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<p>Curious about the ALG vendor/model/version, if it is some
carrier/enterprise grade firewall, just to be aware when meeting
it ... of course, if you can and want to share such details...</p>
<p>Cheers,<br>
Daniel<br>
</p>
<div class="moz-cite-prefix">On 14.01.20 08:42, Lợi Đặng wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAGsrq_t1X4kKrQ_yp4dxp_yCfspafR+qFBao8x9=RCW=nVJ+cQ@mail.gmail.com">
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<div dir="ltr">Nice, be ware of the ALG, sometimes it's an
unpredictable foe.
<div><br>
</div>
<div>rgds,<br clear="all">
<div>
<div dir="ltr" class="gmail_signature"
data-smartmail="gmail_signature">
<div dir="ltr">
<div>
<div dir="ltr">
<div>
<div dir="ltr">
<div>
<div>Loi Dang Thanh</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
<br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Tue, Jan 14, 2020 at 4:42
AM Michael Broughton <<a
href="mailto:mbroughton@advanis.net" moz-do-not-send="true">mbroughton@advanis.net</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">Just to provide some closure to this, the
problem did end up being with the Via headers and our
firewall ALG.
<div><br>
</div>
<div>
<div>In the top Via header of the INVITE requests the ALG
was transforming the internal proxy address to our
external address and adding port 5060. In subsequent
negative ACK and CANCEL requests, the ALG was
transforming the internal proxy address to our external
address with no port number. Thus the Via's did not
exactly match, and this prevented our telco from
matching the existing transaction.</div>
<div><br>
</div>
<div>I was able to fix the issue by modifying our Kam
config with the advertise parameter:</div>
</div>
<div><br>
</div>
<div>listen = 10.x.y.z advertise 10.x.y.z:5060<br>
</div>
<div><br>
</div>
<div>With this setting in place the ALG is forced to behave
itself.</div>
<div><br>
</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Thu, Jan 9, 2020 at
9:27 AM Michael Broughton <<a
href="mailto:mbroughton@advanis.net" target="_blank"
moz-do-not-send="true">mbroughton@advanis.net</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="ltr">I'm using 5.3.1+stretch from <a
href="http://deb.kamailio.org" target="_blank"
moz-do-not-send="true">deb.kamailio.org</a> for our
new setup. Our old setup was using 4.4.4+wheezy.</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Thu, Jan 9, 2020 at
9:16 AM Daniel-Constantin Mierla <<a
href="mailto:miconda@gmail.com" target="_blank"
moz-do-not-send="true">miconda@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px
0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div>
<p>Is it a recent version of kamailio, or an older
one?</p>
<p>Cheers,<br>
Daniel<br>
</p>
<div>On 09.01.20 16:55, Michael Broughton wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">Thank you, this was a helpful
sanity check.
<div><br>
</div>
<div>We have been capturing SIP traces to try
and debug this. I normally just look at the
traffic on our Kam box because it is
convenient to do so, but I have also taken
traces on our firewall to check the ALG
behaviour. The provider techs are also tracing
these calls on their network as well. The ALG
is new equipment in our setup, but as far as I
can tell it is behaving correctly.</div>
<div><br>
</div>
<div>The one rather annoying discovery that I
made is that when I call directly out from the
source (Freeswitch in this case) and bypass
Kamailio, the negative ACK's seem to work. I
do not see any retransmissions of their final
response. And of course the only significant
difference in the SIP traces is the Via
headers.</div>
<div><br>
</div>
<div>Anyway, thanks again for your input.</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Thu, Jan 9,
2020 at 4:04 AM Lợi Đặng <<a
href="mailto:loi.dangthanh@gmail.com"
target="_blank" moz-do-not-send="true">loi.dangthanh@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote"
style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="ltr">
<div>Hi, </div>
<div>You're not going to have the Via header
from your `source` sent to your `telco
provider` in the negative ACK when the
call is not answered, because the ACK in
the right hand side of the call is created
by the kamailio itself, not a forwarding
one by the `source`.</div>
<div>Yes, you've guessed it, ACK for an
answered call is a forwarding one which
contains all the Via headers. It's the SIP
spec, not kamailio, you may want to dive
into rfc3261 for more details.</div>
<div><br>
</div>
<div>In this case, your telco's
expectation is not correct, my best guess
is something went wrong with either your
SIP ALG or Telco Provider. SIP capturing
may help.</div>
<div><br>
</div>
<div>rgds,</div>
<div>
<div dir="ltr">
<div dir="ltr">
<div>
<div dir="ltr">
<div>
<div dir="ltr">
<div>
<div>Loi Dang Thanh<br>
</div>
Phone : +84. 774.735.448<br>
</div>
Email : <a
href="mailto:loi.dangthanh@gmail.com"
target="_blank"
moz-do-not-send="true">loi.dangthanh@gmail.com</a><br>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
<br>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Thu,
Jan 9, 2020 at 2:42 AM Michael Broughton
<<a
href="mailto:mbroughton@advanis.net"
target="_blank" moz-do-not-send="true">mbroughton@advanis.net</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote"
style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="ltr">Hello,
<div><br>
</div>
<div>Long time Kam/Ser user, first time
poster.</div>
<div><br>
</div>
<div>I'm running into a problem with one
of our telco providers when we make a
call that ends up being not in service
or some other error. In this case our
ACK's are not working and the phone
line stays open for a period of time
until something times out on their
end.</div>
<div><br>
</div>
<div>They claim the issue is that our
negative ACK message is dropping one
of the Via headers. This is the only
case I can find in our setup where
Kamailio does this. But it does drop
the first Via, which is the first hop
in our internal network.</div>
<div><br>
</div>
<div>I don't understand why this is a
problem for them, and I'm still trying
to get a reasonable explanation out of
them. Technically, I don't see why it
would be a problem. This behaviour is
not an issue with our other telco
providers. Strangely enough, it is
also not an issue for this provider
when we make the calls over their MPLS
network (we are switching to the
internet).</div>
<div><br>
</div>
<div>My question is, can this behaviour
be changed in Kamailio somehow? Is
there a way for it to keep all the Via
headers for negative ACK's?</div>
<div><br>
</div>
<div>Or, do I just need to poke them
harder to fix their issues?</div>
<div><br>
</div>
<div>My setup:</div>
<div><br>
</div>
<div>Source -> Kamailio ->
Firewall (NAT, SIP ALG) -> Telco
Provider</div>
<div><br>
</div>
<div>I hope I have provided enough
information.</div>
<div><br>
</div>
<div>Thanks!</div>
<div>Michael</div>
<div><br>
</div>
<div><br>
</div>
</div>
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<pre cols="72">--
Daniel-Constantin Mierla -- <a href="http://www.asipto.com" target="_blank" moz-do-not-send="true">www.asipto.com</a>
<a href="http://www.twitter.com/miconda" target="_blank" moz-do-not-send="true">www.twitter.com/miconda</a> -- <a href="http://www.linkedin.com/in/miconda" target="_blank" moz-do-not-send="true">www.linkedin.com/in/miconda</a>
Kamailio World Conference - April 27-29, 2020, in Berlin -- <a href="http://www.kamailioworld.com" target="_blank" moz-do-not-send="true">www.kamailioworld.com</a></pre>
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_______________________________________________<br>
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moz-do-not-send="true">sr-users@lists.kamailio.org</a><br>
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<pre class="moz-quote-pre" wrap="">_______________________________________________
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<pre class="moz-signature" cols="72">--
Daniel-Constantin Mierla -- <a class="moz-txt-link-abbreviated" href="http://www.asipto.com">www.asipto.com</a>
<a class="moz-txt-link-abbreviated" href="http://www.twitter.com/miconda">www.twitter.com/miconda</a> -- <a class="moz-txt-link-abbreviated" href="http://www.linkedin.com/in/miconda">www.linkedin.com/in/miconda</a>
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