PM
> *To:* sr-users at lists.kamailio.org
> *Subject:* [SR-Users] Kamailio propagates 180 and 200 OK OUT OF ORDER
>
>
>
> Good day,
>
> I am testing the dispatcher module, using Kamailio as stateless proxy. I
> have a pool of UAC (scripts in SIPP) and a pool of UAS (also scripts in
> SIPP) for the destinations. Kamailio version is kamailio-5.3.3-4.1.x86_64.
>
> Problem I have is, if UAS responds 180 and 200 OK to Invite immediately,
> sometimes they are propagated out of order. 200 OK before 180, like this :
>
> UAS is 172.30.4.195:5061. UAC is 172.30.4.195:5080. Kamailio is
> 192.168.253.4:5070
>
> Difference between 180 and 200 is just about 50 microseconds.
>
> My guess is that both messages are received by different instances of
> Kamailio, and then because of context switches, even though the 180 is
> received before, that process ends after the processing of 200. However, I
> had the idea that in order to avoid these problems the kamailio processes
> synchronized with each other using a shared memory. I tried using stateful
> proxy and I obtained the same result.
>
> By the way, anyone has any idea about how Kamailio's share memory is
> implemented? It clearly does not use the typical system calls shmget(),
> shmat(), because they are not shown by ipcs command.
>
> Before posting here I googled, but I couldn't find anything related to
> this. I can't believe I am the only one who ever had this problem, so I
> guess I am doing something wrong...
>
> Please, any help. I'm really stuck on this.
>
> Thanks.
>
> --
>
>
>
> --
>
> Luis Rojas
>
> Software Architect
>
> Sixbell
>
> Los Leones 1200 <https://www.google.com/maps/search/Los+Leones+1200+%0D%0A+++++++++Providencia+%0D%0A+++++++++Santiago,+Chile?entry=gmail&source=g>
>
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>
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>
> Phone: (+56-2) 22001288
>
> mailto:luis.rojas at sixbell.com <luis.rojas at sixbell.com>
>
> http://www.sixbell.com <https://nam02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.sixbell.com%2F&data=02%7C01%7C%7C365ec3c445394a3b0dfa08d7dbc0fe3a%7Cab4a33c2b5614f798601bc921698ad08%7C0%7C0%7C637219494311876634&sdata=25KyYHDQz9BU3XDEGdjjPHgRH4MCZIFOEyXeXUoKjzI%3D&reserved=0>
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>
> --
> Luis Rojas
> Software Architect
> SixbellLos Leones 1200
> Providencia
> Santiago, Chile <https://www.google.com/maps/search/Los+Leones+1200%0D%0AProvidencia%0D%0ASantiago,+Chile?entry=gmail&source=g>
> Phone: (+56-2) 22001288mailto:luis.rojas at sixbell.com <luis.rojas at sixbell.com>http://www.sixbell.com
>
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-- 
Regards,

David Villasmil
email: david.villasmil.work at gmail.com
phone: +34669448337
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