<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:x="urn:schemas-microsoft-com:office:excel" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<!--[if !mso]><style>v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style><![endif]--><style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Consolas;
panose-1:2 11 6 9 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
pre
{mso-style-priority:99;
mso-style-link:"HTML Vorformatiert Zchn";
margin:0cm;
margin-bottom:.0001pt;
font-size:10.0pt;
font-family:"Courier New";}
span.HTMLVorformatiertZchn
{mso-style-name:"HTML Vorformatiert Zchn";
mso-style-priority:99;
mso-style-link:"HTML Vorformatiert";
font-family:Consolas;}
span.E-MailFormatvorlage22
{mso-style-type:personal-reply;
font-family:"Calibri",sans-serif;
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:70.85pt 70.85pt 2.0cm 70.85pt;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang="DE" link="blue" vlink="purple">
<div class="WordSection1">
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Hi Luis,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">I see. Well, you want to use Kamailio as a stateless proxy, on the other hand it should do things that are inherently stateful.
</span><span lang="EN-GB" style="font-family:"Segoe UI Emoji",sans-serif;mso-fareast-language:EN-US">😉</span><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">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.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">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.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">Cheers,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">Henning<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<div>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">-- <o:p>
</o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">Henning Westerholt –
</span><span style="mso-fareast-language:EN-US"><a href="https://skalatan.de/blog/"><span lang="EN-GB" style="color:#0563C1">https://skalatan.de/blog/</span></a></span><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">Kamailio services –
</span><span style="mso-fareast-language:EN-US"><a href="https://gilawa.com/"><span lang="EN-GB" style="color:#0563C1">https://gilawa.com</span></a></span><span style="mso-fareast-language:EN-US">
<span lang="EN-GB"><o:p></o:p></span></span></p>
</div>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<div>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal" style="margin-left:35.4pt"><b>From:</b> Luis Rojas G. <luis.rojas@sixbell.com>
<br>
<b>Sent:</b> Wednesday, April 8, 2020 3:00 PM<br>
<b>To:</b> Henning Westerholt <hw@skalatan.de>; Kamailio (SER) - Users Mailing List <sr-users@lists.kamailio.org><br>
<b>Subject:</b> Re: [SR-Users] Kamailio propagates 180 and 200 OK OUT OF ORDER<o:p></o:p></p>
</div>
</div>
<p class="MsoNormal" style="margin-left:35.4pt"><o:p> </o:p></p>
<div>
<p class="MsoNormal" style="margin-left:35.4pt">Hello, Henning,<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal" style="margin-left:35.4pt"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal" style="margin-left:35.4pt">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<br>
<br>
<a href="https://tools.ietf.org/html/rfc5407#page-22">https://tools.ietf.org/html/rfc5407#page-22</a><br>
<br>
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? <br>
<br>
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.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal" style="margin-left:35.4pt"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal" style="mso-margin-top-alt:0cm;margin-right:0cm;margin-bottom:12.0pt;margin-left:35.4pt">
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?<br>
<br>
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.<br>
<br>
(*) 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.<br>
<br>
Well, thanks for your answer.<br>
<br>
Luis<br>
<br>
<br>
<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal" style="margin-left:35.4pt"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal" style="margin-left:35.4pt"><br>
On 4/8/20 3:01 AM, Henning Westerholt wrote:<o:p></o:p></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal" style="margin-left:35.4pt"><span style="mso-fareast-language:EN-US">Hello Luis,</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span style="mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-GB" style="mso-fareast-language:EN-US">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.</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-GB" style="mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-GB" style="mso-fareast-language:EN-US">Can you elaborate why you think this re-ordering is a problem for you?</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-GB" style="mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-GB" style="mso-fareast-language:EN-US">One idea to enforce some ordering would be to use the dialog module in combination with reply routes and the textops(x) module.</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-GB" style="mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-GB" style="mso-fareast-language:EN-US">About the shared memory question – Kamailio implement its own memory manager (private memory and shared memory pool).</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-GB" style="mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-GB" style="mso-fareast-language:EN-US">Cheers,</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-GB" style="mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-GB" style="mso-fareast-language:EN-US">Henning</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-GB" style="mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-GB" style="mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<div>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-GB" style="mso-fareast-language:EN-US">--
</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-GB" style="mso-fareast-language:EN-US">Henning Westerholt –
</span><span style="mso-fareast-language:EN-US"><a href="https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fskalatan.de%2Fblog%2F&data=02%7C01%7C%7C9909a729fd8a426f81aa08d7db8aab0a%7Cab4a33c2b5614f798601bc921698ad08%7C0%7C1%7C637219260993836600&sdata=ZLmPqvbWKbsXY49s870sElN2I0uIn0DtDQSqJOoxr6I%3D&reserved=0"><span lang="EN-GB" style="color:#0563C1">https://skalatan.de/blog/</span></a></span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-GB" style="mso-fareast-language:EN-US">Kamailio services –
</span><span style="mso-fareast-language:EN-US"><a href="https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgilawa.com%2F&data=02%7C01%7C%7C9909a729fd8a426f81aa08d7db8aab0a%7Cab4a33c2b5614f798601bc921698ad08%7C0%7C1%7C637219260993836600&sdata=Hdgzfwgu80wiwJBOjh9N70hvXSvWjt8abuKFjVRsavo%3D&reserved=0"><span lang="EN-GB" style="color:#0563C1">https://gilawa.com</span></a>
</span><o:p></o:p></p>
</div>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-GB" style="mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<div>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal" style="margin-left:70.8pt"><b>From:</b> sr-users <a href="mailto:sr-users-bounces@lists.kamailio.org">
<sr-users-bounces@lists.kamailio.org></a> <b>On Behalf Of </b>Luis Rojas G.<br>
<b>Sent:</b> Tuesday, April 7, 2020 10:43 PM<br>
<b>To:</b> <a href="mailto:sr-users@lists.kamailio.org">sr-users@lists.kamailio.org</a><br>
<b>Subject:</b> [SR-Users] Kamailio propagates 180 and 200 OK OUT OF ORDER<o:p></o:p></p>
</div>
</div>
<p class="MsoNormal" style="margin-left:70.8pt"> <o:p></o:p></p>
<div>
<p style="margin-left:70.8pt">Good day,<o:p></o:p></p>
<p style="margin-left:70.8pt">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.<o:p></o:p></p>
<p style="margin-left:70.8pt">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 :<o:p></o:p></p>
<p style="mso-margin-top-alt:5.0pt;margin-right:0cm;margin-bottom:12.0pt;margin-left:70.8pt">
<img border="0" width="597" height="209" style="width:6.2187in;height:2.177in" id="_x0000_i1025" src="cid:image001.png@01D60DBA.9CBC1BA0"><o:p></o:p></p>
<p style="margin-left:70.8pt">UAS is 172.30.4.195:5061. UAC is 172.30.4.195:5080. Kamailio is 192.168.253.4:5070<o:p></o:p></p>
<p style="margin-left:70.8pt">Difference between 180 and 200 is just about 50 microseconds.
<o:p></o:p></p>
<p style="margin-left:70.8pt">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.<o:p></o:p></p>
<p style="margin-left:70.8pt">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.<o:p></o:p></p>
<p style="margin-left:70.8pt">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...<o:p></o:p></p>
<p style="margin-left:70.8pt">Please, any help. I'm really stuck on this.<o:p></o:p></p>
<p style="margin-left:70.8pt">Thanks.<o:p></o:p></p>
<pre style="margin-left:70.8pt">-- <o:p></o:p></pre>
</div>
</blockquote>
<p style="margin-left:35.4pt"><o:p> </o:p></p>
<pre style="margin-left:35.4pt">-- <o:p></o:p></pre>
<pre style="margin-left:35.4pt">Luis Rojas<o:p></o:p></pre>
<pre style="margin-left:35.4pt">Software Architect<o:p></o:p></pre>
<pre style="margin-left:35.4pt">Sixbell<o:p></o:p></pre>
<pre style="margin-left:35.4pt">Los Leones 1200<o:p></o:p></pre>
<pre style="margin-left:35.4pt">Providencia<o:p></o:p></pre>
<pre style="margin-left:35.4pt">Santiago, Chile<o:p></o:p></pre>
<pre style="margin-left:35.4pt">Phone: (+56-2) 22001288<o:p></o:p></pre>
<pre style="margin-left:35.4pt"><a href="mailto:luis.rojas@sixbell.com">mailto:luis.rojas@sixbell.com</a><o:p></o:p></pre>
<pre style="margin-left:35.4pt"><a href="http://www.sixbell.com">http://www.sixbell.com</a><o:p></o:p></pre>
</div>
</body>
</html>