[OpenSIPS-Users] UDP fragmentation in reply routes

Wed May 20 17:18:32 EST 2020

Sorry that is what I was trying to let you know.  Is that I had thought 
the same thing that the Fragment was not even sent, but it was just 
because of the tcpdump filter I had not that it actually wasn't being 
sent.  If you have not try capturing all IP traffic to a host IP and see 
if you see it.

20.05.2020 11:11 に Olle Frimanson さんは書きました:
> Hi the issue on my side is that it’s not the network that is the
> problem the second fragment is not even sent. I also kind on lean to
> TCP at the moment but it would be good to get a comment from Opensips
> team on this if and how they setup the sockets and if there is a
> difference on different routes
> 
> Br Olle
> 
> Skickat från min iPhone
> 
>> 20 maj 2020 kl. 17:14 skrev junkmail <junkmail at djrance.com>:
>> 
>> Hello, I had run into the same issue.  One thing I was a bit mistaken 
>> because I was using tcpdump and doing a capture filter of port 5060 or 
>> the such.  So I was missing the Fragment in my sniff as it does not 
>> include the UDP header.  Just something to be aware of.  But I was 
>> having problems specifically traffic inside of GCP < google cloud.  As 
>> well as traffic traversing the VPN to GCP.   I am not certain about 
>> what changed for internal to GCP but that started working and now the 
>> only thing using TCP is over VPNs.   Sorry not a lot of information 
>> here. but my best guess is either the firewall/router on my side or 
>> Googles is dropping the UDP fragment.  I didn't dig into it much 
>> further as TCP fixed the issue and this was just a transit between 
>> opensisps systems.
>> 
>> 
>> 19.05.2020 01:21 に olle at zaark.com さんは書きました:
>>> Hi, this happens one single opensips instance server it receives the
>>> inbound packet fine, then when its send out on the same interface
>>> it’s fragmented, so I don’t think it’s network or router switch
>>> related. Have seen such problems in the past in virtual environments
>>> but this is not the case now.
>>> My prime suspect is Centos since it send out the first part of the
>>> fragmented packet but not the following part that would complete the
>>> packet.
>>> But indeed it is a strange bug, since it does not always happen.
>>> BR/Olle
>>> FRÅN: Users <users-bounces at lists.opensips.org> FÖR Giovanni
>>> Maruzzelli
>>> SKICKAT: den 19 maj 2020 09:13
>>> TILL: OpenSIPS users mailling list <users at lists.opensips.org>
>>> ÄMNE: Re: [OpenSIPS-Users] UDP fragmentation in reply routes
>>> Can be a problem of the virtual env, and/or the router/switch...
>>> Try substitute real hardware to virtual, and different models of
>>> router/switch
>>> In a LAN, UDP fragmentation is not supposed to be a problem at all...
>>> answered from mobile, please pardon terseness and typos,
>>> -giovanni
>>>> On Tue, May 19, 2020, 08:05 <olle at zaark.com> wrote:
>>>> Thanks for the reply Max,
>>>> we are doing all we can to make the packets smaller, but before we
>>>> move over to TCP, which is most likely our next step, I wanted to
>>>> explore what could be happening.
>>>> AFAIK the application have some control of this since these are
>>>> parameters that partly can be set when you open a socket, that’s
>>>> why I wonders if Opensips might use those parameters or not,
>>>> especially since we have so very different behaviour in different
>>>> directions.
>>>> BR/Olle
>>>> FRÅN: Users <users-bounces at lists.opensips.org> FÖR Maxim Sobolev
>>>> SKICKAT: den 18 maj 2020 22:03
>>>> TILL: OpenSIPS users mailling list <Users at lists.opensips.org>
>>>> ÄMNE: Re: [OpenSIPS-Users] UDP fragmentation in reply routes
>>>> Smells like a OS/kernel bug to me. There is little application can
>>>> do in that regard, UDP fragmentation/reassembly happens at much
>>>> lower layers of the OSI stack.
>>>> However, as a workaround as long as SIP goes you can try to reduce
>>>> your SIP signalling packet size by using compact version of SIP
>>>> headers, as well as dropping headers that are not used. That would
>>>> save you 100-150 bytes per SIP message perhaps. I don't know if
>>>> OpenSIP can do that in the proxy mode out of the box though, so you
>>>> might want to add b2b into the flow.
>>>> -Max
>>>> On Mon., May 18, 2020, 12:34 p.m. Olle Frimanson, <olle at zaark.com>
>>>> wrote:
>>>>> Hi,
>>>>> We have an issue on our home proxy (opensips 2.4.6), when it
>>>>> receives  200 OK (over UDP)  from our Freeswitch and the package
>>>>> size is higher than the MTU size , we sometimes get fragmentation
>>>>> of the UDP packets, but only the first part of the fragmented
>>>>> package is sent to our edge proxy. Is this a known issue or is it
>>>>> a OS bug?
>>>>> We have not yet spotted any pattern on this and in most cases
>>>>> bigger packets with MTU around 1600 bytes gets through without an
>>>>> issue.
>>>>> I can add that in the other direction in the normal request routes
>>>>> we don’t have any issue at all can have packets > 2000 bytes
>>>>> without any issues.
>>>>> Does Opensips use IP_MTU_DISCOVER or how is fragmentation
>>>>> controlled and is it expected to have different behavior in reply
>>>>> routes vs other routes?
>>>>> We use Centos 7 in a virtual server environment.
>>>>> I was hoping someone can share some light on this strange issue.
>>>>> BR/Olle
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